MOLECULAR BIOLOGY AND EVOLUTION (OXFORD UNIVERSITY PRESS)
Is mental illness simply the evolutionary toll humans have to pay in return for our unique and superior cognitive abilities when compared to all other species? But if so, why have often debilitating illnesses like schizophrenia persisted throughout human evolutionary history when the affects can be quite negative on an individual’s chances of survival or reproductive success?
In a new study appearing in Molecular Biology and Evolution, Mount Sinai researcher Joel Dudley has led a new study that suggests that the very changes specific to human evolution may have come at a cost, contributing to the genetic architecture underlying schizophrenia traits in modern humans.
“We were intrigued by the fact that unlike many other mental traits, schizophrenia traits have not been observed in species other than humans, and schizophrenia has interesting and complex relationships with human intelligence,” said Dr. Joel Dudley, who led the study along with Dr. Panos Roussos. “The rapid increase in genomic data sequenced from large schizophrenia patient cohorts enabled us to investigate the molecular evolutionary history of schizophrenia in sophisticated new ways.”
The team examined a link between these regions, and human-specific evolution, in genomic segments called human accelerated regions, or HARs. HARs are short signposts in the genome that are conserved among non-human species but experienced faster mutation rates in humans. Thus, these regions, which are thought to control the level of gene expression, but not mutate the gene itself, may be an underexplored area of mental illness research.
The team’s research is the first study to sift through the human genome and identify a shared pattern between the location of HARs and recently identified schizophrenia gene loci. To perform their work, they utilized a recently completed, largest schizophrenia study of its kind, the Psychiatric Genomics Consortium (PGC), which included 36,989 schizophrenia cases and 113,075 controls. It is the largest genome-wide association study ever performed on any psychiatric disease.
They found that the schizophrenic loci were most strongly associated in genomic regions near the HARs that are conserved in non-human primates, and these HAR-associated schizophrenic loci are found to be under stronger evolutionary selective pressure when compared with other schizophrenic loci. Furthermore, these regions controlled genes that were expressed only in the prefrontal cortex of the brain, indicating that HARs may play an important role in regulating genes found to be linked to schizophrenia. They specifically found the greatest correlation between HAR-associated schizophrenic loci and genes controlling the expression of the neurotransmitter GABA, brain development, synaptic formations, adhesion and signaling molecules.
Their new evolutionary approach provides new insights into schizophrenia, and genomic targets to prioritize future studies and drug development targets. In addition, there are important new avenues to explore the roles of HARs in other mental diseases such as autism or bipolar disorder.
The British Museum still has the first platypus sent back to Europe from Australia, by Captain John Hunter in 1799. There are scissor marks on its duck-bill.
The first platypus specimen studied by European scientists, at the British Museum.
That’s because George Shaw, the first scientist who studied the astonishing specimen, was pretty sure it was a hoax, sewn together by pranksters or profiteers. With its webbed feet, furry pelt, venomous claw, and ducky beak, it was too freakish to be believed; moreover, London society had lately been thrilled, then crestfallen, by a wave of Franken-mermaids and other concocted exotica hawked by foreign sailors. So Shaw’s first move upon examining the platypus was to reach for his scissors, to uncover what kind of clever stitches bound the amalgamation together.
First published illustrations of a platypus, by George Shaw, “The Duck-Billed Platypus,” Naturalist’s Miscellany, Vol. X (1799).
Finding that the platypus was held together by flesh, not thread, Shaw stopped snipping and starting measuring, and marveling. He published a dutiful summary of his anatomical observations, together with field notes from Australia, in the impossibly well-named Naturalist’s Miscellany. Even with the benefit of several additional, later-arriving specimens, he wrote that it was “impossible not to entertain some doubts as to the genuine nature of the animal, and to surmise that there might have been practised some arts of deception in its structure.”
When a certain kind of person — OK, an older person, where “old” equals 24— first encounters Snapchat, the reaction is typically some mixture of mystification, disbelief, and annoyance. For people who have gotten used to the dominant evolved anatomies of mobile apps, Snapchat seems like an odd and improbable creature.
A quick cruise through the app reveals why people born before the dawn of Clinton Administration react so strongly to it: Snapchat’s UI is really different from what we’re used to. What we’re used to is desktop software and its lineal descendants, with their predictably-located upper-margin drop-down menus, scrollable windows and swappable tabs, and logo-bearing application icons. On our mobile devices, designers have forged comfortingly similar UI elements, ever-so-slightly tweaked to work on smaller screens: scrollable feeds, sliding drawers with logically stacked navigation and option menus, all signaled by a homescreen hamburger icon.
Here are some of the ways Snapchat is different:
The app opens in camera mode. You don’t start with a social feed like Facebook, Twitter, LinkedIn, or Instagram, an editorial content feed like Digg, Buzzfeed, or the New York Times, a list of friends like Google Hangouts or Line, or a chronology of recent messages like FaceTime, Skype, or Slack. Instead, you start with whatever your phone’s camera is currently aimed at. Snapchat believes that you (should) want to create something — a photo, a short video— for immediate sharing. Snapchat is designed for you to create first, consume later.
There is no options menu. You have to navigate around the app without the crutch of a menu adorned with actual words that spell out what you can do and where you can go. But wait, you cry, there is (sometimes) a hamburger icon right there on the homescreen! Only it doesn’t do what you expect. Tapping the hamburger takes you to Snapchat Stories, a sort of expansive, broadcast-like version of the Snapchat snap. It doesn’t open a sliding drawer with a soothing hierarchical options menu. In Snapchat, navigation is done directly, via left/right/up/down thumb slides, supplemented by a handful of redundant touchable icons. People who are used to tapping well-labeled menu options are often baffled by Snapchat; but conversely, it will feel natural to someone whose first software experiences were on a mobile device, rather than a desktop.
Snapchat uses icons that change shape and color to signal different things. For example, a solid arrow is a sent snap (image or video); red if without audio, purple if with audio, and blue if a text chat only. The arrow becomes hollow once a friend has opened it. A solid square is a received snap or chat, with the same variations of color and hollowness. There are other icons that alert you when a friend has replayed or taken a screenshot of your snap. It’s not a complicated system, but it is esoteric and native to Snapchat; nothing about it is self-evident to new users.
Snapchat doesn’t pester you to keep connecting to more people.Adding friends in Snapchat is bizarrely cumbersome. If you’re used to traditional social apps, your first move will be tap on “Add Friends” (if you can find it), import your phone’s contacts database, and then squint through the entire list, name by name, to see which ones are on Snapchat and manually add them. It’s a huge pain if you have a lot of contacts. But Snapchat conversely makes it super-easy to add a friend when you are physically together by giving you a personally-encoded, QR-like Ghostface Chillah icon that can be snapped by a friend to add you. Notably, when you first set up Snapchat, you find that you can’t import your social graph from Facebook, Twitter, Google, etc. Snapchat draws solely on your phone’s contacts database. Though to some measure driven by necessity (at some point between the introduction of Pinterest’s “Add All My Facebook Friends” feature and the launch of Snapchat, Facebook started blocking new social services from using its social graph to kickstart theirs) Snapchat’s use of the phone’s contacts database reflects its emphasis on intimate, private, person-to-person communications with people you already know (or just met). It also shows Snapchat’s determination not to be dependent on other companies for core elements of its offerings.
So Snapchat’s user interface really is different, and different in ways that turn off a lot of people habituated to the dominant mobile design vocabulary, descended from desktop applications. And yet, Snapchat’s been getting hugely popular, with somebody.
Like any social or communications application, Snapchat has grown through real-world social pathways: its users tell their friends to get on it. If your friends or colleagues don’t use it, you won’t find much value in it. As a result, social and communications services like Snapchat, WhatsApp, WeChat, KakaoTalk, Viber, Line, Kik, etc., can saturate some discrete user clusters (e.g., U.S. Hispanic teens living in Southern California, Brooklyn-based social media junkies, female Korean professionals, etc.) but be almost unknown in others.
In the U.S., for example, Snapchat’s user cohort is overwhelming young — younger than any scaled social app we’ve seen before.
But the fact that Snapchat has become hugely popular with a wide swath of 12-to-24 year-old Americans doesn’t answer Will Oremus’s basic question. At the risk of stretching my metaphor past the breaking point, it doesn’t tell you whether Snapchat is a platypus (an isolated and precarious evolutionary adaptation well-suited to a specific subcontinental ecology), a fake mermaid (an apparent evolutionary advance that falls apart upon close inspection), or something more like a killer whale (a seemingly unlikely but wildly successful branch of the mammalian tree that has become an apex predator prowling every ocean and climate).
A few weeks ago, my betaworks partners and I found ourselves arguing about Snapchat, the merits of its app interface, and the trajectory of its future path. To get some practical data, and to understand Snapchat more thoroughly, we decided to commit to it, hard, for a week. And then to do the same for other fast-rising communications apps.
To reach meaningful scale, we enforced a herd migration among betaworkers. Starting two weeks ago, we announced that all intra-betaworks communications had to happen via Snapchat. If you wanted to reach us, you had to use Snapchat.
The result has been a scissor-test of Snapchat. We still ended up with conflicting opinions about whether Snapchat is poorly or brilliantly designed (or both). But we all agreed that the experience is more intimate, more private, and more creativity-sparking than we had previously understood. (And I learned the hard way how Snapchat punishes procrastination: one morning, my partner Sam sent me a couple of questions about a pending deal; I quickly scanned them while out on the sidewalk across town; when I returned to the office and opened the app to compose a response, Sam’s chats had disappeared and I couldn’t remember what the questions were.)
There’s one part of Snapchat, though, that really does seem to be grafted on like a fake duck-bill. Snapchat Discover is a new section of the app where big media companies like CNN, ESPN, People, Cosmopolitan, and the Daily Mail post slickly-produced packages that have as much in common with the casual, rough-hewn, intimate, person-to-person snap as Air Force One has with a homemade kite. Snapchat Discover is broadcast, not interpersonal; professional, not amateur; branded, not hacked. Snapchat’s ability to drive attention may ultimately make its Discover platform a viable (native, mobile, short-form) alternative to TV. But for now, it feels like an amphibian limb sutured onto a mammalian torso.
A entidade quer que permaneça no ensino o princípio da laicidade e liberdade de crença garantidos pela Constituição federal
A Sociedade Brasileira para o Progresso da Ciência (SBPC) enviou aos deputados federais uma carta solicitando que o Projeto de Lei 8099/2014, de deputado Marco Feliciano (PSC/SP), que propõe a inserção de conteúdos sobre criacionismo na grade curricular das Redes Pública e Privada de Ensino, e seu apensado ao PL 309/2011, de autoria do mesmo deputado, que “altera o Art. 33 da Lei nº 9.394, de 20 de dezembro de 1996, para dispor sobre a obrigatoriedade do ensino religioso nas redes públicas de ensino do país”, sejam rejeitados e arquivados. Segundo a SBPC, isso é necessário para se manter o princípio da laicidade e liberdade de crença garantidos pela Constituição federal, bem como o não comprometimento do ensino das Ciências aos alunos.
O leitor Clécio Fernando Klitzke. envia carta à SBPC onde comenta as ameaças e os retrocessos sobre o que é a Ciência, e o que são dogmas como o criacionismo e o “design inteligente”
Li a matéria no sítio de internet da SBPC a respeito da posição da ABRAPEC e SBEnBIO sobre o projeto de lei que tenta obrigar o ensino de criacionismo nas escolas brasileiras.
Não bastasse o desserviço de alguns políticos evangélicos a respeito do que é ciência e conhecimento científico, nos deparamos também com movimentos organizados no próprio meio acadêmico, visando a deturpação do que seja ciência e teoria científica.
Recentemente tivemos no país um evento neo criacionista onde foi fundada a sociedade brasileira do design inteligente. Mais triste é constatar que páginas que divulgam ciência também divulgam eventos criacionistas.
Esses profissionais esqueceram o que é ciência e objeto de pesquisa científica e se deixaram levar pela fé religiosa e seus dogmas. Agora apresentam o criacionismo travestido de teoria científica, com novo nome e roupagem, a tal da teoria do design inteligente, quem nem teoria é.
Não bastassem os políticos, temos professores e pesquisadores que também sonham com o ensino de criacionismo nas escolas e universidades.
Seria muito útil se a SBPC também divulgasse um manifesto em defesa da ciência e do conhecimento científico, se opondo a essas tentativas de incluir criacionismo como conhecimento científico.
Em 2012 a Sociedade Brasileira de Genética publicou um manifesto em seu sítio de internet.
Seria interessante reforçar para a sociedade que criacionismo é crença, não é ciência e que cientistas que se deixam levar por suas crenças prestam um desserviço ao conhecimento. O mais apavorante é que temos até mesmo membro da Academia Brasileira de Ciências defendendo o criacionismo como conhecimento científico e liderando esse movimento no Brasil.
Clécio Fernando Klitzke é Bacharel em Ciências Biológicas, Mestre em Ecologia, Doutor em Ciências (Química Orgânica).
There are books to read from cover to cover in a week or two, and then there are the ones you dip into over and over again, because they aren’t books so much as encyclopedias.
Russell H. Tuttle’s Apes and Human Evolution is one of these. Like the late Stephen Jay Gould’s magisterial Structure of Evolutionary Theory, Tuttle’s tome is a grand synthesis of all the latest research and data about apes and their relation to us.
Tuttle is Professor of Anthropology, Evolutionary Biology, History of Science and Medicine and the College at the University of Chicago.
Tuttle believes that bipedalism preceded the development of the brain in early humans –and was likely something inherited from smaller apes already used to using their feet to move laterally along branches in trees. Although chimpanzees and bonobos are our closest relatives on the evolutionary tree, they do not represent in their own locomotion good proto-models of what led to human upright posture and walking.
While the book does not need to be read in any particular order, the first two chapters set the stage and the terminology for the rest of Apes and Human Evolution, which consists of five parts, totaling 13 dense chapters. A glossary of terms would have helped, but it’s not too much of a distraction to look up the specialist terms Tuttle introduces in these opening sections.
But lest you think it is intended chiefly for colleagues in the fields of anthropology and evolutionary biology, Tuttle’s style throughout is crisp and often witty. (The chapter on the development of human bipedalism, for example, is called ‘How to Achieve an Erection’.)
Professor Russell H. Tuttle, University of Chicago. Image courtesy of Phys.org.
The opening chapter, ‘Mongrel Models and Seductive Scenarios of Human Evolution’ discusses several hypotheses of human origins, some of which Tuttle argues are biased and which in recent years more detailed study of apes has refuted.
He has a low opinion, for example, of the idea that humans are in essence a species of ‘killer apes’, a notion that gained popularity during the last century. “The views of Charles Darwin,” he writes, “are restrained in comparison with the speculations by the advocates of killer ape scenarios, which flourished for several decades after the horrors of World War I and World War II.”
Darwin portrayed early man (his term) as having “sprung from some comparatively weak creature,” who was not speedy and who lacked natural bodily defenses, namely, formidable canine teeth. Consequently, this bipedal creature was stimulated to use his intellectual powers to make weapons for defense and hunting and to cooperate with “his fellow-men”.
What distinguishes humans among the approximately 400 extant species of primates? In Tuttle’s view, a constellation of morphological and behavioral characteristics, some of which only can be traced precisely through the fossil and archeological records.
Obligate terrestrial bipedalism, precision-gripping hands, reduced teeth and jaws, and ballooned brains can be identified if fossils are complete enough in the skeletal regions under study. Archeological artifacts and features can indicate the presence of tool use and manufacture, control of fire, fabricated shelters, bodily ornamentation, mortuary practice, plastic and graphic arts, and other indications of cognitive skills and culture.
There are also the features that can’t be easily found in fossils or the archeological records, primarily social: cooperation, the ability to enlist new members from outside the immediate community of hominids.
Space does not allow a detailed review of each chapter, summaries of which you can find here. But in the final part, ‘What Makes Us Human?’, Tuttle reveals more of his own philosophical reflections on the matter.
One passage that struck me, for example, occurs in the sub-section, ‘What is More Real: God or Race?’
I believe that God is an ever-increasing collective emergent of the love of all beings past, present and future, but this cannot be proven by available scientific methods of experimentation or controlled comparison. In contrast, the belief in race, in the sense of biological subspecies of Homo Sapiens, lacks a tangible basis; indeed, it has been proven unsupportable genomically, behaviorally, and phenotypically.
Individuals and political groups have manipulated both God and race for nefarious purposes, but actions rooted in the human capacity to affiliate with non-kin, to cooperate, and especially to unite in love and respect for the agency of others has given rise to a variety of constructive social codes that facilitate intragroup and extensive intergroup harmony and mitigate disruptive personal and social behavior.
Whereas scientists possess the means to eliminate belief in human races, they lack the means to eradicate belief in God, and frankly they are probably wasting time and treasure on the exercise.
There’s an optimism here I found somewhat reminiscent of the Jesuit paleontologist Teilhard de Chardin, who had a very goal-oriented view of humanity and its role in cosmic evolution.
I could’t resist asking Tuttle whether Teilhard’s writings had any influence on his own thought as he embarked on his career in the 1960s. This was around the time that Teilhard’s writings were becoming most influential.
“Quite the contrary,” Tuttle replied in an email. “I thought Phenomenon of Man was rubbish. Father Teilhard wanted to be an evolutionary biologist while not giving up God. He did a shoddy job of reconciling deep religious belief with evolutionary biology…for one, he was an orthogenecist [i.e., he believed in progressive, directional evolution, toward a universal goal].”
“I cannot see a reconciliation of the two realms,” Tuttle added. “I believe in the power of love which some or many see as an aspect of God. But I do not think there is a celestial, etherial being that is interested in us or that makes good or bad things happen.”
Tuttle elaborated on this in a recent review he wrote for the American Journal of Psychology: “As a Christian participant observer into my late teens, followed by two decades attempting to be an atheist, and then participation in the music ministry at a wide variety of churches over the past 30 years, I aver that the bonding of congregations based on love of God and one another are substantive enough to withstand the sarcastic remarks and mockery of professed atheists who command notable space in print media and on the airways.”
Apes and Human Evolution is also available in Kindle Edition. But given the slight difference in price, I recommend getting the print edition.
Source: National Evolutionary Synthesis Center (NESCent)
Summary: New research finds that cultures living in harsher ecosystems with limited resources are more prone to a belief in moralizing, high gods. The results indicate that other cross-disciplinary factors, including as political complexity, also influence this belief.
Just as physical adaptations help populations prosper in inhospitable habitats, belief in moralizing, high gods might be similarly advantageous for human cultures in poorer environments. A new study from the National Evolutionary Synthesis Center (NESCent) suggests that societies with less access to food and water are more likely to believe in these types of deities.
“When life is tough or when it’s uncertain, people believe in big gods,” says Russell Gray, a professor at the University of Auckland and a founding director of the Max Planck Institute for History and the Sciences in Jena, Germany. “Prosocial behavior maybe helps people do well in harsh or unpredictable environments.”
Gray and his coauthors found a strong correlation between belief in high gods who enforce a moral code and other societal characteristics. Political complexity–namely a social hierarchy beyond the local community– and the practice of animal husbandry were both strongly associated with a belief in moralizing gods.
The emergence of religion has long been explained as a result of either culture or environmental factors but not both. The new findings imply that complex practices and characteristics thought to be exclusive to humans arise from a medley of ecological, historical, and cultural variables.
“When researchers discuss the forces that shaped human history, there is considerable disagreement as to whether our behavior is primarily determined by culture or by the environment,” says primary author Carlos Botero, a researcher at the Initiative for Biological Complexity at North Carolina State University. “We wanted to throw away all preconceived notions regarding these processes and look at all the potential drivers together to see how different aspects of the human experience may have contributed to the behavioral patterns we see today.”
The paper, which is now available online, will be published in an upcoming issue of the Proceedings of the National Academies of Science. To study variables associated with the environment, history, and culture, the research team included experts in biology, ecology, linguistics, anthropology, and even religious studies. The senior author, Gray, studies the intersection of psychology and linguistics, while Botero, an evolutionary ecologist, has examined coordinated behaviors in birds.
This study began with a NESCent working group that explored the evolution of human cultures. On a whim, Botero plotted ethnographic data of societies that believe in moralizing, high gods and found that their global distribution is quite similar to a map of cooperative breeding in birds. The parallels between the two suggested that ecological factors must play a part. Furthermore, recent research has supported a connection between a belief in moralizing gods and group cooperation. However, prior to this study, evidence supporting a relationship between such beliefs and the environment was elusive.
“A lot of evolutionists have been busy trying to bang religion on the head. I think the challenge is to explain it,” Gray says.
“Although some aspects of religion appear maladaptive, the near universal prevalence of religion suggests that there’s got to be some adaptive value and by looking at how these things vary ecologically, we get some insight.”
Botero, Gray, and their coauthors used historical, social, and ecological data for 583 societies to illustrate the multifaceted relationship between belief in moralizing, high gods and external variables. Whereas previous research relied on rough estimates of ecological conditions, this study used high-resolution global datasets for variables like plant growth, precipitation, and temperature. The team also mined the Ethnographic Atlas– an electronic database of more than a thousand societies from the 20th century– for geographic coordinates and sociological data including the presence of religious beliefs, agriculture, and animal husbandry.
“The goal became not just to look at the ecological variables, but to look at the whole thing. Once we accounted for as many other factors as we could, we wanted to see if we could still detect an environmental effect,” Botero says. “The overall picture is that these beliefs are ultimately shaped by a combination of historical, ecological, and social factors.”
Botero believes that this study is just the tip of the iceberg in examining human behavior from a cross-disciplinary standpoint. The team plans to further this study by exploring the processes that have influenced the evolution of other human behaviors including taboos, circumcision, and the modification of natural habitats.
“We are at an unprecedented time in history,” Botero says. “Now we’re able to harness both data and a combination of multidisciplinary expertise to explore these kinds of questions in an empirical way.”
C. A. Botero, B. Gardner, K. R. Kirby, J. Bulbulia, M. C. Gavin, R. D. Gray. The ecology of religious beliefs. Proceedings of the National Academy of Sciences, 2014; DOI: 10.1073/pnas.1408701111
A característica estava presente em 10% dos 900 criminosos finlandeses analisados em estudo de instituto sueco
Mais um estudo científico conclui que a genética pode estar relacionada a crimes violentos. Desta vez, a partir da análise de quase 900 criminosos na Finlândia, pesquisadores descobriram dois genes que ampliaram em 13 vezes as chances de a pessoa ter comportamento violento repetidamente.
SALT LAKE CITY, Oct. 27, 2014 – When Yanomamö men in the Amazon raided villages and killed decades ago, they formed alliances with men in other villages rather than just with close kin like chimpanzees do. And the spoils of war came from marrying their allies’ sisters and daughters, rather than taking their victims’ land and women.
Those findings – which suggest how violence and cooperation can go hand-in-hand and how culture may modify any innate tendencies toward violence – come from a new study of the so-called “fierce people” led by provocative anthropologist Napoleon Chagnon and written by his protégé, University of Utah anthropologist Shane Macfarlan.
Macfarlan says the researchers had expected to find the Yanomamö fought like “bands of brothers” and other close male kin like fathers, sons and cousins who live in the same community and fight nearby communities. That is how fights are conducted by chimpanzees – the only other apes besides humans that form coalitions to fight and kill.
Instead, “a more apt description might be a ‘band of brothers-in-law,'” in which Yanomamö men ally with similar-age men from nearby villages to attack another village, then marry their allies’ female kin, Macfarlan, Chagnon and colleagues write in the study, published this week in the journal Proceedings of the National Academy of Sciences.
The study provides a mechanism to explain why Yanomamö warriors in a 1988 Chagnon study had more wives and children than those who did not kill.
“We are showing these guys individually get benefits from engaging in killing,” Macfarlan says. “They’re getting long-term alliance partners – other guys they can trust to get things done. And they are getting marriage opportunities.”
Since his 1968 book “Yanomamö: The Fierce People,” Chagnon has been harshly criticized by some cultural anthropologists who claim he places undue emphasis on genes and biology as underpinnings of human violence, based on his 1964-1993 visits to the Yanomamö. Defenders such as Macfarlan say Chagnon takes a much more balanced view, and that “it’s never a genes-versus-culture argument. They operate in tandem.”
Chagnon got what was seen as vindication in 2012 when he was elected to the prestigious National Academy of Sciences. The new study, with Macfarlan as first author and Chagnon as senior author – is Chagnon’s inaugural PNAS article as a member.
Macfarlan joined the University of Utah faculty this year an assistant professor of anthropology. He worked as Chagnon’s postdoctoral fellow at the University of Missouri from January 2013 to June 2014. Chagnon and Macfarlan conducted the study with two Missouri colleagues: anthropologists Robert S. Walker and Mark V. Flinn.
Models of Warfare
The Yanomamö – hunters and farmers who live in southern Venezuela and northern Brazil – once gained social status as “unokai” for killing.
Up to 20 Yanomamö (pronounced yah-NO-mama, but also spelled Yanomami or Yanomama) would sneak up on another village at dawn, “shoot the first person they saw and then hightail back home,” Macfarlan says. Some Yanomamö men did this once, some up to 11 times and some never killed. (Data for the study, collected in the 1980s, covered somewhat earlier times when spears, bows and arrows were the primary weapons.)
IMAGE:University of Utah anthropologist Shane Macfarlan, shown here, is first author of a new study with provocative anthropologist Napoleon Chagnon about the Yanomamo, or so called ‘fierce people’ of…
Macfarlan says the classic debate has been, “does warfare in small-scale societies like the Yanomamö resemble chimpanzee warfare?” – a theory known as the “fraternal interest group” model, in which bands of brothers, fathers, sons and paternal uncles all living in the same community fight other similar communities.
The new study asked whether Yanomamö killing follows that model or the “strategic alliance model,” which the researchers dub the “band of brothers-in-law” model. This model – supported by the study’s findings – indicates that Yanomamö men form alliances not with close kin from the same community, but with men from other communities. After killing together, a bond is formed and they often marry each other’s daughters or sisters and move into one or the other’s village or form a new village.
“When we started off this project, we all assumed it would be the chimpanzee-like model. But in human groups we have cultural rules that allow us to communicate with other communities. You certainly don’t see chimpanzees doing this.”
Is the study a retreat from what Chagnon’s critics see as too much focus on genetic and biological underpinnings of violence? Macfarlan says no, that Chagnon “has never been as all-biology as people have painted him. Most of his published research shows how unique cultural rules make the Yanomamö an interesting group of people.”
Earlier research suggested that for chimps, warfare is adaptive in an evolutionary sense, and that it also benefits small-scale human societies. The new study asked, “If warfare is adaptive, in what way do the adaptive benefits flow?” Macfarlan says.
“Some people, myself included, said, to the victor goes the spoils, because if you conquer another territory, you might take their land, food or potentially their females.”
But the new study indicates “the adaptive benefits are the alliances you build by perpetrating acts of warfare,” he adds. “It’s not that you are taking land or females from the vanquished group, but for the Yanomamö, what you acquire is that you can exchange resources with allies, such as labor and, most importantly, female marriage partners.”
The study’s findings that the Yanomamö form strategic alliances to kill suggest that “our ultracoooperative tendencies tend to go hand-in-hand with our ultralethal tendencies,” Macfarlan says. “We show a relationship between cooperation and violence at a level unseen in other organisms.” That may seem obvious for allied nations in modern wars, but “we’re saying that even in small-scale societies this is the case.”
IMAGE:Men from one Yanomamo village in the Amazon ‘dance’ in a neighboring village to show off their military prowess, weaponry and group cohesion after they were invited to a…
The new study analyzed data collected by Chagnon in the 1980s, when about 25,000 Yanomamö lived in about 250 villages ranging from 25 to 400 people.
The study examined 118 Yanomamö warriors or unokai who had killed a total of 47 people by forming raiding parties of two to 15 men. The researchers analyzed the relationships between every possible pair of men in those raiding parties. Among the 118 unokai men, there were 509 possible pairs. Macfarlan says the findings revealed surprises about the relationship between co-unokai – pairs of men who kill together:
Only 22 percent of men who kill together were from the same lineage.
Only 34 percent of co-unokai pairs were from the same place of birth. “Guys who come from different places of birth are more likely to kill together.”
Among co-killers known to be related, a majority were related on their mother’s side rather than their father’s side – more evidence of forming alliances beyond the immediate paternal kinship group. In Yanomamö culture, true kin are viewed as being on the paternal side, while maternal relatives are seen as belonging to another social group.
The Yanomamö preferred forming coalitions with men within a median of age difference of 8 years. “The more similar in age, the more likely they will kill multiple times,” Macfarlan says.
Of the 118 unokai, 102 got married in a total of 223 marriages to 206 women. Of married killers, 70 percent married at least one woman from the same paternal line as an ally in killing. And “the more times they kill together, the more likely they are going to get marriage partners from each other’s family line,” Macfarlan says.
As a result, “The more times the guys kill together, the more likely they are to move into the same village later in life, despite having come from different village.”
The study found allies-in-killing often are somewhere between maternal first and second cousins, Macfarlan says. Under Yanomamö rules, a man’s ideal marriage partner is a maternal first cousin, who would be the offspring of your mother’s brother. He says Yanomamö rules allow marriage to a maternal first cousin, but not a paternal first cousin.
Despite debate over the biological roots of deadly coalitions in chimps and humans, the new study shows how culture can make it “uniquely human” because if Yanomamö men “kill together, they are plugged into this social scene, this marriage market,” Macfarlan says. “They are playing the game of their culture.”
SALT LAKE CITY, Sept. 22, 2014 – After human ancestors controlled fire 400,000 to 1 million years ago, flames not only let them cook food and fend off predators, but also extended their day.
A University of Utah study of Africa’s Kalahari Bushmen suggests that stories told over firelight helped human culture and thought evolve by reinforcing social traditions, promoting harmony and equality, and sparking the imagination to envision a broad sense of community, both with distant people and the spirit world.
Researchers previously studied how cooking affected diets and anatomy, but “little is known about how important the extended day was for igniting the embers of culture and society,” anthropology professor Polly Wiessner writes in a study published online today in the journal Proceedings of the National Academy of Sciences.
“There is something about fire in the middle of the darkness that bonds, mellows and also excites people. It’s intimate,” says Wiessner, who has studied the Bushmen for 40 years. “Nighttime around a fire is universally time for bonding, for telling social information, for entertaining, for a lot of shared emotions.”
Wiessner’s study, which she calls “exploratory,” analyzed scores of daytime and firelight conversations among !Kung Bushmen – also known as Ju/’hoansi Bushmen – some 4,000 of which now live in the Kalahari Desert of northeast Namibia and northwest Botswana. (The exclamation, slash and apostrophe symbols represent click sounds in their language.) They are among several groups of Kalahari Bushmen.
Why study the campfire tales of Bushmen?
“We can’t tell about the past from the Bushmen,” Wiessner says. “But these people live from hunting and gathering. For 99 percent of our evolution, this is how our ancestors lived. What transpires during the firelit night hours by hunter-gatherers? It helps answer the question of what firelit space contributes to human life.”
She writes: “Stories are told in virtually all hunter-gatherer societies; together with gifts, they were the original social media.”
IMAGE:!Kung Kalahari Bushmen in Africa sit in camp. A University of Utah study of nighttime gatherings around fires by these hunter-gatherers suggests that human cultural development was advanced when human…
From the Workaday World to Nights of Bonding and Wonder
In her study, “Embers of Society: Firelight Talk among the Ju/’hoansi Bushmen,” Wiessner says archaeological evidence indicates human ancestors had sporadic control of fire 1 million or more years ago, and regularly used it after 400,000 years ago.
“Fire altered our circadian rhythms, the light allowed us to stay awake, and the question is what happened in the fire-lit space? What did it do for human development?” asks Wiessner, who earlier this year was among three University of Utah researchers elected to the National Academy of Sciences.
Wiessner says !Kung Bushmen hold firelight gatherings most nights in groups of up to 15 people. A camp has hearths for each family, but at night people often converge at a single hearth. She analyzed only conversations involving five or more people.
Firelight stories deal with topics such as past hunts, fights over meat, marriage, premarital customs, murder, bush fires, birth, getting lost, interactions with other groups, truck breakdowns, being chased by animals, disputes and extramarital affairs. And there also are traditional myths.
For her study, Wiessner analyzed two sets of data:
Notes she took in 1974 (initially for another purpose) of 174 daytime and nighttime conversations at two !Kung camps in northwest Botswana. Each conversation lasted more than 20 to 30 minutes and involved five to 15 people.
Digital recordings, transcribed by educated Bushmen, of 68 firelight stories Wiessner originally heard in the 1970s but came back to have retold and recorded during three visits in 2011-2013 to !Kung villages in Botswana and Namibia.
Wiessner found daytime conversations differed much from firelight discussions. Of daytime conversations, 34 percent were complaints, criticism and gossip to regulate social relationships; 31 percent were economic matters, such as hunting for dinner; 16 percent were jokes; only 6 percent were stories and the rest were other topics
But at night, 81 percent of the conversations involved stories, and only 7 percent were complaints, criticism and gossip and 4 percent were economic.
IMAGE:A group of !Kung Bushmen in Africa’s Kalahari Desert work together to transcribe and translate a recorded firelight conversation into a written text. Such translations were used by University of…
Bonding with People Near and Far – and with the Supernatural
Wiessner found how conversations reinforced major !Kung social institutions and values: arranged marriages, the kinship system, a social structure based on equality, the sharing of food during times of hardship, land rights, trance healing and xaro, a system of exchange that involved pledges of mutual assistance, including housing and food, in troubled times.
“What I found was a big difference between day and night conversation, the kinds of information transmitted and the use of imaginary thought,” Wiessner says.
“Day conversation has a lot to do with economic activities – working, getting food, what resources are where,” she says. “It has a lot to do with social issues and controls: criticism, complaints and gripes.”
“At night, people really let go, mellow out and seek entertainment. If there have been conflicts in the day, they overcome those and bond. Night conversation has more to do with stories, talking about the characteristics of people who are not present and who are in your broader networks, and thoughts about the spirit world and how it influences the human world. You have singing and dancing, too, which bonds groups.”
Healers dance and go into trances, “travel to god’s village and communicate with the spirits of deceased loved ones who are trying to take sick people away,” Wiessner says.
She says nonhuman primates don’t maintain mutually supportive ties outside their group: “We are really unique. We create far-flung ties outside our groups.”
Such extended communities allowed humans “to colonize our planet because they had networks of mutual support, which you see expressed today in our capacity for social networking” she adds. “Humans form communities that are not together in space, but are in our heads – virtual communities. They are communities in our heads. For the Bushmen, they may be up to 120 miles away.”
Wiessner suggests that firelight stories, conversations, ceremonies and celebrations sparked human imagination and “cognitive capacities to form these imagined communities, whether it’s our social networks, all of our relatives on Earth or communities that link us to the spirit world.” She says they also bolstered the human ability to “read” what others are thinking – not just their thoughts or intentions, but their views toward other people.
What Has Electricity Done to Us?
Examining how firelight extended the day prompted Wiessner to wonder about modern society, asking, “What happens when economically unproductive firelit time is turned to productive time by artificial lighting?”
Parents read stories or show videos to their children, but now, “work spills into the night. We now sit on laptops in our homes. When you are able to work at night, you suddenly have a conflict: ‘I have only 15 minutes to tell my kids a bedtime story. I don’t have time to sit around and talk.’ Artificial light turned potential social time into potential work time. What happens to social relations?”
Her research raises that question, but doesn’t answer it.
A queen ant of the host species Mycocepurus goeldii.
A newly-discovered species of ant supports a controversial theory of species formation. The ant, only found in a single patch of eucalyptus trees on the São Paulo State University campus in Brazil, branched off from its original species while living in the same colony, something thought rare in current models of evolutionary development.
“Most new species come about in geographic isolation,” said Christian Rabeling, assistant professor of biology at the University of Rochester. “We now have evidence that speciation can take place within a single colony.”
The findings by Rabeling and the research team were published today in the journal Current Biology.
In discovering the parasitic Mycocepurus castrator, Rabeling and his colleagues uncovered an example of a still-controversial theory known as sympatric speciation, which occurs when a new species develops while sharing the same geographic area with its parent species, yet reproducing on its own.“While sympatric speciation is more difficult to prove,” said Rabeling, “we believe we are in the process of actually documenting a particular kind of evolution-in-progress.”
New species are formed when its members are no longer able to reproduce with members of the parent species. The commonly-accepted mechanism is called allopatric speciation, in which geographic barriers—such as mountains—separate members of a group, causing them to evolve independently.
“Since Darwin’s Origin of Species, evolutionary biologists have long debated whether two species can evolve from a common ancestor without being geographically isolated from each other,” said Ted Schultz, curator of ants at the Smithsonian’s National Museum of Natural History and co-author of the study. “With this study, we offer a compelling case for sympatric evolution that will open new conversations in the debate about speciation in these ants, social insects and evolutionary biology more generally.”
A queen ant of the parasitic species Mycocepurus castrator.
M. castrator is not simply another ant in the colony; it’s a parasite that lives with—and off of—its host, Mycocepurus goeldii. The host is a fungus-growing ant that cultivates fungus for its nutritional value, both for itself and, indirectly, for its parasite, which does not participate in the work of growing the fungus garden. That led the researchers to study the genetic relationships of all fungus-growing ants in South America, including all five known and six newly discovered species of the genus Mycocepurus, to determine whether the parasite did evolve from its presumed host. They found that the parasitic ants were, indeed, genetically very close to M. goeldii, but not to the other ant species.
They also determined that the parasitic ants were no longer reproductively compatible with the host ants—making them a unique species—and had stopped reproducing with their host a mere 37,000 years ago—a very short period on the evolutionary scale.
A big clue for the research team was found by comparing the ants’ genes, both in the cell’s nucleus as well as in the mitochondria—the energy-producing structures in the cells. Genes are made of units called nucleotides, and Rabeling found that the sequencing of those nucleotides in the mitochondria is beginning to look different from what is found in the host ants, but that the genes in the nucleus still have traces of the relationship between host and parasite, leading him to conclude that M. castrator has begun to evolve away from its host.
Rabeling explained that just comparing some nuclear and mitochondrial genes may not be enough to demonstrate that the parasitic ants are a completely new species. “We are now sequencing the entire mitochondrial and nuclear genomes of these parasitic ants and their host in an effort to confirm speciation and the underlying genetic mechanism.”
The parasitic ants need to exercise discretion because taking advantage of the host species is considered taboo in ant society. Offending ants have been known to be killed by worker mobs. As a result, the parasitic queen of the new species has evolved into a smaller size, making them difficult to distinguish from a host worker.
Host queens and males reproduce in an aerial ceremony, in the wet tropics only during a particular season when it begins to rain. Rabeling found that the parasitic queens and males, needing to be more discreet about their reproductive activities, diverge from the host’s mating pattern. By needing to hide their parasitic identity, M. castrator males and females lost their special adaptations that allowed them to reproduce in flight, and mate inside the host nest, making it impossible for them to sexually interact with their host species.
The research team included Ted Schultz of the Smithsonian Institution’s National Museum of Natural History, Naomi Pierce of Harvard University, and Maurício Bacci, Jr of the Center for the Study of Social Insects (São State University, Rio Claro, Brazil).
A highly magnified view of Enterococcus faecalis, a bacterium that lives in the human gut. Microbes may affect our cravings, new research suggests.CreditCenters for Disease Control and Prevention
Your body is home to about 100 trillion bacteria and other microbes, collectively known as your microbiome. Naturalists first became aware of our invisible lodgers in the 1600s, but it wasn’t until the past few years that we’ve become really familiar with them.
This recent research has given the microbiome a cuddly kind of fame. We’ve come to appreciate how beneficial our microbes are — breaking down our food, fighting off infections and nurturing our immune system. It’s a lovely, invisible garden we should be tending for our own well-being.
“One of the ways we started thinking about this was in a crime-novel perspective,” said Carlo C. Maley, an evolutionary biologist at the University of California, San Francisco, and a co-author of the new paper. “What are the means, motives and opportunity for the microbes to manipulate us? They have all three.”
The idea that a simple organism could control a complex animal may sound like science fiction. In fact, there are many well-documented examples of parasites controlling their hosts.
How parasites control their hosts remains mysterious. But it looks as if they release molecules that directly or indirectly can influence their brains.
Our microbiome has the biochemical potential to do the same thing. In our guts, bacteria make some of the same chemicals that our neurons use to communicate with one another, such as dopamine and serotonin. And the microbes can deliver these neurological molecules to the dense web of nerve endings that line the gastrointestinal tract.
Adding certain species of bacteria to a normal mouse’s microbiome can reveal other ways in which they can influence behavior. Some bacteria lower stress levels in the mouse. When scientists sever the nerve relaying signals from the gut to the brain, this stress-reducing effect disappears.
Some experiments suggest that bacteria also can influence the way their hosts eat. Germ-free mice develop more receptors for sweet flavors in their intestines, for example. They also prefer to drink sweeter drinks than normal mice do.
Scientists have also found that bacteria can alter levels of hormones that govern appetite in mice.
Dr. Maley and his colleagues argue that our eating habits create a strong motive for microbes to manipulate us. “From the microbe’s perspective, what we eat is a matter of life and death,” Dr. Maley said.
Different species of microbes thrive on different kinds of food. If they can prompt us to eat more of the food they depend on, they can multiply.
Microbial manipulations might fill in some of the puzzling holes in our understandings about food cravings, Dr. Maley said. Scientists have tried to explain food cravings as the body’s way to build up a supply of nutrients after deprivation, or as addictions, much like those for drugs like tobacco and cocaine.
But both explanations fall short. Take chocolate: Many people crave it fiercely, but it isn’t an essential nutrient. And chocolate doesn’t drive people to increase their dose to get the same high. “You don’t need more chocolate at every sitting to enjoy it,” Dr. Maley said.
John F. Cryan, a neuroscientist at University College Cork in Ireland who was not involved in the new study, suggested that microbes might also manipulate us in ways that benefited both them and us. “It’s probably not a simple parasitic scenario,” he said.
Research by Dr. Cryan and others suggests that a healthy microbiome helps mammals develop socially. Germ-free mice, for example, tend to avoid contact with other mice.
That social bonding is good for the mammals. But it may also be good for the bacteria.
“When mammals are in social groups, they’re more likely to pass on microbes from one to the other,” Dr. Cryan said.
“I think it’s a very interesting and compelling idea,” said Rob Knight, a microbiologist at the University of Colorado, who was also not involved in the new study.
If microbes do in fact manipulate us, Dr. Knight said, we might be able to manipulate them for our own benefit — for example, by eating yogurt laced with bacteria that would make us crave healthy foods.
“It would obviously be of tremendous practical importance,” Dr. Knight said. But he warned that research on the microbiome’s effects on behavior was “still in its early stages.”
The most important thing to do now, Dr. Knight and other scientists said, was to run experiments to see if microbes really are manipulating us.
Mark Lyte, a microbiologist at the Texas Tech University Health Sciences Center who pioneered this line of research in the 1990s, is now conducting some of those experiments. He’s investigating whether particular species of bacteria can change the preferences mice have for certain foods.
“This is not a for-sure thing,” Dr. Lyte said. “It needs scientific, hard-core demonstration.”
Summary: In the first evidence that natural selection favors an individual’s infection tolerance, researchers have found that an animal’s ability to endure an internal parasite strongly influences its reproductive success. The finding could provide the groundwork for boosting the resilience of humans and livestock to infection.
The researchers examined the relationship between each sheep’s body weight and its level of infection by nematodes, tiny parasitic worms that thrive in the gastrointestinal tract of sheep. This scanning electron micrograph shows nematodes on the surface of a sheep’s gut with a field of view of approximately one centimeter. An economic detriment to sheep farmers, nematodes infect both wild and domesticated sheep, resulting in weight loss, reduced wool growth and death. Credit: Photo by David Smith/Moredun Research Institute
In the first evidence that natural selection favors an individual’s infection tolerance, researchers from Princeton University and the University of Edinburgh have found that an animal’s ability to endure an internal parasite strongly influences its reproductive success. Reported in the journalPLoS Biology, the finding could provide the groundwork for boosting the resilience of humans and livestock to infection.
The researchers used 25 years of data on a population of wild sheep living on an island in northwest Scotland to assess the evolutionary importance of infection tolerance. They first examined the relationship between each sheep’s body weight and its level of infection with nematodes, tiny parasitic worms that thrive in the gastrointestinal tract of sheep. The level of infection was determined by the number of nematode eggs per gram of the animal’s feces.
While all of the animals lost weight as a result of nematode infection, the degree of weight loss varied widely: an adult female sheep with the maximum egg count of 2,000 eggs per gram of feces might lose as little as 2 percent or as much as 20 percent of her body weight. The researchers then tracked the number of offspring produced by each of nearly 2,500 sheep and found that sheep with the highest tolerance to nematode infection produced the most offspring, while sheep with lower parasite tolerance left fewer descendants.
To measure individual differences in parasite tolerance, the researchers used statistical methods that could be extended to studies of disease epidemiology in humans, said senior author Andrea Graham, an assistant professor of ecology and evolutionary biology at Princeton. Medical researchers have long understood that people with similar levels of parasite infection can experience very different symptoms. But biologists are just beginning to appreciate the evolutionary importance of this individual variation.
“For a long time, people assumed that if you knew an individual’s parasite burden, you could perfectly predict its health and survival prospects,” Graham said. “More recently, evolutionary biologists have come to realize that’s not the case, and so have developed statistical tools to measure variation among hosts in the fitness consequences of infection.”
Graham and her colleagues used the wealth of information collected over many years on the Soay sheep living on the island of Hirta, about 100 miles west of the Scottish mainland. These sheep provide a unique opportunity to study the effects of parasites, weather, vegetation changes and other factors on a population of wild animals. Brought to the island by people about 4,000 years ago, the sheep have run wild since the last permanent human inhabitants left Hirta in 1930. By keeping a detailed pedigree, the researchers of the St Kilda Soay Sheep Project can trace any individual’s ancestry back to the beginning of the project in 1985, and, conversely, can count the number of descendants left by each individual.
Expending energy to fight infection
Nematodes puncture an animal’s gut and can impede the absorption of nutrients. Therefore, tolerance to nematode infection could result from an ability to make up for the lost nutrition, or from the ability to repair damage the parasites cause to the gut, Graham said. “This island is way out in the North Atlantic, where the sun doesn’t shine much,” she said. “So tolerant individuals might be the ones who are better able to compete for food or better able to assimilate protein and other useful nutrients from the limited forage.”
Tolerant animals might invest energy in gut repair, but would then be expected to incur costs. Graham and her colleagues identified a similar evolutionary tradeoff in a 2010 study that compared immune-response levels and reproductive success in female Soay sheep. They found that animals with strong antibody responses produced fewer offspring each year, but also lived longer. The team has not yet been able to detect costs of parasite tolerance in the sheep, but such costs could help explain variation in tolerance if the most tolerant animals were at a disadvantage under particular conditions.
While the PLoS Biology findings provide strong evidence that natural selection favors infection tolerance, they do raise questions, such as how the tolerance is generated, and why variation might persist from one generation to the next despite the reproductive advantage of tolerance, Graham said. The data in this study did not permit the researchers to detect a genetic component to tolerance. If genetics do play a role, she suspects multiple genes may interact with environmental factors to determine tolerance; ongoing research will help to tease apart these possibilities.
Understanding the genetic underpinnings of nematode tolerance could someday guide efforts to boost tolerance in livestock by identifying and selectively breeding those animals that exhibit a heightened parasite tolerance, said David Schneider, an associate professor of microbiology and immunology at Stanford University.
“This study shows that parasite tolerance can have a profound effect on animal health and breeding success,” said Schneider, who is familiar with the work but was not involved in it. “In the long term, this suggests that it could be profitable to invest in breeding tolerant livestock.”
In humans and domesticated animals, intestinal parasites are becoming increasingly resistant to the drugs used to treat infections, Graham said. If the availability of nutrients, even just during the first few months of life, impacts lifelong parasite tolerance, simple nutritional supplements could be an effective way to promote tolerance in people. About 2 billion people are persistently infected with intestinal nematode parasites worldwide, mostly in developing nations. Children are especially vulnerable to the worms’ effects, which include anemia, stunted growth and cognitive difficulties.
“Ideally, we would clear the worms from the bellies of the kids who have those heavy burdens,” Graham said. “But if we could also understand how to ameliorate the health consequences and thus promote tolerance of nematodes, that could be a very powerful tool.”
Adam D. Hayward, Daniel H. Nussey, Alastair J. Wilson, Camillo Berenos, Jill G. Pilkington, Kathryn A. Watt, Josephine M. Pemberton, Andrea L. Graham. Natural Selection on Individual Variation in Tolerance of Gastrointestinal Nematode Infection. PLoS Biology, 2014; 12 (7): e1001917 DOI:10.1371/journal.pbio.1001917
Artigo de José Eli da Veiga publicado no Valor Econômico
Até o início dos anos 1980 o darwinismo foi amesquinhado pela concepção de que a sobrevivência dos mais aptos só decorreria da feroz competição que caracterizaria a “luta” pela existência. Por oitenta anos foi rejeitada a desviante interpretação das obras de Darwin proposta em “Ajuda Mútua: um Fator de Evolução”, livro com argutas observações sobre a extraordinária cooperação que caracteriza as vidas de abelhas, formigas e vários outros animais, publicado em 1902, no exílio londrino, pelo sessentão príncipe russo Piotr Kropotkin.
Mesmo que não tenha havido reconhecimento explícito, a perspicácia desse expoente do anarquismo começou a ser redimida quando um dos então mais promissores ramos da matemática – a Teoria dos Jogos – foi mobilizado para solucionar uma das questões que mais intrigava os pesquisadores, especialmente os das humanidades: num mundo de egoístas, desprovido de governo central, em que condições pode emergir a cooperação?
Resposta original e persuasiva foi dada em 1981 pelo cientista político da Universidade de Michigan, Robert Axelrod, que três anos depois lançou o hoje clássico “A Evolução da Cooperação” (Ed. Leopardo, 2010). Um livro que deveria tomar o lugar daquelas bíblias gratuitas achadas nos criados-mudos dos hotéis, diz Richard Dawkins, o célebre autor de “O Gene Egoísta” em prefácio à edição de 2006.
A proeza de Axelrod foi executar inéditas simulações computacionais que confirmaram hipóteses formuladas na década anterior por biólogos evolutivos: nepotismo e reciprocidade seriam os dois fatores determinantes da cooperação. Na ausência do primeiro, ela estaria na dependência de um padrão comportamental em que cada um dos atores repete o movimento do outro, reagindo positivamente a atitudes cooperativas e negativamente a gestos hostis.
Ainda em plena Guerra Fria, quando o risco de um “inverno nuclear” exigia a cooperação bipolar entre EUA e URSS, o que poderia fazer mais sucesso do que essa orientação apelidada de “tit-for-tat”, título de uma das populares comédias da dupla “O Gordo e o Magro”? Embora seja traduzida por “olho-por-olho, dente-por-dente”, essa expressão está mais próxima do “toma-lá-dá-cá”, pois é uma estratégia que exige prévio arranque cooperativo.
Como sempre ocorre na ciência, boa resposta a uma grande questão faz com que pipoquem novas dúvidas. Por exemplo: se por mera razão acidental um dos atores falhar em fazer o esperado movimento positivo, isso por si só inviabiliza a continuidade da cooperação? E o que ocorreria quando o esquema de cooperação envolvesse mais do que dois atores? Foram questões como essas que alavancaram o fulgurante avanço da biologia matemática nos últimos vinte anos. O padrão “toma-lá-dá-cá” hoje não passa de uma das três modalidades de uma das cinco dinâmicas de cooperação evidenciadas.
O “tit-for-tat” é manifestação rudimentar do que passou a ser chamado de “reciprocidade direta”. Novas simulações indicaram que eventual passo em falso pode engendrar uma segunda chance, em estratégia apelidada de “toma-lá-dá-cá generoso”, a origem evolutiva do perdão. E desdobramentos ainda mais sofisticados revelaram a existência de uma terceira forma de reciprocidade direta, na qual o agente inverte sua atitude anterior quando nota que as coisas vão mal, mas logo depois volta a cooperar. Algo que já era bem conhecido na etologia como comportamento “Win-Stay, Lose-Shift”, comum entre pombos, macacos, ratos e camundongos.
O segundo vetor da cooperação, chamado de “reciprocidade indireta”, foi crucial para a evolução da linguagem e para o próprio desenvolvimento do cérebro humano, pois se baseia no fenômeno da reputação. Neste caso, o que condiciona as atitudes dos atores são comportamentos anteriores em relações com terceiros. A cooperação avança quando a probabilidade de um agente se inteirar sobre a reputação do outro compensa o custo/benefício do ato altruísta.
Os demais determinantes da cooperação são as três formas em que ocorre a seleção natural, pois, além da já mencionada nepotista (de parentesco), ela não opera apenas entre indivíduos, mas também entre grupos (multinível) e nas redes (espacial).
Mesmo que as observações acima não sejam suficientes para que se possa ter uma boa ideia das descobertas da biologia matemática no âmbito da dinâmica evolutiva, elas certamente permitem notar que o darwinismo aponta tanto para “luta” quanto para “acomodação” pela existência. Exposição rigorosa e extremamente amigável desse darwinismo 2.0 está em “SuperCooperators – Altruism, Evolution, and Why We Need Each Other to Succeed” (Free Press, 2011), do austríaco Martin A. Nowak, biólogo matemático que está em Harvard depois de ter brilhado em Oxford e Princeton, e que contou com a inestimável ajuda do jornalista científico britânico Roger Highfield.
Esse sim é um livro que mereceria ser distribuído gratuitamente. Não para substituir bíblias cristãs, mas para promover o entendimento das origens naturais dos códigos de ética de todas as grandes religiões.
José Eli da Veiga é professor sênior do Instituto de Energia e Ambiente da USP e autor de “A desgovernança mundial da sustentabilidade” (Editora 34, 2013). Escreve mensalmente às terças-feiras. http://www.zeeli.pro.br
Did a focus on local life leave Neanderthals perilously isolated? (Image: Elisabeth Daynes/SPL)
The idea of human as networker is fast replacing the idea of human as toolmaker in the story of the human brain, claim two new books on our evolution
“HELL is other people,” goes Jean-Paul Sartre’s famous line. It is a hell that may have created us and our culture, judging by two new books. They show that the idea that we are defined by our struggles to deal with our fellow humans is shaking up archaeology and how we think about the key force driving human evolution.
The first book is Thinking Big by archaeologists Clive Gamble and John Gowlett and evolutionary psychologist Robin Dunbar. It is the story of a seven-year project – From Lucy to Language – that confronted archaeologists with the social brain hypothesis of human evolution.
The result is a dramatic demolition of the “stones and bones” approach to archaeology, which keeps researchers firmly fixed only on the physical evidence they dig up, and a move towards a grand look at the evolving human mind. There is “more to humanity than the bits of chipped bone”, write the authors as they seek a framework for all human psychological traits, from kinship and laughter to language and ceremony. Old dogma is derided as never moving beyond “WYSWTW” (What You See is What There Was).
The second book is a solo effort by Dunbar, the key thinker behind the social brain hypothesis. In Human Evolution, he lays out the big ideas that the archaeologists later took up. At its heart is the observation that as brains grew bigger, so did the groups we live in: bigger brains were built for and by social life. Modern humans have a cognitive limit of about 150 friends and family (the well-known “Dunbar’s number”). Within that circle are an average of five “intimates”, 15 best friends and 50 good friends. Chimps have an average community size of 55.
Studies of living, non-human primates show why you might need bigger brains to live in bigger groups. The more others are around, the more likely you are to be bullied out of a juicy food patch or a safe sleeping site. Such stress can be hell, especially for low-ranking females, who can be driven into infertility. To cope, primates create cliques of allies which they sustain through the pleasurable endorphin rush induced by regular mutual grooming. This solution fails if groups grow bigger, for there is not enough time for one-on-one attention. Bigger brains are key to developing smarter ways of dealing with others, the theory goes.
For Dunbar, these included laughter and singing, both great endorphin-releasers within groups. There was also fire, which gave light so evenings could be used for cooking and more “social grooming”. Then came language, together with a growing ability to read others’ intentions, which ultimately made it possible to tell stories, maintain far-flung relationships and usereligion to bind communities.
The Thinking Big archaeologists take from Dunbar the grand hypothesis that social life drives human change, switching from a view of “man the toolmaker” to “man the networker”. Alongside that, the proven relationship between brain size, group size and mental skills makes it possible to estimate the size of groups our ancestors lived in and their capacity to interact with others.
A fresh look at the Neanderthals is telling. They dominated Europe for 250,000 years, much longer than modern humans. They were skilled hunters, toolmakers and had mastered fire. Their brain size suggests they lived in groups of about 110 and had the cognitive skills to understand the feelings of others. That fits well with archaeological evidence that older and disabled Neanderthals were cared for: they perhaps knew compassion.
So why did they vanish so fast during a time of changing climate, when modern humans prospered? It may be that their mental skills were not quite adequate to maintain relationships beyond immediate group members, something we can do easily. That may have been crucial to our success: in hard times, bigger networks can mean gaining help from distant friends who are still doing well, and who you’ll help in turn. Without that “social storage” of resources, local extinction may loom. Archaeological evidence again tallies with the social brain theory: one study shows that 70 per cent of the raw materials of Neanderthal tools travelled less than 25 kilometres, while 60 per cent of those of contemporaneous humans had travelled more than 25 kilometres.
The two books fit well together but are very different. Thinking Big inspires, but much wonderful research is passed over too briefly amid general argument. An exception is a story from Beeches Pit, a 400,000-year-old site in the east of England. Archaeologists there painstakingly reassembled the flint flakes struck from a rock in the process of making a hand axe. Two flakes were found burnt bright red; they had fallen into a fire just in front of the axe-maker. We can almost see our ancestors working around what must have been a communal fire, for no one person could have gathered enough wood to keep it burning.
Dunbar’s solo work, Human Evolution, however, is a must-read. It has the great strength of showing you the inner workings of an imaginative mind, while allowing you the freedom to think, and even to disagree about whether that hellish social pressure really has given us our distinct cognitive design, along with science and the arts.
This article appeared in print under the headline “Beyond bones and stones”
Source: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
Summary: The simpler a marine organism is structured, the better it is suited for survival during climate change, researchers have discovered this in a new meta-study. For the first time biologists studied the relationship between the complexity of life forms and the ultimate limits of their adaptation to a warmer climate.
The temperature windows of some ocean dwellers as a comparison: the figures for green algae, seaweed and thermophilic bacteria were determined in the laboratory. The fish data stem from investigations in the ocean. Credit: Sina Löschke, Alfred Wegener Institute
The simpler a marine organism is structured, the better it is suited for survival during climate change. Scientists of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, discovered this in a new meta-study, which appears today in the research journal Global Change Biology. For the first time biologists studied the relationship between the complexity of life forms and the ultimate limits of their adaptation to a warmer climate. While unicellular bacteria and archaea are able to live even in hot, oxygen-deficient water, marine creatures with a more complex structure, such as animals and plants, reach their growth limits at a water temperature of 41 degrees Celsius. This temperature threshold seems to be insurmountable for their highly developed metabolic systems.
The current IPCC Assessment Report shows that marine life forms respond very differently to the increasing water temperature and the decreasing oxygen content of the ocean. “We now asked ourselves why this is so. Why do bacteria, for example, still grow at temperatures of up to 90 degrees Celsius, while animals and plants reach their limits at the latest at a temperature of 41 degrees Celsius,” says Dr. Daniela Storch, biologist in the Ecophysiology Department at the Alfred Wegener Institute (AWI) and first author of the current study.
Since years Storch and her colleagues have been investigating the processes that result in animals having a certain temperature threshold up to which they can develop and reproduce. The scientists found that the reason for this is their cardiovascular system. They were able to show in laboratory experiments that this transport system is the first to fail in warmer water. Blood circulation supplies all cells and organs of a living organism with oxygen, but can only do so up to a certain maximum temperature. Beyond this threshold, the transport capacity of this system is no longer sufficient; the animal can then only sustain performance for a short time. Based on this, the biologists had suspected at an early date that there is a relationship between the complex structure of an organism and its limited ability to continue to function in increasingly warm water.
“In our study, therefore, we examined the hypothesis that the complexity could be the key that determines the ultimate adaptability of diverse life forms, from marine archaea to animals, to different living conditions in the course of evolutionary history. That means: the simpler the structure of an organism, the more resistant it should be,” explains the biologist. If this assumption is true, life forms consisting of a single simply structured cell would be much more resistant to high temperatures than life forms whose cell is very complex, such as algae, or whose bodies consist of millions of cells. Hence, the tolerance and adaptability thresholds of an organism type would always be found at its highest level of complexity. Among the smallest organisms, unicellular algae are the least resistant because they have highly complex cell organelles such as chloroplasts for photosynthesis. Unicellular protozoans also have cell organelles, but they are simpler in their structure. Bacteria and archaea entirely lack these organelles.
To test this assumption, the scientists evaluated over 1000 studies on the adaptability of marine life forms. Starting with simple archaea lacking a nucleus, bacteria and unicellular algae right through to animals and plants, they found the species in each case with the highest temperature tolerance within their group and determined their complexity. In the end, it became apparent that the assumed functional principle seems to apply: the simpler the structure, the more heat-tolerant the organism type.
But: “The adaptation limit of an organism is not only dependent on its upper temperature threshold, but also on its ability to cope with small amounts of oxygen. While many of the bacteria and archaea can survive at low oxygen concentrations or even without oxygen, most animals and plants require a higher minimum concentration,” explains Dr. Daniela Storch. The majority of the studies examined show that if the oxygen concentration in the water drops below a certain value, the oxygen supply for cells and tissues collapses after a short time.
The new research results also provide evidence that the body size of an organism plays a decisive role concerning adaptation limits. Smaller animal species or smaller individuals of an animal species can survive at lower oxygen concentration levels and higher temperatures than the larger animals.
“We observe among fish in the North Sea that larger individuals of a species are affected first at extreme temperatures. In connection with climate warming, there is generally a trend that smaller species replace larger species in a region. Today, however, plants and animals in the warmest marine environments already live at their tolerance limit and will probably not be able to adapt. If warming continues, they will migrate to cooler areas and there are no other tolerant animal and plant species that could repopulate the deserted habitats,” says Prof. Dr. Hans-Otto Pörtner of the Alfred Wegener Institute. The biologist initiated the current study and is the coordinating lead author of the chapter “Ocean systems” in the Fifth Assessment Report.
The new meta-study shows that their complex structure sets tighter limits for multicellular organisms, i.e. animals and plants, within which they can adapt to new living conditions. Individual animal species can reduce their body size, reduce their metabolism or generate more haemoglobin in order to survive in warmer, oxygen-deficient water. However, marine animals and plants are fundamentally not able to survive in conditions exceeding the temperature threshold of 41 degrees Celsius.
In contrast, simple unicellular organisms like bacteria benefit from warmer sea water. They reproduce and spread. “Communities of species in the ocean change as a result of this shift in living conditions. In the future animals and plants will have problems to survive in the warmest marine regions and archaea, bacteria as well as protozoa will spread in these areas. There are already studies showing that unicellular algae will be replaced by other unicellular organisms in the warmest regions of the ocean,” says Prof. Dr. Hans-Otto Pörtner. The next step for the authors is addressing the question regarding the role the complexity of species plays for tolerance and adaptation to the third climatic factor in the ocean, i.e. acidification, which is caused by rising carbon dioxide emissions and deposition of this greenhouse gas in seawater.
Living at the limit
For generations ocean dwellers have adapted to the conditions in their home waters: to the prevailing temperature, the oxygen concentration and the degree of water acidity. They grow best and live longest under these living conditions. However, not all creatures that live together in an ecosystem have the same preferences. The Antarctic eelpout, for instance, lives at its lower temperature limit and has to remain in warmer water layers of the Southern Ocean. If it enters cold water, the temperature quickly becomes too cold for it. The Atlantic cod in the North Sea, by contrast, would enjoy colder water as large specimens do not feel comfortable in temperatures over ten degrees Celsius. At such threshold values scientists refer to a temperature window: every poikilothermic ocean dweller has an upper and lower temperature limit at which it can live and grow. These “windows” vary in scope. Species in temperate zones like the North Sea generally have a broader temperature window. This is due to the extensively pronounced seasons in these regions. That means the animals have to withstand both warm summers and cold winters.
The temperature window of living creatures in the tropics or polar regions, in comparison, is two to four times smaller than that of North Sea dwellers. On the other hand, they have adjusted to extreme living conditions. Antarctic icefish species, for example, can live in water as cold as minus 1.8 degrees Celsius. Their blood contains antifreeze proteins. In addition, they can do without haemoglobin because their metabolism is low and a surplus of oxygen is available. For this reason their blood is thinner and the fish need less energy to pump it through the body — a perfect survival strategy. But: icefish live at the limit. If the temperature rises by a few degrees Celsius, the animals quickly reach their limits.
Daniela Storch, Lena Menzel, Stephan Frickenhaus, Hans-O. Pörtner. Climate sensitivity across marine domains of life: limits to evolutionary adaptation shape species interactions. Global Change Biology, 2014; DOI:10.1111/gcb.12645
* * *
Starting With the Oceans, Single-Celled Organisms Will Re-Inherit the Earth (Motherboard)
I’ll be the first to cop to being guilty of multi-celled chauvinism: Having complex cells with organelles, which form complex systems allowing you to breathe, achieve consciousness, play volleyball, etc, is pretty much as good as it gets. While we enjoy all these advantages now, though, single-celled, simple organisms are just biding their time. More readily adaptable than us multi-celled organisms, it’s really a simple, single-celled world, and we’re just passing through.
Case in point: the oceans. A team of German researchers just published a paper in the journal Global Change Biology that found that the more simple an organism is, the better off it’s going to be as the oceans warm. Trout will die out, whales will fail, but unicellular bacteria and archaea (a type of microorganism) are going to flourish.
Animals can only develop and reproduce up to a temperature threshold in the water of about 41 degrees Celsius, or 105 degrees Fahrenheit. Beyond this, the cardiovascular system can’t deliver necessary oxygen throughout the body. Even as individual animal species can develop smaller bodies or generate more hemoglobin to survive in warmer and oxygen deficient water, the highly developed metabolic systems that allow for things like eyeballs can’t get over the temperature threshold and the other hurdles it brings, like decreasing oxygen.
“The adaptation limit of an organism is not only dependent on its upper temperature threshold, but also on its ability to cope with small amounts of oxygen,”said Daniela Storch, the study’s lead author . “While many of the bacteria and archaea can survive at low oxygen concentrations or even without oxygen, most animals and plants require a higher minimum concentration.”
But as the Earth’s climate changes, and the ocean gets warmer and more acidic, complexity goes from an asset to a liability, and simplicity reigns.
“Communities of species in the ocean change as a result of this shift in living conditions. In the future animals and plants will have problems to survive in the warmest marine regions and archaea, bacteria as well as protozoa will spread in these areas,” said Dr. Hans-Otto Pörtner, one of the study’s co-authors. “There are already studies showing that unicellular algae will be replaced by other unicellular organisms in the warmest regions of the ocean.”
The story of life on Earth is, if nothing else, symmetrical. Three and a half billion years ago, prokaryotic cells showed up, without a nucleus or other organelles. Complex, multicellular life emerged with an increase in biomass and decrease in global surface temperature half a billion years ago. In another billion and a half years that complex multicellular life died back out, leaving the planet to the so-called simpler forms of life, as they basked in the light of a much brighter Sun. The best-case scenario is that life lasts until the Sun runs out of fuel, swells into a red giant,and vaporizes whatever is left of our planet in 7.6 billion years.
Multicellular life will have just been a two billion year flicker against a backdrop of adaptable single-celled life. But hey, we had a good run.
Summary: Figuring out how to survive on a lean-season diet of hard-to-reach ants, slugs and other bugs may have spurred the development of bigger brains and higher-level cognitive functions in the ancestors of humans and other primates, suggests new research.
An adult female tufted capuchin monkey of the Sapajus lineage using a stone tool and a sandstone anvil to crack a palm nut as her infant hangs on. Credit: E. Visalberghi
Figuring out how to survive on a lean-season diet of hard-to-reach ants, slugs and other bugs may have spurred the development of bigger brains and higher-level cognitive functions in the ancestors of humans and other primates, suggests research from Washington University in St. Louis.
“Challenges associated with finding food have long been recognized as important in shaping evolution of the brain and cognition in primates, including humans,” said Amanda D. Melin, PhD, assistant professor of anthropology in Arts & Sciences and lead author of the study.
“Our work suggests that digging for insects when food was scarce may have contributed to hominid cognitive evolution and set the stage for advanced tool use.”
Based on a five-year study of capuchin monkeys in Costa Rica, the research provides support for an evolutionary theory that links the development of sensorimotor (SMI) skills, such as increased manual dexterity, tool use, and innovative problem solving, to the creative challenges of foraging for insects and other foods that are buried, embedded or otherwise hard to procure.
Published in the June 2014 Journal of Human Evolution, the study is the first to provide detailed evidence from the field on how seasonal changes in food supplies influence the foraging patterns of wild capuchin monkeys.
The study is co-authored by biologist Hilary C. Young and anthropologists Krisztina N. Mosdossy and Linda M. Fedigan, all from the University of Calgary, Canada.
It notes that many human populations also eat embedded insects on a seasonal basis and suggests that this practice played a key role in human evolution.
“We find that capuchin monkeys eat embedded insects year-round but intensify their feeding seasonally, during the time that their preferred food — ripe fruit — is less abundant,” Melin said. “These results suggest embedded insects are an important fallback food.”
Previous research has shown that fallback foods help shape the evolution of primate body forms, including the development of strong jaws, thick teeth and specialized digestive systems in primates whose fallback diets rely mainly on vegetation.
This study suggests that fallback foods can also play an important role in shaping brain evolution among primates that fall back on insect-based diets, and that this influence is most pronounced among primates that evolve in habitats with wide seasonal variations, such as the wet-dry cycles found in some South American forests.
“Capuchin monkeys are excellent models for examining evolution of brain size and intelligence for their small body size, they have impressively large brains,” Melin said. “Accessing hidden and well-protected insects living in tree branches and under bark is a cognitively demanding task, but provides a high-quality reward: fat and protein, which is needed to fuel big brains.”
But when it comes to using tools, not all capuchin monkey strains and lineages are created equal, and Melin’s theories may explain why.
Perhaps the most notable difference between the robust (tufted, genus Sapajus) and gracile (untufted, genus Cebus) capuchin lineages is their variation in tool use. While Cebus monkeys are known for clever food-foraging tricks, such as banging snails or fruits against branches, they can’t hold a stick to their Sapajus cousins when it comes to theinnovative use and modification of sophisticated tools.
One explanation, Melin said, is that Cebus capuchins have historically and consistently occupied tropical rainforests, whereas the Sapajus lineage spread from their origins in the Atlantic rainforest into drier, more temperate and seasonal habitat types.
“Primates who extract foods in the most seasonal environments are expected to experience the strongest selection in the ‘sensorimotor intelligence’ domain, which includes cognition related to object handling,” Melin said. “This may explain the occurrence of tool use in some capuchin lineages, but not in others.”
Genetic analysis of mitochondial chromosomes suggests that the Sapajus-Cebus diversification occurred millions of years ago in the late Miocene epoch.
“We predict that the last common ancestor of Cebus and Sapajus had a level of SMI more closely resembling extant Cebus monkeys, and that further expansion of SMI evolved in the robust lineage to facilitate increased access to varied embedded fallback foods,necessitated by more intense periods of fruit shortage,” she said.
One of the more compelling modern examples of this behavior, said Melin, is the seasonal consumption of termites by chimpanzees, whose use of tools to extract this protein-rich food source is an important survival technique in harsh environments.
What does this all mean for hominids?
While it’s hard to decipher the extent of seasonal dietary variations from the fossil record, stable isotope analyses indicate seasonal variation in diet for at least one South African hominin, Paranthropus robustus. Other isotopic research suggests that early human diets may have included a range of extractable foods, such as termites, plant roots and tubers.
Modern humans frequently consume insects, which are seasonally important when other animal foods are limited.
This study suggests that the ingenuity required to survive on a diet of elusive insects has been a key factor in the development of uniquely human skills: It may well have been bugs that helped build our brains.
Amanda D. Melin, Hilary C. Young, Krisztina N. Mosdossy, Linda M. Fedigan.Seasonality, extractive foraging and the evolution of primate sensorimotor intelligence. Journal of Human Evolution, 2014; 71: 77 DOI:10.1016/j.jhevol.2014.02.009
Why does the metabolism of a sloth differ from that of a human? Brains are a big reason, say researchers who recently carried out a detailed comparison of metabolism in humans and other mammals.CreditFelipe Dana/Associated Press
All animals do the same thing to the food they eat — they break it down to extract fuel and building blocks for growing new tissue. But the metabolism of one species may be profoundly different from another’s. A sloth will generate just enough energy to hang from a tree, for example, while some birds can convert their food into a flight from Alaska to New Zealand.
For decades, scientists have wondered how our metabolism compares to that of other species. It’s been a hard question to tackle, because metabolism is complicated — something that anyone who’s stared at a textbook diagram knows all too well. As we break down our food, we produce thousands of small molecules, some of which we flush out of our bodies and some of which we depend on for our survival.
An international team of researchers has now carried out a detailed comparison of metabolism in humans and other mammals. As they report in the journal PLOS Biology, both our brains and our muscles turn out to be unusual, metabolically speaking. And it’s possible that their odd metabolism was part of what made us uniquely human.
When scientists first began to study metabolism, they could measure it only in simple ways. They might estimate how many calories an animal burned in a day, for example. If they were feeling particularly ambitious, they might try to estimate how many calories each organ in the animal’s body burned.
Those tactics were enough to reveal some striking things about metabolism. Compared with other animals, we humans have ravenous brains. Twenty percent of the calories we take in each day are consumed by our neurons as they send signals to one another.
Ten years ago, Philipp Khaitovich of the Max Planck Institute of Evolutionary Anthropology and his colleagues began to study human metabolism in a more detailed way. They started making a catalog of the many molecules produced as we break down food.
“We wanted to get as much data as possible, just to see what happened,” said Dr. Khaitovich.
To do so, the scientists obtained brain, muscle and kidney tissues from organ donors. They then extracted metabolic compounds like glucose from the samples and measured their concentrations. All told, they measured the levels of over 10,000 different molecules.
The scientists found that each tissue had a different metabolic fingerprint, with high levels of some molecules and low levels of others.
These distinctive fingerprints came as little surprise, since each tissue has a different job to carry out. Muscles need to burn energy to generate mechanical forces, for example, while kidney cells need to pull waste out of the bloodstream.
The scientists then carried out the same experiment on chimpanzees, monkeys and mice. They found that the metabolic fingerprint for a given tissue was usually very similar in closely related species. The same tissues in more distantly related species had fingerprints with less in common.
But the scientists found two exceptions to this pattern.
The first exception turned up in the front of the brain. This region, called the prefrontal cortex, is important for figuring out how to reach long-term goals. Dr. Khaitovich’s team found that the way the human prefrontal cortex uses energy is quite distinct from other species; other tissues had comparable metabolic fingerprints across species, and even in other regions of the brain, the scientists didn’t find such a drastic difference.
This result fit in nicely with findings by other scientists that the human prefrontal cortex expanded greatly over the past six million years of our evolution. Its expansion accounts for much of the extra demand our brains make for calories.
The evolution of our enormous prefrontal cortex also had a profound effect on our species. We use it for many of the tasks that only humans can perform, such as reflecting on ourselves, thinking about what others are thinking and planning for the future.
But the prefrontal cortex was not the only part of the human body that has experienced a great deal of metabolic evolution. Dr. Khaitovich and his colleagues found that the metabolic fingerprint of muscle is even more distinct in humans.
“Muscle was really off the charts,” Dr. Khaitovich said. “We didn’t expect to see that at all.”
It was possible that the peculiar metabolism in human muscle was just the result of our modern lifestyle — not an evolutionary shift in our species. Our high-calorie diet might change the way muscle cells generated energy. It was also possible that a sedentary lifestyle made muscles weaker, creating a smaller metabolic demand.
To test that possibility, Dr. Khaitovich compared the strength of humans to that of our closest relatives. They found that chimpanzees and monkeys are far stronger, for their weight, than even university basketball players or professional climbers.
The scientists also tested their findings by putting monkeys on a couch-potato regime for a month to see if their muscles acquired a human metabolic fingerprint.
They barely changed.
Dr. Khaitovich suspects that the metabolic fingerprint of our muscles represents a genuine evolutionary change in our species.
Karen Isler and Carel van Schaik of the University of Zurich have argued that the gradual changes in human brains and muscles were intimately linked. To fuel a big brain, our ancestors had to sacrifice other tissues, including muscles.
Dr. Isler said that the new research fit their hypothesis nicely. “It looks quite convincing,” she said.
Daniel E. Lieberman, a professor of human evolutionary biology at Harvard, said he found Dr. Khaitovich’s study “very cool,” but didn’t think the results meant that brain growth came at the cost of strength. Instead, he suggested, our ancestors evolved muscles adapted for a new activity: long-distance walking and running.
“We have traded strength for endurance,” he said. And that endurance allowed our ancestors to gather more food, which could then fuel bigger brains.
“It may be that the human brain is bigger not in spite of brawn but rather because of brawn, albeit a very different kind,” he said.
The answer lies in changes in the way our genes work
Jerusalem, April 22, 2014 — In parallel with modern man (Homo sapiens), there were other, extinct types of humans with whom we lived side by side, such as Neanderthals and the recently discovered Denisovans of Siberia. Yet only Homo sapiens survived. What was it in our genetic makeup that gave us the advantage?
The truth is that little is known about our unique genetic makeup as distinguished from our archaic cousins, and how it contributed to the fact that we are the only species among them to survive. Even less is known about our unique epigenetic makeup, but it is exactly such epigenetic changes that may have shaped our own species.
While genetics deals with the DNA sequence itself and the heritable changes in the DNA (mutations), epigenetics deals with heritable traits that are not caused by mutations. Rather, chemical modifications to the DNA can efficiently turn genes on and off without changing the sequence. This epigenetic regulatory layer controls where, when and how genes are activated, and is believed to be behind many of the differences between human groups.
Indeed, many epigenetic changes distinguish us from the Neanderthal and the Denisovan, researchers at the Hebrew University of Jerusalem and Europe have now shown.
In an article just published in Science, Dr. Liran Carmel, Prof. Eran Meshorer and David Gokhman of the Alexander Silberman Institute of Life sciences at the Hebrew University, along with scientists from Germany and Spain, have reconstructed, for the first time, the epigenome of the Neanderthal and the Denisovan. Then, by comparing this ancient epigenome with that of modern humans, they identified genes whose activity had changed only in our own species during our most recent evolution.
Among those genetic pattern changes, many are expressed in brain development. Numerous changes were also observed in the immune and cardiovascular systems, whereas the digestive system remained relatively unchanged.
On the negative side, the researchers found that many of the genes whose activity is unique to modern humans are linked to diseases like Alzheimer’s disease, autism and schizophrenia, suggesting that these recent changes in our brain may underlie some of the psychiatric disorders that are so common in humans today.
By reconstructing how genes were regulated in the Neanderthal and the Denisovan, the researchers provide the first insight into the evolution of gene regulation along the human lineage and open a window to a new field that allows the studying of gene regulation in species that went extinct hundreds of thousands of years ago.
Identity crisis (Image: Benedicte Kurzen/The New York Times/Eyevine)
ONE of our closest long-lost relatives may never have existed. The fossils ofAustralopithecus sediba, which promised to rewrite the story of human evolution, may actually be the remains of two species jumbled together.
The first fossils of A. sediba were found at Malapa, South Africa, in 2008. At 2 million years old, they show a mix of features, some similar to the ape-like australopithecines, others more like our genus, Homo. To its discoverers, this hotchpotch means A. sediba was becoming human, and that the Homogenus first evolved in South Africa, not east Africa as is generally thought.
But a new analysis suggests A. sediba didn’t exist. “I think there are two different hominin genera represented at Malapa,” says Ella Been at Tel Aviv University in Israel. One is an Australopithecus and one an early Homo. We can’t yet tell if the australopithecine remains are distinct enough to call them a new species, Been says.
Been studies the spinal columns of ancient hominins, so she was curious when a paper was published last year focusing on the spine of A. sediba(Science, doi.org/r7k). There are fragments from two skeletons at Malapa, a juvenile male and an adult female. Looking at photographs of the vertebrae, she noticed familiar features on the young male.
“I realised they looked a lot like the vertebrae of the Nariokotome Boy,” she says. Also known as Turkana Boy, this is a 1.5-million-year-old skeleton ofHomo erectus, a widespread species that may be our direct ancestor. Its vertebrae, like ours, are much wider than they are tall.
In contrast, the adult female’s vertebrae are taller, says Been, a classicAustralopithecus feature. She concludes that the spines belong to two different species.
When Been shared her findings with Yoel Rak, also at Tel Aviv University, she found an ally. “He sees the same in the [lower jawbone]: an australopithecine and an early Homo,” says Been. But here the species are switched: a notch in the young male jaw looks like Australopithecus, while the same notch in the adult female jaw looks human.
The pair conclude that there are not two but four individuals in the remains from Malapa: an adult and a juvenile of both Homo and Australopithecus. They presented their findings at a meeting of the Paleoanthropology Society in Calgary, Canada, this week.
Unsurprisingly, A. sediba‘s discoverer, Lee Berger of the University of Witwatersrand in South Africa, doesn’t agree. For one thing, he says the positioning of the adult skeleton’s bones in the ground makes it likely they came from a single individual.
Berger admits that the vertebrae of the young A. sediba look like those of H. erectus, but he says vertebrae grow taller throughout childhood. If the youngA. sediba had grown up, his vertebrae may have become moreAustralopithecus-like.
Been isn’t convinced. Fossils of other australopithecine children had tall vertebrae, she says.
Regardless, Berger says that Been and Rak’s observations make sense if A. sediba really was a transitional species between Australopithecus and Homo. “A central tenet of evolutionary theory is that variation within taxa becomes variation between taxa as species diverge,” he says. With anatomy in flux, it is possible that one A. sediba had an Australopithecus-like spine and Homo-like jaw, while another had a Homo-like spine and Australopithecus-like jaw.
There are other features of the A. sediba vertebrae that might explain the differences Been found. Berger’s latest work hints that the young male’s vertebrae may show signs of disease. If so, they are not representative of the species.
This article appeared in print under the headline “Missing link fossils may be a jumble of species”
Bringing extinct animals back to life is really happening — and it’s going to be very, very cool. Unless it ends up being very, very bad.
By NATHANIEL RICHFEB. 27, 2014
CreditStephen Wilkes for The New York Times; Woolly Mammoth, Royal BC Museum, Victoria, British Columbia
The first time Ben Novak saw a passenger pigeon, he fell to his knees and remained in that position, speechless, for 20 minutes. He was 16. At 13, Novak vowed to devote his life to resurrecting extinct animals. At 14, he saw a photograph of a passenger pigeon in an Audubon Society book and “fell in love.” But he didn’t know that the Science Museum of Minnesota, which he was then visiting with a summer program for North Dakotan high-school students, had them in their collection, so he was shocked when he came across a cabinet containing two stuffed pigeons, a male and a female, mounted in lifelike poses. He was overcome by awe, sadness and the birds’ physical beauty: their bright auburn breasts, slate-gray backs and the dusting of iridescence around their napes that, depending on the light and angle, appeared purple, fuchsia or green. Before his chaperones dragged him out of the room, Novak snapped a photograph with his disposable camera. The flash was too strong, however, and when the film was processed several weeks later, he was haunted to discover that the photograph hadn’t developed. It was blank, just a flash of white light.
In the decade since, Novak has visited 339 passenger pigeons — at the Burke Museum in Seattle, the Carnegie Museum of Natural History in Pittsburgh, the American Museum of Natural History in New York and Harvard’s Ornithology Department, which has 145 specimens, including eight pigeon corpses preserved in jars of ethanol, 31 eggs and a partly albino pigeon. There are 1,532 passenger-pigeon specimens left on Earth. On Sept. 1, 1914, Martha, the last captive passenger pigeon, died at the Cincinnati Zoo. She outlasted George, the penultimate survivor of her species and her only companion, by four years. As news spread of her species’ imminent extinction, Martha became a minor tourist attraction. In her final years, whether depressed or just old, she barely moved. Underwhelmed zoo visitors threw fistfuls of sand at her to elicit a reaction. When she finally died, her body was taken to the Cincinnati Ice Company, frozen in a 300-pound ice cube and shipped by train to the Smithsonian Institution, where she was stuffed and mounted and visited, 99 years later, by Ben Novak.
The fact that we can pinpoint the death of the last known passenger pigeon is one of many peculiarities that distinguish the species. Many thousands of species go extinct every year, but we tend to be unaware of their passing, because we’re unaware of the existence of most species. The passenger pigeon’s decline was impossible to ignore, because as recently as the 1880s, it was the most populous vertebrate in North America. It made up as much as 40 percent of the continent’s bird population. In “A Feathered River Across the Sky,” Joel Greenberg suggests that the species’ population “may have exceeded that of every other bird on earth.” In 1860, a naturalist observed a single flock that he estimated to contain 3,717,120,000 pigeons. By comparison, there are currently 260 million rock pigeons in existence. A single passenger-pigeon nesting ground once occupied an area as large as 850 square miles, or 37 Manhattans.
The species’ incredible abundance was an enticement to mass slaughter. The birds were hunted for their meat, which was sold by the ton (at the higher end of the market, Delmonico’s served pigeon cutlets); for their oil and feathers; and for sport. Even so, their rapid decline — from approximately five billion to extinction within a few decades — baffled most Americans. Science magazine published an article claiming that the birds had all fled to the Arizona desert. Others hypothesized that the pigeons had taken refuge in the Chilean pine forests or somewhere east of Puget Sound or in Australia. Another theory held that every passenger pigeon had joined a single megaflock and disappeared into the Bermuda Triangle.
Stewart Brand, who was born in Rockford, Ill., in 1938, has never forgotten the mournful way his mother spoke about passenger pigeons when he was a child. During summers, the Brands vacationed near the top of Michigan’s mitten, not far from Pigeon River, one of the hundreds of American places named after the species. (Michigan alone has four Pigeon Rivers, four Pigeon Lakes, two Pigeon Creeks, Pigeon Cove, Pigeon Hill and Pigeon Point). Old-timers told stories about the pigeon that to Brand assumed a mythic quality. They said that the flocks were so large they blotted out the sun.
Brand’s compassion for the natural world has taken many diverse forms, but none more broadly influential than the Whole Earth Catalog, which he founded in 1968 and edited until 1984. Brand has said that the catalog, a dense compendium of environmentalist tools and practices, among other things, “encouraged individual power.” As it turned out, Whole Earth’s success gave Brand more power than most individuals, allowing him intimate access to the world’s most imaginative thinkers and patrons wealthy enough to finance those thinkers’ most ambitious ideas. In the last two decades, several of these ideas have materialized under the aegis of the Long Now Foundation, a nonprofit organization that Brand helped to establish in 1996 to support projects designed to inspire “long-term responsibility.” Among these projects are a 300-foot-tall clock designed to tick uninterruptedly for the next 10,000 years, financed by a $42 million investment from the Amazon.com founder Jeff Bezos and situated inside an excavated mountain that Bezos owns near Van Horn, Tex.; and a disk of pure nickel inscribed with 1,500 languages that has been mounted on the Rosetta space probe, which this year is scheduled to land on Comet 67P/Churyumov-Gerasimenko, 500 million miles from earth.
Three years ago Brand invited the zoologist Tim Flannery, a friend, to speak at Long Now’s Seminar About Long-Term Thinking, a monthly series held in San Francisco. The theme of the talk was “Is Mass Extinction of Life on Earth Inevitable?” In the question-and-answer period that followed, Brand, grasping for a silver lining, mentioned a novel approach to ecological conservation that was gaining wider public attention: the resurrection of extinct species, like the woolly mammoth, aided by new genomic technologies developed by the Harvard molecular biologist George Church. “It gives people hope when rewilding occurs — when the wolves come back, when the buffalo come back,” Brand said at the seminar. He paused. “I suppose we could get passenger pigeons back. I hadn’t thought of that before.”
Brand became obsessed with the idea. Reviving an extinct species was exactly the kind of ambitious, interdisciplinary and slightly loopy project that appealed to him. Three weeks after his conversation with Flannery, Brand sent an email to Church and the biologist Edward O. Wilson:
Dear Ed and George . . .
The death of the last passenger pigeon in 1914 was an event that broke the public’s heart and persuaded everyone that extinction is the core of humanity’s relation with nature.
George, could we bring the bird back through genetic techniques? I recall chatting with Ed in front of a stuffed passenger pigeon at the Comparative Zoology Museum [at Harvard, where Wilson is a faculty emeritus], and I know of other stuffed birds at the Smithsonian and in Toronto, presumably replete with the requisite genes. Surely it would be easier than reviving the woolly mammoth, which you have espoused.
The environmental and conservation movements have mired themselves in a tragic view of life. The return of the passenger pigeon could shake them out of it — and invite them to embrace prudent biotechnology as a Green tool instead of menace in this century. . . . I would gladly set up a nonprofit to fund the passenger pigeon revival. . . .
Wild scheme. Could be fun. Could improve things. It could, as they say, advance the story.
Passenger Pigeon Extinct 1914. Billions of the pigeons were alive just a few decades earlier. Like the other animals shown here, it has been proposed for de-extinction projects. Credit Stephen Wilkes for The New York Times. Passenger pigeon, Museum of Comparative Zoology, Harvard University.
What do you think?
In less than three hours, Church responded with a detailed plan to return “a flock of millions to billions” of passenger pigeons to the planet.
In February 2012, Church hosted a symposium at Harvard Medical School called “Bringing Back the Passenger Pigeon.” Church gave a demonstration of his new genome-editing technology, and other biologists and avian specialists expressed enthusiasm for the idea. “De-extinction went from concept to potential reality right before our eyes,” said Ryan Phelan, Brand’s wife, an entrepreneur who founded an early consumer medical-genetics company. “We realized that we could do it not only for the passenger pigeon, but for other species. There was so much interest and so many ideas that we needed to create an infrastructure around it. It was like, ‘Oh, my God, look at what we’ve unleashed.’ ” Phelan, 61, became executive director of the new project, which they named Revive & Restore.
Several months later, the National Geographic Society hosted a larger conference to debate the scientific and ethical questions raised by the prospect of “de-extinction.” Brand and Phelan invited 36 of the world’s leading genetic engineers and biologists, among them Stanley Temple, a founder of conservation biology; Oliver Ryder, director of the San Diego Zoo’s Frozen Zoo, which stockpiles frozen cells of endangered species; and Sergey Zimov, who has created an experimental preserve in Siberia called Pleistocene Park, which he hopes to populate with woolly mammoths.
To Brand’s idea that the pigeon project would provide “a beacon of hope for conservation,” conference attendees added a number of ecological arguments in support of de-extinction. Just as the loss of a species decreases the richness of an ecosystem, the addition of new animals could achieve the opposite effect. The grazing habits of mammoths, for instance, might encourage the growth of a variety of grasses, which could help to protect the Arctic permafrost from melting — a benefit with global significance, as the Arctic permafrost contains two to three times as much carbon as the world’s rain forests. “We’ve framed it in terms of conservation,” Brand told me. “We’re bringing back the mammoth to restore the steppe in the Arctic. One or two mammoths is not a success. 100,000 mammoths is a success.”
A less scientific, if more persuasive, argument was advanced by the ethicist Hank Greely and the law professor Jacob Sherkow, both of Stanford. De-extinction should be pursued, they argued in a paper published in Science, because it would be really cool. “This may be the biggest attraction and possibly the biggest benefit of de-extinction. It would surely be very cool to see a living woolly mammoth.”
Ben Novak needed no convincing. When he heard that Revive & Restore had decided to resurrect the passenger pigeon, he sent an email to Church, who forwarded it to Brand and Phelan. “Passenger pigeons have been my passion in life for a very long time,” Novak wrote. “Any way I can be part of this work would be my honor.”
Behind the biohazard signs and double-encoded security doors that mark the entrance of the paleogenomics lab at the University of California, Santa Cruz, I found no mastodon tusks, dinosaur eggs or mosquitoes trapped in amber — only a sterile, largely empty room in which Novak and several graduate students were busy checking their Gmail accounts. The only visible work in progress was Metroplex, a giant Transformers figurine that Novak constructed, which was hunched over his keyboard like a dead robot.
Novak, who is 27, hastened to assure me that the construction of the passenger-pigeon genome was also underway. In fact, it had been for years. Beth Shapiro, one of the scientists who runs the lab, began to sequence the species’ DNA in 2001, a decade before Brand had his big idea. The sequencing process is now in its data-analysis phase, which leaves Novak, who studied ecology in college, but has no advanced scientific degrees, time to consult on academic papers about de-extinction, write his own paper about the ecological relationship between passenger pigeons and chestnut trees and correspond with the scientists behind the world’s other species-resurrection efforts. These include the Uruz project, which is selectively breeding cattle to create a new subspecies that resembles aurochs, a form of wild ox, extinct since 1627; a group hoping to use genetic methods to revive the heath hen, extinct since 1932; and the Lazarus Project, which is trying to revive an Australian frog, extinct for 30 years, that gave birth through its mouth.
As Brand and Phelan’s only full-time employee at Revive & Restore, Novak fields emails sent by scientists eager to begin work on new candidates for de-extinction, like the California grizzly bear, the Carolina parakeet, the Tasmanian tiger, Steller’s sea cow and the great auk, which hasn’t been seen since 1844, when the last two known members of its species were strangled by Icelandic fishermen. Because de-extinction requires collaboration from a number of different disciplines, Phelan sees Revive & Restore as a “facilitator,” helping to connect geneticists, molecular biologists, synthetic biologists and conservation biologists. She also hopes that Revive & Restore’s support will enable experimental projects to proceed. She and Novak realize that the new discipline of de-extinction will advance regardless of their involvement, but, she says, “We just want it to happen responsibly.”
When Novak joined Shapiro’s lab, he knew nothing about Santa Cruz and nobody there. A year later, apart from an occasional dinner on the Brands’ tugboat in Sausalito, little has changed. Novak is largely left alone with his thoughts and his dead animals. But it has always been this way for Novak, who grew up in a house three miles from his closest neighbor, halfway between Williston, the eighth-largest city in North Dakota, and Alexander, which has a population of 269. As a boy, Novak often took solitary hikes through the badlands near his home, exploring a vast petrified forest that runs through the Sentinel Butte formation. Fifty million years ago, that part of western North Dakota resembled the Florida Everglades. Novak frequently came across vertebrae, phalanges and rib fragments of extinct crocodiles and champsosaurs.
This was two hours north of Elkhorn Ranch, where Theodore Roosevelt developed the theories about wildlife protection that led to the preservation of 230 million acres of land. The local schools emphasized conservation in their science classes. In sixth grade, Novak was astonished to learn that he was living in the middle of a mass extinction. (Scientists predict that changes made by human beings to the composition of the atmosphere could kill off a quarter of the planet’s mammal species, a fifth of its reptiles and a sixth of its birds by 2050.) “I felt a certain amount of solidarity with these species,” he told me. “Maybe because I spent so much time alone.”
Great Auk Not seen since 1844, when Icelandic fishermen strangled the last known survivors. Credit Stephen Wilkes for The New York Times. Great Auk, Museum of Comparative Zoology, Harvard University.
After graduating from Montana State University in Bozeman, Novak applied to study under Beth Shapiro, who had already begun to sequence passenger-pigeon DNA. He was rejected. “I appreciated his devotion to the bird,” she told me, “but I worried that his zeal might interfere with his ability to do serious science.” Novak instead entered a graduate program at the McMaster Ancient DNA Center in Hamilton, Ontario, where he worked on the sequencing of mastodon DNA. But he remained obsessed by passenger pigeons. He decided that, if he couldn’t join Shapiro’s lab, he would sequence the pigeon’s genome himself. He needed tissue samples, so he sent letters to every museum he could find that possessed the stuffed specimens. He was denied more than 30 times before Chicago’s Field Museum sent him a tiny slice of a pigeon’s toe. A lab in Toronto conducted the sequencing for a little more than $2,500, which Novak raised from his family and friends. He had just begun to analyze the data when he learned about Revive & Restore.
After Novak was hired, Shapiro offered him office space at the U.C.S.C. paleogenomics lab, where he could witness the sequencing work as it happened. Now, when asked what he does for a living, Novak says that his job is to resurrect the passenger pigeon.
Novak is tall, solemn, polite and stiff in conversation, until the conversation turns to passenger pigeons, which it always does. One of the few times I saw him laugh was when I asked whether de-extinction might turn out to be impossible. He reminded me that it has already happened. More than 10 years ago, a team that included Alberto Fernández-Arias (now a Revive & Restore adviser) resurrected a bucardo, a subspecies of mountain goat also known as the Pyrenean ibex, that went extinct in 2000. The last surviving bucardo was a 13-year-old female named Celia. Before she died — her skull was crushed by a falling tree — Fernández-Arias extracted skin scrapings from one of her ears and froze them in liquid nitrogen. Using the same cloning technology that created Dolly the sheep, the first cloned mammal, the team used Celia’s DNA to create embryos that were implanted in the wombs of 57 goats. One of the does successfully brought her egg to term on July 30, 2003. “To our knowledge,” wrote the scientists, “this is the first animal born from an extinct subspecies.” But it didn’t live long. After struggling to breathe for several minutes, the kid choked to death.
This cloning method, called somatic cell nuclear transfer, can be used only on species for which we have cellular material. For species like the passenger pigeon that had the misfortune of going extinct before the advent of cryopreservation, a more complicated process is required. The first step is to reconstruct the species’ genome. This is difficult, because DNA begins to decay as soon as an organism dies. The DNA also mixes with the DNA of other organisms with which it comes into contact, like fungus, bacteria and other animals. If you imagine a strand of DNA as a book, then the DNA of a long-dead animal is a shuffled pile of torn pages, some of the scraps as long as a paragraph, others a single sentence or just a few words. The scraps are not in the right order, and many of them belong to other books. And the book is an epic: The passenger pigeon’s genome is about 1.2 billion base pairs long. If you imagine each base pair as a word, then the book of the passenger pigeon would be four million pages long.
There is a shortcut. The genome of a closely related species will have a high proportion of identical DNA, so it can serve as a blueprint, or “scaffold.” The passenger pigeon’s closest genetic relative is the band-tailed pigeon, which Shapiro is now sequencing. By comparing the fragments of passenger-pigeon DNA with the genomes of similar species, researchers can assemble an approximation of an actual passenger-pigeon genome. How close an approximation, it will be impossible to know. As with any translation, there may be errors of grammar, clumsy phrases and perhaps a few missing passages, but the book will be legible. It should, at least, tell a good story.
Shapiro hopes to complete this part of the process in the coming months. At that point, the researchers will have, on their hard drives, a working passenger-pigeon genome. If you opened the file on a computer screen, you would see a chain of 1.2 billion letters, all of them A, G, C or T. Shapiro hopes to publish an analysis of the genome by Sept. 1, in time for the centenary of Martha’s death.
Woolly Mammoth Became extinct about 4,000 years ago. Credit Stephen Wilkes for The New York Times; Woolly Mammoth, Royal BC Museum, Victoria, British Columbia
That, unfortunately, is the easy part. Next the genome will have to be inscribed into a living cell. This is even more complicated than it sounds. Molecular biologists will begin by trying to culture germ cells from a band-tailed pigeon. Cell culturing is the process by which living tissue is made to grow in a petri dish. Bird cells can be especially difficult to culture. They strongly prefer not to exist outside of a body. “For birds,” Novak said, “this is the hump to get over.” But it is largely a question of trial and error — a question, in other words, of time, which Revive & Restore has in abundance.
Should scientists succeed in culturing a band-tailed-pigeon germ cell, they will begin to tinker with its genetic code. Biologists describe this as a “cut-and-paste job.” They will replace chunks of band-tailed-pigeon DNA with synthesized chunks of passenger-pigeon DNA, until the cell’s genome matches their working passenger-pigeon genome. They will be aided in this process by a fantastical new technology, invented by George Church, with the appropriately runic name of MAGE (Multiplex Automated Genome Engineering). MAGE is nicknamed the “evolution machine” because it can introduce the equivalent of millions of years of genetic mutations within minutes. After MAGE works its magic, scientists will have in their petri dishes living passenger-pigeon cells, or at least what they will call passenger-pigeon cells.
The biologists would next introduce these living cells into a band-tailed-pigeon embryo. No hocus-pocus is involved here: You chop off the top of a pigeon egg, inject the passenger-pigeon cells inside and cover the hole with a material that looks like Saran wrap. The genetically engineered germ cells integrate into the embryo; into its gonads, to be specific. When the chick hatches, it should look and act like a band-tailed pigeon. But it will have a secret. If it is a male, it carries passenger-pigeon sperm; if it is a female, its eggs are passenger-pigeon eggs. These creatures — band-tailed pigeons on the outside and passenger pigeons on the inside — are called “chimeras” (from the Middle English for “wild fantasy”). Chimeras would be bred with one another in an effort to produce passenger pigeons. Novak hopes to observe the birth of his first passenger-pigeon chick by 2020, though he suspects 2025 is more likely.
At that point, the de-extinction process would move from the lab to the coop. Developmental and behavioral biologists would take over, just in time to answer some difficult questions. Chicks imitate their parents’ behavior. How do you raise a passenger pigeon without parents of its own species? And how do you train band-tailed pigeons to nurture the strange spawn that emerge from their eggs; chicks that, to them, might seem monstrous: an avian Rosemary’s Baby?
Despite the genetic similarity between the two pigeon species, significant differences remain. Band-tailed pigeons are a western bird and migrate vast distances north and south; passenger pigeons lived in the eastern half of the continent and had no fixed migration patterns. In order to ease the transition between band-tailed parents and passenger chicks, a Revive & Restore partner will soon begin to breed a flock of band-tailed pigeons to resemble passenger pigeons. They will try to alter the birds’ diets, migration habits and environment. The behavior of each subsequent generation will more closely resemble that of their genetic cousins. “Eventually,” Novak said, “we’ll have band-tailed pigeons that are faux-passenger-pigeon parents.” As unlikely as this sounds, there is a strong precedent; surrogate species have been used extensively in pigeon breeding.
During the breeding process, small modifications would be made to the genome in order to ensure genetic diversity within the new population. After three to five years, some of the birds would be moved to a large outdoor aviary, where they would be exposed to nature for the first time: trees, weather, bacteria. Small-population biologists will be consulted, as will biologists who study species reintroduction. Other animals would gradually be introduced into the aviary, one at a time. The pigeons would be transferred between aviaries to simulate their hopscotching migratory patterns. Ecologists will study how the birds affect their environment and are affected by it. After about 10 years, some of the birds in the aviary would be set free into the wild, monitored by G.P.S. chips implanted under their skin. The project will be considered a full success when the population in the wild is capable of perpetuating itself without the addition of new pigeons from the aviary. Novak expects this to occur as early as 25 years after the first birds are let into the wild, or 2060. And he hopes that he will be there to witness it.
While Novak’s pigeons are reproducing, Revive & Restore will have embarked on a parallel course with a number of other species, both extinct and endangered. Besides the woolly mammoth, candidates include the black-footed ferret, the Caribbean monk seal, the golden lion tamarin, the ivory-billed woodpecker and the northern white rhinoceros, a species that is down to its final handful of members. For endangered species with tiny populations, scientists would introduce genetic diversity to offset inbreeding. For species threatened by contagion, an effort would be made to fortify their DNA with genes that make them disease-resistant. Millions of North American bats have died in the past decade from white-nose syndrome, a disease named after a deadly fungus that was likely imported from Europe. Many European bat species appear to be immune to the fungus; if the gene responsible for this immunity is identified, one theory holds that it could be synthesized and injected into North American bats. The scientific term for this type of genetic intervention is “facilitated adaptation.” A better name for Revive & Restore would be Revive & Restore & Improve.
This optimistic, soft-focus fantasy of de-extinction, while thrilling to Ben Novak, is disturbing to many conservation biologists, who consider it a threat to their entire discipline and even to the environmental movement. At a recent Revive & Restore conference and in articles appearing in both the popular and academic press since then, they have articulated their litany of criticisms at an increasingly high pitch. In response, particularly in recent months, supporters of de-extinction have more aggressively begun to advance their counterarguments. “We have answers for every question,” Novak told me. “We’ve been thinking about this a long time.”
The first question posed by conservationists addresses the logic of bringing back an animal whose native habitat has disappeared. Why go through all the trouble just to have the animal go extinct all over again? While this criticism is valid for some species, the passenger pigeon should be especially well suited to survive in new habitats, because it had no specific native habitat to begin with. It was an opportunistic eater, devouring a wide range of nuts and acorns and flying wherever there was food.
There is also anxiety about disease. “Pathogens in the environment are constantly evolving, and animals are developing new immune systems,” said Doug Armstrong, a conservation biologist in New Zealand who studies the reintroduction of species. “If you recreate a species genetically and release it, and that genotype is based on a bird from a 100-year-old environment, you probably will increase risk.” A revived passenger pigeon might be a vector for modern diseases. But this concern, said David Haussler, the co-founder of the Genome 10K Project, is overblown. “There’s always this fear that somehow, if we do it, we’re going to accidentally make something horrible, because only nature can really do it right. But nature is totally random. Nature makes monsters. Nature makes threats. Many of the things that are most threatening to us are a product of nature. Revive & Restore is not going to tip the balance in any way.” (Some scientists have speculated that, by competing for acorns with rodents and deer, the passenger pigeon could bring about a decrease in Lyme disease.)
More pressing to conservationists is a practical anxiety: Money. De-extinction is a flashy new competitor for patronage. As the conservationist David Ehrenfeld said at a Revive & Restore conference: “If it works, de-extinction will only target a very few species and is extremely expensive. Will it divert conservation dollars from tried-and-true conservation measures that already work, which are already short of funds?” This argument can be made for any conservation strategy, says the ecologist Josh Donlan, an adviser to Revive & Restore. “In my view,” Donlan wrote in a paper that is scheduled to be published in the forthcoming issue of Frontiers of Biogeography, “[the] conservation strategies are not mutually exclusive — a point conservation scientists tend to overlook.” So far this prediction has held up. Much of the money spent so far for sequencing the passenger-pigeon genome has been provided by Beth Shapiro’s U.C.S.C. research budget. Revive & Restore’s budget, which was $350,000 last year, has been raised largely from tech millionaires who are not known for supporting ecological causes.
De-extinction also poses a rhetorical threat to conservation biologists. The specter of extinction has been the conservation movement’s most powerful argument. What if extinction begins to be seen as a temporary inconvenience? The ecologist Daniel Simberloff raised a related concern. “It’s at best a technofix dealing with a few species,” he told me. “Technofixes for environmental problems are band-aids for massive hemorrhages. To the extent that the public, who will never be terribly well informed on the larger issue, thinks that we can just go and resurrect a species, it is extremely dangerous. . . . De-extinction suggests that we can technofix our way out of environmental issues generally, and that’s very, very bad.”
The extinct heath hen, a candidate for resurrection. CreditStephen Wilkes for The New York Times. Heath hen: Museum of Comparative Zoology, Harvard University.
Ben Novak — who trails Simberloff in professional stature by a doctorate, hundreds of scientific publications and a pair of lifetime-achievement awards — rejects this view. “This is about an expansion of the field, not a reduction,” he says. “We get asked these big questions, but no one is asking people who work on elephants why they’re not working with giraffes, when giraffes need a lot more conservation work than elephants do. Nobody asks the people who work on rhinos why they aren’t working on the Arctic pollinators that are being devastated by climate change. The panda program rarely gets criticized, even though that project is completely pointless in the grand scheme of biodiversity on this planet, because the panda is a cute animal.” If the success of de-extinction, or even its failure, increases public awareness of the threats of mass extinction, Novak says, then it will have been a triumph.
How will we decide which species to resurrect? Some have questioned the logic of beginning with a pigeon. “Do you think that wealthy people on the East Coast are going to want billions of passenger pigeons flying over their freshly manicured lawns and just-waxed S.U.V.s?” asked Shapiro, whose involvement in the passenger-pigeon project will end once she finishes analyzing its genome. (She is writing a book about the challenges of de-extinction.) In an attempt to develop scientific criteria, the New Zealand zoologist Philip Seddon recently published a 10-point checklist to determine the suitability of any species for revival, taking into account causes of its extinction, possible threats it might face upon resurrection and man’s ability to destroy the species “in the event of unacceptable ecological or socioeconomic impacts.” If passenger pigeons, in other words, turn out to be an environmental scourge — if, following nature’s example, we create a monster — will we be able to kill them off? (The answer: Yes, we’ve done it before.)
But the most visceral argument against de-extinction is animal cruelty. Consider the 56 female mountain goats who were unable to bring to term the deformed bucardo embryos that were implanted in their wombs. Or the bucardo that was born and lived only a few minutes, gasping for breath, before dying of a lung deformity? “Is it fair to do this to these animals?” Shapiro asked. “Is ‘because we feel guilty’ a good-enough reason?” Stewart Brand made a utilitarian counterargument: “We’re going to go through some suffering, because you try a lot of times, and you get ones that don’t take. On the other hand, if you can bring bucardos back, then how many would get to live that would not have gotten to live?”
And, finally, what will the courts make of packs of woolly mammoths and millions of passenger pigeons let loose on the continent? In “How to Permit Your Mammoth,” published in The Stanford Environmental Law Journal, Norman F. Carlin asks whether revived species should be protected by the Endangered Species Act or regulated as a genetically modified organism. He concludes that revived species, “as products of human ingenuity,” should be eligible for patenting.
This question of “human ingenuity” approaches one of the least commented upon but most significant points about de-extinction. The term “de-extinction” is misleading. Passenger pigeons will not rise from the grave. Instead, band-tailed-pigeon DNA will be altered to resemble passenger-pigeon DNA. But we won’t know how closely the new pigeon will resemble the extinct pigeon until it is born; even then, we’ll only be able to compare physical characteristics with precision. Our understanding of the passenger pigeon’s behavior derives entirely from historical accounts. While many of these, including John James Audubon’s chapter on the pigeon in “Ornithological Biography,” are vividly written, few are scientific in nature. “There are a million things that you cannot predict about an organism just from having its genome sequence,” said Ed Green, a biomolecular engineer who works on genome-sequencing technology in the U.C.S.C. paleogenomics lab. Shapiro said: “It’s just one guess. And it’s not even a very good guess.”
Shapiro is no more sanguine about the woolly-mammoth project. “You’re never going to get a genetic clone of a mammoth,” she said. “What’s going to happen, I imagine, is that someone, maybe George Church, is going to insert some genes into the Asian-elephant genome that make it slightly hairier. That would be just a tiny portion of the genome manipulated, but a few years later, you have a thing born that is an elephant, only hairier, and the press will write, ‘George Church has cloned a mammoth!’ ” Church, though he plans to do more than just alter the gene for hairiness, concedes the point. “I would like to have an elephant that likes the cold weather,” he told me. “Whether you call it a ‘mammoth’ or not, I don’t care.”
Tasmanian Tiger Also known as the thylacine, it was last spotted in Tasmania in 1930.CreditStephen Wilkes for The New York Times. Tasmanian Tiger, Mammalogy Department, American Museum of Natural History.
There is no authoritative definition of “species.” The most widely accepted definition describes a group of organisms that can procreate with one another and produce fertile offspring, but there are many exceptions. De-extinction operates under a different definition altogether. Revive & Restore hopes to create a bird that interacts with its ecosystem as the passenger pigeon did. If the new bird fills the same ecological niche, it will be successful; if not, back to the petri dish. “It’s ecological resurrection, not species resurrection,” Shapiro says. A similar logic informs the restoration of Renaissance paintings. If you visit “The Last Supper” in the refectory of the Convent of Santa Maria delle Grazie in Milan, you won’t see a single speck of paint from the brush of Leonardo da Vinci. You will see a mural with the same proportions and design as the original, and you may feel the same sense of awe as the refectory’s parishioners felt in 1498, but the original artwork disappeared centuries ago. Philosophers call this Theseus’ Paradox, a reference to the ship that Theseus sailed back to Athens from Crete after he had slain the Minotaur. The ship, Plutarch writes, was preserved by the Athenians, who “took away the old planks as they decayed, putting in new and stronger timber in their place.” Theseus’ ship, therefore, “became a standing example among the philosophers . . . one side holding that the ship remained the same, and the other contending that it was not the same.”
What does it matter whether Passenger Pigeon 2.0 is a real passenger pigeon or a persuasive impostor? If the new, synthetically created bird enriches the ecology of the forests it populates, few people, including conservationists, will object. The genetically adjusted birds would hardly be the first aspect of the deciduous forest ecosystem to bear man’s influence; invasive species, disease, deforestation and a toxic atmosphere have engineered forests that would be unrecognizable to the continent’s earliest European settlers. When human beings first arrived, the continent was populated by camels, eight-foot beavers and 550-pound ground sloths. “People grow up with this idea that the nature they see is ‘natural,’ ” Novak says, “but there’s been no real ‘natural’ element to the earth the entire time humans have been around.”
The earth is about to become a lot less “natural.” Biologists have already created new forms of bacteria in the lab, modified the genetic code of countless living species and cloned dogs, cats, wolves and water buffalo, but the engineering of novel vertebrates — of breathing, flying, defecating pigeons — will represent a milestone for synthetic biology. This is the fact that will overwhelm all arguments against de-extinction. Thanks, perhaps, to “Jurassic Park,” popular sentiment already is behind it. (“That movie has done a lot for de-extinction,” Stewart Brand told me in all earnestness.) In a 2010 poll by the Pew Research Center, half of the respondents agreed that “an extinct animal will be brought back.” Among Americans, belief in de-extinction trails belief in evolution by only 10 percentage points. “Our assumption from the beginning has been that this is coming anyway,” Brand said, “so what’s the most benign form it can take?”
What is coming will go well beyond the resurrection of extinct species. For millenniums, we have customized our environment, our vegetables and our animals, through breeding, fertilization and pollination. Synthetic biology offers far more sophisticated tools. The creation of novel organisms, like new animals, plants and bacteria, will transform human medicine, agriculture, energy production and much else. De-extinction “is the most conservative, earliest application of this technology,” says Danny Hillis, a Long Now board member and a prolific inventor who pioneered the technology that is the basis for most supercomputers. Hillis mentioned Marshall McLuhan’s observation that the content of a new medium is the old medium: that each new technology, when first introduced, recreates the familiar technology it will supersede. Early television shows were filmed radio shows. Early movies were filmed stage plays. Synthetic biology, in the same way, may gain widespread public acceptance through the resurrection of lost animals for which we have nostalgia. “Using the tool to recreate old things,” Hillis said, “is a much more comfortable way to get engaged with the power of the tool.”
“By the end of this decade we’ll seem incredibly conservative,” Brand said. “A lot of this stuff is going to become part of the standard tool kit. I would guess that within a decade or two, most of the major conservation organizations will have de-extinction as part of the portfolio of their activities.” He said he hoped to see the birth of a baby woolly mammoth in his lifetime. The opening line of the first Whole Earth Catalog was “We are as gods and might as well get good at it.” Brand has revised this motto to: “We are as gods and HAVE to get good at it.” De-extinction is a good way to practice.
A passion for bringing a lost pigeon back to life is hardly inconsistent with scientific inquiry. Ben Novak insists that he is motivated purely by ecological concerns. “To some people, it might be about making some crazy new pet or zoo animal, but that’s not our organization,” he told me. The scientists who work beside him in the paleogenomics lab — who hear his daily passenger-pigeon rhapsodies — suspect a second motivation. “I’m a biologist, I’ve seen people passionate about animals before,” Andre Soares, a young Brazilian member of Shapiro’s staff, said, “but I’ve never seen anyone this passionate.” He laughed. “It’s not like he ever saw the pigeon flying around. And it’s not like a dinosaur, a massive beast that walked around millions of years ago. No, it’s just a pigeon. I don’t know why he loves them so much.”
I repeated what Novak told me, that the passenger-pigeon project was “all under the framework of conservation.” Soares shook his head. “I think the birds are his thing,” he said.
Ed Green, the biomolecular engineer down the hall, was more succinct. “The passenger pigeon,” he said, “makes Ben want to write poetry.”
A Missouri lawmaker has proposed what ranks among the most anti-evolution legislation in recent years, which would require schools to notify parents if “the theory of evolution by natural selection” was being taught at their child’s school and give them the opportunity to opt out of the class.
The bill had its first public hearing Thursday after being introduced in late January.
State Rep. Rick Brattin (R), who sponsored the bill, told a local TV station last week that teaching only evolution in school was “indoctrination.”
“Our schools basically mandate that we teach one side,” he told KCTV. “It is an indoctrination because it is not objective approach.”
The bill is one of several anti-evolution proposals that have already appeared in statehouses across the country; the Daily Beast counted four states (Missouri, Oklahoma, South Dakota and Virginia) where legislation had been introduced. The proposals would allow for a range of approaches to evolution, from presenting a “debate” over evolution versus creationism to requiring that local school boards allow intelligent design to be included in biology courses
But Brattin’s bill appears to be the only one, and perhaps the first, that would mandate parental notification that their children were being taught evolution in school, the curriculum that most mainstream science teacher groups endorse.
Glenn Branch, deputy director of the National Center for Science Education, told TPM that he was not aware of any state legislation that had included a provision that parents be notified if evolution was being taught at their local schools.
“It’s an absolute infringement on people’s beliefs,” Brattin told the Kansas City Star of requiring schools to teach evolution. “What’s being taught is just as much faith and, you know, just as much pulled out of the air as, say, any religion.”
Unsurprisingly, the proposal has drawn criticism from those science teacher organizations.
The bill “would eviscerate the teaching of biology in Missouri,” Branch said in a statement. “Evolution inextricably pervades the biological sciences; it therefore pervades, or at any rate ought to pervade, biology education at the K–12 level. There simply is no alternative to learning about it; there is no substitute activity.”
“The value of a high school education in Missouri would be degraded,” Branch said.
Brattin’s bill provides:
The policy shall require the school district or charter school to notify the parent or legal guardian of each student enrolled in the district of:
(1) The basic content of the district’s or school’s evolution instruction to be provided to the student; and
(2) The parent’s right to remove the student from any part of the district’s or school’s evolution instruction.
The bill would also require schools to “make all curriculum materials used in the district’s or school’s evolution instruction available for public inspection … prior to the use of such materials in actual instruction.”
Dec. 13, 2013 — Chimpanzees are sensitive to social influences but they maintain their own strategy to solve a problem rather than conform to what the majority of group members are doing. However, chimpanzees do change their strategy when they can obtain greater rewards, MPI researchers found. The study was published in PLOS ONE on November 28, 2013.
Chimpanzees are sensitive to social influences but they maintain their own strategy to solve a problem rather than conform to what the majority of group members are doing. (Credit: Image courtesy of Max-Planck-Gesellschaft)
Chimpanzees are known for their curious nature. They show a rich palette of learning behaviour, both individually and socially. But they are also rather hesitant to abandon their personal preferences, even when that familiar behaviour becomes extremely ineffective. Under which circumstances would chimpanzees flexibly adjust their behaviour? Edwin van Leeuwen and colleagues from the MPI’s for Psycholinguistics and Evolutionary Anthropology conducted a series of experiments in Germany and Zambia to answer this question.
Wooden balls for peanuts
The researchers studied 16 captive chimpanzees at the Wolfgang Kohler Primate Research Center in Germany (Leipzig) and 12 semi-wild chimpanzees at the Chimfunshi Wildlife Orphanage Trust, a sanctuary that houses more than a hundred chimpanzees under nearly natural conditions in the north-western part of Zambia. Chimpanzees were trained on two different vending machines. A minority of the group was made familiar with one machine and the majority of group members with the other machine. Wooden balls were thrown into their enclosure; the chimpanzees could insert these balls into the machines to receive one peanut for each ball.
Van Leeuwen and his colleagues first aimed to replicate previous research and looked whether the chimpanzees in the minority group would change their behaviour toward using the vending machine that the majority of group members used. However, neither the German nor the Zambian chimpanzees gave up their strategy to join the majority. In the second study, the profitability of the vending machines was changed so that the vending machine that the minority used became more profitable, now spitting out five rewards for every ball inserted. Over time, the majority chimpanzees observed that the minority chimpanzees received more peanuts for the same effort and all but one gradually switched to using this more profitable machine.
“Where chimpanzees do not readily change their behaviour under majority influences, they do change their behaviour when they can maximise their payoffs,” Van Leeuwen says. “We conclude that chimpanzees may prefer persevering in successful and familiar strategies over adopting the equally effective strategy of the majority, but that chimpanzees find sufficient incentive in changing their behaviour when they can obtain higher rewards somewhere else.” “So, it’s peanuts over popularity” he jokingly adds.
The researchers emphasise that these results may be dependent upon the specific trade-offs that were created by the experimental design and that chimpanzees could act differently under the pressures of life in the wild. Van Leeuwen: “Conformity could still be a process guiding chimpanzees’ behaviour. Chimpanzee females, for instance, disperse to other groups in the wild. For these females, it is of vital importance to integrate into the new group. Conformity to local (foraging) customs might help them to achieve this integration.”
Edwin J. C. Van Leeuwen, Katherine A. Cronin, Sebastian Schütte, Josep Call, Daniel B. M. Haun. Chimpanzees (Pan troglodytes) Flexibly Adjust Their Behaviour in Order to Maximize Payoffs, Not to Conform to Majorities. PLoS ONE, 2013; 8 (11): e80945 DOI:10.1371/journal.pone.0080945
The World until Yesterday: What Can We Learn from Traditional Societies? by Jared Diamond. Penguin, 498 pp, £8.99, September, ISBN 978 0 14 102448 6
It’s a good bet a culture is in trouble when its best-known intellectuals start ransacking the cultural inventory of its ancestors and its contemporary inferiors for tips on how to live. The malaise is all the more remarkable when the culture in question is the modern American variant of Enlightenment rationalism and progress, a creed not known for self-doubt or failures of nerve. The deeper the trouble, the more we are seen to have lost our way, the further we must go spatially and temporally to find the cultural models that will help us. In the stronger versions of this quest, there is either a place – a Shangri-la – or a time, a Golden Age, that promises to reset our compass to true north. Anthropology and history implicitly promise to provide such models. Anthropology can show us radically different and satisfying forms of human affiliation and co-operation that do not depend on the nuclear family or inherited wealth. History can show that the social and political arrangements we take for granted are the contingent result of a unique historical conjuncture.
Jared Diamond, ornithologist, evolutionary biologist and geographer, is best known as the author of Guns, Germs and Steel: A Short History of Everybody for the Last 13,000 Years, one of the most influential accounts of how most of us came to live in places with huge concentrations of people, grain and domesticated animals, and how this helped create the world of massive inequalities and disparate life chances with which we now live. Diamond’s was not a simple, self-congratulatory ‘rise of the West’ story, telling how some peoples and cultures showed themselves to be essentially cleverer, braver or more rational than others. Instead, he demonstrated the importance of impersonal environmental forces: plants and herd animals amenable to domestication, pathogens, a favourable climate and geography that aided the rise of early states in the Fertile Crescent and the Mediterranean. These initial advantages were compounded by interstate competition in metallurgy for armaments and navigational devices. His argument was much praised for its bold and original synthesis, and much criticised by historians and anthropologists for reducing the arc of human history to a handful of environmental conditions. There was no denying, however, that Diamond’s simple quasi-Darwinian view of human selection was ‘good to think with’.
The subtitle of his new foray into deep history, ‘What Can We Learn from Traditional Societies?’, suggests, without a trace of irony, that it might be more at home in the self-help section of the bookstore. By ‘traditional societies’, he by and large means hunting and gathering and small horticultural societies that have survived into the modern world in the marginal and stingy environments into which states have pushed them. They span the globe, but Diamond draws his principal examples from New Guinea and Australia, where his bird-watching interests lie, and from the findings of studies of hunter-gatherer societies (the Hadza and !Kung of Africa, the Piraha, Siriono and Yanomamo of Latin America) that fit best with his argument.
What could these historical relics possibly teach the wired, hyper-modernist residents of Diamond’s home village of Los Angeles? The question is not so preposterous. As he explains, Homo sapiens has been around for roughly 200,000 years and left Africa not much earlier than 50,000 years ago. The first fragmentary evidence for domesticated crops occurs roughly 11,000 years ago and the first grain statelets around 5000 years ago, though they were initially insignificant in a global population of perhaps eight million. More than 97 per cent of human experience, in other words, lies outside the grain-based nation-states in which virtually all of us now live. ‘Until yesterday’, our diet had not been narrowed to the three major grains that today constitute 50 to 60 per cent of the world’s caloric intake: rice, wheat and maize. The circumstances we take for granted are, in fact, of even more recent vintage than Diamond supposes. Before, say, 1500, most populations had a sporting chance of remaining out of the clutches of states and empires, which were still relatively weak and, given low rates of urbanisation and forest clearance, still had access to foraged foods. On this account, our world of grains and states is a mere blink of the eye (0.25 per cent), in the historical adventure of our species.
Why, Diamond asks, should we not plumb this vast historical record of human experience for what it might teach our WEIRD – ‘Western, educated, industrialised, rich and democratic’ – societies? Though they are the most thoroughly studied of societies, they are totally unrepresentative. If we wish to generalise about human nature, not to mention the history of human experience, we must, he argues, cast our net more widely.
Traditional societies in effect represent thousands of natural experiments in how to construct a human society. They have come up with thousands of solutions to human problems, solutions different from those adopted by our own WEIRD modern societies. We shall see that some of these solutions – for instance, some of the ways in which traditional societies raise their children, treat their elderly, remain healthy, talk, spend their leisure time and settle disputes – may strike you, as they do me, as superior to normal practices in the First World.
The lens through which Diamond, an unrelenting environmental biologist, sees the world affords striking insights but there are still massive blind spots. His discussion of languages, for example, is both passionate and convincing, as one might expect from a scholar whose New Guinea field site is home to roughly a thousand of Earth’s seven thousand languages. Aside from the ‘nine giants’ (Mandarin, Spanish, English, Arabic, Hindi, Bengali, Portuguese, Russian and Japanese), each with more than a hundred million speakers, the rest have on average only a few thousand speakers and a great many have far fewer. The ‘giants’ create vast heartland zones of monolingual citizens within which minor languages are exterminated. Inasmuch as language ‘speciation’ depends largely on dispersal and isolation, the contemporary processes of concentration and cultural homogenisation militate against the development of new languages and the survival of those already endangered. Half of the roughly 250 Australian languages are extinct, one third of the hundreds of Native American languages spoken in 1492 have disappeared and another third are unlikely to survive another generation. Each heartland of a ‘giant’ language is the graveyard of the languages it has overwhelmed.
The commonest contemporary cause of death is cultural and economic engulfment: the majority language so dominates the public sphere, media, schools and government that mastering it is the sole route to employment, social status and cultural citizenship. Diamond pauses to consider the argument that the consolidation of languages might be a fine thing. After all, eliminating language barriers makes for better mutual understanding. Why would one prefer a world in which hill peoples navigate through a linguistic thicket in which they must operate in five or more languages, as his informants do in the New Guinea Highlands?
Here, Diamond, as evolutionary biologist, has two choices. He could claim that the extinction of languages is the process of natural selection at work, just as the scientific racists of the late 19th century claimed that the extermination of backward tribal peoples like the Herero was a tragic but inevitable result of the expansion of superior races. But instead, he takes up a position not unlike that held by E.O. Wilson on the disappearance of species. He argues that just as natural diversity is a treasury of variation and resilience, so linguistic diversity represents a cultural treasury of expression, thought-ways and cosmology that, once lost, is gone for ever.
Literature, culture and much knowledge are encoded in languages: lose the language and you lose much of the literature, culture and knowledge … Traditional peoples have local-language names for hundreds of animal and plant species around them; those encyclopedias of ethnobiological information vanish when their languages vanish … Tribal peoples also have their own oral literatures, and losses of those literatures also represent losses to humanity.
It is undeniable that we are in danger of irrecoverably losing a large part of mankind’s cultural, linguistic and aesthetic heritage from the effects of ‘steamroller’ languages and states. But what a disappointment it is, after nearly five hundred pages of anecdotes, assertions, snippets of scientific studies, observations, detours into the evolution of religion, reports of near-death experiences – Diamond can be a gripping storyteller – to hear the lessons he has distilled for us. We should learn more languages; we should practise more intimate and permissive child-rearing; we should spend more time socialising and talking face to face; we should utilise the wisdom and knowledge of our elders; we should learn to assess the dangers in our environment more realistically. And, when it comes to daily health tips, you have to imagine Diamond putting on his white coat and stethoscope as he recommends ‘not smoking; exercising regularly; limiting our intake of total calories, alcohol, salt and salty foods, sugar and sugared soft drinks, saturated and trans fats, processed foods, butter, cream and red meat; and increasing our intake of fibre, fruits and vegetables, calcium and complex carbohydrates. Another simple change is to eat more slowly.’ Perhaps wary of resistance to a fully fledged hunter-gatherer diet, he recommends the Mediterranean diet. Those who have trekked all this way with him, through the history of the species and the New Guinea Highlands, must have expected something more substantial awaiting them at the end of the trail.
What were our ancestors like before the domestication of plants and animals, before sedentary village life, before the earliest towns and states? That is the question Diamond sets himself to answer. In doing so, he faces nearly insurmountable obstacles. Until quite recently, archaeology recorded our history as a species in relation to the concentration of debris (middens, building rubble, traces of irrigation canals, walls, fossilised faeces etc) we left behind. Hunter-gatherers were typically mobile and spread their largely biodegradable debris widely; we don’t often find their temporary habitats, which were often in caves or beside rivers or the sea, and the vast majority of such sites have been lost to history. When we do find them, they can tell us something about their inhabitants’ diet, cooking methods, bodily adornment, trade goods, weapons, diseases, local climate and occasionally even causes of death, but not much else. How to infer from this scant evidence our ancestors’ family structure and social organisation, their patterns of co-operation and conflict, let alone their ethics and cosmology?
It is here that Diamond makes his fundamental mistake. He imagines he can triangulate his way to the deep past by assuming that contemporary hunter-gatherer societies are ‘our living ancestors’, that they show what we were like before we discovered crops, towns and government. This assumption rests on the indefensible premise that contemporary hunter-gatherer societies are survivals, museum exhibits of the way life was lived for the entirety of human history ‘until yesterday’ – preserved in amber for our examination.
In the unique case of Highland New Guinea, which was apparently isolated from coastal trade and the outside world until World War Two, Diamond might be forgiven for making this inference, though the people of New Guinea have had exactly the same amount of time to adapt and evolve as homo americanus and they managed somehow to get hold of the sweet potato, which originated in South America. The inference of pristine isolation, however, is completely unwarranted for virtually all of the other 35 societies he canvasses. Those societies have, for the last five thousand years, been deeply involved in a world of trade, states and empires and are often now found in undesirable marginal areas to which they have been pushed by more powerful societies. The anthropologist Pierre Clastres argued that the Yanomamo and Siriono, two of Diamond’s prime examples, were originally sedentary cultivators who turned to foraging in order to escape the forced labour and disease associated with Spanish settlements. Like almost all the groups Diamond considers, they have been trading with outside kingdoms and states (and raiding them) for much of the past three thousand years; their beliefs and practices have been shaped by contact, trade goods, travel and intermarriage. So thoroughly have they come to live in a world of powerful kingdoms and states that one might call these societies themselves a ‘state effect’. That is, their location in the landscape is designed to help them evade or trade with larger societies. They forage forest and marine products desired by urban societies; many groups are ‘twinned’ with neighbouring societies, through which they manage their trade and relationship to the larger world.
Contemporary foraging societies, far from being untouched examples of our deep past, are up to their necks in the ‘civilised world’. Those available for Diamond’s inspection are, one might argue, precisely the most successful examples, showing how some hunter-gatherer societies have avoided extinction and assimilation by creatively adapting to the changing world. Taken together, they might make for an interesting study of adaptation, but they are useless as a metric to tell us what our remote ancestors were like. Even their designations – Yanomamo, !Kung, Ainu – convey a false sense of genealogical and genetic continuity, vastly understating the fluidity of these groups’ ethnic boundaries.
Diamond is convinced that violent revenge is the besetting plague of hunter-gatherer societies and, by extension, of our pre-state ancestors. Having chosen some rather bellicose societies (the Dani, the Yanomamo) as illustrations, and larded his account with anecdotal evidence from informants, he reaches the same conclusion as Steven Pinker in The Better Angels of Our Nature: we know, on the basis of certain contemporary hunter-gatherers, that our ancestors were violent and homicidal and that they have only recently (very recently in Pinker’s account) been pacified and civilised by the state. Life without the state is nasty, brutish and short. Though Hobbes is not directly invoked, his gloomy view of savage life without a sovereign infuses Diamond’s narrative. ‘First and foremost, a fundamental problem of virtually all small-scale societies is that, because they lack a central political authority exerting a monopoly of retaliatory force, they are unable to prevent recalcitrant members from injuring other members, and also unable to prevent aggrieved members from taking matters into their own hands and seeking to achieve their goals by violence. But violence invites counter-violence.’
In a passage that recapitulates the fable of the social contract, Diamond implies that it was explicitly to end this violence that subjects agreed to found a sovereign power that would guarantee peace and order by restraining their habits of violence and revenge.
Maintenance of peace within a society is one of the most important services that a state can provide. That service goes a long way towards explaining the apparent paradox that, since the rise of the first state governments in the Fertile Crescent about 5400 years ago, people have more or less willingly (not just under duress) surrendered some of their individual freedoms, accepted the authority of state governments, paid taxes and supported a comfortable individual lifestyle for the state’s leaders and officials.
Two fatal objections come immediately to mind. First, it does not follow that the state, by curtailing ‘private’ violence, reduces the total amount of violence. As Norbert Elias pointed out more than half a century ago in The Civilising Process, what the state does is to centralise and monopolise violence in its own hands, a fact that Diamond, coming as he does from a nation that has initiated several wars in recent decades and a state (California) that has a prison population of roughly 120,000 – most of them non-violent offenders – should appreciate.
Second, Hobbes’s fable at least has nominally equal contractants agreeing to establish a sovereign for their mutual safety. That is hard to reconcile with the fact that all ancient states without exception were slave states. The proportion of slaves seldom dropped below 30 per cent of the population in early states, reaching 50 per cent in early South-East Asia (and in Athens and Sparta as much as 70 and 86 per cent). War captives, conquered peoples, slaves purchased from slave raiders and traders, debt bondsmen, criminals and captive artisans – all these people were held under duress, as the frequency of state collapse, revolt and flight attests. As either a theory or a historical account of state-formation, Diamond’s story makes no sense.
The straw man in his argument is that contemporary hunter-gatherer societies are oases of peace, co-operation and order. Of course they are not. The question, rather, is how violent they are compared to state-societies and what are the causes of the violence that does exist. There is, contra Diamond, a strong case that might be made for the relative non-violence and physical well-being of contemporary hunters and gatherers when compared with the early agrarian states. Non-state peoples have many techniques for avoiding bloodshed and revenge killings: the payment of compensation or Weregild, arranged truces (‘burying the hatchet’), marriage alliances, flight to the open frontier, outcasting or handing over a culprit who started the trouble. Diamond does not seem to appreciate the strong social forces mobilised by kinsmen to restrain anyone contemplating a hasty and violent act that will expose all of them to danger. These practices are examined by many of the ethnographers who have carried out intensive fieldwork in the New Guinea Highlands (for example by Edward L. Schieffelin in The Sorrow of the Lonely and the Burning of the Dancers, Marilyn Strathern inWomen in Between, and Andrew Strathern and Pamela Stewart’s work on compensation), but they make no dent in Diamond’s one-dimensional view of the desire for revenge.
On the other side of the ledger, when it comes to violence in early agrarian states, one must weigh rebellion, war and systematic violence against slaves and women (as a rule of thumb, agrarian states everywhere created patriarchal property regimes which reduced the status and freedom of women) against ‘tribal conflicts’. We also know, and Diamond notes, that hunter-gatherers even today have healthier diets and far fewer communicable diseases. Believing, against the evidence, that hunters and gatherers live in daily fear of starvation, he fails to note that they also work far less hard and thus have far more leisure. Marshall Sahlins called hunter-gatherers, even when relegated to the most undesirable environments, ‘the original affluent society’. It’s hard to imagine Diamond’s primitives giving up their physical freedom, their varied diet, their egalitarian social structure, their relative freedom from famine, large-scale state wars, taxes and systematic subordination in exchange for what Diamond imagines to be ‘the king’s peace’. Reading his account one can get the impression that the choice facing hunters and gatherers was one between their world and, say, the modern Danish welfare state. In practice, their option was to trade what they had for subjecthood in the early agrarian state.
No matter how one defines violence and warfare in existing hunter-gatherer societies, the greater part of it by far can be shown to be an effect of the perils and opportunities represented by a world of states. A great deal of the warfare among the Yanomamo was, in this sense, initiated to monopolise key commodities on the trade routes to commercial outlets (see, for example, R. Brian Ferguson’s Yanomami Warfare: A Political History, a strong antidote to the pseudo-scientific account of Napoleon Chagnon on which Diamond relies heavily). Much of the conflict among Celtic and Germanic peoples on the fringes of Imperial Rome was essentially commercial war as groups jockeyed for access to Roman markets. The unprecedented riches conjured by the ivory trade in the late 19th century set off hundreds of wars among Africans for whom tusks were the currency that purchased muskets, power and trade goods. Borneo/Kalimantan was originally settled more than a millennium ago, it is now believed, by Austronesians who regarded it as an ideal foraging ground for the Chinese luxury market in feathers, camphor wood, tortoiseshell, bezoar stones, hornbill and rhinoceros ivory, and edible birds’ nests. They were there for trade, and that meant conflict over the most profitable sites for foraging and exchange. It would be impossible to understand intertribal warfare in colonial North America without considering the competition for fur trade profits that allowed the winners to buy firearms and allies, and to dominate their rivals.
In the world of states, hunter-gatherers and nomads, one commodity alone dominated all others: people, aka slaves. What agrarian states needed above all else was manpower to cultivate their fields, build their monuments, man their armies and bear and raise their children. With few exceptions, the epidemiological conditions in cities until very recently were so devastating that they could grow only by adding new populations from their hinterlands. They did this in two ways. They took captives in wars: most South-East Asian early state chronicles gauge the success of a war by the number of captives marched back to the capital and resettled there. The Athenians and Spartans might kill the men of a defeated city and burn its crops, but they virtually always brought back the women and children as slaves. And they bought slaves: a slave merchant caravan trailed every Roman war scooping up the slaves it inevitably produced.
The fact is that slaving was at the very centre of state-making. It is impossible to exaggerate the massive effects of this human commodity on stateless societies. Wars between states became a kind of booty capitalism, where the major prize was human traffic. The slave trade then completely transformed the non-state ‘tribal zone’. Some groups specialised in slave-raiding, mounting expeditions against weaker and more isolated groups and then selling them to intermediaries or directly at slave markets. The oldest members of highland groups in Laos, Thailand, Malaysia and Burma can recall their parents’ and grandparents’ memories of slave raids. The fortified, hilltop villages, with thorny, twisting and hidden approaches that early colonists found in parts of South-East Asia and Africa were largely a response to the slave trade.
There is plenty of violence in the world of hunter-gatherers, though it is hardly illuminated by resorting to statistical comparisons between the mortality rates of a tiny tribal war in Kalimantan and the Battle of the Somme or the Holocaust. This violence, however, is almost entirely a state-effect. It simply cannot be understood historically from 4000 BC forward apart from the appetite of states for trade goods, slaves and precious ores, any more than the contemporary threat to remote indigenous groups can be understood apart from the appetite of capitalism and the modern state for rare minerals, hydroelectric sites, plantation crops and timber on the lands of these peoples. Papua New Guinea is today the scene of a particularly violent race for minerals, aided by states and their militias and, as Stuart Kirsch’s Mining Capitalismshows, its indigenous politics can be understood only in this context. Contemporary hunter-gatherer life can tell us a great deal about the world of states and empires but it can tell us nothing at all about our prehistory. We have virtually no credible evidence about the world until yesterday and, until we do, the only defensible intellectual position is to shut up.
Reportagem da Folha de SP mostra que pesquisa descobriu que diferenças entre espécies está em genes ativos
A comparação da atividade genética de humanos com a de chimpanzés sugere que o Homo sapiens está evoluindo de forma mais lenta que os macacos. A descoberta foi feita por cientistas que investigam por que o homem e seu primo mais próximo são tão diferentes, apesar de terem 98% do DNA idêntico.
O segredo das diferenças físicas e comportamentais está em quais genes são de fato ativos em cada espécie. Analisando células embrionárias, a brasileira Carolina Marchetto, do Instituto Salk, de San Diego (EUA), descobriu mecanismos que freiam a taxa de transformação genética da espécie humana.
A descoberta favorece a hipótese de que o advento da cultura desacelerou a evolução biológica: uma vez que humanos se adaptam a distintos ambientes usando o conhecimento, nossa espécie não depende mais tanto de variação genética para evoluir e sobreviver a mudanças.
Já os macacos, mamíferos de cognição mais limitada, precisam que seu DNA evolua de forma rápida para sobreviver a mudanças: eles não têm como compensar a falta de características inatas necessárias usando apenas conhecimento e tecnologia.
Mas o DNA humano também não carece de evoluir? “Não sabemos o que estamos pagando por isso em termos de adaptação, mas por enquanto funciona de forma eficiente”, diz Marchetto.
O trabalho da cientista, descrito hoje na revista “Nature”, ajuda a explicar o mistério da maior diversidade do DNA símio. Um leigo pode achar que todos os chimpanzés são iguais, mas uma só colônia selvagem desses macacos na África tem mais variabilidade genética do que toda a humanidade.
O PULO DO GENE
Segundo o estudo de Marcheto, a maior variabilidade genética dos macacos tem a ver com os chamados transpósons, genes que saltam de um lugar para outro dos cromossomos. Nesse processo, os transpósons reorganizam o genoma, ativando alguns genes e desativando outros.
Esses “genes saltadores” são bastante ativos em chimpanzés e bonobos (macacos igualmente próximos da linhagem humana). Em humanos, o transpóson é suprimido por dois outros genes que são ativados em abundância e inibem o “pulo” genético.
Chimpanzés, de certa forma, precisam de transpósons. Com ferramentas rudimentares e sem linguagem para transmitir conhecimento, eles têm de oferecer maior variabilidade genética à seleção natural para que ela os torne mais bem adaptados, caso o ambiente se altere.
A pesquisa de Marchetto só foi possível porque seu o laboratório no Salk, liderado pelo biólogo Fred Gage, domina a técnica de reverter células ao estágio embrionário.
O material usado na pesquisa foi extraído da pele de macacos e pessoas, pois há uma série de limitações para o uso de embriões em experimentos científicos.
Revertido ao estágio de “células pluripotentes induzidas”, o tecido cutâneo se comporta como embrião, e é possível investigar a biologia molecular dos estágios iniciais do desenvolvimento, quando o surgimento de diversidade genética tem consequências futuras.
“Uma das coisas especiais do nosso estudo é que a reprogramação de células de chimpanzés e bonobos nos dá um modelo para começar a estudar questões evolutivas que antes não tínhamos como abordar”, diz Marchetto.
RUMO AO CÉREBRO
As diferenças de ativação de genes entre humanos e chimpanzés, explica, não se restringem a células embrionárias. A ideia de Marcheto e de seus colegas agora é transformar essas células em neurônios, por exemplo, para entender como a biologia molecular de ambos se altera durante a formação do cérebro.
May 15, 2013 — Two fossil discoveries from the East African Rift reveal new information about the evolution of primates, according to a study published online in Nature this week led by Ohio University scientists.
Artist’s reconstruction of Rukwapithecus (front, center) and Nsungwepithecus (right). (Credit: Mauricio Anton)
The team’s findings document the oldest fossils of two major groups of primates: the group that today includes apes and humans (hominoids), and the group that includes Old World monkeys such as baboons and macaques (cercopithecoids).
Geological analyses of the study site indicate that the finds are 25 million years old, significantly older than fossils previously documented for either of the two groups.
Both primates are new to science, and were collected from a single fossil site in the Rukwa Rift Basin of Tanzania.Rukwapithecus fleaglei is an early hominoid represented by a mandible preserving several teeth. Nsungwepithecus gunnelli is an early cercopithecoid represented by a tooth and jaw fragment.
The primates lived during the Oligocene epoch, which lasted from 34 to 23 million years ago. For the first time, the study documents that the two lineages were already evolving separately during this geological period.
“The late Oligocene is among the least sampled intervals in primate evolutionary history, and the Rukwa field area provides a first glimpse of the animals that were alive at that time from Africa south of the equator,” said Nancy Stevens, an associate professor of paleontology in Ohio University’s Heritage College of Osteopathic Medicine who leads the paleontological team.
Documenting the early evolutionary history of these groups has been elusive, as there are few fossil-bearing deposits of the appropriate age, Stevens explained. Using an approach that dated multiple minerals contained within the rocks, team geologists could determine a precise age for the specimens.
“The rift setting provides an advantage in that it preserves datable materials together with these important primate fossils,” said lead geologist Eric Roberts of James Cook University in Australia.
Prior to these finds, the oldest fossil representatives of the hominoid and cercopithecoid lineages were recorded from the early Miocene, at sites dating millions of years younger.
The new discoveries are particularly important for helping to reconcile a long-standing disagreement between divergence time estimates derived from analyses of DNA sequences from living primates and those suggested by the primate fossil record, Stevens said. Studies of clock-like mutations in primate DNA have indicated that the split between apes and Old
World monkeys occurred between 30 million and 25 million years ago.
“Fossils from the Rukwa Rift Basin in southwestern Tanzania provide the first real test of the hypothesis that these groups diverged so early, by revealing a novel glimpse into this late Oligocene terrestrial ecosystem,” Stevens said.
The new fossils are the first primate discoveries from this precise location within the Rukwa deposits, and two of only a handful of known primate species from the entire late Oligocene, globally.
The scientists scanned the specimens in the Ohio University’s MicroCT scanner, allowing them to create detailed 3-dimensional reconstructions of the ancient specimens that were used for comparisons with other fossils.
“This is another great example that underscores how modern imaging and computational approaches allow us to address more refined questions about vertebrate evolutionary history,” said Patrick O’Connor, co-author and professor of anatomy in Ohio University’s Heritage College of Osteopathic Medicine.
In addition to the new primates, Rukwa field sites have produced several other fossil vertebrate and invertebrate species new to science. The late Oligocene interval is interesting because it provides a final snapshot of the unique species inhabiting Africa prior to large-scale faunal exchange with Eurasia that occurred later in the Cenozoic Era, Stevens said.
A key aspect of the Rukwa Rift Basin project is the interdisciplinary nature of the research team, with paleontologists and geologists working together to reconstruct vertebrate evolutionary history in the context of the developing East African Rift System.
“Since its inception this project has employed a multifaceted approach for addressing a series of large-scale biological and geological questions centered on the East African Rift System in Tanzania,” O’Connor said.
The team’s research, funded by the U.S. National Science Foundation, the Leakey Foundation and the National Geographic Society, underscores the integration of paleontological and geological approaches that are essential for addressing complex issues in vertebrate evolutionary history, the scientists noted.
Co-authors on the study are Patrick O’Connor, Cornelia Krause and Eric Gorscak of Ohio University, Erik Seiffert of SUNY Stony Brook University, Eric Roberts of James Cook University in Australia, Mark Schmitz of Boise State University, Sifa Ngasala of Michigan State University, Tobin Hieronymus of Northeast Ohio Medical University and Joseph Temu of the Tanzania Antiquities Unit.
Nancy J. Stevens, Erik R. Seiffert, Patrick M. O’Connor, Eric M. Roberts, Mark D. Schmitz, Cornelia Krause, Eric Gorscak, Sifa Ngasala, Tobin L. Hieronymus, Joseph Temu.Palaeontological evidence for an Oligocene divergence between Old World monkeys and apes.Nature, 2013; DOI: 10.1038/nature12161
Você precisa fazer login para comentar.