Arquivo da tag: Evolução humana

The Six Legacies of Edward O. Wilson (This View of Life)

By David Sloan Wilson – Published On: January 5, 2022

Note: An abbreviated version of this article is published in Nautilus Magazine.

Edward O. Wilson, who passed away at the age of 92 on December 26, 2021, is widely recognized as a giant of the Arts and Sciences. I include the Arts because Wilson regarded the creative dimension of science as an artistic endeavor, worked toward unifying the Arts and Sciences, and wrote beautifully for the general public, resulting in two Pulitzer prizes for nonfiction and one novel.

Wilson’s stature is so great, and reflections on his legacy upon his death are so numerous, that another reflection might seem unnecessary. The purpose of my reflection, however, is to make a novel point: Wilson left at least six legacies, which need to be combined to fully realize his vision. Combining the legacies of Edward O. Wilson requires first identifying them separately and then integrating them with each other.

The six legacies are:

1) His contributions to evolutionary biology.

2) His contributions to the conservation of biodiversity.

3) His contributions to a sociobiology that includes humans.

4) His contributions to the unification of knowledge.

5) His encouraging stance toward young scientists and other learners.

6) The new frontier that he was working on at the time of his death was ecosystems.   

My relationship with Edward O. Wilson

Before turning to these legacies and their integration, I will briefly recount my own relationship with Ed. I am 20 years younger so that he was already famous as a Harvard professor when I entered graduate school at Michigan State University in 1971. I first met him during the summer of that year. I was a student in an ecology course at the Marine Biological Laboratory in Woods Hole, Massachusetts. He was sitting in on the student project reports. After I reported my experiments on food size selection in zooplankton, Ed remarked “That’s new, isn’t it?” I was so proud to have impressed the great E.O. Wilson and contributed to the vast storehouse of scientific knowledge that I have remembered his comment ever since!

My graduate education was shaped in part by Ed’s influence on evolutionary biology, as I will elaborate below. My next personal interaction came near the end of my graduate career. I had constructed a mathematical model that provided support for the theory of group selection, which had been almost universally rejected by evolutionary biologists, as I will also elaborate below. Convinced of its importance, I wrote Ed asking if he would consider sponsoring it for the Proceedings of the National Academy of Sciences. Ed invited me to visit him at Harvard’s Museum of Comparative Zoology. As with my first encounter, I have a vivid memory of the visit, which began with a tour of his ant laboratory. Then he stood me in front of a blackboard, sat down in a chair, and said “you have 30 minutes until my next appointment.”

I talked like an auctioneer, filling the board with my equations. Ed was sufficiently intrigued to sponsor my article for PNAS after sending it out for review by two experts in theoretical biology. The article became my Ph.D. thesis, which is probably the shortest in the history of evolutionary science (four pages).

In the years that followed, I became one of the main advocates of group selection without directly crossing paths with Ed. I also took part in most of the other initiatives associated with Ed’s legacies without directly interacting with him. We were both involved in the formation of the Human Behavior and Evolution Society (HBES) and I hosted its third annual conference in 1993. On the theme of consilience, I started the first campus-wide program for teaching evolution across the curriculum and wrote one of the first book-length accounts of religion from an evolutionary perspective. It might seem strange that Ed and I shared so many interests without directly interacting, but just about everything associated with Ed’s legacies are in fact broad developments in the history of science involving many protagonists, a point to which I will return.

My next and by far most substantive interaction with Ed began at the 2006 annual conference of HBES. Ed was a plenary speaker and I was in the audience. Even though HBES members were in the avant-garde of studying human behavior from an evolutionary perspective, most of them were doctrinaire in their rejection of group selection. On his own, Ed had embraced group selection, converging on my own advocacy, and chose to break the news to the unsuspecting audience in his plenary. You could have heard a pin drop. Afterward, we found a corner of the lobby to talk alone.

“Did you like the grenade that I tossed in their midst?” Ed asked with a conspiratorial smile. On the spot, I suggested that we write a major article together, which became “Rethinking the Theoretical Foundation of Sociobiology”, published in the Quarterly Review of Biology in 2007. To reach a larger audience, we also wrote “Evolution for the Good of the Group”, which was published in the American Scientist in 2008. These were written by trading drafts and discussing them by email and phone. I still remember his voicemails, which sometimes went on for several minutes and were spoken in flawless extemporaneous prose.

At the end of our “Rethinking” article, we summarized our argument for group selection as the theoretical foundation of sociobiology by stealing from Rabbi Hillel, who was reputedly asked to explain the meaning of the Torah while standing on one foot and replied “What is hateful to you, do not do to your neighbor. Everything else is commentary.” Our one-foot version of sociobiology was: “Selfishness beats altruism within groups. Altruistic groups beat selfish groups. Everything else is commentary.” This meme has become widely known and Ed repeated it all the way up to his final publications and interviews.

After this intense collaboration, Ed and I went our separate ways to continue pursuing our largely overlapping interests. The last time I saw him was at a conference at MIT, which was close enough to his home that he could attend without arduous travel. In the few minutes that we spoke together, he told me excitedly about ecosystems as the next big topic that he planned to synthesize. He retained his youthful spirit of exploration right up to the end.

I have one more story about Ed to tell before turning to his six legacies. In 2014, the evolutionary psychologist Barry X. Kuhle recorded a series of interviews with pioneers of HBES, including both Ed and myself. Ed must have relished the opportunity to talk at a professional level with someone as well informed as Barry because his interview lasted two hours. I was president of the newly founded Evolution Institute and Editor in Chief of its online magazine This View of Life (TVOL), which was named after the final passage of Darwin’s On the Origin of Species (“There is grandeur in this view of life…”). I was eager to feature a print version of Barry’s interview with Ed on TVOL, so I offered to transcribe it myself. There is something about transcribing a recording, word by word, that burns it into your memory more than merely listening to the recording or reading the transcription. This experience adds to my knowledge of Ed and his legacies, along with his published work and my personal relationship with him.

The Six Legacies

History—including the history of science–is a complex systemic process involving many actors and environmental (including cultural) contingencies. Attention often becomes focused on a few key people, such Albert Einstein, Sigmund Freud, and B.F. Skinner, which under-represents the contributions of many dozens of others. Iconic status is thrust upon a person as much as actively sought by the person. There seems to be a need to personify ideas as a form of simplification, among the general public and even, to a degree, among the experts.  

A few evolutionary biologists such as Ed Wilson, Richard Dawkins, and the late Stephen Jay Gould have achieved this iconic status. Yes, they made outsized contributions as individuals, but they also represent something larger than themselves. I think that Ed would agree. In his book Sociobiology: The New Synthesis, for example, he was relying upon the work of many hundreds of scientists to support his claim that there can be a single theory of social behavior informed by evolution.

The world “catalyst” also bears examination. In chemistry, a catalyst is a substance that increases the rate of a chemical reaction without being used up in the process. The way a catalytic molecule works is by holding other molecules in an orientation that binds them to each other and releases the catalytic molecule to repeat the operation. A person can play a catalytic role in cultural change in much the same way. As we will see, Ed was a catalyst par excellence. He made things happen that otherwise would have occurred much more slowly or not at all.

Against this background, calling Ed an “icon” and a “catalyst” honors the individual while also going beyond the individual to examine systemic trends in the history of science. It is in this spirit that I will review his six legacies.     

1) His contributions to evolutionary biology.

Here is how Ed described his contribution to evolutionary biology in his interview with Barry Khule:

We have to go back to the 1950’s. In the 1950’s, the molecular revolution had begun. It was clear that the golden age of modern biology was going to be molecular and would endure a long time. In fact, it did occupy the second half of the 20th century and beyond. We felt here at Harvard immediately the pressure to start giving up positions to molecular biology. The Dean of the faculty and the President at that time were entirely in accord. We found—I say we, the organismic and evolutionary biologists here, comparative anatomists, comparative zoologists and so on–realized that we would not to be given much additional space anymore, that we probably would not get many if any new positions for a long time. They would be reserved to build up Harvard’s strength in molecular and cellular biology. What this did was have a tremendous impact on me personally because I realized…that those of us, my generation of what we came to call evolutionary biologists and organismic biologists, were not going to get anywhere by complaining by any means but we were going to have to—and we should be tremendously excited to plan this—develop an equivalent to molecular biology on our own. 

Ed then set about trying to modernize the biology of whole organisms, as part of a younger generation following the architects of the Modern Synthesis, which included names such as Ernst Mayr, Julian Huxley, and George Gaylord Simpson. This required finding and collaborating with people who had complementary expertise—especially the ability to build mathematical models of ecological and evolutionary processes. Names that Ed mentions as part of this younger generation include Robert MacArthur, Larry Slobodkin, and Richard Lewontin. These were some of the rock stars whose work I avidly read as a graduate student in the 1970s.

One of Ed’s most productive collaborations was with Robert MacArthur, an ecologist with mathematical training, leading to their landmark book The Theory of Island Biogeography, published by Princeton University Press in 1967 with Ed as the second author. What made the book so important was a theoretical framework that made sense of the great mass of natural history information on the distribution and abundance of species on islands—some of it collected by Ed for ant species around the world. The theory applied not only to actual islands but to all habitats that are island-like, such as mountains separated by valleys or patches of forest separated by deforested areas.  

While Ed played a prominent role in modernizing whole organism biology, he was by no means alone. Also during my time as a graduate student, a Nobel prize was awarded to Konrad Lorenz, Niko Tinbergen, and Carl von Frisch for pioneering the study of animal behavior and the geneticist Theodosius Dobzhansky titled an article for biology teachers “Nothing in biology makes sense except in the light of evolution”. Evolutionary theory was proving its explanatory scope and many people were taking part in the effort. What this meant to me as a graduate student was that I could choose any topic, begin asking intelligent questions based on evolutionary theory (often with the help of mathematical models), and then test my hypotheses on any appropriate organism. I didn’t need to become a taxonomic specialist and I could change topics at will. In short, I could become a polymath, based not on my personal attributes but on a theory that anyone can learn. This is the legacy of evolutionary biology, to which Ed made an outsized contribution.

2) His contributions to the conservation of biodiversity

As first and foremost a naturalist and ant taxonomic expert, Ed was passionate about the conservation of biological diversity and made room for it alongside his scientific career. His book Biophilia argued that we are genetically adapted to be surrounded by nature, with mental and physical health consequences if we are not. This bold conjecture has been largely supported by research. For example, hospital patients recover faster if their room has a window or is decorated with foliage and flowers.

Ed collaborated with Thomas Lovejoy, who coincidentally passed away just a day earlier at the age of 80, to preserve the biodiversity of the Amazon. According to a remembrance in the New Yorker magazine, it was they who coined the term biological diversity, which became shortened to biodiversity. They even drew upon the theory of Island Biogeography by studying the effect of the size of forest reserves on species loss.

With his gift for marketing whole disciplines and initiatives, Ed coined the term “Half Earth” for the goal of preserving half of the earth for nature and the other half for humankind—not in separation, but in a way that is interdigitated, so that humans can live within nature and nature can flow along corridors. Anyone who values nature should want to continue this legacy but doing so requires changing the minds and hearts of people, along with their cultural practices, in the real world.

3) His contributions to a sociobiology that includes humans

Ed’s 1975 book, Sociobiology: The New Synthesis, was in the same mold as Darwin’s “there is grandeur in his view of life” and Dobzhansky’s “nothing in biology makes sense except in the light of evolution”. Ed’s claim was that evolutionary theory provides a single conceptual toolkit for studying the social behaviors of all creatures great and small. Thanks to Ed’s gift for identifying whole fields of inquiry and writing for non-specialists, Sociobiology combined the authority of an academic tome with the look and feel of a coffee table book, complete with over 200 illustrations by the artist Sarah Landry. Thanks to his stature and gift for promotion, its publication was noted on the front page of the New York Times.

It was the last chapter on human social behavior that landed Ed in trouble and a systemic view of the history of science is needed to understand why. For all its explanatory scope, the study of evolution was restricted to genetic evolution for most of the 20th century, as if the only way that offspring can resemble their parents is by sharing the same genes. This is patently false when stated directly since it ignores the cultural transmission of traits entirely, but it essentially describes what became known as the modern synthesis and was consolidated by the molecular biology revolution described by Ed in his interview with Barry Kuhle.

What became of the study of cultural evolution? It was ceded to other disciplines in the human social sciences and humanities. Each discipline developed into a sophisticated body of knowledge, but not in reference and sometimes in perceived opposition to evolutionary theory. And all of those disciplines did not remotely become integrated with each other. Instead, they became an archipelago of knowledge with little communication among the islands. The lack of consilience for human-related knowledge stands in stark contrast with the consilience of biological knowledge, at least when it comes to genetic evolution.

Darwin’s theory is often said to have earned a bad reputation for itself in the human-related disciplines by providing a moral justification for inequality (Social Darwinism). The real history of Darwinism in relation to human affairs is more complex and interesting. Socialists such as Peter Kropotkin and progressive thinkers such as William James and John Dewey were inspired by Darwin along with “nature red and truth in claw” types. The bottom line is that any powerful tool can also be used as a weapon and Darwin’s theory is no different than any other theory in this regard.1

Returning to the reception to Sociobiology, when critics accused Ed of genetic determinism, they were absolutely right. The entire field of evolutionary biology was gene-centric and Ed was no exception. Yet, critics from the human social sciences and humanities had no synthesis of their own.

Only after the publication of Sociobiology did evolutionary thinkers begin to take cultural evolution seriously. Ed was among them with books such as On Human NatureGenes, Mind, and Culture (with Charles J. Lumsden), Promethean Fire (also with Lumsden), and The Social Conquest of Earth. Other major thinkers included Richard Dawkins and his concept of memes, Luigi Luca Cavalli-Sforza and Marcus Feldman (Cultural Transmission and Evolution), and Robert Boyd and Peter Richerson (Culture and the Evolutionary Process, Not By Genes Alone). The importance of symbolic thought began to occupy center stage with books such as The Symbolic Species by Terrence Deacon and Evolution in Four Dimensions by Eva Jablonka and Marion Lamb.

Today, Darwinian evolution is widely defined as any process that combines the three ingredients of variation, selection, and replication, no matter what the mechanism of replication. This definition is true to Darwin’s thought (since he knew nothing about genes) and can accommodate a plurality of inheritance mechanisms such as epigenetics (based on changes in gene expression rather than gene frequency), forms of social learning found in many species, and forms of symbolic thought that are distinctively human. While human cultural inheritance mechanisms evolved by genetic evolution, that doesn’t make them subordinate, as if genes hold cultures on a leash (one of Ed’s metaphors). On the contrary, as the faster evolutionary process, cultural evolution often takes the lead in adapting humans to their environments, with genetic evolution playing a following role (gene-culture co-evolution).

Part of the maturation of human cultural evolutionary theory is the recognition of group selection as an exceptionally strong force in human evolution—something else that Ed got right. According to Harvard evolutionary anthropologist Richard Wrangham in his book The Goodness Paradox, naked aggression is over 100 times more frequent in a chimpanzee community than in small-scale human communities. This is due largely to social control mechanisms in human communities that suppress bullying and other forms of disruptive self-serving behaviors so that cooperation becomes the primary social strategy (this is called a major evolutionary transition). Nearly everything distinctive about our species is a form of cooperation, including our ability to maintain an inventory of symbols with shared meaning that is transmitted across generations. Our capacity for symbolic thought became a full-blown inheritance system that operates alongside genetic inheritance (dual inheritance theory). Cultural evolution is a multilevel process, no less than genetic evolution, and the increasing scale of cooperation over the course of human history can be seen as a process of multilevel cultural evolution.

While the critique of genetic determinism was accurate for Sociobiology and evolutionary biology as a whole in 1975, this is no longer the case for the modern study of humans from an evolutionary perspective—which brings us to Ed’s next legacy.

4) His contributions to the unification of knowledge.

Something that can be said about Ed’s books is that they are all visionary—imagining whole new fields of inquiry—but vary in the degree to which Ed has made progress carrying out the vision. He made the most progress for ants and other social insects, of course, and Sociobiology reflected a thorough reading of the literature on animal social behaviors. A book such as Consilience, however, is long on vision and short on execution.

I do not intend this observation as a criticism. Ed had only 24 hours in a day, like the rest of us, and his visionary gaze is worthwhile even if the execution is left to others. In Consilience, the vision is “a conviction, far deeper than a mere working proposition, that the world is orderly and can be explained by a small number of natural laws (p4)”. While this vision stretches back to antiquity and includes knowledge of the physical world in addition to the living world, there is something about evolutionary theory that fulfills the vision for the living world in an extraordinary way. Here is how Ed describes his first encounter with evolutionary theory in the opening pages of Consilience. He’s an 18-year old kid newly arrived at the University of Alabama, with a passion for identifying plants and animals using field guides.

Then I discovered evolution. Suddenly—that is not too strong a word—I saw the world in a wholly new way. This epiphany I owed to my mentor Ralph Chermock, an intense, chain-smoking young assistant professor newly arrived in the provinces with a Ph.D. in entomology from Cornell University. After listening to me natter for a while about my lofty goal of classifying all the ants of Alabama, he handed me a copy of Ernst Mayr’s 1942 Systematics and the Origin of Species. Read it, he said, if you want to become a real biologist.

The thin volume in the plain blue cover was one of the New Synthesis works, uniting the nineteenth-century Darwinian theory of evolution and modern genetics. By giving a theoretical structure to natural history, it vastly expanded the Linnaean enterprise. A tumbler fell somewhere in my mind, and a door opened to a new world. I was enthralled, couldn’t stop thinking about the implications evolution has for classification and for the rest of biology. And for philosophy. And for just about everything. Static pattern slid into fluid process…A new enthusiasm surged through me. The animals and plants I loved so dearly reentered the stage as lead players in a grand drama. Natural history was validated as real science.

Coincidentally, Ernst Mayr’s Animal Species and Evolution was one of the first evolution books that I read as an undergraduate student. While it was not thin (811 pp!), I was similarly enthralled. Compare Ed’s epiphany with passages from Charles Darwin, such as “I can remember the very spot on the road…” and “he who understands the baboon would do more toward metaphysics than Locke”, which was scribbled in his notebook in 1838. There is something about the simplicity and generality of evolutionary theory that starts working at the very beginning, for Darwin as the originator and Ed Wilson as an unschooled kid. Now recall what I said about being a graduate student in the 1970s—that I could become a polymath, based not on my personal attributes but on a theory that anyone can learn. What this means is that by the 1970s, what Darwin and Ed glimpsed from the start was now proving itself for the length and breadth of the biological sciences. Every time an evolutionary biologist decides to switch to a new topic and/or organism–which happens all the time—consilience is being demonstrated in action.

The prospect that human-related knowledge can become unified in this way is both old and new. It was how Darwin thought and he originated group selection theory as much to explain human morality as “for the good of the group” traits in nonhuman species. But you can’t make sense of humanity without acknowledging its groupish nature and the importance of culturally transmitted symbolic meaning systems. As Emile Durkheim wisely put it: “Social life, then, in every aspect and throughout its history, is only possible thanks to a vast body of symbolism.” Only now are we in a position to synthesize human-related knowledge in the same way as biological knowledge, thanks to an expanded definition of Darwinism as any variation/selection/replication process. Ed’s vision in Consilience is right on and its fulfillment is now in progress.

5) His encouraging stance toward young scientists and other learners.

No remembrance of Ed would be complete without noting the way that he encouraged people to become scientists, to follow their hearts, and to cultivate a reverence for nature. Visit #eowilson on Twitter and you’ll find quotes such as these offered by those whose lives he touched.

“Adults . . . are prone to undervalue the mental growth that occurs during daydreaming and aimless wandering.” — The late great Edward O. Wilson

“Nature first, then theory. Love the organisms for themselves first, then strain for general explanations, and with good fortunes discoveries will follow.”

“You are capable of more than you know. Choose a goal that seems right for you and strive to be the best, however hard the path. Aim high. Behave honorably. Prepare to be alone at times, and to endure failure. Persist! The world needs all you can give.”

“Nature holds the key to our aesthetic, intellectual, cognitive and even spiritual satisfaction.

“There can be no purpose more enspiriting than to begin the age of restoration, reweaving the wondrous diversity of life that still surrounds us.”

“The evolutionary epic is the best myth we will ever have.”

“You teach me, I forget. You show me, I remember. You involve me, I understand.”

“Humanity is part of nature, a species that evolved among other species. The more closely we identify ourselves with the rest of life, the more quickly we will be able to discover the sources of human sensibility and acquire the knowledge on which an enduring ethic, a sense of preferred direction, can be built.”

Passages such as these spell the difference between science and a science-based worldview. By itself, science merely tells us what is. A worldview provides a sense of values and motivates action. A science-based worldview does this based on reverence of the natural world rather than a supernatural agency. Ed is remembered at least as much for the science-based worldview that he offered as his scientific discoveries.

6) Ecosystems as Ed’s final frontier

Ed’s next book was to be titled “Ecosystems and the Harmony of Nature”. I don’t know if it will be published posthumously but we can get a glimpse of what he had in mind from its title, a brief article on the E.O. Wilson Biodiversity Foundation website,2 and a short lecture on YouTube.3

In the article, Ed is quoted as saying: “We know that ecosystems, which are really what we are trying to protect–not just single species but ensembles of species that have come together and have reached the ability—sometimes over thousands or even in some places millions of years—have formed ecosystems that equilibrate. And we don’t really know how equilibration comes about.” Ed also encourages young people to join “the coming development of a new biological science, one of the next big things, which is ecosystem studies.”

I must confess that I am puzzled by these statements since the study of whole ecosystems dates back to the beginning of the 20th century and has become increasingly integrated with evolutionary ecology over the last 50 years. It turns out that multilevel selection theory is essential for understanding the nature of ecosystems, no less than single species societies. I will be fascinated to know if Ed has converged upon this conclusion.

To explain what I mean, a critical distinction needs to be made between two meanings of the term “complex adaptive system (CAS)”: A complex system that is adaptive as a system (CAS1), and a complex system composed of agents following their respective adaptive strategies (CAS2). A human society in the grip of civil war is an example of CAS2. It can be understood in terms of the conflicting interests of the warring factions, but it does not function well at the level of the whole society (CAS1) and no one would expect it to.

Many single-species societies in nature are like my human civil war example. Members of social groups are largely in conflict with each other and at most cooperate in specific contexts. We need look no further than chimpanzee communities for an example, where naked aggression is over 100 times more frequent than in small-scale human communities and the main context for community-wide cooperation is aggression against neighboring communities. Social strife in chimpanzee communities is stable—there is no reason to expect it to change, given the selection pressures that are operating—but that doesn’t make them harmonious or desirable from a human perspective.

Many multispecies ecosystems are also like this. For example, if you want to understand the nature of beaver ecosystems, ask the question “what’s in it for the beavers?” They are modifying the environment for their own benefit, flooding it to protect themselves from predators and eating the most palatable plants. Consequences for biodiversity and ecosystem processes such as nutrient cycling are collateral effects of beavers pursuing their interests. There is no reason to expect the whole ecosystem to be functionally organized and harmonious, any more than a chimpanzee community or a human society in the grip of civil war.

This is a hard lesson to learn about nature. We want it to be harmonious. Religious cosmologies often portray nature as harmonious (e.g., the Garden of Eden) except when disturbed by humans. The early study of ecosystems often treated them axiomatically as harmonious.  But Darwin’s theory of evolution tells a different story. It tells us that functional organization for any given system, at any given scale, requires a process of selection at that scale. That is the only way to achieve the status of CAS1 rather than merely CAS2, where functionally organized agents impose suffering on each other in the course of pursuing their respective adaptive strategies. That statement goes for human society, single-species animal societies, and multispecies ecosystems.   

Are there examples of whole ecosystems that have evolved into superorganisms? Yes! Microbiomes are an example. Every multicellular organism is not only a collection of mostly identical genes but also an ecosystem composed of trillions of microbes comprising thousands of species. When the host organisms differentially survive and reproduce, this is due in part to variation in their microbiomes along with variation in their genes. Thanks to selection at this level, microbiomes have evolved to be largely mutualistic with their hosts. There is also potential for selection among microbes within each host, however, leading to the evolution of pathogenic strains. It all depends on the level of selection.

Nowadays, whole forests are being imagined as mutualistic networks, with trees connected into a network by mycorrhizal fungi. Is such a thing possible? Yes, but only if selection has operated at the scale of whole forests with sufficient strength to counteract selection at lower scales. Otherwise, forests become merely CAS2 systems, composed of species that interact at cross purposes, rather than CAS1 systems.

Above all, it is important to avoid confusing “harmony” with “equilibrium”. Ecologists have started to use the word “regime” to describe stable assemblages of species. This is a well-chosen word because it evokes what we already know about human political regimes. All political regimes have a degree of stability, or we wouldn’t call them regimes, but they span the range from despotic (benefitting a few elites at the expense of everyone else) to inclusive (sharing their benefits with all citizens). Some of the worst regimes are also depressingly the most stable. Using the language of complex systems theory, there are multiple local stable equilibria and positive change requires escaping the gravitational pull of one local equilibrium to enter another local equilibrium. This requires active management and will not necessarily happen by itself. The management of ecosystems must itself be a human cultural evolutionary process informed by multilevel selection theory.

Combining the legacies

In this remembrance of Ed Wilson, I have tried to honor the person while also placing him in the context of broad trends in the history of science. Without mentioning Ed, we can say that Darwin’s theory of evolution has an amazing explanatory scope, that this scope was largely restricted to the study of genetic evolution for most of the 20th century, but now is rapidly expanding to include all aspects of humanity in addition to the rest of life. As I put it in my own book This View of Life: Completing the Darwinian Revolution, Dobzhansky’s statement “nothing in biology makes sense except in the light of evolution” can be extended to include everything associated with the words “human”, “culture”, and “policy”.

Without mentioning Ed, we can also say that evolutionary theory is capable of functioning as a worldview in addition to a body of scientific knowledge. Science only tells us what is, whereas a worldview inspires us psychologically and moves us to action. Creating a worldview informed entirely by science, as opposed to supernatural belief, is part of the enlightenment project that led to humanism as a philosophical worldview and social movement. While humanists accept Darwin’s theory as a matter of course, the recent developments that I have recounted have not been incorporated into the humanist movement for the most part. Thus, humanism and what it stands for is due for a renaissance, along with a renaissance of basic scientific knowledge.

Some simple calculations will help to put Ed’s career into historical perspective. Starting from when he received his Ph.D. in 1955 to his death in 2021, his career lasted for 66 years. If we mark the beginning of evolutionary science with the publication of Darwin’s On the Origin of Species in 1859, then Ed was present for 40% of the history of evolutionary thought. If we mark the beginning of the scientific revolution with the publication of Copernicus’s On the Revolution of the Heavenly Spheres in 1543, then Ed was present for 14% of the scientific revolution. As 20 years Ed’s junior, my numbers work out to 28% and 10% respectively.

These numbers remind us that evolutionary science and the scientific revolution are still works in progress. If science in general and evolutionary science, in particular, have revolutionized the way we see and therefore act upon the world, then we can look forward to further improvements in the near future. This leads to a form of hope and optimism, even in the darkest of times, that is part of Ed’s legacy.

For me, the next frontier is not just ecosystems but becoming wise stewards of evolution in all its forms. Variation/selection/replication processes are taking place all around us at different time scales, including genetic evolution, cultural evolution, and intra-generational personal evolution. Without wise stewardship, these evolutionary processes result merely in CAS2—complex systems composed of agents following their respective adaptive strategies, often inflicting harm on each other and on the entire system over the long term. Work is required to transform CAS2 into CAS1—systems that are adaptive as whole systems. This work will be required for all forms of positive change—individual, cultural, and ecosystemic. The ability to see this clearly and to act upon it has only become available during the last few decades and is currently shared by only a tiny fraction of those who need to know about it. Catalysis is needed, so that positive evolution can take place in a matter of years rather than decades or not at all. The best way to honor Ed’s combined legacies is to join in this catalysis.


[1] For more, see the TVOL special edition titled “Truth and Reconciliation for Social Darwinism”.



Por que somos a única espécie humana do planeta (El País)

Nuño Domínguez, 04 jul 2021 – 12:48 BRT

Três grandes descobertas feitas nos últimos dias nos obrigam a repensar as origens da humanidade

Três descobertas nos últimos dias acabam de mudar o que sabíamos sobre a origem da raça humana e da nossa própria espécie, Homo sapiens. Talvez − dizem alguns especialistas − precisemos abandonar esse conceito para nos referir a nós mesmos, pois as novas descobertas sugerem que somos uma criatura de Frankenstein com partes de outras espécies humanas com as quais, não muito tempo atrás, compartilhamos planeta, sexo e filhos.

As descobertas da última semana indicam que cerca de 200.000 anos atrás havia até oito espécies ou grupos humanos diferentes. Todos faziam parte do gênero Homo, que nos engloba. Os recém-chegados apresentam uma interessante mistura de traços primitivos − arcos enormes acima das sobrancelhas, cabeça achatada − e modernos. O “homem dragão” da China tinha uma capacidade craniana tão grande quanto a dos humanos atuais, ou até superior. O Homo de Nesher Ramla, encontrado em Israel, pode ter sido o que deu origem aos neandertais e aos denisovanos que ocuparam, respectivamente, a Europa e a Ásia e com quem nossa espécie teve repetidos encontros sexuais, dos quais nasceram filhos mestiços que foram aceitos em suas respectivas tribos como mais um.

Agora sabemos que devido àqueles cruzamentos todas as pessoas de fora da África têm 3% de DNA neandertal, ou que os habitantes do Tibete têm genes transmitidos pelos denisovanos para poder viver em grandes altitudes. Algo muito mais inquietante foi revelado pela análise genética das populações atuais da Nova Guiné: é possível que os denisovanos − um ramo irmão dos neandertais − tenham vivido até apenas 15.000 anos atrás, uma distância muito pequena em termos evolutivos.

A terceira grande descoberta dos últimos dias é quase detetivesca. Na análise de DNA conservado no solo da caverna de Denisova, na Sibéria, foi encontrado material genético dos humanos autóctones, os denisovanos, de neandertais e de sapiens em períodos tão próximos que poderiam até se sobrepor. Lá foram encontrados há três anos os restos do primeiro híbrido entre espécies humanas que se conhece: uma menina filha de uma neandertal e de um denisovano.

O paleoantropólogo Florent Detroit descobriu para a ciência outra dessas novas espécies humanas: o Homo luzonensis, que viveu em uma ilha das Filipinas há 67.000 anos e que apresenta uma estranha mistura de traços que poderiam ser o resultado de sua longa evolução em isolamento durante mais de um milhão de anos. É um pouco parecido com o que experimentou seu contemporâneo Homo floresiensis, ou “homem de Flores”, um humano de um metro e meio que viveu em uma ilha indonésia. Tinha um cérebro do tamanho do de um chimpanzé, mas se for aplicado a ele o teste de inteligência mais usado pelos paleoantropólogos, podemos dizer que era tão avançado quanto o sapiens, pois suas ferramentas de pedra eram igualmente evoluídas.

Imagem radiográfica da mandíbula do ‘Homo’ de Nesher Ramla descoberta em Israel.
Imagem radiográfica da mandíbula do ‘Homo’ de Nesher Ramla descoberta em Israel.Ariel Pokhojaev

A esses dois habitantes insulares se soma o Homo erectus, o primeiro Homo viajante que saiu da África há cerca de dois milhões de anos. Ele conquistou a Ásia e lá viveu até pelo menos 100.000 anos atrás. O oitavo passageiro desta história seria o Homo daliensis, um fóssil encontrado na China com uma mistura de erectus e sapiens, embora seja possível que acabe sendo incluído na nova linhagem do Homo longi.

“Não me surpreende que houvesse várias espécies humanas vivas ao mesmo tempo”, afirma Detroit. “Se considerarmos o último período geológico que começou há 2,5 milhões de anos, sempre houve diferentes gêneros e espécies de hominídeos compartilhando o planeta. A grande exceção é a atualidade, nunca havia existido apenas uma espécie humana na Terra”, reconhece. Por que nós, os sapiens, somos os únicos sobreviventes?

Para Juan Luis Arsuaga, paleoantropólogo do sítio arqueológico de Atapuerca, no norte da Espanha, a resposta é que “somos uma espécie hipersocial, os únicos capazes de construir laços além do parentesco, ao contrário dos demais mamíferos”. “Compartilhamos ficções consensuais como pátria, religião, língua, times de futebol; e chegamos a sacrificar muitas coisas por elas”, assinala. Nem mesmo a espécie humana mais próxima de nós, os neandertais, que criavam adornos, símbolos e arte, tinham esse comportamento. Arsuaga resume assim: “Os neandertais não tinham bandeira”. Por razões ainda desconhecidas, essa espécie se extinguiu há cerca de 40.000 anos.

Os sapiens não eram “estritamente superiores” a seus congêneres, opina Antonio Rosas, paleoantropólogo do Conselho Superior de Pesquisas Científicas da Espanha. “Agora sabemos que somos o resultado de hibridações com outras espécies, e o conjunto de características que temos foi o perfeito para aquele momento”, explica. Uma possível vantagem adicional é que os grupos sapiens eram mais numerosos que os neandertais, o que significa menos endogamia e melhor saúde das populações.

Detroit acredita que parte da explicação está na própria essência da nossa espécie sapiens, “sábio” em latim. “Temos um cérebro enorme que devemos alimentar, por isso precisamos de muitos recursos e, portanto, de muito território”, assinala. “O Homo sapiens teve uma expansão demográfica enorme e é bem possível que a disputa pelo território fosse muito dura para as demais espécies”, acrescenta.

María Martinón-Torres, diretora do Centro Nacional de Pesquisa sobre Evolução Humana, com sede em Burgos, acredita que o segredo seja a “hiperadaptabilidade”. “A nossa é uma espécie invasiva, não necessariamente mal-intencionada, mas somos como o cavalo de Átila da evolução”, compara. “Por onde passamos, e com nosso estilo de vida, diminui a diversidade biológica, incluindo a humana. Somos uma das forças ecológicas de maior impacto do planeta e essa história, a nossa, começou a se delinear no Pleistoceno [o período que começou há 2,5 milhões de anos e terminou há cerca de 10.000, quando o sapiens já era a única espécie humana que restava no planeta]”, acrescenta.

As descobertas dos últimos dias voltam a expor um problema crescente: os cientistas estão denominando cada vez mais espécies humanas. Tem sentido fazer isso? Para o paleoantropólogo israelense Israel Hershkovitz, autor da descoberta do Homo de Nesher Ramla, não. “Há muitas espécies”, afirma. “A definição clássica diz que duas espécies diferentes não podem ter filhos férteis. O DNA nos diz que sapiens, neandertais e denisovanos tiveram, por isso deveriam ser considerados a mesma espécie”, aponta.

“Se somos sapiens, então essas espécies que são nossos ancestrais por meio da miscigenação também são”, reforça João Zilhão, professor da Instituição Catalã de Pesquisa e Estudos Avançados na Universidade de Barcelona.

Essa questão é objeto de discórdia entre especialistas. “A hibridação é muito comum em espécies atuais, especialmente no mundo vegetal”, lembra José María Bermúdez de Castro, codiretor das pesquisas em Atapuerca. “Pode-se matizar o conceito de espécie, mas acho que não podemos abandoná-lo, porque é muito útil para podermos nos entender”, ressalta.

Escavações no sítio arqueológico de Nesher Ramla.
Escavações no sítio arqueológico de Nesher Ramla. Zaidner

Muitas nuances entram em jogo nessa questão. A evidente diferença entre sapiens e neandertais não é a mesma coisa que a identidade como espécie do Homo luzonensis, do qual só conhecemos alguns poucos ossos e dentes, ou dos denisovanos, dos quais a maioria das informações vem do DNA extraído de fósseis minúsculos.

“Curiosamente, apesar dos cruzamentos frequentes, tanto os sapiens como os neandertais foram espécies perfeitamente reconhecíveis e distinguíveis até o fim”, destaca Martinón-Torres. “Os traços do neandertal tardio são mais marcados que os dos anteriores, em vez de terem se apagado como consequência do cruzamento. Houve trocas biológicas, e talvez culturais também, mas nenhuma das espécies deixou de ser ela, distintiva, reconhecível em sua biologia, seu aspecto, suas adaptações específicas, seu nicho ecológico ao longo de sua história evolutiva. Acredito que esse é o melhor exemplo de que a hibridação não colide necessariamente com o conceito de espécie”, conclui. Seu colega Hershkovitz alerta que o debate continuará: “Estamos fazendo escavações em outras três cavernas em Israel onde encontramos fósseis humanos que nos darão uma nova perspectiva sobre a evolução humana”.

Greater than the sum of our parts: The evolution of collective intelligence (EurekaAlert!)

News Release 15-Jun-2021

University of Cambridge

Research News

The period preceding the emergence of behaviourally modern humans was characterised by dramatic climatic and environmental variability – it is these pressures, occurring over hundreds of thousands of years that shaped human evolution.

New research published today in the Cambridge Archaeological Journal proposes a new theory of human cognitive evolution entitled ‘Complementary Cognition’ which suggests that in adapting to dramatic environmental and climactic variabilities our ancestors evolved to specialise in different, but complementary, ways of thinking.

Lead author Dr Helen Taylor, Research Associate at the University of Strathclyde and Affiliated Scholar at the McDonald Institute for Archaeological Research, University of Cambridge, explained: “This system of complementary cognition functions in a way that is similar to evolution at the genetic level but instead of underlying physical adaptation, may underlay our species’ immense ability to create behavioural, cultural and technological adaptations. It provides insights into the evolution of uniquely human adaptations like language suggesting that this evolved in concert with specialisation in human cognition.”

The theory of complementary cognition proposes that our species cooperatively adapt and evolve culturally through a system of collective cognitive search alongside genetic search which enables phenotypic adaptation (Darwin’s theory of evolution through natural selection can be interpreted as a ‘search’ process) and cognitive search which enables behavioural adaptation.

Dr Taylor continued, “Each of these search systems is essentially a way of adapting using a mixture of building on and exploiting past solutions and exploring to update them; as a consequence, we see evolution in those solutions over time. This is the first study to explore the notion that individual members of our species are neurocognitively specialised in complementary cognitive search strategies.”

Complementary cognition could lie at the core of explaining the exceptional level of cultural adaptation in our species and provides an explanatory framework for the emergence of language. Language can be viewed as evolving both as a means of facilitating cooperative search and as an inheritance mechanism for sharing the more complex results of complementary cognitive search. Language is viewed as an integral part of the system of complementary cognition.

The theory of complementary cognition brings together observations from disparate disciplines, showing that they can be viewed as various faces of the same underlying phenomenon.

Dr Taylor continued: “For example, a form of cognition currently viewed as a disorder, dyslexia, is shown to be a neurocognitive specialisation whose nature in turn predicts that our species evolved in a highly variable environment. This concurs with the conclusions of many other disciplines including palaeoarchaeological evidence confirming that the crucible of our species’ evolution was highly variable.”

Nick Posford, CEO, British Dyslexia Association said, “As the leading charity for dyslexia, we welcome Dr Helen Taylor’s ground-breaking research on the evolution of complementary cognition. Whilst our current education and work environments are often not designed to make the most of dyslexia-associated thinking, we hope this research provides a starting point for further exploration of the economic, cultural and social benefits the whole of society can gain from the unique abilities of people with dyslexia.”

At the same time, this may also provide insights into understanding the kind of cumulative cultural evolution seen in our species. Specialisation in complementary search strategies and cooperatively adapting would have vastly increased the ability of human groups to produce adaptive knowledge, enabling us to continually adapt to highly variable conditions. But in periods of greater stability and abundance when adaptive knowledge did not become obsolete at such a rate, it would have instead accumulated, and as such Complementary Cognition may also be a key factor in explaining cumulative cultural evolution.

Complementary cognition has enabled us to adapt to different environments, and may be at the heart of our species’ success, enabling us to adapt much faster and more effectively than any other highly complex organism. However, this may also be our species’ greatest vulnerability.

Dr Taylor concluded: “The impact of human activity on the environment is the most pressing and stark example of this. The challenge of collaborating and cooperatively adapting at scale creates many difficulties and we may have unwittingly put in place a number of cultural systems and practices, particularly in education, which are undermining our ability to adapt. These self-imposed limitations disrupt our complementary cognitive search capability and may restrict our capacity to find and act upon innovative and creative solutions.”

“Complementary cognition should be seen as a starting point in exploring a rich area of human evolution and as a valuable tool in helping to create an adaptive and sustainable society. Our species may owe our spectacular technological and cultural achievements to neurocognitive specialisation and cooperative cognitive search, but our adaptive success so far may belie the importance of attaining an equilibrium of approaches. If this system becomes maladjusted, it can quickly lead to equally spectacular failures to adapt – and to survive, it is critical that this system be explored and understood further.”

Humans were apex predators for two million years (Eureka Alert!)

News Release 5-Apr-2021

What did our ancestors eat during the stone age? Mostly meat

Tel-Aviv University

IMAGE: Human Brain. Credit: Dr. Miki Ben Dor

Researchers at Tel Aviv University were able to reconstruct the nutrition of stone age humans. In a paper published in the Yearbook of the American Physical Anthropology Association, Dr. Miki Ben-Dor and Prof. Ran Barkai of the Jacob M. Alkov Department of Archaeology at Tel Aviv University, together with Raphael Sirtoli of Portugal, show that humans were an apex predator for about two million years. Only the extinction of larger animals (megafauna) in various parts of the world, and the decline of animal food sources toward the end of the stone age, led humans to gradually increase the vegetable element in their nutrition, until finally they had no choice but to domesticate both plants and animals – and became farmers.

“So far, attempts to reconstruct the diet of stone-age humans were mostly based on comparisons to 20th century hunter-gatherer societies,” explains Dr. Ben-Dor. “This comparison is futile, however, because two million years ago hunter-gatherer societies could hunt and consume elephants and other large animals – while today’s hunter gatherers do not have access to such bounty. The entire ecosystem has changed, and conditions cannot be compared. We decided to use other methods to reconstruct the diet of stone-age humans: to examine the memory preserved in our own bodies, our metabolism, genetics and physical build. Human behavior changes rapidly, but evolution is slow. The body remembers.”

In a process unprecedented in its extent, Dr. Ben-Dor and his colleagues collected about 25 lines of evidence from about 400 scientific papers from different scientific disciplines, dealing with the focal question: Were stone-age humans specialized carnivores or were they generalist omnivores? Most evidence was found in research on current biology, namely genetics, metabolism, physiology and morphology.

“One prominent example is the acidity of the human stomach,” says Dr. Ben-Dor. “The acidity in our stomach is high when compared to omnivores and even to other predators. Producing and maintaining strong acidity require large amounts of energy, and its existence is evidence for consuming animal products. Strong acidity provides protection from harmful bacteria found in meat, and prehistoric humans, hunting large animals whose meat sufficed for days or even weeks, often consumed old meat containing large quantities of bacteria, and thus needed to maintain a high level of acidity. Another indication of being predators is the structure of the fat cells in our bodies. In the bodies of omnivores, fat is stored in a relatively small number of large fat cells, while in predators, including humans, it’s the other way around: we have a much larger number of smaller fat cells. Significant evidence for the evolution of humans as predators has also been found in our genome. For example, geneticists have concluded that “areas of the human genome were closed off to enable a fat-rich diet, while in chimpanzees, areas of the genome were opened to enable a sugar-rich diet.”

Evidence from human biology was supplemented by archaeological evidence. For instance, research on stable isotopes in the bones of prehistoric humans, as well as hunting practices unique to humans, show that humans specialized in hunting large and medium-sized animals with high fat content. Comparing humans to large social predators of today, all of whom hunt large animals and obtain more than 70% of their energy from animal sources, reinforced the conclusion that humans specialized in hunting large animals and were in fact hypercarnivores.

“Hunting large animals is not an afternoon hobby,” says Dr. Ben-Dor. “It requires a great deal of knowledge, and lions and hyenas attain these abilities after long years of learning. Clearly, the remains of large animals found in countless archaeological sites are the result of humans’ high expertise as hunters of large animals. Many researchers who study the extinction of the large animals agree that hunting by humans played a major role in this extinction – and there is no better proof of humans’ specialization in hunting large animals. Most probably, like in current-day predators, hunting itself was a focal human activity throughout most of human evolution. Other archaeological evidence – like the fact that specialized tools for obtaining and processing vegetable foods only appeared in the later stages of human evolution – also supports the centrality of large animals in the human diet, throughout most of human history.”

The multidisciplinary reconstruction conducted by TAU researchers for almost a decade proposes a complete change of paradigm in the understanding of human evolution. Contrary to the widespread hypothesis that humans owe their evolution and survival to their dietary flexibility, which allowed them to combine the hunting of animals with vegetable foods, the picture emerging here is of humans evolving mostly as predators of large animals.

“Archaeological evidence does not overlook the fact that stone-age humans also consumed plants,” adds Dr. Ben-Dor. “But according to the findings of this study plants only became a major component of the human diet toward the end of the era.”

Evidence of genetic changes and the appearance of unique stone tools for processing plants led the researchers to conclude that, starting about 85,000 years ago in Africa, and about 40,000 years ago in Europe and Asia, a gradual rise occurred in the consumption of plant foods as well as dietary diversity – in accordance with varying ecological conditions. This rise was accompanied by an increase in the local uniqueness of the stone tool culture, which is similar to the diversity of material cultures in 20th-century hunter-gatherer societies. In contrast, during the two million years when, according to the researchers, humans were apex predators, long periods of similarity and continuity were observed in stone tools, regardless of local ecological conditions.

“Our study addresses a very great current controversy – both scientific and non-scientific,” says Prof. Barkai. “For many people today, the Paleolithic diet is a critical issue, not only with regard to the past, but also concerning the present and future. It is hard to convince a devout vegetarian that his/her ancestors were not vegetarians, and people tend to confuse personal beliefs with scientific reality. Our study is both multidisciplinary and interdisciplinary. We propose a picture that is unprecedented in its inclusiveness and breadth, which clearly shows that humans were initially apex predators, who specialized in hunting large animals. As Darwin discovered, the adaptation of species to obtaining and digesting their food is the main source of evolutionary changes, and thus the claim that humans were apex predators throughout most of their development may provide a broad basis for fundamental insights on the biological and cultural evolution of humans.”

Israeli Archaeologists Present Groundbreaking Universal Theory of Human Evolution (Haaretz)

Tel Aviv University archaeologists Miki Ben-Dor and Ran Barkai proffer novel hypothesis, showing how the greed of Homo erectus set us careening down an anomalous evolutionary path

Ruth Schuster, Feb. 25, 2021

Why the human brain evolved as it did never has been plausibly explained. Apparently, not since the first life-form billions of years ago did a single species gain dominance over all others – until we came along. Now, in a groundbreaking paper, two Israeli researchers propose that our anomalous evolution was propelled by the very mass extinctions we helped cause. Or: As we sawed off the culinary branches from which we swung, we had to get ever more inventive in order to survive.

As ambling, slow-to-reproduce large animals diminished and gradually went extinct, we were forced to resort to smaller, nimbler animals that flee as a strategy to escape predation. To catch them, we had to get smarter, nimbler and faster, according to the universal theory of human evolution proposed by researchers Miki Ben-Dor and Prof. Ran Barkai of Tel Aviv University, in a paper published in the journal Quaternary.

In fact, the great African megafauna began to decline about 4.6 million years ago. But our story begins with Homo habilis, which lived about 2.6 million years ago and apparently used crude stone tools to help it eat flesh, and with Homo erectus, which thronged Africa and expanded to Eurasia about 2 million years ago. The thing is, erectus wasn’t an omnivore: it was a carnivore, Ben-Dor explains to Haaretz.

“Eighty percent of mammals are omnivores but still specialize in a narrow food range. If anything, it seems Homo erectus was a hyper-carnivore,” he observes.

And in the last couple of million years, our brains grew threefold to a maximum capacity of about 1,500 cranial capacity, a size achieved about 300,000 years ago. We also gradually but consistently ramped up in technology and culture – until the Neolithic revolution and advent of the sedentary lifestyle, when our brains shrank to about 1,400 to 1,300cc, but more on that anomaly later.

The hypothesis suggested by Ben-Dor and Barkai – that we ate our way to our present physical, cultural and ecological state – is an original unifying explanation for the behavioral, physiological and cultural evolution of the human species.

Out of chaos

Evolution is chaotic. Charles Darwin came up with the theory of the survival of the fittest, and nobody has a better suggestion yet, but mutations aren’t “planned.” Bodies aren’t “designed,” if we leave genetic engineering out of it. The point is, evolution isn’t linear but chaotic, and that should theoretically apply to humans too.

Hence, it is strange that certain changes in the course of millions of years of human history, including the expansion of our brain, tool manufacture techniques and use of fire, for example, were uncharacteristically progressive, say Ben-Dor and Barkai.

“Uncharacteristically progressive” means that certain traits such as brain size, or cultural developments such as fire usage, evolved in one direction over a long time, in the direction of escalation. That isn’t what chaos is expected to produce over vast spans of time, Barkai explains to Haaretz: it is bizarre. Very few parameters behave like that.

So, their discovery of correlation between contraction of the average weight of African animals, the extinction of megafauna and the development of the human brain is intriguing.

From mammoth marrow to joint of rat

To be clear, just this month a new paper posited that the late Quaternary extinction of megafauna, in the last few tens of thousands of years, wasn’t entirely the fault of humanity. In North America specifically, it was due primarily to climate change, with the late-arriving humans apparently providing the coup de grâce to some species.

In the Old World, however, a human role is clearer. African megafauna apparently began to decline 4.6 million years ago, but during the Pleistocene (2.6 million to 11,600 years ago) the size of African animals trended sharply down, in what the authors term an abrupt reversal from a continuous growth trend of 65 million years (i.e., since the dinosaurs almost died out).

When Homo erectus the carnivore began to roam Africa around 2 million years ago, land mammals averaged nearly 500 kilograms. Barkai’s team and others have demonstrated that hominins ate elephants and large animals when they could. In fact, originally Africa had six elephant species (today there are two: the bush elephant and forest elephant). By the end of the Pleistocene, by which time all hominins other than modern humans were extinct too, that average weight of the African animal had shrunk by more than 90 percent.

And during the Pleistocene, as the African animals shrank, the Homo genus grew taller and more gracile, and our stone tool technology improved (which in no way diminished our affection for archaic implements like the hand ax or chopper, both of which remained in use for more than a million years, even as more sophisticated technologies were developed).

If we started some 3.3 million years ago with large, crude stone hammers that may have been used to bang big animals on the head or break bones to get at the marrow, over the epochs we invented the spear for remote slaughter. By about 80,000 years ago, the bow and arrow was making its appearance, which was more suitable for bringing down small fry like small deer and birds. Over a million years ago, we began to use fire, and later achieved better control of it, meaning the ability to ignite it at will. Later we domesticated the dog from the wolf, and it would help us hunt smaller, fleet animals.

Why did the earliest humans hunt large animals anyway? Wouldn’t a peeved elephant be more dangerous than a rat? Arguably, but catching one elephant is easier than catching a large number of rats. And megafauna had more fat.

A modern human can only derive up to about 50 percent of calories from lean meat (protein): past a certain point, our livers can’t digest more protein. We need energy from carbs or fat, but before developing agriculture about 10,000 years ago, a key source of calories had to be animal fat.

Big animals have a lot of fat. Small animals don’t. In Africa and Europe, and in Israel too, the researchers found a significant decline in the prevalence of animals weighing over 200 kilograms correlated to an increase in the volume of the human brain. Thus, Ben-Dor and Barkai deduce that the declining availability of large prey seems to have been a key element in the natural selection from Homo erectus onward. Catching one elephant is more efficient than catching 1,000 rabbits, but if we must catch 1,000 rabbits, improved cunning, planning and tools are in order.

Say it with fat

Our changing hunting habits would have had cultural impacts too, Ben-Dor and Barkai posit. “Cultural evolution in archaeology usually refers to objects, such as stone tools,” Ben-Dor tells Haaretz. But cultural evolution also refers to learned behavior, such as our choice of which animals to hunt, and how.

Thus, they posit, our hunting conundrum may have also been a key element to that enigmatic human characteristic: complex language. When language began, with what ancestor of Homo sapiens, if any before us, is hotly debated.

Ben-Dor, an economist by training prior to obtaining a Ph.D. in archaeology, believes it began early. “We just need to follow the money. When speaking of evolution, one must follow the energy. Language is energetically costly. Speaking requires devotion of part of the brain, which is costly. Our brain consumes huge amounts of energy. It’s an investment, and language has to produce enough benefit to make it worthwhile. What did language bring us? It had to be more energetically efficient hunting.”

Domestication of the dog also requires resources and, therefore, also had to bring sufficient compensation in the form of more efficient hunting of smaller animals, he points out. That may help explain the fact that Neolithic humans not only embraced the dog but ate it too, going by archaeological evidence of butchered dogs.

At the end of the day, wherever we went, humans devastated the local ecologies, given enough time.

There is a lot of thinking about the Neolithic agricultural revolution. Some think grain farming was driven by the desire to make beer. Given residue analysis indicating that it’s been around for over 10,000 years, that theory isn’t as far-fetched as one might think. Ben-Dor and Barkai suggest that once we could grow our own food and husband herbivores, the megafauna almost entirely gone, hunting for them became too energy-costly. So we had to use our large brains to develop agriculture.

And as the hunter-gathering lifestyle gave way to permanent settlement, our brain size decreased.

Note, Ben-Dor adds, that the brains of wolves which have to hunt to survive are larger than the brain of the domesticated wolf, i.e., dogs. We did promise more on that. That was it. Also: The chimpanzee brain has remained stable for 7 million years, since the split with the Homo line, Barkai points out.

“Why does any of this matter?” Ben-Dor asks. “People think humans reached this condition because it was ‘meant to be.’ But in the Earth’s 4.5 billion years, there have been billions of species. They rose and fell. What’s the probability that we would take over the world? It’s an accident of nature. It never happened before that one species achieved dominance over all, and now it’s all over. How did that happen? This is the answer: A non-carnivore entered the niche of carnivore, and ate out its niche. We can’t eat that much protein: we need fat too. Because we needed the fat, we began with the big animals. We hunted the prime adult animals which have more fat than the kiddies and the old. We wiped out the prime adults who were crucial to survival of species. Because of our need for fat, we wiped out the animals we depended on. And this required us to keep getting smarter and smarter, and thus we took over the world.”