The horse is a prey animal, the human a predator. Our shared trust and athleticism is a neurobiological miracle
Janet Jones – 14 January 2022
Horse-and-human teams perform complex manoeuvres in competitions of all sorts. Together, we can gallop up to obstacles standing 8 feet (2.4 metres) high, leave the ground, and fly blind – neither party able to see over the top until after the leap has been initiated. Adopting a flatter trajectory with greater speed, horse and human sail over broad jumps up to 27 feet (more than 8 metres) long. We run as one at speeds of 44 miles per hour (nearly 70 km/h), the fastest velocity any land mammal carrying a rider can achieve. In freestyle dressage events, we dance in place to the rhythm of music, trot sideways across the centre of an arena with huge leg-crossing steps, and canter in pirouettes with the horse’s front feet circling her hindquarters. Galloping again, the best horse-and-human teams can slide 65 feet (nearly 20 metres) to a halt while resting all their combined weight on the horse’s hind legs. Endurance races over extremely rugged terrain test horses and riders in journeys that traverse up to 500 miles (805 km) of high-risk adventure.
No one disputes the athleticism fuelling these triumphs, but few people comprehend the mutual cross-species interaction that is required to accomplish them. The average horse weighs 1,200 pounds (more than 540 kg), makes instantaneous movements, and can become hysterical in a heartbeat. Even the strongest human is unable to force a horse to do anything she doesn’t want to do. Nor do good riders allow the use of force in training our magnificent animals. Instead, we hold ourselves to the higher standard of motivating horses to cooperate freely with us in achieving the goals of elite sports as well as mundane chores. Under these conditions, the horse trained with kindness, expertise and encouragement is a willing, equal participant in the action.
That action is rooted in embodied perception and the brain. In mounted teams, horses, with prey brains, and humans, with predator brains, share largely invisible signals via mutual body language. These signals are received and transmitted through peripheral nerves leading to each party’s spinal cord. Upon arrival in each brain, they are interpreted, and a learned response is generated. It, too, is transmitted through the spinal cord and nerves. This collaborative neural action forms a feedback loop, allowing communication from brain to brain in real time. Such conversations allow horse and human to achieve their immediate goals in athletic performance and everyday life. In a very real sense, each species’ mind is extended beyond its own skin into the mind of another, with physical interaction becoming a kind of neural dance.
Horses in nature display certain behaviours that tempt observers to wonder whether competitive manoeuvres truly require mutual communication with human riders. For example, the feral horse occasionally hops over a stream to reach good food or scrambles up a slope of granite to escape predators. These manoeuvres might be thought the precursors to jumping or rugged trail riding. If so, we might imagine that the performance horse’s extreme athletic feats are innate, with the rider merely a passenger steering from above. If that were the case, little requirement would exist for real-time communication between horse and human brains.
In fact, though, the feral hop is nothing like the trained leap over a competition jump, usually commenced from short distances at high speed. Today’s Grand Prix jump course comprises about 15 obstacles set at sharp angles to each other, each more than 5 feet high and more than 6 feet wide (1.5 x 1.8 metres). The horse-and-human team must complete this course in 80 or 90 seconds, a time allowance that makes for acute turns, diagonal flight paths and high-speed exits. Comparing the wilderness hop with the show jump is like associating a flintstone with a nuclear bomb. Horses and riders undergo many years of daily training to achieve this level of performance, and their brains share neural impulses throughout each experience.
These examples originate in elite levels of horse sport, but the same sort of interaction occurs in pastures, arenas and on simple trails all over the world. Any horse-and-human team can develop deep bonds of mutual trust, and learn to communicate using body language, knowledge and empathy.
Like it or not, we are the horse’s evolutionary enemy, yet they behave toward us as if inclined to become a friend
The critical component of the horse in nature, and her ability to learn how to interact so precisely with a human rider, is not her physical athleticism but her brain. The first precise magnetic resonance image of a horse’s brain appeared only in 2019, allowing veterinary neurologists far greater insight into the anatomy underlying equine mental function. As this new information is disseminated to horse trainers and riders for practical application, we see the beginnings of a revolution in brain-based horsemanship. Not only will this revolution drive competition to higher summits of success, and animal welfare to more humane levels of understanding, it will also motivate scientists to research the unique compatibility between prey and predator brains. Nowhere else in nature do we see such intense and intimate collaboration between two such disparate minds.
Three natural features of the equine brain are especially important when it comes to mind-melding with humans. First, the horse’s brain provides astounding touch detection. Receptor cells in the horse’s skin and muscles transduce – or convert – external pressure, temperature and body position to neural impulses that the horse’s brain can understand. They accomplish this with exquisite sensitivity: the average horse can detect less pressure against her skin than even a human fingertip can.
Second, horses in nature use body language as a primary medium of daily communication with each other. An alpha mare has only to flick an ear toward a subordinate to get him to move away from her food. A younger subordinate, untutored in the ear flick, receives stronger body language – two flattened ears and a bite that draws blood. The notion of animals in nature as kind, gentle creatures who never hurt each other is a myth.
Third, by nature, the equine brain is a learning machine. Untrammelled by the social and cognitive baggage that human brains carry, horses learn in a rapid, pure form that allows them to be taught the meanings of various human cues that shape equine behaviour in the moment. Taken together, the horse’s exceptional touch sensitivity, natural reliance on body language, and purity of learning form the tripod of support for brain-to-brain communication that is so critical in extreme performance.
One of the reasons for budding scientific fascination with neural horse-and-human communication is the horse’s status as a prey animal. Their brains and bodies evolved to survive completely different pressures than our human physiologies. For example, horse eyes are set on either side of their head for a panoramic view of the world, and their horizontal pupils allow clear sight along the horizon but fuzzy vision above and below. Their eyes rotate to maintain clarity along the horizon when their heads lie sideways to reach grass in odd locations. Equine brains are also hardwired to stream commands directly from the perception of environmental danger to the motor cortex where instant evasion is carried out. All of these features evolved to allow the horse to survive predators.
Conversely, human brains evolved in part for the purpose of predation – hunting, chasing, planning… yes, even killing – with front-facing eyes, superb depth perception, and a prefrontal cortex for strategy and reason. Like it or not, we are the horse’s evolutionary enemy, yet they behave toward us as if inclined to become a friend.
The fact that horses and humans can communicate neurally without the external mediation of language or equipment is critical to our ability to initiate the cellular dance between brains. Saddles and bridles are used for comfort and safety, but bareback and bridleless competitions prove they aren’t necessary for highly trained brain-to-brain communication. Scientific efforts to communicate with predators such as dogs and apes have often been hobbled by the use of artificial media including human speech, sign language or symbolic lexigram. By contrast, horses allow us to apply a medium of communication that is completely natural to their lives in the wild and in captivity.
The horse’s prey brain is designed to notice and evade predators. How ironic, and how riveting, then, that this prey brain is the only one today that shares neural communication with a predator brain. It offers humanity a rare view into a prey animal’s world, almost as if we were wolves riding elk or coyotes mind-melding with cottontail bunnies.
Highly trained horses and riders send and receive neural signals using subtle body language. For example, a rider can apply invisible pressure with her left inner calf muscle to move the horse laterally to the right. That pressure is felt on the horse’s side, in his skin and muscle, via proprioceptive receptor cells that detect body position and movement. Then the signal is transduced from mechanical pressure to electrochemical impulse, and conducted up peripheral nerves to the horse’s spinal cord. Finally, it reaches the somatosensory cortex, the region of the brain responsible for interpreting sensory information.
Riders can sometimes guess that an invisible object exists by detecting subtle equine reactions
This interpretation is dependent on the horse’s knowledge that a particular body signal – for example, inward pressure from a rider’s left calf – is associated with a specific equine behaviour. Horse trainers spend years teaching their mounts these associations. In the present example, the horse has learned that this particular amount of pressure, at this speed and location, under these circumstances, means ‘move sideways to the right’. If the horse is properly trained, his motor cortex causes exactly that movement to occur.
By means of our human motion and position sensors, the rider’s brain now senses that the horse has changed his path rightward. Depending on the manoeuvre our rider plans to complete, she will then execute invisible cues to extend or collect the horse’s stride as he approaches a jump that is now centred in his vision, plant his right hind leg and spin in a tight fast circle, push hard off his hindquarters to chase a cow, or any number of other movements. These cues are combined to form that mutual neural dance, occurring in real time, and dependent on natural body language alone.
The example of a horse moving a few steps rightward off the rider’s left leg is extremely simplistic. When you imagine a horse and rider clearing a puissance wall of 7.5 feet (2.4 metres), think of the countless receptor cells transmitting bodily cues between both brains during approach, flight and exit. That is mutual brain-to-brain communication. Horse and human converse via body language to such an extreme degree that they are able to accomplish amazing acts of understanding and athleticism. Each of their minds has extended into the other’s, sending and receiving signals as if one united brain were controlling both bodies.
Analysis of brain-to-brain communication between horses and humans elicits several new ideas worthy of scientific notice. Because our minds interact so well using neural networks, horses and humans might learn to borrow neural signals from the party whose brain offers the highest function. For example, horses have a 340-degree range of view when holding their heads still, compared with a paltry 90-degree range in humans. Therefore, horses can see many objects that are invisible to their riders. Yet riders can sometimes guess that an invisible object exists by detecting subtle equine reactions.
Specifically, neural signals from the horse’s eyes carry the shape of an object to his brain. Those signals are transferred to the rider’s brain by a well-established route: equine receptor cells in the retina lead to equine detector cells in the visual cortex, which elicits an equine motor reaction that is then sensed by the rider’s human body. From there, the horse’s neural signals are transmitted up the rider’s spinal cord to the rider’s brain, and a perceptual communication loop is born. The rider’s brain can now respond neurally to something it is incapable of seeing, by borrowing the horse’s superior range of vision.
These brain-to-brain transfers are mutual, so the learning equine brain should also be able to borrow the rider’s vision, with its superior depth perception and focal acuity. This kind of neural interaction results in a horse-and-human team that can sense far more together than either party can detect alone. In effect, they share effort by assigning labour to the party whose skills are superior at a given task.
There is another type of skillset that requires a particularly nuanced cellular dance: sharing attention and focus. Equine vigilance allowed horses to survive 56 million years of evolution – they had to notice slight movements in tall grasses or risk becoming some predator’s dinner. Consequently, today it’s difficult to slip even a tiny change past a horse, especially a young or inexperienced animal who has not yet been taught to ignore certain sights, sounds and smells.
By contrast, humans are much better at concentration than vigilance. The predator brain does not need to notice and react instantly to every stimulus in the environment. In fact, it would be hampered by prey vigilance. While reading this essay, your brain sorts away the sound of traffic past your window, the touch of clothing against your skin, the sight of the masthead that says ‘Aeon’ at the top of this page. Ignoring these distractions allows you to focus on the content of this essay.
Horses and humans frequently share their respective attentional capacities during a performance. A puissance horse galloping toward an enormous wall cannot waste vigilance by noticing the faces of each person in the audience. Likewise, the rider cannot afford to miss a loose dog that runs into the arena outside her narrow range of vision and focus. Each party helps the other through their primary strengths.
Such sharing becomes automatic with practice. With innumerable neural contacts over time, the human brain learns to heed signals sent by the equine brain that say, in effect: ‘Hey, what’s that over there?’ Likewise, the equine brain learns to sense human neural signals that counter: ‘Let’s focus on this gigantic wall right here.’ Each party sends these messages by body language and receives them by body awareness through two spinal cords, then interprets them inside two brains, millisecond by millisecond.
The rider’s physical cues are transmitted by neural activation from the horse’s surface receptors to the horse’s brain
Finally, it is conceivable that horse and rider can learn to share features of executive function – the human brain’s ability to set goals, plan steps to achieve them, assess alternatives, make decisions and evaluate outcomes. Executive function occurs in the prefrontal cortex, an area that does not exist in the equine brain. Horses are excellent at learning, remembering and communicating – but they do not assess, decide, evaluate or judge as humans do.
Shying is a prominent equine behaviour that might be mediated by human executive function in well-trained mounts. When a horse of average size shies away from an unexpected stimulus, riders are sitting on top of 1,200 pounds of muscle that suddenly leaps sideways off all four feet and lands five yards away. It’s a frightening experience, and often results in falls that lead to injury or even death. The horse’s brain causes this reaction automatically by direct connection between his sensory and motor cortices.
Though this possibility must still be studied by rigorous science, brain-to-brain communication suggests that horses might learn to borrow small glimmers of executive function through neural interaction with the human’s prefrontal cortex. Suppose that a horse shies from an umbrella that suddenly opens. By breathing steadily, relaxing her muscles, and flexing her body in rhythm with the horse’s gait, the rider calms the animal using body language. Her physical cues are transmitted by neural activation from his surface receptors to his brain. He responds with body language in which his muscles relax, his head lowers, and his frightened eyes return to their normal size. The rider feels these changes with her body, which transmits the horse’s neural signals to the rider’s brain.
From this point, it’s only a very short step – but an important one – to the transmission and reception of neural signals between the rider’s prefrontal cortex (which evaluates the unexpected umbrella) and the horse’s brain (which instigates the leap away from that umbrella). In practice, to reduce shying, horse trainers teach their young charges to slow their reactions and seek human guidance.
Brain-to-brain communication between horses and riders is an intricate neural dance. These two species, one prey and one predator, are living temporarily in each other’s brains, sharing neural information back and forth in real time without linguistic or mechanical mediation. It is a partnership like no other. Together, a horse-and-human team experiences a richer perceptual and attentional understanding of the world than either member can achieve alone. And, ironically, this extended interspecies mind operates well not because the two brains are similar to each other, but because they are so different.
Janet Jones applies brain research to training horses and riders. She has a PhD from the University of California, Los Angeles, and for 23 years taught the neuroscience of perception, language, memory, and thought. She trained horses at a large stable early in her career, and later ran a successful horse-training business of her own. Her most recent book, Horse Brain, Human Brain (2020), is currently being translated into seven languages.
Edited by Pam Weintraub
In Ethiopia’s grasslands, huge herds of gelada monkeys might be in the process of domesticating wolves.
In the grasslands of Ethiopia, scientists were amazed to find a striking example of inter-species collaboration. Ethiopian wolves were seen casually strolling among herds of gelada monkeys, which you would expect to flee out of the way of such a predator. But it seems like the monkeys tolerate the wolves in their presence and are not frightened by them. The wolves, on the other hand, ignore the geladas’ potential as meals, preferring to linger around the herd because it helps them catch more rodents. This odd relationship resembles the ancient domestication of dogs or cats by humans, some researchers say.
Live and let live
Gelada monkeys (Theropithecus gelada) look a lot like baboons. These primates are known to live in close-knit family groups, but can also live as part of shockingly vast communities consisting of hundreds of individuals. They live peacefully even in the most numerous communities, a relatively rare achievement in the wilds of Africa.
Geladas are graminivores, meaning their diet consists of 90% grass. Essentially, they’re the only living primates that subsist almost entirely on grass, a trait more commonly seen in ungulates like deer and cattle.
While the primates congregate in huge herds, munching on grass for hours upon hours, the shrewd (and endangered) Ethiopian wolf (Canis Simensis) mingles with the geladas. Usually, the wolves travel in zig-zag, sprinting when they sense prey is within their grasp. But, around the geladas, the wolves roam casually, being careful not to startle the herd.
Researchers at Dartmouth College observed the dynamics between the species for a new study. They conclude that the Ethiopian wolf is not interested in geladas for food, although they have no qualms hunting juvenile sheep and goat. The monkeys seem to know this, as they don’t seem to feel threatened in the predators’ presence. But why is that?
After following Ethiopian wolves for 17 days, the researchers found that those individuals which hunted rodents within a gelada herd were successful 67% of the time, compared to a success rate of only 25% when they prowled on their own. The findings were reported in the Journal of Mammalogy.
“For Ethiopian wolves, establishing proximity to geladas as foraging commensals could be an adaptive strategy to elevate foraging success. The novel dynamics documented here shed light on the ecological circumstances that contribute to the stability of mixed groups of predators and potential prey,” wrote the authors of the new study.
For now, it’s not clear what makes the wolves more successful when hunting within gelada groups. The monkeys might be flushing out rodents from their burrows due to their insistent grazing, but that’s just an unverified hypothesis at the moment. Alternatively, the monkeys might be providing cover for the wolves, distracting the rodents from the dangerous predator.
Sometimes, a wolf will attack a gelada young. During one instance when this happened, the other monkeys in the herd quickly attacked the wolf, forcing it to drop the infant. After the wolf was driven away, it was never allowed in the midst of the herd again. Other individuals seem to understand this dynamic very well and will resist the temptation of grabbing a quick gelada meal in favor of the prospect of better dividends in the long run.
The researchers say that the Ethiopian wolf might be hanging around other species, such as cattle, to hunt more rodents. It’s also possible other predator species may be doing something similar without us finding out about it yet.
What’s intriguing is that the gradual toleration between the two species is very similar to the domestication process performed by humans on dogs. The first wolves began to be domesticated by humans sometime between 40,000 and 11,000 years ago, but the details pertaining to how this happened are not clear. According to one hypothesis, wolves started hanging around humans, who would leave large carcasses behind them after each big hunt. Gradually, the two species became more accustomed to one another. Later, wolves may have helped humans on the hunt, cementing the relationship between the two.
Could the same thing be happening in Ethiopia’s grasslands? Given a couple thousand of years, could we see geladas with wolves as pets? That would be quite the sight — but it’s rather unlikely. The monkeys don’t seem to derive any benefit from tolerating the wolves in their presence, and without a two-way value exchange between the two species, domestication won’t likely happen.
What’s more, the Ethiopian wolf might become extinct soon before there’s any reasonable time for domestication to play out. Researchers estimate that there are only 450 adult Ethiopian wolves left in the wild. Continuous loss of habitat due to high-altitude subsistence agriculture represents the major current threat to the Ethiopian wolf.
June 2, 2016
The first domesticated animals may have been tamed twice.
Tens of thousands of years ago, before the internet, before the Industrial Revolution, before literature and mathematics, bronze and iron, before the advent of agriculture, early humans formed an unlikely partnership with another animal—the grey wolf. The fates of our two species became braided together. The wolves changed in body and temperament. Their skulls, teeth, and paws shrank. Their ears flopped. They gained a docile disposition, becoming both less frightening and less fearful. They learned to read the complex expressions that ripple across human faces. They turned into dogs.
Today, dogs are such familiar parts of our lives—our reputed best friends and subject of many a meme—that it’s easy to take them, and what they represent, for granted. Dogs were the first domesticated animals, and their barks heralded the Anthropocene. We raised puppies well before we raised kittens or chickens; before we herded cows, goats, pigs, and sheep; before we planted rice, wheat, barley, and corn; before we remade the world.
“Remove domestication from the human species, and there’s probably a couple of million of us on the planet, max,” says archaeologist and geneticist Greger Larson. “Instead, what do we have? Seven billion people, climate change, travel, innovation and everything. Domestication has influenced the entire earth. And dogs were the first.” For most of human history, “we’re not dissimilar to any other wild primate. We’re manipulating our environments, but not on a scale bigger than, say, a herd of African elephants. And then, we go into partnership with this group of wolves. They altered our relationship with the natural world.”
Larson wants to pin down their origins. He wants to know when, where, and how they were domesticated from wolves. But after decades of dogged effort, he and his fellow scientists are still arguing about the answers. They agree that all dogs, from low-slung corgis to towering mastiffs, are the tame descendants of wild ancestral wolves. But everything else is up for grabs.
Some say wolves were domesticated around 10,000 years ago, while others say 30,000. Some claim it happened in Europe, others in the Middle East, or East Asia. Some think early human hunter-gatherers actively tamed and bred wolves. Others say wolves domesticated themselves, by scavenging the carcasses left by human hunters, or loitering around campfires, growing tamer with each generation until they became permanent companions.
Dogs were domesticated so long ago, and have cross-bred so often with wolves and each other, that their genes are like “a completely homogenous bowl of soup,” Larson tells me, in his office at the University of Oxford. “Somebody goes: what ingredients were added, in what proportion and in what order, to make that soup?” He shrugs his shoulders. “The patterns we see could have been created by 17 different narrative scenarios, and we have no way of discriminating between them.”
The only way of doing so is to look into the past. Larson, who is fast-talking, eminently likable, and grounded in both archaeology and genetics, has been gathering fossils and collaborators in an attempt to yank the DNA out of as many dog and wolf fossils as he can. Those sequences will show exactly how the ancient canines relate to each other and to modern pooches. They’re the field’s best hope for getting firm answers to questions that have hounded them for decades.
And already, they have yielded a surprising discovery that could radically reframe the debate around dog domestication, so that the big question is no longer when it happened, or where, but how many times.
* * *
On the eastern edge of Ireland lies Newgrange, a 4,800-year-old monument that predates Stonehenge and the pyramids of Giza. Beneath its large circular mound and within its underground chambers lie many fragments of animal bones. And among those fragments, Dan Bradley from Trinity College Dublin found the petrous bone of a dog.
Press your finger behind your ear. That’s the petrous. It’s a bulbous knob of very dense bone that’s exceptionally good at preserving DNA. If you try to pull DNA out of a fossil, most of it will come from contaminating microbes and just a few percent will come from the bone’s actual owner. But if you’ve got a petrous bone, that proportion can be as high as 80 percent. And indeed, Bradley found DNA galore within the bone, enough to sequence the full genome of the long-dead dog.
Larson and his colleague Laurent Frantz then compared the Newgrange sequences with those of almost 700 modern dogs, and built a family tree that revealed the relationships between these individuals. To their surprise, that tree had an obvious fork in its trunk—a deep divide between two doggie dynasties. One includes all the dogs from eastern Eurasia, such as Shar Peis and Tibetan mastiffs. The other includes all the western Eurasian breeds, and the Newgrange dog.
The genomes of the dogs from the western branch suggest that they went through a population bottleneck—a dramatic dwindling of numbers. Larson interprets this as evidence of a long migration. He thinks that the two dog lineages began as a single population in the east, before one branch broke off and headed west. This supports the idea that dogs were domesticated somewhere in China.
But there’s a critical twist.
The team calculated that the two dog dynasties split from each other between 6,400 and 14,000 years ago. But the oldest dog fossils in both western and eastern Eurasia are older than that. Which means that when those eastern dogs migrated west into Europe, there were already dogs there.
Here’s the full story, as he sees it. Many thousands of years ago, somewhere in western Eurasia, humans domesticated grey wolves. The same thing happened independently, far away in the east. So, at this time, there were two distinct and geographically separated groups of dogs. Let’s call them Ancient Western and Ancient Eastern. Around the Bronze Age, some of the Ancient Eastern dogs migrated westward alongside their human partners, separating from their homebound peers and creating the deep split in Larson’s tree. Along their travels, these migrants encountered the indigenous Ancient Western dogs, mated with them (doggy style, presumably), and effectively replaced them.
Today’s eastern dogs are the descendants of the Ancient Eastern ones. But today’s western dogs (and the Newgrange one) trace most of their ancestry to the Ancient Eastern migrants. Less than 10 percent comes from the Ancient Western dogs, which have since gone extinct.
This is a bold story for Larson to endorse, not least because he himself has come down hard on other papers suggesting that cows, sheep, or other species were domesticated twice. “Any claims for more than one need to be substantially backed up by a lot of evidence,” he says. “Pigs were clearly domesticated in Anatolia and in East Asia. Everything else is once.” Well, except maybe dogs.
* * *
Other canine genetics experts think that Larson’s barking up the wrong tree. “I’m somewhat underwhelmed, since it’s based on a single specimen,” says Bob Wayne from the University of California, Los Angeles. He buys that there’s a deep genetic division between modern dogs. But, it’s still possible that dogs were domesticated just once, creating a large, widespread, interbreeding population that only later resolved into two distinct lineages.
In 2013, Wayne’s team compared the mitochondrial genomes (small rings of DNA that sit outside the main set) of 126 modern dogs and wolves, and 18 fossils. They concluded that dogs were domesticated somewhere in Europe or western Siberia, between 18,800 and 32,100 years ago. And genes aside, “the density of fossils from Europe tells us something,” says Wayne. “There are many things that look like dogs, and nothing quite like that in east Asia.”
Peter Savolainen from the KTH Royal Institute of Technology in Stockholm disagrees. By comparing the full genomes of 58 modern wolves and dogs, his team has shown that dogs in southern China are the most genetically diverse in the world. They must have originated there around 33,000 years ago, he says, before a subset of them migrated west 18,000 years later.
That’s essentially the same story that Larson is telling. The key difference is that Savolainen doesn’t buy the existence of an independently domesticated group of western dogs. “That’s stretching the data very much,” he says. Those Ancient Western dogs might have just been wolves, he says. Or perhaps they were an even earlier group of migrants from the east. “I think the picture must seem a bit chaotic,” he says understatedly. “But for me, it’s pretty clear. It must have happened in southern East Asia. You can’t interpret it any other way.”
Except, you totally can. Wayne does (“I’m certainly less dogmatic than Peter,” he says). Adam Boyko from Cornell University does, too: after studying the genes of village dogs—free-ranging mutts that live near human settlements—he argued for a single domestication in Central Asia, somewhere near India or Nepal. And clearly, Larson does as well.
Larson adds that his gene-focused peers are ignoring one crucial line of evidence—bones. If dogs originated just once, there should be a neat gradient of fossils with the oldest ones at the center of domestication and the youngest ones far away from it. That’s not what we have. Instead, archaeologists have found 15,000-year-old dog fossils in western Europe, 12,500-year-old ones in east Asia, and nothing older than 8,000 years in between.
“If we’re wrong, then how on earth do you explain the archaeological data?” says Larson. “Did dogs jump from East Asia to Western Europe in a week, and then go all the way back 4,000 years later?” No. A dual domestication makes more sense. Mietje Genompré, an archaeologist from the Royal Belgian Institute of Natural Sciences, agrees that the bones support Larson’s idea. “For me, it’s very convincing,” she says.
But even Larson is hedging his bets. When I ask him how strong his evidence is, he says, “Like, put a number on it? If was being bold, I’d say it’s a 7 out of 10. We lack the smoking gun.”
Why is this is so hard? Of all the problems that scientists struggle with, why has the origin of dogs been such a bitch to solve?
For starters, the timing is hard to pin down because no one knows exactly how fast dog genomes change. That pace—the mutation rate—underpins a lot of genetic studies. It allows scientists to compare modern dogs and ask: How long ago must these lineages have diverged in order to build up this many differences in their genes? And since individual teams use mutation rate estimates that are wildly different, it’s no wonder they’ve arrive at conflicting answers.
Regardless of the exact date, it’s clear that over thousands of years, dogs have mated with each other, cross-bred with wolves, travelled over the world, and been deliberately bred by humans. The resulting ebb and flow of genes has turned their history into a muddy, turbid mess—the homogeneous soup that Larson envisages.
Wolves provide no clarity. Grey wolves used to live across the entire Northern Hemisphere, so they could have potentially been domesticated anywhere within that vast range (although North America is certainly out). What’s more, genetic studies tell us that no living group of wolves is more closely related to dogs than any other, which means that the wolves that originally gave rise to dogs are now extinct. Sequencing living wolves and dogs will never truly reveal their shrouded past; it’d be, as Larson says, like trying to solve a crime when the culprit isn’t even on the list of suspects.
“The only way to know for sure is to go back in time,” he adds.
* * *
The study informally known as the Big Dog Project was born of frustration. Back in 2011, Larson was working hard on the origin of domestic pigs, and became annoyed that scientists studying dogs were getting less rigorous papers in more prestigious journals, simply because their subjects were that much more charismatic and media-friendly. So he called up his longstanding collaborator Keith Dobney. “Through gritted teeth, I said: We’re fucking doing dogs. And he said: I’m in.”
Right from the start, the duo realized that studying living dogs would never settle the great domestication debate. The only way to do that was to sequence ancient DNA from fossil dogs and wolves, throughout their range and at different points in history. While other scientists were studying the soup of dog genetics by tasting the finished product, Larson would reach back in time to taste it at every step of its creation, allowing him to definitively reconstruct the entire recipe.
In recent decades, scientists have become increasingly successful at extracting and sequencing strands of DNA from fossils. This ancient DNA has done wonders for our understanding of our own evolution. It showed, for example, how Europe was colonized 40,000 years ago by hunter-gatherers moving up from Africa, then 8,000 years ago by Middle Eastern farmers, and 5,000 years ago by horse-riding herders from the Russian steppes. “Everyone in Europe today is a blend of those three populations,” says Larson, who hopes to parse the dog genome in the same way, by slicing it into its constituent ingredients.
Larson originally envisaged a small project—just him and Dobney analyzing a few fossils. But he got more funding, collaborators, and samples than he expected. “It just kind of metastasized out of all proportion,” he says. He and his colleagues would travel the world, drilling into fossils and carting chips of bone back to Oxford. They went to museums and private collections. (“There was a guy up in York who had a ton of stuff in his garage.”) They grabbed bones from archaeological sites.
The pieces of bone come back to a facility in Oxford called the Palaeo-BARN—the Palaeogenomics and Bioarchaeology Research Network. When I toured the facility with Larson, we wore white overalls, surgical masks, oversoles, and purple gloves, to keep our DNA (and that of our skin microbes) away from the precious fossil samples. Larson called them ‘spacesuits.’ I was thinking ‘thrift-store ninja.’
In one room, the team shoves pieces of bone into a machine that pounds it with a small ball bearing, turning solid shards into fine powder. They then send the powder through a gauntlet of chemicals and filters to pull out the DNA and get rid of everything else. The result is a tiny drop of liquid that contains the genetic essence of a long-dead dog or wolf. Larson’s freezer contains 1,500 such drops, and many more are on the way. “It’s truly fantastic the kind of data that he has gathered,” says Savolainen.
True to his roots in archaeology, Larson isn’t ignoring the bones. His team photographed the skulls of some 7,000 prehistoric dogs and wolves at 220 angles each, and rebuilt them in virtual space. They can use a technique called geometric morphometrics to see how different features on the skulls have evolved over time.
The two lines of evidence—DNA and bones—should either support or refute the double domestication idea. It will also help to clear some confusion over a few peculiar fossils, such as a 36,000 year old skull from Goyet cave in Belgium. Genompré thinks it’s a primitive dog. “It falls outside the variability of wolves: it’s smaller and the snout is different,” she says. Others say it’s too dissimilar to modern dogs. Wayne has suggested that it represents an aborted attempt at domestication—a line of dogs that didn’t contribute to modern populations and is now extinct.
Maybe the Goyet hound was part of Larson’s hypothetical Ancient Western group, domesticated shortly after modern humans arrived in Europe. Maybe it represented yet another separate flirtation with domestication. All of these options are on the table, and Larson thinks he has the data to tell them apart. “We can start putting numbers on the difference between dogs and wolves,” he says. “We can say this is what all the wolves at this time period look like; does the Goyet material fall within that realm, or does it look like dogs from later on?”
Larson hopes to have the first big answers within six to twelve months. “I think it’ll clearly show that some things can’t be right, and will narrow down the number of hypotheses,” says Boyko. “It may narrow it down to one but I’m not holding my breath on that.” Wayne is more optimistic. “Ancient DNA will provide much more definitive data than we had in the past,” he says. “[Larson] convinced everyone of that. He’s a great diplomat.”
Indeed, beyond accumulating DNA and virtual skulls, Larson’s greatest skill is in gathering collaborators. In 2013, he rounded up as many dog researchers as he could and flew them to Aberdeen, so he could get them talking. “I won’t say there was no tension,” he says. “You go into a room with someone who has written something that sort of implies you aren’t doing very good science… there will be tension. But it went away very quickly. And, frankly: alcohol.”
“Everyone was like: You know what? If I’m completely wrong and I have to eat crow on this, I don’t give a shit. I just want to know.”
A ilusão, que desempenhou um papel estrutural na constituição subjetiva da nossa espécie, pode já não estar ao nosso alcance
Talvez o mal-estar do nosso tempo seja o de que já não é possível escolher entre a pílula azul e a vermelha – ou entre continuar cego ou começar a enxergar o que está por trás da trama dos dias. O mal-estar se deve ao fato de que talvez já não exista a pílula azul – ou já não seja mais possível a ilusão, esta que desempenhou um papel estrutural na constituição subjetiva da nossa espécie ao longo dos milênios.
Se fosse um de nós o membro da resistência disposto a trair os companheiros, a negociar a rendição com as máquinas diante de um suculento filé num restaurante, aqui, agora, e não mais no final dos anos 90, o dilema poderia sofrer um deslocamento. O drama não seria enxergar o filé como filé, no sentido de poder acreditar que ele existe, assim como acreditar que o restaurante existe e que o cenário a que chamamos de mundo existe tal qual está diante dos nossos olhos.
Não. O dilema atual pode ser também este, mas só na medida em que também é outro. O drama é que acreditamos no filé, sabemos que ele existe e sabemos que é gostoso. Desejamos o filé, nos lambuzamos dele e temos prazer com ele. Ao olhar para ele, porém, não enxergamos apenas “o deserto do real”, mas algo muito mais encarnado e cada vez mais inescapável: enxergamos o boi.
É terrível enxergar o boi. E, como os mais sensíveis já descobriram, é impossível deixar de enxergá-lo. Nossa superpopulação de humanos extrapolou a lógica dos vivos, matar para comer. E impôs a escravização e a tortura cotidiana de outras espécies. Milhões de bois, galinhas e porcos nascem apenas para nos alimentar em campos de concentração aos quais damos nomes mais palatáveis. São sacrificados em holocaustos diários sem que nem mesmo tenham tido uma vida.
Animais confinados, presos, às vezes sem sequer poder se mover por uma existência inteira. Criamos profissões capazes de reconhecer em segundos se um pinto é macho ou fêmea para separar as fêmeas que viverão espremidas, muitas vezes sem conseguir sequer abrir as asas, botando ovos e depois virando bandejas no supermercado e jogar os machos para serem moídos ainda vivos no triturador de lixo. Escravidão e tortura/sacrifício e lixo, estes são os destinos que determinamos aos frangos.
Somos os nazistas das outras espécies – e produzimos holocaustos cotidianos
Somos os nazistas das outras espécies. E, se antes era possível ignorar, desqualificando a questão como algo menor ou coisa de “adoradores de alface”, a internet e a disseminação de informações tornaram impossível não enxergar o olho do boi. Ao olhar para o filé, o olho do boi nos olha de volta. O olho vidrado de quem está aterrorizado porque pressente que caminha no corredor da morte, o boi que se caga de medo enquanto é obrigado a dar o passo para o sacrifício, o boi que tenta escapar, mas não encontra saída. O olho do boi alcança até gente como eu, que pode ser colocada na categoria “adoradores de churrasco”.
A publicidade do século 20 perdeu a ressonância em tempos de internet. Porque a ilusão já não é possível. Nada era mais puro do que o leite branco tirado de uma vaquinha no pasto. Era fácil acreditar na imagem bucólica do alimento saudável. Nosso leite vinha do paraíso, de nosso passado rural perdido, da vida nos bosques de Walden. Assim como a longa série de produtos dele originados, como queijo, iogurte e manteiga.
Mas a vaca da imagem não existe. A real é a vaca que nasce em cativeiro, filha de outra escrava. A vaca que quase não se move, cuja existência consiste numa longa série de estupros por instrumentos que se enfiam pelo seu corpo para fecundá-la com o sêmen de outro escravo. Então ela engravida e engravida e engravida de bezerros que dela serão sequestrados para virar filés, para que suas tetas sigam dando leite delas tirados por outras máquinas. E, como sabemos disso, o leite que chega à nossa mesa já não pode mais ser branco, mas vermelho do horror da vaca cujo corpo virou um objeto, a vaca para quem cada dia é tortura, estupro e escravidão.
Para não beber sangue procuramos nas prateleiras leites à base de vegetais. Vegetais não gritam. Soja, apenas um dos tantos exemplos. Bifes de soja, hambúrgueres de soja, linguiças de soja, leite de soja. Mas como ignorar o desmatamento, a destruição de ecossistemas inteiros e com eles toda a vida que lá havia? Como ignorar que a soja pode ter sido plantada em terra indígena e que, enquanto ela vira mercadoria no supermercado, jovens Guarani Kaiowá se enforcam porque já não sabem como viver? Já não é possível fingir que não enxergamos isso. Assim, nem os veganos mais radicais podem se salvar do pecado original.
Os mais sensíveis sentem a textura de suas roupas e sabem que são costuradas com carne humana
Olhamos para nossas roupas e horrorizados sabemos que em algum lugar da linha globalizada de produção há nelas o sangue de crianças, homens e mulheres em regime de trabalho análogo à escravidão. Como o casal que morreu abraçado na fábrica de Bangladesh, gerando a fotografia que comoveu o mundo mas não eliminou o horror que seguiu em escala industrial. Ou mesmo de um imigrante boliviano enfiado num quarto insalubre trabalhando horas e horas por quase nada bem aqui ao lado. Mas os mais sensíveis sentem a textura de suas roupas e sabem que são costuradas com carne humana. E já não sabem como vesti-las. Nem sabem como dar brinquedos para seus filhos porque sabem que os bonecos, os carrinhos, os castelos e os dinossauros contêm neles o sangue das crianças sem infância, ou o de suas mães e pais.
Já não é possível levar crianças a zoológicos ou aquários porque sabemos que a única educação próxima da verdade que receberiam ali é a do horror a que os animais são submetidos para serem exibidos, por melhor que seja a imitação de seu habitat. Lembro uma reportagem que fui fazer num zoológico, planejada para ser divertida, e só pude contar, entre outros horrores, que o babuíno chamado Beto era mantido à custa de Valium, para evitar que arrancasse pedaços do próprio corpo. Mesmo dopado jogava-se contra as grades, atirava fezes nos visitantes e espancava a companheira. Pinky, a elefanta, vivia só. Seus dois companheiros tinham morrido ao cair no fosso tentando escapar do cativeiro. Sabemos hoje que os golfinhos e as baleias dos shows acrobáticos são escravos brutalizados para servir de entretenimento a humanos. E, desde que sabemos, aqueles que gozam com esses espetáculos de morte podem se descobrir não mais como famílias felizes num momento de lazer, como nas imagens dos folhetos publicitários, mas como hordas de sádicos.
No simples ato de acender a luz já existe a consciência de que estamos destruindo o mundo de alguém e de que nada mais será simples. Neste momento, para ficar apenas num exemplo, dezenas de milhares já perderam suas casas no rio Xingu, na Amazônia, para a operação da Hidrelétrica de Belo Monte. Povos indígenas que vivem na região atingida já não conseguem suportar o aumento exponencial de mosquitos desde que o lago da usina começou a encher, alterando o ecossistema e dizimando culturas, no que já foi denunciado pelo Ministério Público Federal como etnocídio. Os impactos mal começaram e, em menos de três meses, mais de 16 toneladas de peixes morreram. E talvez também esteja chegando ao fim o tempo em que ainda é aceitável contar vidas por toneladas, mesmo que seja a vida de peixes. Ou a morte de peixes. Um dedo no interruptor e uma cadeia de mortes. E agora também já sabemos disso.
Ao pedir um café e um pão com manteiga na padaria, nos implicamos numa cadeia de horrores
O tempo das ilusões acabou. Nenhum ato do nosso cotidiano é inocente. Ao pedir um café e um pão com manteiga na padaria, nos implicamos numa cadeia de horrores causados a animais e a humanos envolvidos na produção. Cada ato banal implica uma escolha ética – e também uma escolha política.
A descrição das atrocidades que cometemos rotineiramente pode aqui seguir por milhares de caracteres. Comemos, vestimos, nos entretemos, transportamos e nos transportamos à custa da escravidão, da tortura e do sacrifício de outras espécies e também dos mais frágeis da nossa própria espécie. Somos o que de pior aconteceu ao planeta e a todos que o habitam. A mudança climática já anuncia que não apenas tememos a catástrofe, mas nos tornamos a catástrofe. Desta vez, não só para todos os outros, mas também para nós mesmos.
Já não é possível a pílula azul – ou já não é possível à adesão às ilusões. Há várias implicações profundas numa época em que o conhecimento não liberta, mas condena. A começar, talvez, pela pergunta: quem é o inocente num mundo em que a inocência já não é possível? Seria o inocente o pior humano de todos? Seria o inocente um psicopata?
O que seremos nós, subjetivamente, agora que estamos condenados a enxergar? As redes sociais têm nos dado algumas pistas. O que a internet fez foi arrancar da humanidade as ilusões sobre si mesma. O cotidiano nas redes sociais nos mostrou a verdade que sempre esteve lá, mas era protegida – ou mediada – pelo mundo das aparências. Sobre isso já escrevi um artigo, chamado A boçalidade do mal, que pode ser lido aqui. As implicações de perder este véu tão arduamente tecido são profundas e recém começam a ser investigadas. O impacto sobre a subjetividade estrutural de nossa espécie é tremendo, exatamente porque é estrutural e desabou num espaço de tempo muito curto, quase num soluço.
Já não é mais possível pensar apenas em humanos quando se aborda o tema dos direitos
O que faremos diante da impossibilidade da pílula azul, a que garantia as ilusões? A ridicularização daqueles que levantam esse tema ainda é um caminho, mas convencem menos que no passado. Também a piada se torna anacrônica. As interrogações vêm mudando, e já não é possível afirmar, sem revelar considerável ignorância, inclusive sobre a ciência produzida, que os animais não têm vida mental nem emocional, são “irracionais”. Ou, lembrando um argumento religioso, “que não têm alma”. Toda a ideologia que um dia justificou a escravidão de humanos, até que foi questionada, derrubada e transformada numa mancha de crime e vergonha na história da humanidade, passou a ser confrontada também com relação aos animais.
Cada vez mais as outras espécies começam a ser vistas como diferentes – e não mais como inferiores. Assim, o que se coloca no campo da ética são questões fascinantes e muito mais espinhosas. Mesmo o termo “direitos humanos” passa a ser questionável, porque pensar apenas em “humanos” já não é mais possível. No momento em que nos tornamos a própria definição de catástrofe, o conceito de “espécie”, em sua expressão cultural, se desloca. Outras formas de compreender e nomear o lugar dos humanos ganham espaço no horizonte filosófico e no exercício da política.
Resta o cinismo, sempre o último reduto. Dizer que, diante de mais de 7 bilhões de seres humanos ocupando o planeta e crescendo, não há outra maneira a não ser comer e vestir exploração, escravidão e tortura é a afirmação mais óbvia. É a afirmação expandida usada para todas as desigualdades de direitos. Desde que não seja eu – ou os meus – os sacrificados, tudo bem.
Vale a pena dedicar um parágrafo aos cínicos, essa categoria que prolifera com o ímpeto de um Aedes aegypti no Brasil e no mundo. O cínico é aquele que olha com calculado enfado para todos os outros, porque ele acredita que entende o mundo como ele de fato é. Ele é o que sabe das coisas, o único esperto. Todos os outros são tolinhos com ideias irreais. O cínico é aquele que deixa o mundo como está. Mas talvez, neste momento, o cínico seja justamente o inocente. Sua inocência consiste em acreditar que a pílula azul ainda está disponível.
Como ser ético num mundo sem ilusões, em que cada ato implica na tortura e no sacrifício de um outro?
Há um preço para enxergar e, mesmo assim, assumir o extermínio cotidiano como dado, como parte intrínseca da condição de ser um humano. Nem toda a crescente gourmetização da comida, nem todas as narrativas ficcionais que contam uma história idílica sobre a origem daquele produto, nada ocultará esse preço. E nada reduzirá seu impacto subjetivo. Não é fácil viver na pele do algoz. Não é simples viver sabendo-se. Aquele que se olha no espelho e se enxerga carregará essa autoimagem consigo. E se tornará algo que já não é mais o mesmo.
Há uma imagem recente que pode dar algumas pistas sobre esse caminho. Numa praia da Argentina, um golfinho foi carregado por turistas. Alguns dizem que ainda estava vivo, outros que já estava morto. Vivo ou morto, os turistas preocuparam-se apenas com tirar selfies para postar nas redes sociais. O site de humor Sensacionalista postou: “Golfinho morre ao ser retirado do mar para turistas fazerem selfie e Deus anuncia recall do ser humano”.
Ainda assim, quem se horrorizou com a falta de horror alheia, à noite seguiu diante do olho do boi. O que fazer diante do olho do boi? Como ser ético num mundo sem ilusões, em que cada ato implica na tortura e no sacrifício de um outro, humano e não humano? Se somos os nazistas das outras espécies, quando não da mesma, aceitar que assim é não seria se tornar um Eichmann, o nazista julgado em Jerusalém que alegou apenas cumprir ordens, o homem tão banalmente ordinário que inspirou a filósofa Hannah Arendt a criar o conceito da “banalidade do mal”? Não seríamos, aos olhos do boi, todos Eichmann, justificando-nos pelo senso comum de que assim é e se faz o que é preciso para sobreviver? Se sim, o que implica viver assumidamente nesta pele?
Talvez estejamos, como espécie que se pensa, diante de um dos maiores dilemas éticos da nossa história. Sem poder optar pela pílula azul, a das ilusões, condenados à pílula vermelha, a que nos obriga a enxergar, como construir uma escolha que volte a incluir a ética? Como não paralisar diante do espelho, reduzidos ou ao horror ou ao cinismo, eliminando a possibilidade de transformação? Como nos mover?
Diante do filé que desejamos e do olho boi que nos interroga, há pelo menos uma hipótese cada vez mais forte: o inocente é um assassino.
Date: April 17, 2014
Source: Washington University in St. Louis
Summary: A review of recent research on the domestication of large herbivores suggests that neither intentional breeding nor genetic isolation were as significant as traditionally thought. “Our findings show little control of breeding, particularly of domestic females, and indicate long-term gene flow, or interbreeding, between managed and wild animal populations,” a co-author said.
It is from Darwin that we inherit the ideas that domestication involved isolation of captive animals from wild species and total human control over breeding and animal care.
But animal management in this industrial setting has been applied too broadly in time and space, said Fiona Marshall, PhD, professor of anthropology at Washington University in St. Louis. It is not representative of the practices of the Neolithic herders who first domesticated animals nor — for that matter — of contemporary herders in nonindustrial societies.
Together with Keith Dobney, PhD, of the University of Aberdeen in Scotland; Tim Denham, PhD, of the Australian National University; and José Capriles, PhD, of the Universidad de Tarapacá in Chile, Marshall wrote a review article that summarizes recent research on the domestication of large herbivores for “The Modern View of Domestication,” a special feature of The Proceedings of the National Academy of Sciencespublished April 29.
Recent research on the domestication of donkeys, camelids (which includes dromedaries, Bactrian camels, llamas and alpacas) pigs, cattle, sheep and goats suggests that neither intentional breeding nor genetic isolation were as significant as traditionally thought, the scientists said.
“Our findings show little control of breeding, particularly of domestic females, and indicate long-term gene flow, or interbreeding, between managed and wild animal populations,” Marshall said.
Why is it important to get domestication right? “Our livestock is losing genetic diversity even faster than some wild animals, because of management practices like artificial insemination,” Marshall said. “We took only a bit of the diversity from the wild for domestication, and what we’re looking at now is lopping it off really fast so we’ll be left with little diversity to survive all the climate and disease issues we’re facing. It really is a crisis situation.
“If we don’t understand what it is we might be about to lose, then we don’t count the cost of loss accurately or know how to plan for the future,” she said.
A walk on the wild side
For most of history, artificial selection on large herbivores was probably weak, Marshall said. “Herders could not afford to kill many animals, particularly large-bodied animals with long gestation periods. To keep herd size stable, herders probably culled or castrated males surplus to the growth needs of the herd, allowing all females to breed,” she said. These management practices placed only light selection pressure on the herd’s gene pool.
Paradoxically, environmental selection may, in many instances, have been stronger than artificial selection. Early herds were vulnerable to disease, droughts and storms, disasters that would have forced pastoralists to replenish herds from wild populations better adapted to harsh local conditions.
Sometimes domesticated animals were intentionally bred with wild ones, Marshall said. “Wild animals are generally faster, stronger and better adapted to the local conditions than domesticated ones. So, for example, Beja herders in Northeastern Africa intentionally bred their donkeys with African wild asses in order to produce stronger transport animals.”
“And sometimes interbreeding was accidental,” she said. “Even today in the Gobi, researchers report that domestic camels sometimes join wild herds after becoming separated from their own. Wild and domestic camels meet at shared oases, and wild males also can become extremely aggressive and may collect domestic females to the dismay of pastoralists.”
In the Andes, Capriles said, wild and domestic camelids have interbred in such complex ways that alpacas are maternally related to both wild vicunas and guanacos, and the same is true for llamas.
Artificial selection was probably weakest and gene flow highest in the case of pack animals such as donkeys or camelids. But even in the case of pigs or cattle, interbreeding between domestic and wild animals has created long and complex evolutionary and domestication histories that challenge assumptions regarding genetic isolation and long-held definitions of domestication.
The curl in the pigs’ tails
The domestication of pigs is one of these stories. Dobney, Greger Larson, PhD, and their team have shown that pigs were domesticated at least twice, in eastern Anatolia and in central China. Analysis of mitochondrial DNA (DNA in a cell organelle that is inherited from the mother) shows that early herders took pigs with them from Anatolia to western Europe. And analysis of ancient DNA shows that, once in Europe, the domesticated pigs interbred with the wild boars. These hybridized populations then rapidly replaced the original domesticates, first in Europe and then, later, across Anatolia itself.
In China, the story is somewhat different. There is little evidence that the domestic herds in central China interbred with wild boars. But early agriculturists took their pigs to southeastern Asia and there, deliberately or accidentally, recruited local wild boar lineages into their domestic stock.
All of the New Guinea domestic pigs and those of the islands in the tropical Pacific Ocean carry DNA from those southeast Asian wild boar populations.
The interesting question is why the pigs in central China didn’t interbreed with wild boar populations in central China. Dobney suggests that management practices may have made a difference. It is possible that in China where settlements were dense, people started keeping pigs in pens, whereas in Europe, even in medieval times, people took their pigs to forage in the forests, where they might encounter wild boars.
The pig story illustrates how much our understanding of domestication events has changed. The anomaly is the isolated domestic population, not the prolonged interbreeding among domestic and wild animals, which in most domesticated species seems to have continued to recent times.
What would Darwin say?
“The research is really exciting because it is making us completely rethink what it means to be domesticated,” Marshall said. “The boundaries between wild and domesticated animals were much more blurred for much longer than we had realized.”
“To untangle the history of domestication,” Denham said, “scientists will need to bring to bear all of the evidence at their disposal, including archeological and ethnographic evidence, and the analysis of both modern and ancient DNA.”
“We must also investigate sources of selection more critically,” Marshall said, “bearing in mind the complex interplay of human and environmental selection and the likelihood of long-term gene flow from the wild.”
It’s probably fortunate the Darwin had clear examples of animal breeding to consider as he thought about evolution. The first chapter of “On the Origin of Species” discusses the domestication of animals such as as pigeons, cattle and dogs, and Darwin then uses artificial selection as a springboard to introduce the theory of natural selection.
It turns out that animal domestication is more complex, and the role of natural selection more important than Darwin thought. It is also the case that the people who first domesticated animals valued wild ones more than did Darwin’s Victorian neighbors.
“The Modern View of Domestication,” a special issue of PNAS edited by Greger Larson and Dolores R. Piperno, resulted from a meeting entitled “Domestication as an Evolutionary Phenomenon: Expanding the Synthesis,” held April 7-11, 2011, that was funded and hosted by the National Evolutionary Synthesis Centre (National Science Foundation EF-0905606) in 2011.