The Self-Domesticated Ape

We aren’t the only species on this planet that have domesticated another species. There is one kind of ancient ant that herds and cares for insect aphids in order to milk them of honeydew sugar. But we are the only species to have domesticated more than one species. Over time humans have domesticated dogs, cats, cows, horses, chickens, ducks, sheep, goats, camels, pigs, guinea pigs, and rabbits, among many others. We have modified their genes with selective breeding so that their behavior aligns with ours. For example, we have tweaked the genetic makeup of a wild dog so that it wants to guard our sheep. And we have designed wild cattle to allow us to milk it in exchange for food. In each case of domestication we alter genetics by clever breeding over time, using our minds to detect and select traits. In a very real sense, the tame dog and milk cow were invented by humans, and were among the earliest human inventions. Along each step of the process our ancestors imagined a better version of what they had, and then made a better version happen. Domestication is for the most part, an act of imagination.

One of the chief characteristics of domesticated animals is their reduced aggression compared to wild types. Tame dogs, cats, cattle and goats, are much more tolerant of others and more social than their feral versions. This acquired tameness is why we can work close with them. In addition, domestication brings morphological changes to the skulls of adults – they resemble the young more with larger wider eyes, smaller teeth, flatter rounder faces, and more slender bones. Tame dogs look like wolf puppies, and domesticated cats more like lion kittens.

This retention of juvenile traits into adulthood is called neoteny and is considered a hallmark of domestication. The reduction of certain types of aggression is also a form of neoteny. The behavior of domesticated animals is similar to that of juvenile animals: more trusting of strangers, less hostile aggression over threats, less violent in-group fighting.

In the 1950s, the Russian geneticist Dmitry Belyaev started breeding wild silver foxes in captivity, selecting the friendliest of each generation to breed into the next. Each generation of less aggressive foxes displayed more puppy-like features: rounder, flatter heads, wider eyes, floppy ears. Within 20 generations he had bred domesticated foxes.

Later analysis of their genomes in 2018 showed the presence of a set of genes shared with other domesticated animals, suggesting that there are “domestication” genes. Some scientists propose that dozens of interacting genes form a “domestication syndrome” that will alter features and behaviors in a consistent direction across many species at once.

Although wolves were domesticated into dogs in several regions of the world around 15 to 40 thousand years ago, they were not the first animals to be domesticated. We were. Homo sapiens may have been the first species to select for these genes. When anthropologists compare the morphological features of modern humans to our immediate ancestors like the Neanderthal and Denisovans, humans display neoteny. Humans resemble juvenile Neanderthal, with rounder flatter faces, shorter jaws with smaller teeth, and slender bones. And in fact the differences between a modern human skull and a Neanderthal skull parallel those between a dog and its wild wolf ancestor. [See figure below; Source.]

Comparisons of craniofacial traits. Top: Modern human vs. Neanderthal skull, showing reduced brow ridge, nasal projection, jaw projection, and tooth size in H. sapiens. Bottom: Dog vs. wolf skull, showing analogous reductions (e.g. shorter muzzle, smaller teeth) in the domesticated dog.

The gene BAZ1B influences a network of developmental genes, and is one of the gene networks found in the domesticated silver foxes. In a rare human genetic disorder, the gene BAZ1B is duplicated twice, resulting in a person with longer jaws and longer teeth, and social awkwardness. In another rare genetic disorder called Williams-Beuren syndrome, the same BAZ1B gene is not doubled, it is missing. This omission results in “elfin” features, rounder face, short chin, and extreme overly friendliness and trust of strangers – a type of extreme neoteny. A network of developmental genes controlled by BAZ1B are common in all modern humans but absent in Neanderthals, suggesting our own juvenile-like domestication has been genetically selected.

What’s distinctive about humans is that homo sapiens domesticated themselves. We are self-domesticated apes. Anthropologist Brian Hare characterizes recent human evolution (Late Pleistocene) as “Survival of the Friendliest”, arguing that in our self-domestication we favored prosociality – the tendency to be friendly, cooperative, and empathetic. We chose the most cooperative, the least aggressive, the less bullying types, and that trust in others resulted in greater prosperity, which in turn spread neoteny genes, and other domestication traits, into our populations.

Domesticated species often show increased playfulness, extended juvenile behavior, and even enhanced social learning abilities. Humans continued to extend their childhood far later than almost any other animal. This extended childhood enabled an extended time to learn beyond inherent instincts, but it also demanded greater parental resources and nuanced social bonds.

We are the first animals we domesticated. Not dogs. We first domesticated ourselves, and then we were able to domesticate dogs. Our domestication is not just about neoteny and reduced aggression and increased sociability. We also altered other genes and traits.

For at least a million years hominins have been using fire. Many animals and all apes have the manual dexterity to start a fire, but only hominins have the cognitive focus needed to ignite a fire from scratch and keep it going. Fires serve many purposes, including heat, light, protection from predators, annealing sharp points, and control burns for flushing out prey. But its chief consequence was fire’s ability to cook food. Cooking significantly reduced the time humans needed to forage, chew, and digest, freeing up time for other social activities. Cooking acted as a second stomach for humans, by pre-digesting hard-to-digest ingredients, releasing more nutrients that could be used to nourish a growing brain. Over many generations of cooking-fed humans, this invention altered our jaws and teeth, reduced our gut, and enlarged our brains. Our invention changed our genes.

Once we began to domesticate ungulates like cows and sheep, we began to consume their milk in many forms. This milk was especially important in raising children to healthy adults. But fairly quickly (on biological time scales, 8,000 years) in areas with domesticated ungulates, adults acquired the genetic ability to digest lactose. Again our invention altered our genes, enlarging our options. We changed ourselves in an elemental, foundational way.

In my 2010 book, What Technology Wants, I made this argument, which I believe is the first time anyone suggested that humans domesticated themselves:

We are not the same folks who marched out of Africa. Our genes have coevolved with our inventions. In the past 10,000 years alone, in fact, our genes have evolved 100 times faster than the average rate for the previous 6 million years. This should not be a surprise. As we domesticated the dog (in all its breeds) from wolves and bred cows and corn and more from their unrecognizable ancestors, we, too, have been domesticated. We have domesticated ourselves. Our teeth continue to shrink (because of cooking, our external stomach), our muscles thin out, our hair disappears. Technology has domesticated us. As fast as we remake our tools, we remake ourselves. We are coevolving with our technology, and so we have become deeply dependent on it. If all technology—every last knife and spear—were to be removed from this planet, our species would not last more than a few months. We are now symbiotic with technology….We have domesticated our humanity as much as we have domesticated our horses. Our human nature itself is a malleable crop that we planted 50,000 years ago and continue to garden even today.

Our self-domestication is just the start of our humanity. We are self-domesticated apes, but more important, we are apes that have invented ourselves. Just as the control of fire came about because of our mindful intentions, so did the cow and corn arise from our minds. Those are inventions as clear as the plow and the knife. And just as domesticated animals were inventions, as we self-domesticated, we self-invented ourselves, too. We are self-invented humans.

We invented our humanity. We invented cooking, we invented human language, we invented our sense of fairness, duty, and responsibility. All these came intentionally, out our imaginations of what could be. To the fullest extent possible, all the traits that we call “human” in contrast to either “animal” or “nature,” are traits that we created for ourselves. We self-selected our character, and crafted this being called human. In a real sense we collectively chose to be human.

We invented ourselves. I contend this is our greatest invention. Neither fire, the wheel, steam power, nor anti-biotics or AI is the greatest invention of humankind. Our greatest invention is our humanity.

And we are not done inventing ourselves yet.