Civilization is a pretty astounding thing. The idea that one species can rise up from the struggle of nature to separate itself into an organized, globally-connected network of distinct but related cultures is pretty impressive; but it is also wrong. The connectedness bit is fair enough, but the idea that humans built civilization without help from any other species just doesn’t stand up to scrutiny. To say nothing of the immensely cooperative plant species we have manipulated to make our way of life possible, there are a handful of animals that have contributed substantially to our comfort and well-being.
Domesticated animals are ingrained in every society in the world to the point where their names and sounds of their names are among the first things that children learn. But the curious thing about these creatures is why there aren’t more of them. Given that animals have proven so useful to people (and vice versa), why, out of the millions of species that exist, are there only eight real cornerstone species of human society? What is so special about cows, sheep, pigs, goats, chickens, horses, cats, and dogs?
In his enormously popular book Guns, Germs and Steel, biologist Jared Diamond lays out six criteria that determine if a species is eligible for domestication. Many animals demonstrate a few of these traits, but all six are required to turn beast into buddy. The rarity of finding all of them in the same animal goes a long way to beginning to solve the mystery of domestication. They are:
- Easygoing eating habits – domesticated animals have to be able to live off food they can forage and scavenge in and around human settlements.
- Fast growth (relative to humans) – an animal isn’t much use if it takes a decade of care to become big enough to pull a plow.
- Willingness to breed in captivity – you can’t be shy if you live and love in a barn.
- Docility – cows are a lot calmer by nature than water buffalo.
- They don’t panic and flee when startled – or they have a stronger instinct to stay in a herd than run off on their own.
- They conform to social hierarchy – they follow a leader like… well, sheep.
As awesome as it would be to have a grizzly bear bounce at your night club, they are severely lacking in trait number 4. A lack of docility also explains why horses have provided transportation for millennia, while the more aggressive zebra is left to graze the savannah in peace. Elephants have been tamed here and there, but have never achieved true domestication because they take 15 years to reach their adult size. These criteria matter.
When humans have identified and latched onto these six characteristics, we have been able to form some amazing partnerships, but as interesting as what we have been able to achieve is, there are the unintended consequences of selectively breeding for desired traits; what evolutionary biologists have dubbed “domestication syndrome.”
As it turns out, when you take a wild animal and domesticate it, there are a set of physical changes that occur that have little to do with any of the six criteria, but seem to go along with them anyway. Domesticated animals – when compared to their wild cousins – general have smaller brains, shorter faces, smaller teeth, weaker muscles, floppy ears, and blotchy coats.
The reason for these changes has long been a mystery, but recent research into the genes responsible for some of them has provided some clues as to why domestication syndrome is a thing. Apparently, selective breeding has tapped into a set of cells called the neural crest which, during the development of a fetus, shapes many of the features that change when animals are domesticated. Interestingly, changes to the genes that control the growth of these cells have also been connected to calmer, friendlier dispositions. There is even a human condition called Williams Syndrome which manifests as a mild variation in facial development and unusual levels of friendliness. In other words, friendliness and floppy ears are genetically linked.
But perhaps the most interesting thing about the features of domestication syndrome is that a lot of them can also be found in people. We may have big brains but our teeth, muscles, faces, and general physical presence pale in comparison to a below average chimpanzee. As we have domesticated animals, society has domesticated us. Something to remember next time you start to suffer from human superiority syndrome.