Unnatural Selection: The Ape Who Tamed Itself

It’s early morning rush hour in the North Bronx in the coldest February since 1934. I’m on the 6 train out of Pelham Bay as we pick up still more passengers at East 177th Street, Parkchester. Ordinarily, we would now switch to the fast track and run express to 125th Street in Harlem.

The 7:05am Number 6 at Pelham Bay

The 7:05am Number 6 at Pelham Bay

But extreme cold last night has frozen the switches, so this train is stuck on the local track until after we go underground at Hunts Point in the South Bronx.
Already packed, our train will take on dozens more people. Bags and coats are getting caught and at each successive stop it takes longer for the doors to close. There’s grumbling as we all get squeezed tighter together. I hear some shoving and shouting down the car. but eventually peace prevails, doors close and the train trundles forward on the elevated icy tracks. No one here is at fault and we grudgingly accept that it’s just going to get worse until we get to Harlem where folks can transfer to the 4 and 5 trains.

And I’m thinking: we are the only primates who can do this. We’ve grown tame when compared to our closest relatives, the other apes. We have an extraordinary tolerance for crowding and stress. You couldn’t pack other primates into confined spaces without one of them getting killed or maimed along the way.

The Long Road to Civilized Behavior

By 80,000 years ago we Homo sapiens were well on our way to self-domestication, or tameness. I’ve remarked in an earlier post that warfare is a recently established institution, less than 10,000 years old. But the in-your-face, bar-room type of explosive violence is different. Though we still get in fights and inflict bodily harm on each other, such behavior has declined over the long time-span since our lineage split from the other great apes. Among our closest living relatives, Chimpanzees get into fights a hundred times more often than we do. Male chimps are responsible for almost all of the violence, which is often fatal.

Bonobos, our other closest relatives are another story entirely but I’ll return to them in another post.

Darwin’s “Domestication Syndrome”

Charles Darwin described the biology of domesticating animals in 1871. He discovered that when animals are bred to get along with people, anatomical changes also occur. Dogs get floppy ears and curly tails. But notice that wolves and coyotes, their undomesticated relatives, don’t have these traits. The anatomical changes over human evolutionary history tell the story of our own domestication. Over time our once prominent brow crests have diminished; we have smaller teeth and shorter faces. Particularly among males, those trends can be traced back through the fossil record for at least a half million years.

From right: our ancestor, Homo heidelbergensis, with large brow crests modern Homo sapiens (Cromagnon), juvenile chimp, adult male chimp. (Note juvenile chimp looks more human than adult. We look like the docile young ape because our development takes longer)

From right: our ancestor, Homo heidelbergensis, with large brow crests, modern Homo sapiens (Cromagnon), juvenile chimp, adult male chimp. (Note juvenile chimp looks more human than adult. We look like the docile young ape because our development takes longer)

Docility of temperament in people and animals is linked to a more drawn out development and childhood, lower levels of stress hormones and testosterone. Between women and men, there is much less anatomical difference (sexual dimorphism) than between male and female chimps or gorillas. But it is men who have come to look more like women than the other way around.

Taming Ourselves

We domesticated animals by deliberate selective breeding for tame behavior and tolerance for being around people. But if we also domesticated ourselves, how could that have happened? There are clues to this among the social practices of hunter/gather people who have continued to exist into the industrial era, and whose ways anthropologists have observed and recorded. Out of the reach of modern legal systems, these tight cooperative social networks cannot tolerate an aggressive, violent male among them. A strong ethic of cooperation and egalitarianism prevails among hunter/gather people, who will collectively shun and socially sanction anyone who attempts to dominate other members of the group. If all non-violent sanctions fail, the group will by agreement kill the offending individual (note this is not the same as capital punishment, a relatively modern institution).

The hundreds of thousands of years of prehistory during which aggressive males were weeded out of the human population have made males more cooperative. Along the way we men have developed a more feminine facial structure partly due to lowered testosterone and stress hormones. (not that masculinity is disappearing exactly… it’s just been getting a facelift on the way to civilization)

Civilization: Homo sapiens boarding the 6 train at Pelham Bay Park

Civilization: Homo sapiens boarding the 6 train at Pelham Bay Park

Our 6 train finally pulls into 125th Street Station below the streets of Manhattan. The doors slide open disgorging a flood of people who hurry across the platform toward a much less crowded 4 train now arriving from the west Bronx. I stay on board the 6 as both trains proceed south toward lower Manhattan. I’m happy to have a seat now, and that more than half a million years of prehistory has made us such a cooperative species.

The Meek Inherit the Earth

As Rome was extending its imperial reach, a prophet living on its eastern periphery declared that the meek shall inherit the earth.
But by that time, they already had.


About guy robinson

General Biology teacher, paleoecologist, pollen counter, tracker of mastodons and other Ice Age mammals through New York's wetlands
This entry was posted in culture, evolution, history, paleolithic, science. Bookmark the permalink.

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