Humans started making art when their personalities got 'gentler'

The study, which is based on measurements of more than 1,400 ancient and modern skulls, makes the argument that human society advanced when people started being nicer to each other, which entails having a little less testosterone in action.

Heavy brows were out, rounder heads were in, and those changes can be traced directly to testosterone levels acting on the skeleton, according to Duke University anthropologist Steven Churchill, who supervised Cieri's work.

What they can't tell from the bones is whether these humans had less testosterone in circulation, or fewer receptors for the hormone.

The research team also included Duke animal cognition researchers Brian Hare and Jingzhi Tan, who say this argument is in line with what has been established in non-human species.

In a study of Siberian foxes, animals that were less wary and less aggressive toward humans took on a different, more juvenile appearance and behaviour after several generations of selective breeding.

Dr Hare, who also studies differences between our closest ape relatives - aggressive chimpanzees and mellow, free-loving bonobos, said: "If we're seeing a process that leads to these changes in other animals, it might help explain who we are and how we got to be this way.

He said chimps and bonobos develop differently, and they respond to "social stress" differently. Chimpanzee males experience a strong rise in testosterone during puberty, but bonobos do not. When stressed, the bonobos don't produce more testosterone, as chimps do, but they do produce more cortisol, the stress hormone.

He said their social interactions are profoundly different and their faces are different, too.

Dr Hare added: "It's very hard to find a brow-ridge in a bonobo."

Cieri compared the brow ridge, facial shape and interior volume of 13 modern human skulls older than 80,000 years, 41 skulls from 10,000 to 38,000 years ago, and a global sample of 1,367 20th Century skulls from 30 different ethnic populations.

Originally posted here:
Humans started making art when their personalities got 'gentler'

Word Count: 321