scientist measures a skull

Did drop in testosterone make humans more civilized?

A comparison of more than 1,400 ancient and modern skulls suggests human society advanced after people started being nicer to each other. And researchers say that change in behavior was likely due to a dip in testosterone.



composite skull
A composite image shows the facial differences between an ancient modern human with heavy brows and a large upper face and the more recent modern human who has rounder features and a much less prominent brow. (Credit: Robert Cieri/University of Utah)

“The modern human behaviors of technological innovation, making art and rapid cultural exchange probably came at the same time that we developed a more cooperative temperament,” says Robert Cieri, a biology graduate student at the University of Utah who began this work as a senior at Duke University.

Heavy brows were out, rounder heads were in, and those changes can be traced directly to testosterone levels acting on the skeleton, according to anthropologist Steven Churchill, who supervised Cieri’s work on a senior honors thesis at Duke that led to the study published in the journal Current Anthropology.



Mellow vs. angry apes



Those two apes develop differently, Hare explains, 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.


“It’s very hard to find a brow-ridge in a bonobo,” Hare says.

Softer faces






“If prehistoric people began living closer together and passing down new technologies, they’d have to be tolerant of each other,” Cieri says. “The key to our success is the ability to cooperate and get along and learn from one another.”

The National Science Foundation, the Leakey Foundation, and the University of Iowa Orthodontics Department supported the project.

Source: Duke University


chat2 Comments


  1. CaveMan

    “Did drop in testosterone make humans more civilized?”
    I respond…
    “Did drop in Estrogen make humans more civilized?”

  2. Jim Keneipp

    I think the days of the Y chromosome are numbered.

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