A new study has revealed that ancient humans started making progress in art and technology as their testosterone levels began to decline. Their faces became more feminine and their personalities gentler with the falling hormone levels. Modern humans appeared about 200,000 years ago. But they had made little progress for about 150,000 years.

testosterone levels

Startling correlation between falling testosterone and human advancements

Suddenly, they leapt forward in art and technology about 50,000 years ago. They began making grindstone, projectile weapons, birding and fishing equipment, flaked flint and antler tools. There have been multiple theories about whether this advancement was driven by the advent of language, brain mutation, cooked foods or just population density.

But a new study conducted by researchers at the universities of Utah and Iowa and Duke University shows that researchers have found a startling correlation between human advancements and falling testosterone levels. The study was published in the journal Current Anthropology. Scientists studied more than 1,400 skulls, some modern and some ancient. They found that as testosterone levels dipped, males became nicer and gentler to each other, and skulls became softer and rounder.

Testosterone-fueled changes clearly visible in our ape relatives

Robert Cieri, lead author of the study, said that a dip in testosterone levels led to lowered aggression and a cooperative temperament. It gave rise to cultural exchange and technological advances. At the same time, there were more visible facial changes such as shortening of the upper face and a reduction in the brow ridge. These traits reflect a reduction in testosterone activity.

Scientists are confident that the skeletal changes were driven by less testosterone. However, they said these changes came either from falling testosterone in circulation or the decline in the number of testosterone receptors. Brian Hare, co-author of the study, said that the changes driven by testosterone are clearly evident in our closest ape relatives chimpanzees and bonobos. Aggressive chimps produce more testosterone when stressed. In contrast, mellow, free-loving bonobos produce more cortisol.