A new study has found a connection between dropping levels of testosterone and the development of modern behaviors. In other words – the “feminization” of our early ancestors is what led to the development of modern behaviors.
The study, which was run by researchers from Duke University and the University of Utah, looked at the the remains of humans that lived some 50,000 years ago. Although moderns humans evolved around 200,000 years ago, they did not start using advanced tools and creating art until 50,000 years ago, the researchers noted.
They think came about after a drop in testosterone levels.
“Humans are uniquely able to communicate complex thoughts and cooperate even with strangers,” said Robert Cieri, University of Utah graduate biology student and lead author of the paper.
“New research on fossilized Stone Age humans from Europe, Africa and the Near East suggests these traits are linked, developed around 50,000 years ago, and were a driving force behind the development of complex culture.”
The researchers looked at the bone structure of more than 1,400 skulls of both ancient and modern humans. They noticed that ancient skulls had a heavy brow and sharp features, indicating high levels of testosterone.
The skulls from around 50,000 years ago, however, have rounder features and more feminine qualities, indicating a decrease in testosterone levels.
“Human fossils from after modern behavior became common have more feminine faces, and differences between the younger and older fossils are similar to those between faces of people with higher and lower testosterone levels living today,” explained Cieri.
The researchers think that lower testosterone levels meant the early humans were more likely to work together, as high levels of testosterone can lead to more aggressive behavior.
“Whatever the cause, reduced testosterone levels enabled increasingly social people to better learn from and cooperate with each other, allowing the acceleration of cultural and technological innovation that is the hallmark of modern human success,” said Cieri.
The study was published in the journal Current Anthropology.