The decline in testosterone levels in ancient humans 50 thousand years ago was the beginning of the development of culture and communication. This was reflected in the structure of the skulls, the brow ridges were reduced and, in general, the upper part of the face became shorter.
According to official science, modern man (Homo sapiens) emerged as a species about 200 thousand years ago, but only 50 thousand years ago he experienced a sharp leap in the development of culture and technology. New tools have appeared.
“The model of behavior of a modern person, aimed at searching for new technologies, the development of art and cultural exchange, apparently arose precisely when a person learned to interact with his own kind in a more peaceful way. When I learned to negotiate,”says biologist Robert Cieri of Duke University.
A recent study led by Siri was published in the journal Current Anthropology. Comparative measurements were made of 1400 modern and ancient human skulls: 13 skulls 80 thousand years old, 41 skulls between 10 and 38 thousand years old and 1367 skulls of people who lived in the 20th century from 30 different ethnic groups.
As a result of the measurements, a trend was followed with a significant decrease in the size of the brow ridges and a general shortening of the upper part of the face. The skull has also become more rounded. All this can be attributed to a decrease in testosterone levels. Roughly speaking, the facial features of the "younger" skulls were more "feminine" than those of the older ones.
The skulls began to change about 50 thousand years ago (Upper Paleolithic) and then there was a sharp jump in the level of development of human culture. Bone tools, heat treatment, flint knives, throwing weapons, and a variety of household items such as sharpening stones or fishing gear appeared in abundance. Apparently due to the drop in testosterone levels, which is closely associated with aggressive behavior, people became kinder to each other, learned to negotiate and make cultural exchanges.
Another Duke University research group that works with animals has confirmed these observations for their four-legged charges. The domestication of the Siberian fox, when the most non-aggressive individuals (low testosterone levels) were selected by selection, showed that modern animals also differ in appearance and behavior.
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Professor Brian Hare studied the differences between common chimpanzees and bonobos. Ordinary ones are more aggressive, bonobos, on the contrary, are more meek and loving. The difference is that testosterone levels rise sharply in male chimpanzees during puberty, while bonobos do not.
What could have caused a significant drop in testosterone levels in ancient men?
“It is possible that this happened when the number of people grew to a certain critical point and they involuntarily had to learn to get along with each other,” suggests Siri.
Testosterone is the main male sex hormone. Experiments on animals show that it strongly affects aggressiveness, sexual behavior, anxiety, learning, as well as those parts of the brain and neurotransmitters on which the corresponding responses depend.