Emasculation of Humans Linked to Surge in Culture, Technology
The emasculation of modern humans may have led to the rapid development of culture and technology 50,000 years ago, new research suggests.
Fossil records show that modern humans started appearing around 200,000 years ago. However, it was only about fifty thousand years ago that artistry and tool making became popular.
New research shows that society bloomed when testosterone levels in humans started dropping.
"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," lead author Robert Cieri, a biology graduate student at the University of Utah who began this work as a senior at Duke University, said in a news release.
The latest study, which involved more than 1,400 ancient and modern skulls, show that society experienced rapid advancements after the development of gentler personalities and more feminine faces. Previous research has linked being and looking "nicer" correlated to a lowering of testosterone level.
"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," said lead author Robert Cieri, a biology graduate student at the University of Utah who began this work as a senior at Duke University.
Fossilized skulls revealed that heavy brows started fading out and rounder heads became more prevalent about 50,000 years ago. Furthermore, these changes in features can be traced directly to testosterone levels acting on the skeleton.
Researchers said that this theory also supports changes in non-human species.
Previous studies on Siberian foxes revealed that juvenile-looking foxes were less suspicious and aggressive toward humans.
"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," researcher Brian Hare, who also studies differences between chimpanzees and bonobos.
Hare explains that these two apes develop and respond differently to social stress. Chimpanzees, the more aggressive species, have a greater brow ridge than easy-going, free-loving bonobos.
"It's very hard to find a brow-ridge in a bonobo," Hare explained.
Chimps also experience a surge in testosterone during puberty. However, bonobos experience higher cortisol levels.
After comparing the brow ridge, facial shape and interior volume of 13 modern human skulls, researchers found that there was a trend toward a shortening of the brow ridge and upper face. Researchers explain that these changes generally suggest a decrease in the action of the masculine hormone testosterone.
Researchers said that the latest finding suggest that living in a community and cooperating may have led to evolution of gentler personalities and effeminate faces as societal and cultural advancement profits from agreeableness and lowered aggression.
"If prehistoric people began living closer together and passing down new technologies, they'd have to be tolerant of each other," Cieri said. "The key to our success is the ability to cooperate and get along and learn from one another."