Human Faces Evolved Through 'Self-Domestication' With Ancestors Apparently Choosing Friendly, Less Aggressive Mates

The human face may have evolved through a process of "self-domestication" with our ancient ancestors tending to choose mates who had less aggressive, friendlier personality types. Scientists have found evidence to suggest a gene involved in facial shape and personality may have been favored by humans, eventually leading to our small, slender appearance.

The team, led by Matteo Zanella from the University of Milan, Italy, and senior author Giuseppe Testa, from the Laboratory of Stem Cell Epigenetics at the European Institute for Oncology, looked at the gene BAZ1B to see if it was involved in changes to the human face over time.

Humans have domesticated other animals for thousands of years. One of the most notable species is dogs, which were descended from wolves. Previous research has shown the gene BAZ1B was involved in the shift from wolf to dog, with these genetic changes helping to make dogs smaller, with softer faces.

The BAZ1B gene is also involved in Williams-Beuren syndrome. People with this disorder have distinctive facial features, including smaller noses and chins, wide mouths, full lips and cheeks. They are also known for having very friendly, social personalities, with strong verbal skills.

In their study published in Science Advances, Zanella and his team looked at this gene and how it may have influenced the evolution of the human face. They studied BAZ1B in stem cell lines from patients with deleted or duplicated genes in the Williams-Beuren region of the brain. Findings show a "key contribution" of the gene to facial shape.

Using this, the researchers then looked at paleogenic data that showed early modern humans, one Denisovan and two Neanderthals. This allowed them to look at differences between ancient human species.

They discovered there were mutations in regions that depend on BAZ1B compared with the Neanderthals and the Denisovan sample. Their research revealed the enrichment of regulatory changes in BAZ1B, providing what they say is the "first empirical validation of the human self-domestication hypothesis," and showing this gene is a "master regulator" of the modern human face.

These findings potentially suggest ancient humans were choosing mates who were less aggressive, more social and better communicators—and these favorable traits came with changes to our faces. In an email to Newsweek, the study authors explained: "We suspect the facial changes were part of a process of reduction in reactive aggression, boosting our prosocial, cooperative profile."

Rodrigo Lacruz, from the Department of Basic Science and Craniofacial Biology at the New York University College of Dentistry, who was not involved in the research, commented on the study. He told Newsweek the idea humans domesticated themselves has been around for a long time, with even Charles Darwin tinkering with the idea.

"[The] researchers have...zeroed around BAZ1B with the potential to elucidate the biological bases for a purported domestication of modern humans," he said. "In an elegant study [the team] exploited the links between BAZ1B and facial and behavioral changes in Williams-Beuren, and detail how this gene mediates the induction and migration of specialized cells at the core of facial development."

He said the "thought-provoking" research helps to bridge boundaries between genetics and behavior. "As you brush teeth in the morning, maybe thank BAZ1B for helping you to look more human than Neanderthal," he added.

Penny Spikins, senior lecturer in the archaeology of human origins at the U.K.'s University of York, who was also not involved in the study, said the research "confirms suspicions" that changes to this region of the brain may have played a key role in human self-domestication.

"It is all too easy to view human evolution as about individualistic success, but these findings illustrate another example of how interpersonal social processes were critical in what made us human," she told Newsweek. Similar genetic and craniofacial changes have been recorded in the transition between wolves and dogs, and illustrate not only how important emotional and social sensitivity is to what makes us human."

She said some of the findings do not necessarily fit with our understanding of the changes taking place late in human evolution. However, she said it shows we are only at the start of the process of understanding how genetic selection was involved. "Who knows, in a few years time we may be surprised that we ever considered that competition to be more 'clever' or more technologically advanced were the key drivers in our evolutionary past."

This story has been updated to include more information on the study authors.