Here's Why We Have Chins And Archaic Humans Didn't

Modern humans standout from primates, Neanderthals and archaic humans for a number of reasons, but an obvious facial aesthetic comes to mind: we have a chin and they don't.

New findings published in the Journal of Anatomy examines how this detail is not linked to mechanical features like chewing, but rather, hormonal levels that occurred, perhaps, as we grew into more communicative individuals in society. 

For the study, researchers examined advanced facial and cranial biochemical analyses that involved over 40 individuals whose measurements were tracked from toddlers to adulthood.

"In some way, it seems trivial, but a reason why chins are so interesting is we're the only ones who have them," said Nathan Holton, who studies craniofacial features and mechanics at the University of Iowa, in a news release. "It's unique to us."

The findings suggested that certain mechanical forces were actually incapable of producing resistance when needed to create new bones in the lower mandible, suggesting that the chin came about from simple geometry as our faces grew to be more defined. Yet it wasn't till around 80,000 years ago that this development began to accelerate as we migrated from Africa 20,000 years later.

Men became less territorial during this period of evolution and more artistic, communicative and open to the idea of exchanging goods and ideas with each other. Researchers believe this may have been responsible for a reduction in hormone levels, particularly testosterone, resulting in shifts of craniofacial regions and a reduction of overall face size; this also yielded a more defined period of chin growth in which the feature later adapted to head size.

"What we're arguing is that modern humans had an advantage at some point to have a well-connected social network, they can exchange information, and mates, more readily, there's innovation," said UI anthropologists led by Robert Franciscus, "And for that to happen, males have to tolerate each other. There had to be more curiosity and inquisitiveness than aggression, and the evidence of that lies in facial architecture."