Why Human Faces are So Odd
Our mugs are unique in many ways. Blame fire, farming, prehistoric bar fights and socializing.
You’ve got a small, rather short face and some wildly expressive eyebrows. Nothing wrong with any of that, but just so you know, your features are unique among hominins.
Your late relatives, the Neanderthals, had longer faces with more pronounced bone structure. Chimps and bonobos — your closest living relatives — have longer faces. None of them are near as expressive as yours, nor as unique compared to others in their species.
And now scientists have one more idea, to add to many, trying to explain why we evolved such odd faces: developing social skills.
The First Bar Fights
It’s not clear why our ancestors had such bulky faces to begin with. One long-held idea is it had do with serious chewing required for the original paleo and Mediterranean diets, before the invention of fire and nutcrackers. Another possibility, presented in the journal Biological Reviews in 2014, is that prehistoric bar fights — over the usual disagreements that have caused men to evolve (or not) across the ages — led to strong face bones to protect against punches.
“When modern humans fight hand-to-hand the face is usually the primary target,” explained University of Utah biologist David Carrier. “What we found was that the bones that suffer the highest rates of fracture in fights are the same parts of the skull that exhibited the greatest increase in robusticity during the evolution” of our ancestors.
But that was then. Human faces have been shrinking since long before boxing moved from the cave to the ring.
Scientists have chewed on many ideas for why we developed comparatively small, short faces to go with our oversized brains. One idea: Learning to cook made chewing easier, which likely led to smaller chompers and an evolving facial structure, according to long-held ideas. Then the agricultural revolution, which started just some 12,000 years ago, allowed hunter-gatherers to move to cities and eat even more refined foods, requiring yet less effort. Oatmeal comes to mind.
But here’s a new thought:
Our mugshots evolved also as we developed “more opportunities for gesture and nonverbal communication — vital skills for establishing the large social networks which are believed to have helped Homo sapiens to survive,” researchers write in a review of studies published April 15, 2019 in the journal Nature Ecology and Evolution.
“We can now use our faces to signal more than 20 different categories of emotion via the contraction or relaxation of muscles,” said study team member Paul O’Higgins, professor of anatomy at the University of York. “It’s unlikely that our early human ancestors had the same facial dexterity as the overall shape of the face and the positions of the muscles were different.”
Your newfound dexterity allows you to wiggle those hairy eyebrows quite noticeably on that nice smooth forehead, for example. The range of expressions help you get beyond brute anger, or what appears to be laughing among chimps, and express things like sympathy, and recognition of others.
“We know that other factors such as diet, respiratory physiology and climate have contributed to the shape of the modern human face, but to interpret its evolution solely in terms of these factors would be an oversimplification,” O’Higgins said.
Another interesting explanation of facial evolution was put forth in the journal Nature Communications a few years back. It holds that the human obsession with all things visual led to the evolution of many distinct faces — a wider range than most creatures — so that we’d be able to recognize each other without butt sniffs.
The evidence revolved around finding that facial traits — a big nose, say — are more variable than other body dimensions and less correlated than other traits. So, for example, people with long arms tend to have long legs, but a long nose doesn’t reliably predict a wide nose or wide-set eyes or anything else other than a steady stream of schnoz jokes.
“Humans are phenomenally good at recognizing faces; there is a part of the brain specialized for that,” said behavioral ecologist Michael J. Sheehan at the University of California, Berkeley. “Our study now shows that humans have been selected to be unique and easily recognizable. It is clearly beneficial for me to recognize others, but also beneficial for me to be recognizable. Otherwise, we would all look more similar.”
However it happened, your makeover isn’t complete.
“Softer modern diets and industrialized societies may mean that the human face continues to decrease in size,” said O’Higgins, the theorizer of socializing. Botox notwithstanding, there are limits to how much our faces can evolve, though. “For example, breathing requires a sufficiently large nasal cavity,” he said. “However, within these limits, the evolution of the human face is likely to continue as long as our species survives, migrates and encounters new environmental, social and cultural conditions.”