A Tale of Two Chins

Cell phones . . . couches . . . gyms and community centers . . . archaeologists of the future will unearth countless artifacts and buildings that will testify to the nature of our lives as social creatures.

Recently, anthropologists have argued for evidence of a different sort that tells a far earlier story of our social nature: to wit, some ancient chins.

Yes, our evolving chin shape apparently demonstrates some major alternations in our species’ profile.

Nowadays, women’s fashion magazines might dispense advice about how to choose sunglasses depending on one’s chin shape.
Screenshot 2015-04-18 19.03.20
But these small differences pale compared to that between our current, species-wide, facial shape and that of our much older ancestors.

For, before 80,000 years ago, our ancestors pretty much lacked chins altogether.
2 Chins

Left: Note the chin on this modern human; Right: No chin on this Neanderthal!
[Image: Tim Schoon]

Many changes happened in a short time. Among other notable alterations, our early ancestors’ head sizes shrank overall, while their brains grew out of all proportion. In turn, the enlarging brains of these pre-modern humans shrank the space available for their faces. (Today, most people boast faces some 15 percent shorter than the faces of Neanderthals.) In turn, those smaller faces pushed out our ancestors’ chins.

According to biological anthropologist Nathan Holton, the development of a chin—a facial feature unique to our über-social species—correlates temporally with other transformations.

For this bony shift in facial shape occurred while males’ testosterone levels lowered, social cooperation between groups heightened, and our early ancestors produced the first art.

So it’s not that our chins actually made us more sociable. Rather, their sudden appearance on the facial scene signals the development of our social nature.

Biological anthropologist Robert Franciscus explains: “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 . . . 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.”

Nowadays, in the midst of daily headlines that scream examples of violence on scales both massive (war) and intimate (rape), we easily forget that the impulse to violence that captures our collective attention is, somewhere deep inside our genetic makeup, counterbalanced by an impulse to cooperation.

What will it take for us to reclaim that pointy-chin part of our species’ capacities?

Read more: “Feminization, Social Tolerance, and the Origins of Behavioral Modernity,” by Robert L. Cieri, et al.

P.S. A recent lecture at Harvard by my Illinois colleague, archaeologist Stan Ambrose, argues that our lineage of modern humans beat out Neanderthals some 74,000 years ago because of our close ancestors’ capacity for cooperation; he builds his argument by looking at the changing relationship between testosterone levels, face shape, deep voice, and trust (skip to 47’47 to get to the heart of the argument).

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