Why Do Humans Have Chins? We’re the Only Species That Does.
According to new research, that knobby slab of bone jutting from our lower jaw is more than just a bit of angular bone or a sign of facial superiority. It’s likely just an evolutionary accident.
In a study published in PLOS One, anthropologist Noreen von Cramon-Taubadel and colleagues argue that the human chin likely evolved “by accident.” Rather than being shaped by natural selection for chewing, speaking, or being the perfect canvas for a well-placed dimple, the chin appears to be what evolutionary biologists call a “spandrel,” a byproduct of other structural changes, not a standalone adaptation.
Humans are the only primates with a true chin. Not even our evolutionary ancestors, like Neanderthals or Denisovans. Not even our closest great ape relatives have them. The fact that we’re the sole chin-havers made scientists think there was something special going on with us.
Turns out there isn’t.
When researchers analyzed craniofacial evolution across hominins, the chin didn’t show strong signs of being directly selected for survival. Instead, all the research gathered seemed to indicate that our chins emerged when our skulls reorganized themselves with each iterative evolutionary step we took,
As early humans evolved larger brains, the angle of the cranium shifted. At the same time, our lower faces shrank. We can count our teeth getting smaller, one of the reasons our faces aren’t huge. The chin seems like it was just the geometric consequence of all those micro adjustments, just some bone filling up space created by a shrinking face and expanding to make room for a bigger brain.
To test this, the researchers examined specific features of the chin and found little evidence that natural selection directly shaped them. All this means that the chin didn’t evolve to, say, brace the jaw or to make us better suited for cracking our teeth through hard stuff. Our chins are just the byproduct of our skulls being warped and twisted by evolution, just a weird leftover nub that can make us look ridiculous if we have too much or not enough of it.
