The body part that baffles science: the mystery behind this human feature that scientists can’t figure out

When I first read that no other animal has a chin, I had to double-check. Gorillas don’t have one. Neither do chimps, dolphins, or even our Neanderthal cousins. It turns out only Homo sapiens have this jutting little piece of jawbone – and nobody really knows why.

From testicles to chins

We can now trace the evolutionary reason for things as oddly specific as testicle size. In fact, human testicles, as highlighted in The Tree of Life, by author Max Telford, and discussed in a recent article in The Conversation, sit awkwardly mid-table among our primate peers. Not as massive as those of the rather promiscuous chimp, but still a healthy step up from the monogamous gorilla.

The consistent pattern is clear: more mating competition, bigger balls. That’s what they call convergent evolution, when similar traits evolve separately in different animals facing the same pressures.

But the chin? Well, the chin doesn’t exactly play ball.

What’s the chin for, anyway?

Scientists have tossed around plenty of theories. Maybe it was to strengthen the jaw during fistfights. Maybe it helped hold up a beard. Maybe it’s the flabby leftover of evolution softening our bite after we discovered cooking. All interesting, but none are really testable. Because, again, no other animal ever evolved a chin... not even by accident. Without the aforementioned convergent evolution to give us natural comparisons, we’re left guessing. While fun, also a little futile.

You can read more on this in Telford’s book but the bottom line seems to be that unless we dig up a new mammal from the fossil record, the biological question mark remains. We’ll just have to take it on the chin.

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