Serious question: Why do humans have chins?

Have you ever thought about why we have chins? Yes, I am completely sober and completely serious right now. Along with a relative lack of body hair, strategic planning abilities, and Benihana restaurants, chins are among the few features that truly set humans apart from other primates. So what’s the deal? Why have humans been blessed with chins (or as I like to call them, the original bibs)?

A new study from the University of Iowa tackles just that. Led by Nathan Holton, assistant professor in the Department of Orthodontics, researchers analyzed the cranial structures of 40 people—from toddlers to fully grown adults—attempting to identify why chins develop.

For years, scientists have believed the chin developed to adjust to the mechanics of chewing—essentially, that it was a product of function.

“Any time you put a load on a bone, whether it’s running or chewing … that results in certain types of stresses and strains in the bone,” Holton told Fusion. “So the chin was thought to be a way to accommodate those stresses and strains.”

For example, one theory has been that the chin evolved to resist the bending that occurs on the front of the mandible (right where that ‘lil ridge is) when we chew. These biodynamics can be seen in our ape and monkey cousins.

But human faces are shaped differently, and therefore work differently. Holton’s crew analyzed the heads of participants and found no evidence suggesting mechanical force warranted more bone on the chin. In fact, those who exhibited more mechanical force had less prominent chins. So what gives? Welp, humans may still be adjusting to the fact that we’ve got small faces compared to neanderthals and primates.

Holton’s colleague Robert Franciscus, a professor of anthropology, has hypothesized that the reduction of the human face occurred as a result of hormonal changes (a reduction in testosterone) that took place as humans became less hunter-gatherer-y and more cooperative and social network-y. But while that change may help explain the broader evolutionary gears at work, Holton is trying to get to the bottom of how the chin, specifically, has adjusted to a smaller face.

“One thing that we argue is that the development of chins in humans has less to do with mechanics and more to do with this pattern of facial reduction,” says Holton. “What we think is happening is that the chin and other parts of the face that are unique to modern humans are secondary consequences of the reduction of facial size.”

Holton and his team now plan to study whether the amount of chin bone and the way it’s deposited has more to do with genetics or environment. Stay tuned and keep your chins up in the meantime.