Here's why we have chins

A new study has given the reason behind why did human chins evolve if Neanderthals and archaic humans didn't possess them.

University of Iowa's Nathan Holton said that in some way, it seems trivial, but a reason why chins are so interesting is humans are the only ones who have them. None of the primates, Neanderthals, archaic humans or any other species posses them and so it's unique to modern humans.

The study posits that our chins don't come from mechanical forces such as chewing, but instead results from an evolutionary adaptation involving face size and shape, possibly linked to changes in hormone levels as we became more societally domesticated.

Using advanced facial and cranial biomechanical analyses with nearly 40 people whose measurements were plotted from toddlers to adults, the UI team concludes mechanical forces, including chewing, appear incapable of producing the resistance needed for new bone to be created in the lower mandible or jaw area.

Rather, they write, it appears the chin's emergence in modern humans arose from simple geometry: As our faces became smaller in our evolution from archaic humans to today, in fact, our faces are roughly 15 percent shorter than Neanderthals', the chin became a bony prominence, the adapted, pointy emblem at the bottom of our face.

Lead author Holton added that they do not find any evidence that chins are tied to mechanical function and in some cases they find that chins are worse at resisting mechanical forces as people grow, suggesting that chins are unlikely related to the need to dissipate stresses and strains and that other explanations are more likely to be correct.

What the researchers did notice is chin "growth" has more to do with how each feature in our face adapts as our head size increases, much like you'd fit individual pieces together in an expanding, shape-shifting, three-dimensional puzzle.

Holton concluded that their study suggests that chin prominence is unrelated to function and probably has more to do with spatial dynamics during development.

The study is published online in the Journal of Anatomy.