Why Humans Have Chins: The Evolution of This Strange Feature

Why do humans have chins? It turns out that the chin is not a mechanical advantage, but instead results from an evolutionary adaptation involving face size and shape, possibly linked to changes in hormone levels.

If you look at a primate or a Neanderthal skull and compare it with a modern human's, you'll notice that they lack the chin that humans have. In order to find out how and why humans evolved this chin, researchers used advanced facial and cranial biomechanical analyses with nearly 40 people whose measurements were plotted from toddlers to adults.

So what did they find? It turns out that mechanical forces, including chewing, appear incapable of producing the resistance needed for new bone to be created in the lower mandible, or jaw area. Instead, it appears as if the chin's evolution is due to simple geometry. As our faces became smaller in our evolution, the chin became a bony prominence.

"In short, we do not find any evidence that chins are tied to mechanical function and in some cases we find that chins are worse as resisting mechanical forces as we grow," said Nathan Holton, one of the researchers, in a news release. "Overall this suggests that chins are unlikely related to the need to dissipate stresses and strains and that other explanations are more likely to be correct."

Interestingly, it seems the chin may be a secondary consequence of lifestyle change. Modern humans evolved from hunter-gatherer groups that were isolated from each other to increasingly cooperative groups that formed social networks. People became more tranquil during this period and less likely to fight over territory and belongings. This change in behavior was tied to reduced hormone levels which resulted in changes to the craniofacial region; the face became smaller and the chin more prominent.

The findings are published in the Journal of Anatomy.

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