SciTech

Duke anthropologist wonders: ‘Why do humans have chins?’

Famous chins: John Travolta and Oprah Winfrey. James Pampush, an evolutionary anthropologist at Duke University, dedicated the majority of this decade studying why humans have chins.
Famous chins: John Travolta and Oprah Winfrey. James Pampush, an evolutionary anthropologist at Duke University, dedicated the majority of this decade studying why humans have chins. AP

We often stroke our chins when we’re thinking, but has anyone ever done so while pondering why we have chins at all?

That bony mass at the bottom of the face is unique to humans. No other animals on earth, past or present, come with one – not dinosaurs, chimpanzees, not even chinchillas.

So what is its purpose?

James Pampush, an evolutionary anthropologist at Duke University, has dedicated the majority of this decade chasing the answer, even writing his doctoral dissertation on the perplexity of the chin.

It’s their oddness that first attracted him.

“They’re so bizarre,” said Pampush.“We emerge on the scene 200,000 years ago and we have this extra bit of bone on our jaws. Nothing on Earth has ever had them before.”

Other evolutionary anthropologists have studied the chin in the past, but their hypotheses as to why chins exist have always come up short, in Pampush’s view.

Some researchers theorize humans developed chins to help with speech – that they’re used as a means to support the force of our wagging tongues so our jaws don’t acquire small cracks.

Pampush disagrees with that claim, though, offering that plenty of other animals use their tongues inside their mouths with similar force.

“Dogs panting are probably putting every bit as much tongue movement related forces on the front of their jaws, and they don’t have chins,” he said.

Others believe we were given chins to attract mates, another theory Pampush disputes. The kinds of features designed to appeal to a mate are usually found in just one sex. In cardinals, for example, only the males have bright red feathers.

“Male and female humans have chins,” said Pampush. “If it only occurred in men, and women were attracted to chins, then that would give a lot more credence to the idea.”

The reason for differing theories among evolutionary anthropologists boils down to their philosophies regarding natural selection, and how much of a role it plays in the evolutionary process.

Some researchers believe that every part of the human body is an example of our ability to adapt to the changing environment. Others think natural selection is just one of many influences affecting our evolution.

Pampush falls into the latter group, and has his own theory as to why we have chins.

“The chin isn’t an adaption, rather I think it’s a byproduct of teeth getting smaller,” he said.

As humans began using their hands more to smash, cut and grind food, their need for the large teeth in the front of their mouths began to diminish, which eventually led to our smaller jaws. Pampush believes sections of the jaw may not have shrunk as quickly as others – causing the protruding bone jutting out below, which we call the chin.

So there you have it: There’s no real purpose for your chin. It’s just a legacy feature leftover from your ancestors.

Pampush admits that it’s not the sexiest answer, but he believes it’s the most likely, and that further research into the theory may lead to additional revelations about the evolution process that led humans to appear as they do today.

“Asking why we have chins and saying, ‘We just sort of do,’ is sometimes seen as an unacceptable answer because they’re so weird,” he said. “But I think there’s intrinsic value in knowing everything there is to know about humans.”

Learn more

Read “The Enduring Puzzle of the Human Chin,” by James Pampush and David Daegling,” published in January in the Journal of Human Evolution: At www.researchgate.net/publication, type “Pampush” in the search window, then scroll to article.

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