April 1, 2026

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The chin is an evolutionary puzzle. Researchers may have finally solved it

Humans are the only species that has chins. A recent study sheds light on how that came to be and why evolution doesn’t always follow the rules

By Kendra Pierre-Louis, Sushmita Pathak & Alex Sugiura

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Kendra Pierre-Louis: For Scientific American’s Science Quickly, I’m Kendra Pierre-Louis, in for Rachel Feltman.

Most of us, if we think about chins at all, do so rarely. But it turns out that chins are an evolutionary clue. Among our primate kin, chins are a distinctly human trait, which raises a question: Why do we have them?

Research that was published in January presents a strong potential answer. To dig into the murky origins of the human chin, we spoke to one of the study’s co-authors, Lauren Schroeder, a paleoanthropologist at the University of Toronto Mississauga.

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Pierre-Louis: Thank you for joining us today, Lauren.

Lauren Schroeder: Thank you so much for having me.

Pierre-Louis: You recently wrote a paper looking into the evolution of the human chin. This is maybe a very silly question, but, like, what is a chin?

Schroeder: Yeah, so a chin is just a bony sort of protuberance at the lower part of the jaw; in sort of scientific terms we call this a mental protuberance. But it’s basically where the jaw comes together, you have this bone that is sort of sticking out a little bit.

We are the only species to have one.

Pierre-Louis: Mm-hmm.

Schroeder: Even our closest ancestor, Neanderthals, did not have a chin. So it is unique [Laughs] to our species.

Pierre-Louis: You do raise an interesting—is it “The Three Little Pigs” where they say, “Not by the hair of my chinny chin chin”?

Schroeder: [Laughs.]

Pierre-Louis: Apparently, that is fake! Pigs don’t have chins. We’ve all been lied to as children.

Schroeder: [Laughs.]

Pierre-Louis: Before we get into sort of the theories that your paper posits, what are some of the theories about, like, why humans have [a] chin?

Schroeder: Yeah, so because the chin is unique to humans, it has been a question that has been sort of asked and tried to be answered over a very long time in the literature, and many different proposals exist, things like helping with chewing or reinforcing the jaw in some way, so sort of a structural buffering of jaw forces. There’s also been proposals about the chin being—or playing a role in speech and language. Even shaped by sexual selection, this is also another proposal that has been put out there. Basically, you know, if you have a large chin, that makes you sexier. [Laughs.]

Pierre-Louis: [Laughs.]

Schroeder: I don’t know quite what to say. There’s also been this other proposal that basically posits that the chin is a byproduct of natural selection or evolution acting on other structures in the jaw and the cranium. And so the paper that we wrote was trying to sort of answer these questions.

Pierre-Louis: Yeah, and I feel like sort of in the culture we only think about chins when they’re, like, very large, sort of like Jay Leno—I don’t know if you remember who that is.

Schroeder: Yeah. [Laughs.] Yes.

Pierre-Louis: So it’s really interesting that scientists are really fascinated by the chin when I feel like most people aren’t. And I guess the question I have for you is: What got you into this research?

Schroeder: My research is sort of focused on looking at morphology, or the way we look as a whole, and how, if evolution was acting over time, how that evolution has sort of structured our morphology. So we sort of understand morphology as not, you know, separate parts but as a whole that works together.

And so looking at the chin within this sort of integrated structure is what really got me interested because this is sort of what I do—so how morphology is integrated and how evolution affects that whole structure.

Pierre-Louis: So before we get to what your paper concludes, can you tell me sort of what you did in your paper, the steps that led you to this conclusion, if you will?

Schroeder: Yeah, sure, so we sort of tested three broad possibilities. So whether the chin has been under direct selection—whether there’s an adaptive meaning to the chin, whether there’s an adaptive function to the chin. And so we tested that one hypothesis versus two others: one, that the chin is a byproduct of natural selection on other structures in the jaw and the cranium, and then the other is that the chin is sort