Why are humans the only animals with chins?

“Little pig, little pig, let me come in,” says the big, bad wolf. “No, no, not by the hair on my chinny chin chin,” say the three little pigs. This scene is deeply unrealistic and not just because of the pigs’ architectural competence, the wolf’s implausible lung capacity, and everyone’s ability to talk.

The thing is: Pigs don’t have chins. Nor do any animals, except for us.

The lower jaw of a chimpanzee or gorilla slopes backwards from the front teeth. So did the jaw of other hominids like Homo erectus. Even Neanderthal jaws ended in a flat vertical plane. Only in modern humans does the lower jaw end in a protruding strut of bone. A sticky-outy bit. A chin.

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