On the Origin of Chins

Here's an evolutionary puzzle I had never thought about. Why do we have chins?

That bony protuberance at the end of your jaw may be hidden by a beard or a fleshy throat, but it is still there. Chimpanzees don't have chins, neither do gorillas, orangutans, spider monkeys, dogs, horses, frogs, or fish. Did you know that only humans have chins,? I didn't, but then I never studied vertebrate anatomy. It seems that having a chin is diagnostic of being a modern human. Even Neanderthals may have l...