What sets Homo sapiens apart from other animals? Among other things, our chins, NPR reports. That piece of bone jutting out from your jaw is somewhat of a mystery—one that’s inspired a diversity of wild theories to explain its purpose, according to a paper published this month in Evolutionary Anthropology. The author of the paper dismisses a number of these explanations, such as the possibility that the chin serves as a sexual signal (such traits usually only appear in one sex—like the mane of a male lion). Another proposal is that the chin acts to protect your throat—an idea the paper’s author also shoots down, because for this to be a substantial advantage, humans would have to be constantly punching each other in the face.