Humans are the only animal with chins. Other critters have jaw bones that form the bottom of their faces, but no other animals have this little pointy bit, and neither do any of our extinct relatives. So we just need to figure out why??? 

And people have come up with all sorts of intriguing hypotheses. Maybe it helps us talk? Maybe it helps us bite harder? My personal favorite: it's all about looks, because you know, this, it's gonna definitely attract a mate. Right?

The thing is, none of these have held up to scientific scrutiny. So now, scientists think the chin may be what's called a spandrel. A trait with no inherit benefit that just appeared as a side effect of something else. Now, we just have to figure out what that something else is. 

And that, as they say, is gonna be a real chin-stroker. Maybe it's just for this?