Why do we have chins?

John Hawks ‏@johnhawks  

@That802BeerGuy @BrianPardy Mandible yes, chin no: 

There are many things we don't know, including why we have chins. Great perspective: http://www.theatlantic.com/science/archive/2016/01/were-the-only-animals-with-chins-and-no-one-knows-why/431625/ … #biology by @edyong209