I just finished reading a compelling story at NPR's website, "Teary-Eyed Evolution: Crying Serves a Purpose".

As humans, we are unique in that we shed tears to show emotions.  Why don't we just yelp or whimper like other animals?

The story presents an intriguing argument: that the ability to cry may have carried a certain evolutionary advantage within early human communities:

Within these communities, Bering says, tears could be powerful tools. They did more than just signal vulnerability — they were perhaps a way of keeping social and reproductive bonds strong. Maybe good criers were survivors.

"Crying seems to elicit compassion and guilt," Bering says, "and that itself may be an evolved mechanism to save relationships in distress."

It's pretty hard to be pissed off at someone who's crying.  So maybe, just maybe, crying provides a means for us to keep those close social bonds in tact.  Bonds, which at least in part, make us human.

photo via Flickr/cornerofart