Tears
As a parent, it seems like a glaring omission that most crying is done by babies.  It's right there in the article that humans have the "most dependent babies," and signaling behaviors are often repurposed responses, so it's a good starting point to say that crying (with big inhales and audible sobs) evolved as a "baby in distress" alarm, in which a baby makes a lot of noise because it needs help.  We go to that place when we feel small or want the kind of support a parent would give.Babies often don't have tears for the first few months, but I'm not sure that's important.  I do think they play a role on the playground, and a lot of the speculation about their effects in social situations sounds right.  I don't have any ideas to contribute on why crying is accompanied by tears.In any other species, wearing a signal that advertises, "I recently lost in a dominance challenge," is a strict liability — an invitation for others to pile on, opportunistically, and attack you while you're down (or else to mentally note that you're no longer a good, strong ally). There's no upside, therefore, to using anything other than a quick facial expression or flash of body language, to show your submission only to the aggressor.That sounds like an overly harsh picture of non-humans to me!  I'm pretty sure at least certain apes help their potentially-non-kin in distress.  Humans aren't the only social mammals.