Today I learned that crying is still not well understood. Why do we cry?

Here’s the answer (spoiler alert!): we don’t know.

Humans are the only species that cry for emotional reasons (there was some suggestion in the past that elephants might cry in mourning, but it hasn’t stood up to scrutiny). It’s an oddly under-researched topic. We don’t know why we cry in physical pain. We don’t know why we cry from emotional trauma (so-called psychic tears), or even in moments of great happiness. As we are such social beasts, it might be an indicator, an external way of conveying profound and important internal mental state. But this is all guesswork.