system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why tears come out of our eyes when we became sad.

what is the purpose of crying. basically why we cry when we are sad.
gpt
Why do we smile? why do we have more facial muscles? A lot of our social behaviours are there... to show others how we feel.

By communicating with other humans we can more easily form a group that can work together.

Our body took something we could do: "tearducts form liquid to help eye be lubricated and protected" and just repurposed it for a social use.