... but when humans do it, it's automatically NSFW.

I'm not encouraging people to go outside like that, to be clear. I'm just curious. Back before clothes were invented, humans must've walked around naked before covering up for some period of time, right?

Somewhere in between that and now, covering up became the norm, and now our brains are wired to complain about how naked we feel if we try to not wear clothes. When did the shift happen?

(Edit: fixed typo)