Okay. Basic disambiguation: do you mean emotions as in complex aggregations, e.g. a thought with valence attached, or down to the level of body sensations like those you get when you're sad?
Because those serve fairly different functions.
1
1
You’re unable to view this Tweet because this account owner limits who can view their Tweets. Learn more
Okay. Without "feelings", i.e. somatic sensations and drives, you almost certainly die.
It's all basic survival stuff with basic survival functions. You'll want to read some nonshitty evpsych, but I'm short on recommendations here. I mostly read textbooks in uni, long ago.
Emotions are a bit more complex to get into. They seem to be a more recent thing in our history, and serve more diverse functions.
A lot of emotion, a truly humongous amount, is prosocial adaptation, and sometimes they're defense mechanisms around trauma.