system
Given the following post, respond as if you're commenting on Reddit:
human
What exactly are Goosebumps?

What are goosebumps, and what really causes them? Do they actually do anything and if so, what do they do?
gpt
They are an evolutionary trait that humans no longer need. Originally it made your fur stand on end. This achieved two things: one, it trapped warm air next to your skin to keep you warm  and  two : it made you appear bigger and more frightening. 

This explains why you get goosebumps when you are cold and when your flight/fight response is activated.