system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why I get goosebumps when I hear a song I like that I haven't heard in a while or when someone is an excellent singer?
gpt
Goose bumps are created when little muscles in the skin pull your hair so it stands up.  The mechanism evolved in hairy animals so that their fur could trap more air and keep them warmer when it is cold.  They don't do  anything useful that we know of in humans.

They are controlled by the sympathetic nervous system, which controls the way we prepare for fight-or-flight reactions.  When furry animals are scared or otherwise emotionally aroused, their hair stands on end which makes the animal appear larger and stronger to potential enemies.  Because humans have evolved from apes with this reaction, we still show it-- and the same muscles contract when we feel strong emotions-- of fear, or awe-- we get goosebumps.