We get goosebumps when we are cold. Goosebumps are when our hair sticks up because of muscles under our hair folicles. This is actually a leftover trait from when humans had fur and more hair on their bodies. This helped early humans because it helped them trap heat in between their hair and acted as a blanket! Over time, humans evolved to have less hair, but still have the goosebumps as a remaining feature of human evolution!