Goose bumps

[sabrinah]

What are the point of goose bumps?

[Kev]

Goose bumps are when your bodily hair stands on end, the purpose being to trap air which serves as insulation.
Not so effective now we're not monkeys.

[JohnPPotts]

As well as providing a (largely ineffective) extra layer of insulation, it is also a signal when frightened to make you look bigger to deter an attacker (again, not very effective with humans, but quite effective if you're covered in hair - as you could see if you ever see a spooked cat).