Question: why do we get goosebumps?

Kevin Arbuckle answered on 20 Mar 2014:

Goosebumps are actually fairly useless for us now – at least compared to earlier in our evolutionary history. Goosebumps are when our hair stands on end and pulls up the skin it’s attached to. When we were far more hairy, goosebumps (or at least the hair standing up, called piloerection) had two main functions.

Firstly, to keep us warm – when we were very hairy the hair could stick up and insulate us against cold, by trapping a layer of air between the outside and our skin. Secondly, to make us look bigger. In the same way as blue tits fluff up their feathers as a defence or cobras spread their hoods, having our hair stick up when we are threatened (or, more generally, when we have an emotional reaction to something) made us look more intimidating.

Nowadays with our lack of hair it doesn’t help much in either situation so it’s mostly just a remnant of our evolutionary past.