why do nipples get hard
In: Biology
It’s the same muscle behaviour that creates goosebumps.
It’s not that useful for us without much hair, but if we were still furry, it would help us stay warm when cold, or look bigger when scared. Just like when a cat fluffs up its tail.
But because evolution doesn’t get rid of unnecessary features if they don’t lower our survival rate, we still have a lot of these autonomic responses that don’t really apply to our current biology. At least as far as we can tell.
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