system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why does wool work at keeping you warm but cotton doesn't?

Edit: WET WOOL vs WET COTTON. Sorry can't type.
gpt
Wool evolved on an animal which lives outside in places where it rains a lot.  The function of the wool is to keep the animals warm by trapping air in fibers protected from water by oils.  The purpose of wool is to keep the sheep warm and dry.

Cotton evolved on a plant where the objective was to permit a seed to be easily transported by the wind.  Once on the ground, the cotton's job was to collect water to hold the seed to the ground and enhance it's chances of sprouting.  The purpose of cotton is to keep the seed wet.

These purposes are the opposite of each other, so that's why they are different.