system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what possible reason could the human race have for evolving with chemical capsaicin receptors on the anus?
gpt
What you call "Capsaicin receptors" are just heat receptors. Capsaicin triggers them so they respond the same way they do to heat.

The skin has lots of these receptors, and especially the mucous membranes, since it is good to be able to detect heat in order to avoid burns.