system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does the human body know when it's 37°C if its only reference point (the outside world) doesn't have a stable temperature?
gpt
Your hypothalamus knows it wants a certain temperature. If it's too hot or too cold, it adjusts the rest of your body to lose or conserve heat. It doesn't know what that temperature is. It just knows it wants it at a certain temperature. This is because humans have evolved to favor that temperature. The advanced mammals who set their thermostat lower ended up getting more fungal infections and dying. The ones who set it higher burned a lot more energy and ended up starving. The one's who set it in the middle did the best. Then years later when doctors measured it, it turned out the temperature was 37 degrees C.