system
Given the following post, respond as if you're commenting on Reddit:
human
Why are testicles stores in a thin, sensitive sack outside our body instead of a protective casing inside our bodies?

I don't understand how we never evolved to have our testicles inside our bodies (such as behind our pelvises) instead of being exposed to extreme pain when they are even just tapped a little.
gpt
Sperm require a fairly specific temperature to be most healthy, and this temperature is lower than body temperature. So, hang the baby makers outside the body in a sack that can expand and contract to cool it or warm it, and you're good to go.

Until you get kicked in the nards.

But, evolution decreed it's 'good enough', which is all evolution can ever do.