system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do people go bald on the top of their head and still have some on the sides and not vice-versa?
gpt
While many say it's just genetics, there isn't enough data to give a conclusive answer. Of course, genetics play a large role in everything. There is some evidence that mechanical stress is involved in the common pattern of male pattern baldness. The skin on the temples and crown of the scalp are "tighter" than the other parts. This causes more stress in these areas, and may be why people tend to bald in these spots first. 

We do know that mechanical stress itself can cause balding, because of a condition called traction alopecia. Women who pull their hair tight constantly may lose hair this way.