system
Given the following post, respond as if you're commenting on Reddit:
human
Why does the hair on the average human head continue to grow while all other primates have hair that stops naturally at a relatively short length?
gpt
Think Peacocks.

Peacock feathers likely evolved because Peahens saw brilliant plumage as a sign of health.  So, Peahens who liked brilliant plumage mated with Peacocks who had brilliant plumage.

The male children of these Peacocks and Peahens likely had more brilliant plumage, while the female children likely had a preference for brilliant plumage.  So, they mated.

Their male children likely even had *even more* brilliant plumage, and their female children likely had *even more* of a preference for brilliant plumage.  And so on and so forth, until you get the ridiculous Peacock feathers of today.

This process is called Fisherian runaway sexual selection.

It's ~~theorized~~ **speculated** that long human hair came about much in the same way.  After early humans lost much of their body hair, longer head hair became a sign of good health.  So humans who had long hair and a preference for long hair mated, producing children who had longer hair and a bigger preference for longer hair.  And so on, and so forth.