system
Given the following post, respond as if you're commenting on Reddit:
human
Why does human hair (head) grow continuously as opposed to animals?
gpt
Animal hair does continuously grow. All hair does. The limit to the length of hair is the growth cycle.

Basically, every hair follicle has a cycle it goes through. The hair grows, then after a while stops growing, and then falls out. The follicle then rests for a period of time before starting a new hair growth. For human hair, the growth period is on the order of several years. 

Fur, like the hairs on other parts of the body, has a much shorter growth stage, resulting in shorter hair.