How does a cat's body know how long to make its whiskers?

I found this‘s%20whiskers%20are%20proportionate,is%2C%20the%20longer%20its%20whiskers article. (I don’t know why the link won’t paste right.) Let me know if it’s not coming up.

@Pandora Thanks. Just temporarily interested. I liked your link. Your link works for me.

Some jerks 40 years ago would go around and burn feral cats whiskers off with a match. Its good that they grow back.

The same way your eyelashes know how long to grow—you just have to think about it hard enough and they’ll stop growing at the right length. I could be wrong.

@gorillapaws And how does my eyelashes know? Is it genetics. DNA? The brain? Instinct?

Hairs on each part of the body have an average time they go through each part of the growth cycle, including shedding. Supposedly, stress can alter the cycle for hair and can make hair fall out faster than usual. I would guess evolution has perfected how long a cat’s whiskers should be. Providing protection so the cat survives, and maybe looks attractive to other cats.

I believe they just fall off at a certain point. Like pubes.

Why single out cats? How does a human body know when to stop growing? How does the body know how long to make armpit hairs? How does a deer’s body know how long to make antlers? How does an elephant’s body know how long to make tusks? How does a tree know how big to make leaves?