Why does the fur of animals stop growing/shed past a certain length but we have to manually cut our own hairs?
In: Biology
The hair on our heads also has a maximum length, barring certain person-to-person exceptions. It’s just that we usually have it cut before it reaches that length.
Your hair also stops growing and sheds past a certain length.
You just want it shorter than that length, so you’re cutting it before it gets that long.
Also, why does the hair on our head and facial hair like a beard grow super long but all other hair on our bodies grows very short then stops?
Do you cut your arm hair?
Humans have a natural hair limit like animals. It’s just that men and women alike often prefer to cut it shorter than that. This does bring up a good question.
Why then does human head hair so greatly exceed the head hair lengths of other creatures?
Because women.
Through sexual selection in our history, female humans with longer hair limits were preferred over their shorter counterparts likely because it came to represent good health and fertility which made them ideal partners and offspring-bearers.
The phenotype of long hair however, would still be passed onto male offspring and before long, all humans whether male or female had the capacity to grow their head hair multiple feet longer than those of animals. This would then also make it so males had to constantly trim their hair because our preferred manageable length is still far shorter than what our biology dictates.
Have you ever trimmed your arm hair?
Human hair stops growing at a certain length too, but that can vary. Some people’s hair starts splitting and shedding when it gets to their shoulders, others can grow it right down their back just fine. Same goes for leg hair, or beards, or pubes.
We don’t have to manually cut our hair, we just have a preferred length.
Plus primates have a history of different head fur types (some monkeys have some very distinctive head hair). This makes your species more noticeable over a distance. Standing out on the savanna, look at the other apes over in the distance and you would note they were your species because of the hair on the head. Full disclosure, not a scientist just some guy that thinks monkeys and apes are cool.
Fur grow a certain length before it will shed. So the average length for this to happen is the length of the fur.
The same thing happen do us. Thats why you don’t need to cut most of your hair. Hair on the head and beard will on average grow very long before shedding. If you want it shorter you manually cut it, but you are not ending up with long fur all over your body if you don’t shave.
I own enormous mustache, at some point they just stop to grow any bigger. Probably the same will happen to your head hair at some point.
Each hair has a genetic time limit.
The life cycle of human head hair is 2-6 years. An individual hair will grow for up to 6 years and then it falls out.
The hair on your arm has a life cycle of a few weeks and then falls out – less time to grow less length!
Same for animals. Pet a cat for 20 minutes. They’ll shed all over you. Your nails lightly scratching will help the dead hairs come out, and allow new ones to come in. Furry animals have hair with very short life cycles.
Pet a humans head and they hopefully won’t shed much at all.
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