why do we have hair on our body
We're a pretty resourceful species, but when it comes to body parts, humans definitely have a couple that seem like a waste of space. After all, we could do perfectly well without the appendix, male nipples, and our wisdom teeth, and scientists think these could simply be a hangover from our evolutionary past. But what's the point of all that hair on our bodies, and why do we have eyebrows anyway? The
of the University of New South Wales' (UNSW) How Did We Get Here explains. For starters, even though we might consider ourselves pretty hairless, humans are actually covered in around five million hair follicles - tiny organs on our skin's surface that produce hair. In fact, after our heads, the area with the highest concentration of hair is our nostrils.
But why aren't we as hairy as our ape cousins? As evolutionary biologist Darren Curnoe, it's believed that our ancestor's body hair got a lot shorter as they evolved from walking on all fours to standing, and this allowed them to keep cool while walking and running long distances in pursuit of food. And our hair still plays a very important role in regulating our body temperature. When it's cold outside, tiny muscles surrounding the hair follicle cause the hairs to stand up, to trap more heat near the body. This is what happens when you get goosebumps. So those tiny hairs all over our bodies make sense. As do nostril hairs and eyelashes, which keep dirt out of our bodies.
But what about things like chest hair, pubic hair, and eyebrows? Why do they grow so much longer than the hair on our arms, and what's the point of them? Scientists still aren't entirely sure, and we'll let you to find out why. But one thing's for sure, our hair definitely isn't useless. Don't forget to to see new episodes of How Did We Get Here? as they're released, and find out more about the research happening at Grooming your body hair can seem like cutting the grass in the summertime. You devote an afternoon to the chore, and the next thing you know, the grass has shot up and you're hauling the lawn mower outside again. When landscaping your body, there are to tweeze, mustaches to trim and coiffures to condition daily.
The average man spends more than a month out of his lifetime shaving his beard [source: ]. Women hunch over their legs with razor in hand for hundreds of hours to meticulously strip away of thousands of unwanted hairs. While the hair we see on the outside of our bodies may appear to be actively growing, the real action takes place below the surface of our skin, or epidermis. inside of our hair follicles divide and multiply, and as space fills up inside of the follicle, it pushes older cells out. After those older cells harden and exit the follicle, they form the hair shaft. The shaft is mostly comprised of dead tissue and a protein called keratin.
But human body hair doesn't grow indefinitely -- if that were the case, you'd probably look a lot more like Cousin Itt from The Addams Family. Instead, individual hairs go through active and resting phases. The process of cellular division that increases the length of the hair shaft is the active, or anagen, phase. The anagen phase continues for a period depending on the type of body hair, then slows down for the resting, or telogen, phase. Since your hair is made up of dead matter, it falls off during the telogen phase. These varying durations of growth explain why the hair on your head grows longer than your arm hair. Your body hair's anagen phase usually lasts only a few months, while your scalp's phase lasts a few years.
Differences in growth phases, size and shaft density also define the different types ]of human body hair. In the womb, fetuses are covered in tiny hairs called lanugo. Shortly after birth, babies grow vellus, or fine, unpigmented hairs, across the body. When hits, vellus hairs give way to coarser terminal hairs in places such as the underarms and genitals. The longer, thicker hairs on your scalp, eyebrows and eyelashes are also terminal. Tally those body hair categories on the average person, and it adds up to around 5 million individual hairs. Wouldn't life be simpler if you were just bare everywhere?
- Autor: DallasMaruff
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