Why Body Hair

here's a crazy statistic the average man spends more than a month of his life shaving his faith presumably for the Steampunk stache it's just one of the many forms of human Peled your hair and fur which mammals use to regulate body temperature state camouflage to enhance our sense of touch and look fabulous but if they're so great why do we have so little of it compared to even our closest evolutionary ancestors why do we have it at all and what's going on up here as opposed to everything below the up here well you might say scishow has got you covered all animal hair from the stuff on your head to a porcupines quills to the twitchy whiskers of a mongoose is made of the same stuff the protein keratin but humans like other animals have several different kinds of hair and they change in surprising ways over time venus is in the womb for instance are covered in tiny hairs called lanugo when a baby is born these hairs fall out and fine unpigmented vellus hairs or peach fuzz grow to take their place then of course when awkward teen years roll around we start seeing certain vellus hairs morph into coarse new growths called terminal androgenic hairs these developed in response to growing levels of sex hormones called androgens both men and women produce androgens but men make a lot more which is why they usually have more body hair so thankfully all our different kinds of hair don't grow at the same rate if they did we'd all look like Afghan hounds that's because your hair follicles go through different phases and rates of growth turning on and off throughout your lifetime for example the antigen or active growing phase of the hair on your head lasts for years compared to your armpit or nether regions whose antigen phase lasts just for a few months your armpit hair can never grow longer than a couple of inches because it's growth pattern is limited which is nice you wouldn't want that going down to your knees so your terminal head hair may be able to reach Rapunzel record book lengths if you never cut it but sometimes hair needs a break so it goes through a resting or telogen phase which often results in breaking and shedding these different phases along with things like shafts density and follicle size that make up the recipe for head hair versus leg hair versus eyebrow hair still unless you suffer from the exceedingly rare condition of congenital hypertrichosis in which the lanugo hair of your childhood continues to grow your whole life on a bait all over your face and body humans appear to be practically bear compared to other mammals it is a fun fact we actually have the same number of follicles as our great ape cousins about 5 million individual hairs it's just that our hair is much shorter in finer than that of Apes which raises the question what happened to our fur one theory suggests that it started with early hominids shift to bipedalism human hair likely started to fade away around 1.7 million years ago around the time early human ancestors began living the hot shadeless African savanna life and started walking upright exposing less of their bodies to direct sunlight the fact that we still have hairy heads compared to the rest of our bodies may come from the fact that our domes needed built-in shelter from the Sun more than other parts though that does beg the question why aren't our shoulders hairy another theory maintains that less hair meant fewer parasites and better health a super hairy body provides lots of shelter for parasites whereas less hair leaves fewer hiding spots for bugs so bare skin may have been a good advertisements to potential mates for overall health and fitness and considering that of course everything has an evolutionary purpose our head hair to help to protect us from the Sun and light body hair to deter bugs we may likewise have kept our pubic and underarm hair to help us get it on both of these areas how's apocrine glands which release the pheromones that help attract potential mates we have extra thick hair in these hot moist areas to help trap and transmit these pheromones whether we like having it or not so the next time you pull onto your razor take a second to think about all of the advantages your hair provides you and that it has been millions of years in the making and then probably just shave it off because that's what society demands thanks for watching this episode of scishow if you have any questions or comments or ideas for us were on facebook and twitter and down in the comments below and if you want to keep getting smarter with us here at scishow you can go to youtube.com/scishow and subscribe

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