new thread
I was thinking about something... humans seem to have much longer hair than primates - who are supposed to share a common ancestor with us. what I'm wondering is, how come man has evolved to have much less body-hair and much more "head-hair" than primates? (if you don't believe in evolution, then nevermind hehe) also, if someone never has had a haircut in his whole life, how long hair will he get by the time he's, say, 20? does our habits of cutting our hair change the way it grows?
and one more thing, has men and women the same length of hair naturally?
we sweat in order to keep cool. sweat glands probably replaced hair follicles as we evolved. a fresh breeze will cool just about any skin surface exposed to the air, but heat rises to escape- leaving the tops of our heads as the most critical physical surface needing insulation. the 'stuff' of hair is probably scavenged from the bloodstream and without a dense physical distribution of body hair follicles, our head hair is left an abundance of 'ingredients' to develop long hair. our species likely evolved in a tropical setting- migrating to cooler climates in search of food. hair long enough to cover our shoulders and back helped insulate us against the less tropical temperatures. we likely killed animals first for skins and developed our taste for meat subsequently.
terminal hair length varies from person to person- some people can't seem to grow much past their shoulders while others can cultivate floor length tresses. cutting hair may not change an individual's course of hair growth over one lifetime but the altered temperature dynamics may translate to his / her offspring a tendency to grow exaggeratedly long hair to compensate what is genetically perceived as a need for natural insulation.
i suspect men and women on average can grow similar hair length proportionate to their physical size.
all this is conjecture and i welcome any well thought-out difference of opinion.
some good points there...
I came to think of another thing... it seems to me that africans always have very short, curled hair. do you think we got longer hair as we moved to colder climates?
it would make sense. our need for evaporative cooling decreased as our need for covering increased.
they needed to get as MUCH sunlight (Vitamin D) as possible...
J.S. mentioned the "sweat" thing, but the other side of the coin - the need for insulation - definitely comes into play when man talks about his head, and I'll elaborate a bit on that. I hike a lot, and all the hiking books mention how humans lose a LOT of heat from their heads. They even have an adage, "If your feet get cold, put on a hat!"
I've found that, as a longhaired and bearded man, I can wear at least one layer of clothing less than other hikers, and sometimes two. But the crucial time comes at night - when one sleeps his head remains exposed. Long hair and a beard not only keep your head warm, they completely seal the space around your neck. Freezing cold air leaking down into your sleeping bag is a faint memory, once you have your hair. Also, back to the daytime, when one is walking, wind will stream your hair in front of your face, and those dancing strands will form a shear boundary between the cold air outside and a layer of warm air next to your face. Your face will feel like the weather is a LOT warmer than it actually is. All this adds up to my being toasty warm while others shivver.
Even in tropical climes, it can often be cool at night. We all need our manes in the wild. Races that don't grow great beards tend to grow longer and thicker manes. If that is what nature gives you, she intends at night for you to wrap that mane around your neck dude. :-)
Keep it growin'!
Bill
i would assume that we started to lose hair as we began to wear clothes. the clothes were basicly hair anyway, so having our own simply go in the way.
as for the hair on the head... we walk upright. our heads are closest to the sun and we dont tend to cover them. perhaps ut grew becuase that part needed shade.
This has been discussed here before, and I've seen articles in scientific journals about this as well. First, I'm not so sure that humans have the longes hair of all mammals. Take musk oxen, for example. They grow hair about a yard long all over their bodies. What is more, they lose most of it every year. I would not be surprised if they produce the most hair in total volume.
Another thing about musk oxen is that they live in the arctic. Obviously, they need their hair for warmth. On the other hand, naked mole rats live in Antarctica with hardly a stitch (only their whiskers, I think). They survive the cold by living under the snow and supporting their high metabolism by eating calorie rich penguins, which they keep fresh by storing in their deep freeze. These animals are quite possibly the most amazing animals in the world in my view. They catch their prey by melting the snow under the feet of the penguins with their foreheads.
Tibetan monks also seem to have no poblem surviving a cold night with not much more than a sheet, high up in the Himalayas. Obviously, from these two examples, it is possible to survive cold weather using something other than insulation.
Surviving the heat is another matter. For whatever reason, humans evolved to keep cool by sweating. One of the articles I referred to, above, was about what the best body configuration is to keep cool in the heat. Besides sweating over the whole body, humans are unique in being mostly vertical. A computer simulation showed that maximum cooling occurred on a vertical body if only the top was covered -- more than with no covering and more than when the whole body was covered. Horizontal animals, however, achieved maximum cooling by being completely covered, thus shielding their skin from the direct rays of the sun.
Exceptions in nature immediately come to mind: elephants and hippos. Hippos stey in the water most of the time, so they need not be considered. Elephants, rhinos, etc., probably substitute a thick skin for fur. Notice also, that they love to get themselves muddy.
OK. But that doesn't explain why our head hair is so long. I have a couple ideas about this. First, although we are mainly vertical, we do a lot of stooping, at least primitive hunter/gatherers and early farmers did. Long head hair mostly keeps covering the back during a stoop, still offering a covering when in that position.
Hair quality is also a sign of health. Malnourished people tend to lose their hair. Hair, then, is a marker of health. Choosing a mate with long hair would tend to favor ones that are also healthy, and hence mates more likely to propagate the species.
Finally, like the peacock tail, it could simply be a sex-related trait. Many species have characteristics that exist only to attract a mate. I think hair could be such an item in people.
PROTECTION from sharp weapons and falling objects.
We all know of the famous stories about how long hair
had to be moved OUT of the WAY of the GUILLOTINE since the
blade could actually prevent the blade from penetrating the skin. (This example
clearly demonstrates the strength of hair!)
The same could be said about hair stopping a sword from cutting
the arteries in the neck.
Just the other day a fairly large branch fell and hit the side of my head
and neck. What happened? Well, my hair gently guided it away from
my neck without a scratch!
Oddly, humans are the only animals with such long HEAD hair when
it is compared with hair distribution on the rest of the body.
Even horses and lions--who have relatively short body hair--do
not have such long terminal growth.
Man is truly unique and beautiful in many ways.
I have seen Andalusian horses with long manes and tails dragging the ground by at least a meter. Friesians also have extremely luxurious manes. Pictured is an Andalusian horse. Admittedly, these are not natural hair styles for horses but have been bred into them. I guess that in itself says something about man's preference for long hair.
hmmmmmm...guess a mane might count as 'head' hair I suppose...
then again, it is 'balanced out' by that tail so it might break the
proportion rule?
I wonder why they used to be called the "National Barber" during the French Revolution if they can't even cut through the hair?-)
But what about mammoths? Or did you forget about them when they became extinct? Remember, a mammoth never forgets about extinct species!
I think that the only purpose of hair is to look good. Its like horses. They have hair too and its only for looks. But as to why hair appeared on humans, I have no idea. Maybe the specimens with longer than average hair on their head reproduced more than the others, because they were considered more attractive?
Have you considered "warmth" since it wasn't just hair on their heads? Hair didn't just appear on humans, modern humans evolved from more hair laden species of earlier humans and seem to have lost a bit of that body hair.
There is a family in Central America going back several generations that has a unique genetic trait that causes most of the men and women to have unusually large amounts of hair covering their bodies (including faces). The more extreme examples in this family would make you think of the werewolf fairytales.
The theory has been advanced that pre-human species lived primarily in the water. There's a 6 million year gap in the fossil record spanning the early man years to today. Many believe our ancestors may have lived in the water at that time. The aquatic period changed our evolution from other apes, giving us the relatively hairless bodies and long head hair. Check this out for more info:
Like all controverial theories, there are fanatics and total dis-believers. Decide for yourself what you think.
The Rev
If you have never seen gelada baboons, you should take a look. The males have long hair going half way down their backs. They also seem to have a particular fascination with chests, as humans do. I saw a program on TV that I think was about the origins of language. These baboons were pointed out because their complex society of large groups seems to have rudimentary language.
Other primates, such as some marmosets have extremely long moustache hairs, for example, when compared to other parts of the body. There is a South American monkey that has no hair at all on its brilliant red head, but is luxuriently pelted elsewhere. Colobus monkeys also have very long hair in specific parts of their body, along the white patches of fur going down the sides of their backs and their tails.
The point is that we are not unique in having a unique hair distribution pattern, although our particular pattern may be unique.