Why do humans have long hair?

My husband was pleased with answers from another science thread, so he asked if I could post this one.

We're the only mammals whose hair grows so long that we have to cut it or keep it long.
Why is that? What is the advantage for evolving this characteristic?

Hair is nothing more than dead cells. The woolly mammoth would have used its hair to keep warm.
Human hair’s primary use is not for warmth but for attracting a mate. If our ancestors found long hair attractive and short hair unattractive then the unattractive would not reproduce.

Desert ... I've also thought about that, and this is what I've come with from my own thoughts about it.

Hair on Head: I think it's to protect the brain from blazing heat and from blistering cold. In cold weather, the hair acts as a blanket and keeps our head (brain) warm. In blazing heat, the hair acts as a shade. Also, the sweat glands on our scalps keep the hair moist in order to help in the cooling process.

Hair in Ears and Nose: The work as filters from dust, allergons and bacteria.

Eyelashes: Same as ear and nose.

Eyebrows: These work the same way that the black marks work that football players put under their eyes. They help absorb or redirect bright light to help us see. They are also used in the communication processs of humans.

Genitals: While I can understand the hair coverage of the female genitalia, which would work much like the ears and nose hairs given the structure of the female sex organs. I really do not understand the need for the hair coverage of the male genitals, other than working somewhat like the hair on our heads would work. Keep the testicles warm in cold and help cool them in heat.

Arms & Legs: This is something I have never understood, other than to think the hair would help protect the sensitive human skin against the elements. Sunlight, Heat and Cold. As a man, eventhough it's not what our soceity thinks, I shave my arms and legs. I shave because I think it's nasty and my wife likes it.

Arm Pits: The pits act as the bodies "air conditioners and heaters". They help by releasing heat when the body is hot, sweat glands and hair help to keep it cool. They also help produce heat when the body is cold.

Facial Hair: My first thought would be to act like the hairs of the arms and legs, but the human female body does not produce as much facial hair as the male body, so it wouldn't make sense for the hair to protect the face if it's a dominant male occurence.

Anyway, that's my thoughts on it ... Did any of it make sense? I'm also curious to know what answer your husband got from the science forums.

I think that Umbrax and DZ, have got it right on.
To clarify what DZ said, facial and genital hair exist to say “hi I'm ready to reproduce”
hope I helped some.

Thanks for replies so far!
Hmmmm, Umbrax, I get a picture of some distant female ancestor, surrounded by males staring at her long hair and saying, "Yeah, Baby! Now that's evolution!" I wonder if the other females became jealous? My husband especially appreciates my long hair, so maybe something to this.
DZ, interesting about you shaving. I shave my legs only because my husband likes it, not because I think it's something women should do. I think he wouldn't complain if I didn't, but it's a "marriage gift" for him, just like he'ld do something for me if he knew it mattered to me (like not wearing the same shirt day after day without washing it). Now, as relaxed as I am about leg hair, the reason I shave underarm hair is only for my benefit, as I think it's hygenically better; I could care less what society says about it. We've seemed to have gotten into anthropology (and personal!), but hair is an interesting topic.

Your question is basicly in error really, we are far from the only species of animal who's hair grows longer and longer and continue's to do so if we don't cut it, practicly every hairgrowing creature's hair grows without end.

Most animals in the wild shed old hair or keep their hair short by grooming or plain old wear & tear.

Because most domestic dogs that have long hair don't get to wear & tear like an animal would in the wild, they need to have a haircut on a regular basis too, for my dog thats every 3 months and imho it could be benificial for her to change that to every 1.5 months.

Pubic hair exists to protect the genetalia from all sorts of things, with females it is most relevant still so that dirt doesn't get into the vagina since it easely gets infections when cleaning isn't done thoroughly enough..

If you don't have the opportunity to wash on a regular basis, it can start getting really messy and stinky down there, not to mention the posibility of descease from a lack of hygene.

Head hair remains mainly to protect the cranium from overheating or undercooling while for males the general body hair remains as a purely sexual trait that gets worse depending on certain hormonal levels.

Men with heavy body hair are generly very macho, even with homosexuals, the ones with alot of body hair are usualy the "man" or macho in the relationship.

Hmmm, Thematrix, why do we not see family house dogs with continually growing hair when the family never has the dog's hair cut?
There are women whose hair continues to grow longer, but some women complain that they couldn't grow long hair if they tried. Probably same for men, but men thesedays tend to keep hair short, so I haven't heard men talk about this.
I always wondered what did our ancestors do pre-scissors or even pre-cutting tools.
Husband busy at his computer, so I will relay posts to him later.

A couple of things I've read is that pubic hair is a lubricant of sorts that comes into play during sex.

Underarm hair - and pubic hair as well - was so infants and the very young would have something to hang onto when the mother needed all limbs available for traveling or other things.

Facial hair for men may have come about because man was the hunter and probably exposed to cold and bad weather more than the female.

I agree with the comments about head hair being mainly useful to assist in regulating temperatures of the head.
As well as it being a sexual attractant.

Interesting part nowadays is that most women, when they get a little older cut their hair short.
I think that's more of a convenience thing than it is an age signifying device.

I've got a ponytail and taking care of it has been an education of sorts.
Mainly in appreciating what women go through with their hair.

Take a look at the fine hair on the back of a man or woman.
The hair lies in the same direction water would flow if the person was swimming.
There are theories that talk of mankind being aquatic and that's why the body hair lies as it does.

One other small one along the evolutionary front, women get cellulite and men don't.
That's because under the surface of the skin are fibers that cross one another very similar to a fishnet.
In men, the crossover points are close together so as to hold the skin together better under severe stresses - like being tossed down canyon by a mammoth or similar.
Since women are the gatherers in early society their skin fiber crossover points are further apart because they don't need the rugged skin the men do.

Therefore, with the women having wider/further apart crossover points with their skin fiber, fat can protrude from between the crossover points more than it does with men.
Which is . . . a shame since success in the gene pool depends on a womans physical beauty and all that's required from the men is that they be good warriors and providers.

Sorta explains why every once in a while you see a stunningly beautiful woman with a guy who looks like he fell out of a coconut tree....

Wear & tear, shedding, scrathing, grooming, whatever, there's so many ways to loose hair.

If you don't ever wash your hair so it turns brittle and run around naked on all 4rs like a dog does, do you think your hair will get very long?

Human beings wash their hair, extending its lifetime, making it more durable and strong. Most champoo's are designed specificaly for that, making the hair stronger and more vital.

Part of the reason for our hair getting as long as it does is us using artificial means to make it happen.

I grew my hair to about shoulder-length for a while, and I did notice that I did seem to be shedding a lot more hair. Like shampooing your hair and you will actually have hair in your hands afterwards. I never had this happen until my hair got to be about 2 inches long or so.

I would think that a more primitive human that never/rarely washed his/her hair would have dreadlocks. I don't know how that fits into the hair equation though.

As for animals with hair that really doesn't make evolutionary sense, what about those dogs whose hair goes right in front of their eyes? .

Actually not washing your hair does not result in bad hair. Some people say that it infact enriches your hair. A friend of mine a few years back stopped washing his hair and the rest of us had time to witness the effect. For the first 2/3 weeks his hair stunk, so much so you could smell it from a distance, but after that it did indeed turn out just fine and the smell vanished. Something to do with the natural oils produced by the hair. 2 years he went without washing his hair and kept it at a medium length. And he had great hair. So there lol

I'ld love to never wash my hair and run around naked, but on two legs (but still go about my daily business)!
To share more in light of this topic, I don't use any special shampoo, and my hair would be down to my ankles if I didn't trim it once in a while. Most other women I know buy special shampoo and complain they can't grow long hair. What did people do before shampoo? I know women and some men could grow their hair long and keep it up in a bun, out of the way rather than cut it.
I think, Kode and Yarcofin, I've seen what you describe in my son's college town. Yes, dreadlocks count.
Continued thanks to all replies.

the natural oils in our hair are good for us, an im sure by not washing, your doing no more then conditioning your hair, i mean u will need to wash once in a bit to get dirt out but otherwise if u lived in a tissue box, your hair would clean itself i think...

Originally posted by Umbrax
Hair is nothing more than dead cells. The woolly mammoth would have used its hair to keep warm.
Human hair’s primary use is not for warmth but for attracting a mate. If our ancestors found long hair attractive and short hair unattractive then the unattractive would not reproduce.

so honestly we could say humans mentaly trigger evolution?

[edit on 11-6-2006 by Tranceopticalinclined]

[edit on 11-6-2006 by Tranceopticalinclined]

Dont forget males get long hair too. And hair hasnt appeared to serve a purpose, it has remained to serve a purpose. Heat, water retention, lubrication of rubbing body parts (crotch, armpits), or any number of filters on the face.

I have a feeling most Caucasian hair can grow lengthy is just because of growth rate. It grows pretty fast. I'm thinking because caucasians evolved in the Northern hemisphere needing hair to grow faster to keep warm. The same with a high percentage of Mongoloid. Negro hair however evolved in heat. Hair growth rate is significantly reduced with a number of unique qualities.

yeah apc i think your about right with that.
every inch of your body is covered with hair, except the palms of your hands and the soles of your feet, the degree to which it grows is to a small amount related to direct environmental stimulus and to a much larger degree related to environmentaol factors on a generational level. the main reason that the hair on you head grows faster than on the rest of your body is because you head is the only part of the body that has remained uncovered for the last 50,000 years or so.

another thing, pubic hair, in the groin and under the arms, exhists mainly to trap BO, sweat gland in these areas produse a slightly milky sweat containing large quantites of pheromones that congeal and stick to the hair, advertising at a distance gender, health, sexual maturity and other such useful indicators, and are thought to play a large part in attraction, even to this day, although we are not uasually aware of it, but to proove my point, hands up who quite enjoys the smell of their partner after a workout, or other vigourous activities.

Dreadlocks are where it's at! I'm in the process of turning almost 2' of hair into dreads, got about half my head done now, and the dread side is way easier to care for than the ponytail side. The dread side stays clean longer, less dirt and stuff gets in it, when i wash it, once every week to 10 days the dread side washes easily while i have to really work on geting the other side clean. The dread side dries extremely fast, shake your head a few times with dread and you're dry. Without dreads, i shed crazy hair, everytime i'd brush i'd take out a bird's nest worth of hair. Dreads stay together.

My hair seems to grow a bit slow, but it'll keep growing as long as i have patience to let it.

I could see where hair in northern climes could grow long for warmth. I certainly use mine to that advantage, letting my hair flow over my back in cold weather. But in warm weather I have to put it up (a la ponytail, Flinstones Pebbles) to keep cooler. So short hair advantage in warm climes.
I still think that the Wooly Mammoth had a point where hair stopped growing, whereas human HEAD hair does not seem to.
Oh, and Desert Dawg, thanks for the bonus info on cellulite. Having a scientific basis for it does make it easier to feel better about it, that and a loving, chivalrous husband.

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[edit on 12/6/2006 by Umbrax]

Originally posted by Tranceopticalinclined
so honestly we could say humans mentaly trigger evolution?

Actually, human perception (specifically in choosing a mate) has been known to direct human evolution. Part of the process of natural selection. In addition to the well-known concept that the people best suited for a specific enviornment tend to survive the longest, mate selection is also a strong factor.

For instance, primitive women tended to have very small breasts (essentially flat-chested) which only grew when producing milk for offspring. This is because they tended to get in the way of their daily tasks within a hunter-gatherer society. However, modern women, on average, have larger breasts, due to the fact that over the years, the breasts became thought of as a symbol of womanhood, and men typically preferred the larger breasts. The trait of small breasts, however, has (obviously) not been completely erradicated, because even though the most common preference was for large breasts, it was never a universal preference.


To address the hair question for which the thread was authored, I have a little to add to that as well. Evolution states that humans are evolved from the apes. The similarities between apes and humans (assuming both are shaved) are quite apparent. (I also know that not everyone believes in evolution, so for sake of argument - and not wanting to turn this into a religious debate - assume for the moment that evolution is true.) Early humans would have had just as much body hair as the apes - mainly to keep warm. As humans became more skilled hunters, developed the use of tools, and knowledge of tanning hides, they started to wear animal furs to keep warm. Because of this, the majority of body hair became unnecessary, and eventually disappeared, leaving only the fine hairs on the body that we have now. Hair on the head remained, as was stated previously in this thread, to keep the head warm/cool, since it has remained mostly uncovered the entire time.

I also think that men tend to have more body hair than women because of testosterone, which in primitive man, made a male stronger, more rugged, and therefore a more capable hunter. In modern days, we no longer live in a hunter-gatherer society, so much of the prior beneft of testosterone has been lost, but trace amounts remain, in the form of the typically more muscular male body, and the existence of more body hair on males. Typically, also, the men in the modern world that have more body hair also have higher levels of testosterone. The two are pretty closely related. This is also why, many women, after menopause, start to develop more body hair. The woman's estrogen levels drop, and as such, there's less to retard the influence of the trace amounts of testosterone in a woman's body, so small amounts of body and facial hair develop. This is part of the reason that many women take estrogen suppliments after menopause (besides the known health reasons).

My favourite idea on the long hair for humans issue is this, though I don't necessarily accept it.

This is from the Aquatic Ape Theory.

Man evovled, for a period, in water.

That is why, for example, man has a well developed layer of adipose tissue (unlike other land mammals or so they say).

The long hair is because it is what young human babies would hold on to while being carried about by their mothers in the water.

Accurate and true? Perhaps not. But fun, nonetheless.