I dont really know if this had been asked before but here it goes: Why
do we have hair? For the head hair, well atleast they say it protects
us from heat or some sort of radiation from the sun (or does it?), they
also say that it helps keep the skin cool. Are those answers true? Then
does that function of hair also applies in our armpits and genital?
Does our eyebrows have purpose? How about the thin hair on our fingers and
toes? Thank you to anyone who bothers to answer me, this would be a very enlightening thing for me.
– curious man
I read somewhere on this board, that ass hair between the cheeks provides maximum lubrication so when you walk it doesn’t rub and irritate.
And it keeps the butt cool. 
Actually, the question is why do we not have hair. Or why do we not have long hair all over our bodies. Since we are mammals, we have hair. The difference is that we have lots of very short hair over most of our bodies. We’re pretty much as hairy as our closest relatives, chimps, but it’s shorter. As to why we have long hair where we do, there are lots of theories (you alluded to at least one), but no one knows for sure. There is no factual answer to your question.
Hair in the armpits and around the genitals is thought to capture scent which might play a role in any number of behaviors (eg, sex).
Head hair serves three purposes.
First it acts as a shade.
Secondly it acts as a cushion. As bipedal mammals we have very string legs that proel us upwards at high speed. It is more than possible for a human to do serious damage by simply standing up suddenly under a low branch. A cushion of hair on top of the skull is a plus.
The third reason is related to the second. Our head hair acts like whiskers. They detect pressure long before pressure on the scalp could be felt, and thus enable us to flinch before we brain ourselves.
Eyebrows serve the vital purpose of channelling sweat away from the eyes. They also serve as expression markers so we can read emotions easily at distance.
I am in no way smart but I know I can contribute one: eyebrows redirect the flow of sweat so that it does not get into the eyes, possibly while running away from a predator.
All theories, of course!
That wasn’t even a minute… damn!
All about human hair:
Not everybody has hair on the fingers. It’s called mid-digital hair and is one of those traits (I can’t remember if it’s dominant or recessive) like hitchhiker’s thumb. And I remember reading a column where Cecil addresses the purpose of head hair, of course I can’t find it now, but it was for both shade and “sexual display.”
Head hair is there, because it is sexy.
If it were for shade, then those of us, who adapted in northern lands (IE: Europeans, Asians) would have less. What a great place to produce Vitamin D. Also, those of us who adapted to southern climates (IE: Africans) woulod have hair that covered a little better.
If it were for cushion, we’d all have afros.
I’ll give you number three, but not to explain the length of the mop-on-top. Hair, all over the body (everyone has it everywhere, 'cept palms and soles) increases sensitivity. But for it to be truely effective, it couldn’t be more than an inch or teo long. Once it flops over under it’s own weight, it becomes useless.
Nope, it’s there for the same reason a lion’s mane is there. It helps pass the DNA.
Well, no. Those form northern climes would retain the feature until it bacame a serous enoiugh hinderance to be selected against select against, and then only if an alternative evolved. As an example tasmanian Aborigines remoan black after 50, 000 years living in a frigid, sunlight deprived climate. Despite such a maladpation being more detrimental than head hair it remains simply because no alternativ presneted itself. Evolution isn’t a directed process int thenormal sense of the owrd. It works with what is avaialable. What isn’t avaialable doesn’t get worked on.
Unless of course Afros were in theselves detrimental.
Nonsense. Find a person with hair shoulder length or longer. Move your hand towards the top of their head starting 1 foot away. Ask them to tell you when they can feell your hand. It will still be several inches away because even long hair has some short fibres at the crown.
Body hair is there for warmth. In human it’s mostly a vestigial trait, but you can tell what it’s supposed to be doing when you’re cold.
Why do we get “goosebumps?” To orient the hairs optimally to hold an insulating layer of warm air in place. It would make more sense if we were densely covered, but there it is.
As for eyebrow hair, any punk who’s shaved their’s off will tell you eyebrows do keep the sweat out of your eyes, especially when you’re under hot lights. Silly punks.
I see your point, Blake, but have to say that I don’t particularly agree.
First things first, and not to split hairs ;), but the aboriginal people of Tasmania have been there for 35,000 years, not 50,000. Additionally, Tasmania was a connected to the mainland until 10,000 years ago. There would have been enough interbreeding with the rest of Australia to prohibit such a specialized adaptation. Besides if they were really spending that much time in the cold, at such a southern latitude, they’d be white.
Secondly, evolution is driven by advantage, not disadvantage. I know it seems like two sides of the same coin (and maybe it is), but for an evolutionary change to occur, the change must produce a survival advantage before DNA is passed on. We have a lot of things that are detrimental to us. The thing is that we haven’t come up with anything better. (I know, 98% of that is identical to what you said)
So…
Exactly. Afros are hard to keep and require the use of hair care products to maintain. If left alone, that type of hair (I’m trying to be as PC as possible) breaks off and stays fairly short, thus defeating the sex appeal. The advantage is that heat is more readily dispersed and parasites don’t have such a habitat.
But…if bumping our heads were such a threat to our survival, then:
1] Hair would do a better job. It’d be more “cushiony”.
2] Babies would be born with more of it.
3] We’d have evolved something else, like woodpeckers or rams have.
I can’t imagine evolution taking the time to adapt an early warning system to alert us to the possibility of someone trying to touch our heads. We would never be able to avoid anything, which would be moving fast enough to injure us, after being warned that it was a few inches away.
I’m staying with the sex appeal, like a lion’s mane or a bird’s crest.
Larry Mudd:
Body hair was for warmth, when it covered better. Goose bumps are a remnant of this. The reason we lost the density is open for debate (you don’t to get me started on the aquatic ape theory).
[hi-jack]Ya know what, Blake? Your posts will jump in credibility if you just take the time to hit that Preview Post button, and check your spelling before you hit the Submit button.
Try it. We’ll like it.
Bad spelling in a forum that professes to fight ignorance is pretty gauche, ya know?
Just in case you know how to spell, but happen to be really bad at typing, the Preview Post button is still there to let you copy and paste into a word-processing application, like Word, or even into your email app., which has a spell-checker.
Think of it as forum etiquette.
[/hi-jack]
Speaking as one who is, shall we say, follically challenged up on top, let me assure you that even in the Northern climes, the loss of sun protection on the scalp can lead to lots of burning.
There’s also a warmth factor. You might not think that the rather short length of hair on a typical men’s heaircut would make that much difference, but I can definitely feel the difference between the lightly covered and the uncovered portions of the scalp in winter.
One theory I have heard for eyebrows is that they used to be a lot bigger, and were there to protect our eyes from the sun.
The Master’s words on this subject:
http://www.straightdope.com/classics/a1_097b.html
pcroughn is in agreement with Cecil and his sources, in re: “long hair is sexy.” A quote from the column, “…some anthropologists believe the purpose of long head hair is to give you something to tie ribbons in.”
And yet for some reason this continuous interbreeding didn’t prevent specialized adpatation of hair types between Europe and Africa. Hmmmm.
The reason of course is that genetic drift is possible even between interbreeding populations. There can be no dispute that human populations have evolved in diferent direction even in the presence of continuous interbreeding. To suggest that interbreeding would prevent evolution is riiculous. If this were true all European and African populations would need to have identical hair, since they have constantly interbred.
Nonsense. A completely neutral trait or even a detrimental trait will always be passed on. It need not produce any survival advantage whatsoever. I don’t know where you get the idea that traits must produce an advanatge to be passed on. Provided a trait does not prevent itself from being replictaed it will be passed on by definition.
I already explained this. If we don’t respond when things touch our heads, we brain ourselves. The experiment I proposed was to demonstrte that long hair functions perfectly in this regard, in direct contradiction to your claims that it did not. It was not intended to suggest that the hair evolved so that you could do the experiment.
Hey, look at that. A preview button. Thanks GM.
Slight nit-pick. Are you sure about the 50k yr for human occupation of Tasmania? I’ve seen dates of 20k and possibly 30k, but never 50k. There are some sites showing human occupation of Australia proper (north and west) at 50k, but nothing earlier than that (Mungo Man was originally dated at 60k yrs ago, but more recent data puts it at 40k).
Hate to nitpick and far be it from me to defend Tasmania, but I think you may be exaggerating a touch there. Tasmania is hardly a frigid sunlight deprived climate. It’s 25C (77F) in Hobart today (far South Tassie) average max temp ranges between about 22C in summer to about 12C in winter. Average rainfall ranges between 63mm in spring and 40mm in late summer
.
True, but you’re forgetting the loss of sun and warmth would both be overcome by the use of a hat. The same conditions are true for the rest of the body, and following your logic. we should all be as hairy as gorillas. (OK, I am, but that’s another story) Once again, an evolved intellect drives human evolution.
[QUOTE]
And yet for some reason this continuous interbreeding didn’t prevent specialized adpatation of hair types between Europe and Africa. Hmmmm.
The reason of course is that genetic drift is possible even between interbreeding populations. There can be no dispute that human populations have evolved in diferent direction even in the presence of continuous interbreeding. To suggest that interbreeding would prevent evolution is riiculous. If this were true all European and African populations would need to have identical hair, since they have constantly interbred.QUOTE]
There’s a pretty between the populations of Europe and Africa and the populations of Australia and it’s southwest tip breeding. Europe and Africa are separated by thousands of miles of desert.
There was no constant interbreeding between European and Africans. Interbreeding, locally did occur, and the gradual change between what is defined as “African”, “European” and “Asian” is evidence of this. For example, Vikings, the Chinese and the Massi look nothing alike, but looking at the peoples of India, Siberia and the Middle and Near East all show ‘middlegrounds’ with attributes of both neighboring groups."
So go ahead and “Hmmmm” all you want.
Ya feel that? That’s a 3.2 on the Richter scale from 'ol Charley Darwin spinning in his grave.
If a trait is detrimental, and present less of a survival advantage, it will disappear. I don’t suppose you have an example or even proof?
But hair acting as an early warning system, to protecting us from getting “brained”, is just plain silly. As I stated, by the time any object got close enough to move our hair, it’d be unavoidable. For us to have time to react, the object would have to be moving so slowly, it wouldn’t cause injury.
Tell you what. You and I will meet in a park. I’ll stand about 20 feet away. You’ll turn your back and I’ll chuck a baseball at your head. You can then show me how wonderful this advanced warning system really is. I’m guessing that it does not “work perfectly in this regard”.