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Author Topic:   Is body hair a functionless vestige?
Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 3 of 143 (559527)
05-10-2010 4:27 AM
Reply to: Message 1 by Ken Fabos
05-09-2010 6:41 PM


A vestige,certainly, but perhaps not entirely without function.

But it's hard to say. Your own post say perhaps this and perhaps that. And then again, perhaps not.

Perhaps it serves some minor function. How would we find out? We could forcibly shave off all the body hair of a million men, and compare them to ... what WOULD be the control group? Double-blind testing is right out.


This message is a reply to:
 Message 1 by Ken Fabos, posted 05-09-2010 6:41 PM Ken Fabos has replied

Replies to this message:
 Message 4 by Ken Fabos, posted 05-10-2010 7:00 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 7 of 143 (559710)
05-11-2010 8:22 AM
Reply to: Message 4 by Ken Fabos
05-10-2010 7:00 PM


It should be pointed out that there are some ethnic groups of Africans who don't have any body hair at all, not even the fine fuzz that most people have (that is, they have the normal concentrations of hair on the head, armpits, and pubic area, but none on their arms, legs, etc). I write this from memory, so I can't give a reference. I've also seen it for myself.

They seem to get by without it.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 9 of 143 (559715)
05-11-2010 8:45 AM
Reply to: Message 6 by RAZD
05-10-2010 8:41 PM


I can verify this, as when I lost all my body hair (chemo) I had to use talc powder to lubricate the skin or it got raw.

I think perhaps your confounding cause and effect: that is, the reason that these regions chafed was because they had been so long protected.

After all, you didn't chafe in these areas when you were prepubescent, did you?

The fact that such hair is acquired at puberty suggests to me that it has something to do with sex; if it had any other purpose it would develop earlier.


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Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 21 of 143 (559884)
05-12-2010 12:44 AM


A Non-Adaptationist Explanation?
I read recently (I think in a book on supernormal stimuli) that the places where we do get hair are also the places where chimps get it first.

So the distribution of hair in humans could be the side effect of a (hormonal?) adaptation towards neoteny that had nothing to do with hair as such but was favored for its effect on something else, such as brain plasticity. It would be what Gould called a spandrel.


  
Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 24 of 143 (559916)
05-12-2010 3:48 AM
Reply to: Message 23 by dennis780
05-12-2010 1:55 AM


Re: Perfect perfect body hair...
Another point to notice is that generally humans grow hair where apes do not. the face and chest are prime examples, since apes are hairless there, or sparse, but humans (especially males) grow hair in these areas.

Well I'm not sure that this is particularly sparse as compared to a human.

Sparse compared to the rest of the chimpanzee, perhaps. But to suggest that we "grow hair where apes do not" seems unjustified.


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 Message 23 by dennis780, posted 05-12-2010 1:55 AM dennis780 has replied

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 Message 25 by dennis780, posted 05-12-2010 4:14 AM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 26 of 143 (559924)
05-12-2010 4:25 AM
Reply to: Message 25 by dennis780
05-12-2010 4:14 AM


Re: Perfect perfect body hair...
I'm not comparing, I'm pointing out that apes are MORE hairy everywhere but their face and chest.

What you said was "humans grow hair where apes do not".

thats one hairy ape, how long did it take you to find that one pic of a monkey with a hairy chest? Cause I found lots to show they are FAR more sparse on their face and chest:

Most of those pictures don't look that much different.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 28 of 143 (559939)
05-12-2010 5:16 AM
Reply to: Message 27 by dennis780
05-12-2010 5:04 AM


Re: Perfect perfect body hair...
Less hair on chest and face, more on rest of body.

Humans opposite. Follow?

Yes. This does not support your claim that "humans grow hair where apes do not". Follow?


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Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 29 of 143 (559944)
05-12-2010 5:28 AM
Reply to: Message 22 by dennis780
05-12-2010 1:49 AM


Re: Perfect perfect body hair...
I much prefer to jump into conversations unannounced and blurt random facts.

You seem to be better at the "random" bit than the "fact" bit.


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Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 31 of 143 (560365)
05-14-2010 5:16 PM
Reply to: Message 30 by Ken Fabos
05-13-2010 10:09 PM


Re: Anyone disagree that body hair has sensory function?
It seems to me that if it had a sensory function, then the best place for it would be on the fingertips. Its actual distribution doesn't suggest a sensory function, does it?

Here's a sensory homunculus.

That's how brain function is distributed over the body. It's not how hair's distributed, is it?

And chimps and moneys have hands which are naked on the inside. The one place where the sense of touch is most important ... no hair.

Edited by Dr Adequate, : No reason given.


This message is a reply to:
 Message 30 by Ken Fabos, posted 05-13-2010 10:09 PM Ken Fabos has replied

Replies to this message:
 Message 33 by Ken Fabos, posted 05-14-2010 6:35 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 35 of 143 (560416)
05-15-2010 3:22 AM
Reply to: Message 33 by Ken Fabos
05-14-2010 6:35 PM


Re: Anyone disagree that body hair has sensory function?
Dr Adequate, when you brush something across your body hairs -without touching the skin - can't you feel it? I know that I can.

Yes, but I can't say that I've ever found this particularly useful.

For the purpose of alerting us to the presence of insects and ecto-parasites a whole body covering looks useful. To feel air movements and shift in breeze, likewise.

Bare skin would do just as well.

To an animal with thick fur, doubtless it is useful that hair follicles are innervated. But in us this too could be a vestige.

The sensory input from hairs may merge in our perception with what we feel from direct skin contact but I'm astonished that, even after participation in this discussion, you could think it doesn't exist. Actually I find it surprising that anyone could think that a form of sensory input that's so universal and fundamental and that they've lived with their whole lives doesn't exist.

But no-one has said that the sensory input doesn't exist. Just that it's not particularly functional.


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Dr Adequate
Member (Idle past 325 days)
Posts: 16112
Joined: 07-20-2006


Message 41 of 143 (560563)
05-16-2010 1:41 AM
Reply to: Message 39 by Ken Fabos
05-15-2010 7:41 PM


Re: Anyone disagree that body hair has sensory function?
So far one vote for no sensory function revised to functional but not significantly useful .
Two more say functional but not significantly useful.
And me, both functional and useful.

What distinction are you trying to draw between useful and functional?


This message is a reply to:
 Message 39 by Ken Fabos, posted 05-15-2010 7:41 PM Ken Fabos has replied

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