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Author Topic:   evolution of human hair
Randy
Member (Idle past 6247 days)
Posts: 420
From: Cincinnati OH USA
Joined: 07-19-2002


Message 46 of 55 (83168)
02-04-2004 8:39 PM
Reply to: Message 44 by Peter
02-04-2004 5:07 AM


Hair today, still gone tomorrow
I am going to combine some replies here.
With respect to the Celts, Goths and Picts and the length of their hair and beards, where do you think the term barbarian came from?
Regarding the L’Oreal studies on the time hair spends in growth and resting cycles the papers are published in the British Journal of Dermatology.
Courtois M, Loussouarn G, Hourseau C, Grollier JF. Ageing and hair cycles. Br J Dermatol 1995 Jan;132(1):86-93
Courtois M, Loussouarn G, Hourseau S, Grollier JF. Periodicity in the growth and shedding of hair. Br J Dermatol 1996 Jan;134(1):47-54
The studies were done on men and not women, probably because of the economic importance of male pattern baldness. They made measurements for 14 years. In the study I have a copy of there were only 10 men in the group. In one of the subjects 28% of the hair stayed in the growing phase (anagen) for up to 5.2 years. By that time the rest of his hair had cycled or was cycling and the time in anagen was less for the all the other subjects. There seem to be a few people who can grow their hair 4 to 5 feet long but most people can’t under any circumstances.
Hair length is also discussed here.
http://www.keratin.com/aa/aa010.shtml
quote:
Similarly guys with higher testosterone grow facial hair faster
Perhaps. Apparently beard hairs do have androgen receptors that stimulate growth that scalp hairs lack. (See Thronton et al.(1998) J. Investigative Dermatology 111:727-732.)
However, the same author has published data showing that a lack of 5 alpha reductase activity is correlated with poor beard growth. (Thornton et al. Clin Endocrinol (Oxf). 1993 Dec;39(6):633-9.
Several years ago I measured beard growth rates in about two-dozen different men (all Caucasian) and never saw significant differences. I seem to remember some reports about testerone productions and 5 O'clock shadow many years ago but I couldn't come up with the science backing up that specific claim.
quote:
As far as I know straight vs. curly (and in between) is the amount of disulfide bonds in the protein.
Not necessarily. I am not sure there are differences in disulphide bond content between straight and curly hair, though highly curly African American hair is weaker than Caucasian or Asian hair. Hair has two main types of cells, cortical cells that form the central shaft and cuticle cells that protect the outside. Wool that is curly has two different types of cortical cells, ortho and para. This was not thought to occur in human hair. However, J. Alan Swift, who is the guru of hair microscopy, claims that there are two types of cortical cells in curly human hair. By his definitions, which are different than those for wool, the keratin is more tightly packed in paracortical cells. Straight hair has only paracortex and curly hair has both ortho and para.
(Swift JA: Morphology and histochemistry of human hair, in Jolles P, Zahn H, Hocker H (eds), Formation and Structure of Human Hair, Boston, Birkhauser Verlag, 1997, 149-176.)
I recently spoke at a meeting on ethnic hair and skin in Chicago and Bernard from L’Oreal showed data from in vitro hair growth studies indicating that the shape of the hair is programmed into the follicle, which is not necessarily incompatible with Swift’s claims.
Regarding the evolution of hairlessness, here is a reference to a paper suggesting that the eccrine sweat gland system in humans evolved along with hairlessness.
Folk GE Jr, Semken HA Jr., The evolution of sweat glands. Int J Biometeorol. 1991 Nov;35(3):180-6.
Peter Wheeler has published calculations suggesting that hairlessness evolved both for thermoregulatory reasons and to reduce requirements for drinking water requirements in bipedal hominids in equatorial savannah.
Wheeler, P.E. The influence of the loss of functional body hair on the energy and water budgets of early hominids. ( 1992) J. Human Evolution, 23, 379-388
Wheeler, P.E. The thermoregulatory advantages of heat storage and shade-seeking behaviour to hominids foraging it equatorial savannah environments. J. Human Evolution(1994) 26, 339-350.
Amaral has challenged this interpretation suggesting that hairlessness evolved in a forested environment, perhaps before bipedality.
Amaral, L. Q. Loss of body hair, bipedality and thermoregulation. Comments on recent papers in the Journal of Human Evolution, J. Human Evolution (1996) 30, 357-366.
Wheeler has of course challenged this reinterpretation.
Wheeler, P.E. The environmental context of functional body hair loss in hominids (a reply to Amaral, 1996) J. Human Evolution 30, 367-371
I'd say this is still a pretty open question and the answer may never be known for sure. Right now I find Wheeler's ideas most likely but still pretty speculative.
Randy

This message is a reply to:
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MoonGoddessAriana
Inactive Member


Message 47 of 55 (321410)
06-14-2006 10:44 AM
Reply to: Message 16 by Brian
01-28-2004 5:35 PM


Caveman in the forum??
"women have small feet to be near the sink"
Ahem, my mistake.. I thought this was a board of Science. How fuc*ed up are you jacka**, if women evolved small feet to be in the sinks if back in the cavemen days... there WERE NO SINKS! you corny as* bastard.
In actuality, you are a sad and lonely man confused about the world around you.
Can I take you and your stup*d phrase down to the governement in order to prove that men are horrible with science? Maybe this could be proof that you are not human and it would be then legal to kill your as*es.
Here's a good sexist joke, sweetheart.
Man evolutionized from the ape, and women evolutionized from man... you see, the science behind this would explain why we are more civilized, clean, and LESS HAIRY!
Whereas if you hand man anything... Sex, love, power.. he corrupts it into something vulgar and animalistic... just like handing a baboon something highly valuable.. they will destroy it senselessness..
so you see, this "joke" of mine.. makes more sense than that kitchen joke of yours jackass. Women have small feet because they have small body you imbecile! Men have big feet in order to shove it up their asses
Human beings who are of the MALE gender, forgive my horrid jokes.. this is merely directed to all the "men" out there or "macho" creeps.. who dont know that the term "macho" is spanish for "animal male"
what fools..
Anyway, hope you jerks learned something from this woman. I am nowhere near the sink but I am a helluva lot smarter than you are, sink should be your role..
Edited by MoonGoddessAriana, : No reason given.
Edited by AdminNWR, : off topic
Edited by MoonGoddessAriana, : No reason given.

This message is a reply to:
 Message 16 by Brian, posted 01-28-2004 5:35 PM Brian has replied

Replies to this message:
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AdminNWR
Inactive Member


Message 48 of 55 (321412)
06-14-2006 10:54 AM
Reply to: Message 47 by MoonGoddessAriana
06-14-2006 10:44 AM


Welcome to EvCforum
Welcome.
Your first post sets a poor tone, and violates the forum guidelines. May your future posts be more thoughtful.


This message is a reply to:
 Message 47 by MoonGoddessAriana, posted 06-14-2006 10:44 AM MoonGoddessAriana has not replied

  
rgb
Inactive Member


Message 49 of 55 (321462)
06-14-2006 1:10 PM


Has anyone talked about the aquatic ape "theory"? I know almost nothing about it except for some layman's concepts.
Added by edit.
Hair.
Supposedly, our hair grows longer than other primates so that our children can hang onto them in the water. And supposedly, this aquatic ape concept explains why we're the only primate to have an extra layer of fat, etc.
Edited by rgb, : No reason given.

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Chiroptera
Inactive Member


Message 50 of 55 (321468)
06-14-2006 1:25 PM
Reply to: Message 49 by rgb
06-14-2006 1:10 PM


quote:
And supposedly, this aquatic ape concept explains why we're the only primate to have an extra layer of fat, etc.
Heh. And why we have flippers instead of hands. And why we can hold our breath for up to thirty minutes at a time. Oh, wait....
The aquatic ape "theory" is pretty much like the "aliens built the pyramids theory", the "ancient Europeans lived in a matriarchal, Moon-goddess worshipping society theory", and the "God created the universe in 6 days about 6000 years ago theory". It is basically a bunch of ad hoc explanations for a bunch of random facts that are contradicted by the mass of actual evidence.
At any rate, my guess is that long hair is a result of sexual selection. However, unlike beards, breasts, and wide-hips, it is exhibited on both sexes, so perhaps there is another explanation.

"We must respect the other fellow's religion, but only in the same sense and to the extent that we respect his theory that his wife is beautiful and his children smart."
-- H. L. Mencken (quoted on Panda's Thumb)

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 51 of 55 (321630)
06-14-2006 10:11 PM
Reply to: Message 1 by Silent H
01-28-2004 1:29 PM


See {Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution} thread for some other comments on this topic.
What needs to be explained as much as the length of human head hair is the sexual dimorphism in hair patterns -- it's the dimorphism that says sexual selection to me, starting with it being a signal for health\fitness as mentioned above, but then it (long head hair) is taken to the extreme condition that is the mark of fisherian runaway sexual selection in any other species.
Enjoy.
Edited by RAZD, : finished first line

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Replies to this message:
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Brian
Member (Idle past 4959 days)
Posts: 4659
From: Scotland
Joined: 10-22-2002


Message 52 of 55 (321781)
06-15-2006 9:10 AM
Reply to: Message 47 by MoonGoddessAriana
06-14-2006 10:44 AM


Re: Caveman in the forum??
So what is it, time of the month or not gettin any
You do know why I put the ' ' in the original post?
Brian.

This message is a reply to:
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Chiroptera
Inactive Member


Message 53 of 55 (321846)
06-15-2006 11:57 AM
Reply to: Message 51 by RAZD
06-14-2006 10:11 PM


additional note
quote:
...starting with it being a signal for health\fitness....
Although, as Dawkins explains in The Blind Watchmaker, traits that are due to selectual selection may be selected for no other reason than they are being selected.

"These monkeys are at once the ugliest and the most beautiful creatures on the planet./ And the monkeys don't want to be monkeys; they want to be something else./ But they're not."
-- Ernie Cline

This message is a reply to:
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Replies to this message:
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obmitty
Inactive Member


Message 54 of 55 (321942)
06-15-2006 2:46 PM
Reply to: Message 1 by Silent H
01-28-2004 1:29 PM


Human hair does stop growing
Rather than get bogged down in explaining this, we can put a stop to it by saying human hair does stop growing after a finite time...
Eye brows, pubes, leg hair.... Hair on your head just takes longer to reach the same point, and obviosly also longer in different individuals. Some extreme individuals may grow meters of the stuff, most will struggle to get it past their lower back.
The reason for this could be postulated to be due to the same reasons a peacock has a huge tail, and a lion has a mane. It forms part of a signal of an indivuals health and ability to reproduce.

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 55 of 55 (322073)
06-15-2006 11:11 PM
Reply to: Message 53 by Chiroptera
06-15-2006 11:57 AM


Re: additional note
... may be selected for no other reason than they are being selected.
If the selection is for the purpose of mating, it is sexual selection.

Join the effort to unravel {AIDSHIV} with Team EvC! (click)

we are limited in our ability to understand
by our ability to understand
RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ...
to share.

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