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Why Humans and Their Fur Parted Ways
The New York Times (Science Times) ^ | August 19, 2003 | NICHOLAS WADE

Posted on 08/19/2003 5:41:06 AM PDT by Pharmboy


Illustration by Michael Rothman
Before
An Australopithecus, sporting full-bodied
fur about four million years ago.


After
An archaic human walked fur-free about
1.2 million years ago, carrying fire on the savanna

ONE of the most distinctive evolutionary changes as humans parted company from their fellow apes was their loss of body hair. But why and when human body hair disappeared, together with the matter of when people first started to wear clothes, are questions that have long lain beyond the reach of archaeology and paleontology.

Ingenious solutions to both issues have now been proposed, independently, by two research groups analyzing changes in DNA. The result, if the dates are accurate, is something of an embarrassment. It implies we were naked for more than a million years before we started wearing clothes.

Dr. Alan R. Rogers, an evolutionary geneticist at the University of Utah, has figured out when humans lost their hair by an indirect method depending on the gene that determines skin color. Dr. Mark Stone- king of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, believes he has established when humans first wore clothes. His method too is indirect: it involves dating the evolution of the human body louse, which infests only clothes.

Meanwhile a third group of researchers, resurrecting a suggestion of Darwin, has come up with a novel explanation of why humans lost their body hair in the first place.

Mammals need body hair to keep warm, and lose it only for special evolutionary reasons. Whales and walruses shed their hair to improve speed in their new medium, the sea. Elephants and rhinoceroses have specially thick skins and are too bulky to lose much heat on cold nights. But why did humans, the only hairless primates, lose their body hair?

One theory holds that the hominid line went through a semi-aquatic phase — witness the slight webbing on our hands. A better suggestion is that loss of body hair helped our distant ancestors keep cool when they first ventured beyond the forest's shade and across the hot African savannah. But loss of hair is not an unmixed blessing in regulating body temperature because the naked skin absorbs more energy in the heat of the day and loses more in the cold of the night.

Dr. Mark Pagel of the University of Reading in England and Dr. Walter Bodmer of the John Radcliffe Hospital in Oxford have proposed a different solution to the mystery and their idea, if true, goes far toward explaining contemporary attitudes about hirsuteness. Humans lost their body hair, they say, to free themselves of external parasites that infest fur — blood-sucking lice, fleas and ticks and the diseases they spread.


Paul Smith for The New York Times
Included on the list of hairless mammals is the hippopotamus.
It is believed that mammals lose their hair only for particular
evolutionary reasons.

Once hairlessness had evolved through natural selection, Dr. Pagel and Dr. Bodmer suggest, it then became subject to sexual selection, the development of features in one sex that appeal to the other. Among the newly furless humans, bare skin would have served, like the peacock's tail, as a signal of fitness. The pains women take to keep their bodies free of hair — joined now by some men — may be no mere fashion statement but the latest echo of an ancient instinct. Dr. Pagel's and Dr. Bodmer's article appeared in a recent issue of The Proceedings of the Royal Society.

Dr. Pagel said he had noticed recently that advertisements for women's clothing often included a model showing a large expanse of bare back. "We have thought of showing off skin as a secondary sexual characteristic but maybe it's simpler than that — just a billboard for healthy skin," he said.

The message — "No fleas, lice or ticks on me!" — is presumably concealed from the conscious mind of both sender and receiver.

There are several puzzles for the new theory to explain. One is why, if loss of body hair deprived parasites of a refuge, evolution allowed pubic hair to be retained. Dr. Pagel and Dr. Bodmer suggest that these humid regions, dense with sweat glands, serve as launching pads for pheromones, airborne hormones known to convey sexual signals in other mammals though not yet identified in humans.

Another conundrum is why women have less body hair than men. Though both sexes may prefer less hair in the other, the pressure of sexual selection in this case may be greater on women, whether because men have had greater powers of choice or an more intense interest in physical attributes. "Common use of depilatory agents testifies to the continuing attractions of hairlessness, especially in human females," the two researchers write.

Dr. David L. Reed, a louse expert at the University of Utah, said the idea that humans might have lost their body hair as a defense against parasites was a "fascinating concept." Body lice spread three diseases — typhus, relapsing fever and trench fever — and have killed millions of people in time of war, he said.

But others could take more convincing. "There are all kinds of notions as to the advantage of hair loss, but they are all just-so stories," said Dr. Ian Tattersall, a paleoanthropologist at the American Museum of Natural History in New York.

Causes aside, when did humans first lose their body hair? Dr. Rogers, of the University of Utah, saw a way to get a fix on the date after reading an article about a gene that helps determine skin color. The gene, called MC1R, specifies a protein that serves as a switch between the two kinds of pigment made by human cells. Eumelanin, which protects against the ultraviolet rays of the sun, is brown-black; pheomelanin, which is not protective, is a red-yellow color.

Three years ago Dr. Rosalind Harding of Oxford University and others made a worldwide study of the MC1R gene by extracting it from blood samples and analyzing the sequence of DNA units in the gene. They found that the protein made by the gene is invariant in African populations, but outside of Africa the gene, and its protein, tended to vary a lot.

Dr. Harding concluded that the gene was kept under tight constraint in Africa, presumably because any change in its protein increased vulnerability to the sun's ultraviolet light, and was fatal to its owner. But outside Africa, in northern Asia and Europe, the gene was free to accept mutations, the constant natural changes in DNA, and produced skin colors that were not dark.

Reading Dr. Harding's article recently as part of a different project, Dr. Rogers wondered why all Africans had acquired the same version of the gene. Chimpanzees, Dr. Harding had noted, have many different forms of the gene, as presumably did the common ancestor of chimps and people.

As soon as the ancestral human population in Africa started losing its fur, Dr. Rogers surmised, people would have needed dark skin as a protection against sunlight. Anyone who had a version of the MC1R gene that produced darker skin would have had a survival advantage, and in a few generations this version of the gene would have made a clean sweep through the population.

There may have been several clean sweeps, each one producing a more effective version of the MC1R gene. Dr. Rogers saw a way to put a date on at least the most recent sweep. Some of the DNA units in a gene can be changed without changing the amino acid units in the protein the gene specifies. The MC1R genes Dr. Harding had analyzed in African populations had several of these silent mutations. Since the silent mutations accumulate in a random but steady fashion, they serve as a molecular clock, one that started ticking at the time of the last sweep of the MC1R gene through the ancestral human population.

From the number of silent mutations in African versions of the MC1R gene, Dr. Rogers and two colleagues, Dr. David Iltis and Dr. Stephen Wooding, calculate that the last sweep probably occurred 1.2 million years ago, when the human population consisted of a mere 14,000 breeding individuals. In other words, humans have been hairless at least since this time, and maybe for much longer. Their article is to appear in a future issue of Current Anthropology.

The estimated minimum date for human hairlessness seems to fall in reasonably well with the schedule of other major adaptations that turned an ordinary ape into the weirdest of all primates. Hominids first started occupying areas with few shade trees some 1.7 million years ago. This is also the time when long limbs and an external nose appeared. Both are assumed to be adaptations to help dissipate heat, said Dr. Richard Klein, an archaeologist at Stanford University. Loss of hair and dark skin could well have emerged at the same time, so Dr. Rogers' argument was "completely plausible," he said.

From 1.6 million years ago the world was in the grip of the Pleistocene ice age, which ended only 10,000 years ago. Even in Africa, nights could have been cold for fur-less primates. But Dr. Ropers noted that people lived without clothes until recently in chilly places like Tasmania and Tierra del Fuego.

Chimpanzees have pale skin and are born with pale faces that tan as they grow older. So the prototype hominid too probably had fair skin under dark hair, said Dr. Nina Jablonski, an expert on the evolution of skin color at the California Academy of Sciences. "It was only later that we lost our hair and at the same time evolved an evenly dark pigmentation," she said.

Remarkable as it may seem that genetic analysis can reach back and date an event deep in human history, there is a second approach to determining when people lost their body hair, or at least started to wear clothes. It has to do with lice. Humans have the distinction of being host to three different kinds: the head louse, the body louse and the pubic louse. The body louse, unlike all other kinds that infect mammals, clings to clothing, not hair. It presumably evolved from the head louse after humans lost their body hair and started wearing clothes.

Dr. Stoneking, together with Dr. Ralf Kittler and Dr. Manfred Kayser, report in today's issue of Current Biology that they compared the DNA of human head and body lice from around the world, as well as chimpanzee lice as a point of evolutionary comparison. From study of the DNA differences, they find that the human body louse indeed evolved from the louse, as expected, but that this event took place surprisingly recently, sometime between 42,000 and 72,000 years ago. Humans must have been wearing clothes at least since this time.

Modern humans left Africa about 50,000 years ago. Dr. Stoneking and his colleagues say the invention of clothing may have been a factor in the successful spread of humans around the world, especially in the cooler climates of the north.

Dr. Stoneking said in an interview that clothing could also have been part of the suite of sophisticated behaviors, such as advanced tools, trade and art, that appear in the archaeological record some 50,000 years ago, just before humans migrated from Africa.

The head louse would probably have colonized clothing quite soon after the niche became available — within thousands and tens of thousands of years, Dr. Stoneking said. So body lice were probably not in existence when humans and Neanderthals diverged some 250,000 or more years ago. This implies that the common ancestor of humans and Neanderthals did not wear clothes and therefore probably Neanderthals didn't either.

But Dr. Klein, the Stanford archeologist, said he thought Neanderthals and other archaic humans must have produced clothing of some kind in order to live in temperate latitudes like Europe and the Far East. Perhaps the body lice don't show that, he suggested, because early clothes were too loose fitting or made of the wrong material.

Dr. Stoneking said he got the idea for his louse project after one of his children came home with a note about a louse infestation in school. The note assured parents that lice could only live a few hours when away from the human body, implying to Dr. Stoneking that their evolution must closely mirror the spread of humans around the world.

The compilers of Genesis write that as soon as Adam and Eve realized they were naked, they sewed themselves aprons made of leaves from the fig tree, and that the Creator himself made them more durable skin coats before evicting them. But if Dr. Rogers and Dr. Stoneking are correct, humans were naked for a million years before they noticed their state of undress and called for the tailor.

Copyright the NY Times. For educational purposes only and not for commercial use.


TOPICS: Culture/Society; Front Page News; Philosophy
KEYWORDS: anthropology; archaeology; archaic; crabs; cromagnon; erectus; eve; ggg; godsgravesglyphs; heidelbergensis; helixmakemineadouble; history; humanevolution; lice; multiregionalism; neandertal; neanderthal; originofclothing; replacement
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To: Little Ray; mewzilla
You are wasting your efforts, I no longer wish to argue either side of this controversy but it would behoove creationists who want to be taken seriously if they would at least learn the theory instead of arguing against some theory which never existed except in the mind of creationists. Unfortunately they never understand this. I don't think most of them are even capable of making the distinction.
41 posted on 08/19/2003 7:19:05 AM PDT by RipSawyer (Mercy on a pore boy lemme have a dollar bill!)
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To: SengirV
"And just because WE KNOW the universe is 13+ billion year old universe does not mean there is no God - as some here would have you believe."

Precisely, I have never believed in the literal truth of Genesis and I don't understand how anyone can but that is a matter which has nothing to do with the existence of the Creator. Unfortunately, many of those who have tried to convince me of the literal truth of Genesis are ignorant of the meaning of the word literal.

42 posted on 08/19/2003 7:31:14 AM PDT by RipSawyer (Mercy on a pore boy lemme have a dollar bill!)
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To: happygrl
Humans still have the same number of hair follicles as other primates.
43 posted on 08/19/2003 7:31:17 AM PDT by blam
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To: Maria S
Ingenious solutions to both issues have now been proposed
It implies
resurrecting a suggestion
One theory holds
A better suggestion
their idea, if true
Dr. Pagel and Dr. Bodmer suggest
There are all kinds of notions
"There are all kinds of notions as to the advantage of hair loss, but they are all just-so stories," said Dr. Ian Tattersall
Dr. Rogers' argument was "completely plausible

It is all story telling. Of course, they would never consider that we humans were originally without "fur" and that we were designed that way by a Creator Who in the end is going to have the Last Laugh!

44 posted on 08/19/2003 7:32:06 AM PDT by LiteKeeper
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To: Pharmboy
I was told to eat my spinach because "it'll put hair on your chest" Well, it worked all over. Remember "birds make no nest in bare trees"
45 posted on 08/19/2003 7:33:24 AM PDT by Frankss
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To: Pharmboy
...and I thought it was because of PETA.
I don't know if this has any great anthropological significance, but I still teach my boys how to separate animals from THEIR fur...bear hunting this weekend just below B.C.
46 posted on 08/19/2003 7:40:37 AM PDT by Spok
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To: Pharmboy
Many shaky suppositions...

The whole thing is shaky, and the idea of humans ever living on the African savannahs is idiotic. Humans are too slow and too noisy to live on the savannahs. The young of prey animals know how to keep quiet; the first time some human infant ever started crying on the savannahs, with lions and hyenas walking around anywhere within five miles, it would be all over.

47 posted on 08/19/2003 7:42:00 AM PDT by martianagent
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To: Pharmboy
As an intalian american gentleman, I've been accused of having fur on more than one occasion! Maybe I'm just so retro.....
48 posted on 08/19/2003 7:44:54 AM PDT by HitmanLV (I will not be pushed, filed, stamped, indexed, briefed, debriefed or numbered. My life is my own.)
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To: Pharmboy
" The result, if the dates are accurate, is something of an embarrassment. It implies we were naked for more than a million years before we started wearing clothes."

Of course we were. Now then, there's a good research group... now take your medication and try to relax, N'Kay?

"If" the dates are accurate? Get a grip. Stop wasting taxpayer dollars on this junk science and get a real job. Please.

49 posted on 08/19/2003 7:56:32 AM PDT by Gargantua (Embrace clarity.)
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To: Pharmboy
600,000 years ago.

I thought that was 600,003 years ago!!
50 posted on 08/19/2003 7:58:24 AM PDT by WKB (3!~ ( You can hear it anywhere but only here can you tell the world what you think about it))
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To: RipSawyer
Given the choice, I'll take wasted efforts over a wasted life, RS.
51 posted on 08/19/2003 7:59:28 AM PDT by Gargantua (Embrace clarity.)
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To: Pharmboy
<< The compilers of Genesis write that as soon as Adam and Eve realized they were naked, they sewed themselves aprons made of leaves from the fig tree, and that the Creator himself made them more durable skin coats before evicting them. But if Dr. Rogers and Dr. Stoneking are correct, humans were naked for a million years before they noticed their state of undress and called for the tailor. >>

At least this shows clearly that certain theories are contradictory with Scripture. So is the Bible correct or Drs. Rogers and Stoneking? hmmmmmmm...
52 posted on 08/19/2003 8:29:09 AM PDT by pkjeff ( <><)
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To: WKB
I thought that was 600,003 years ago!!

You forgot to take leap years into account. That's the 3-year difference.

53 posted on 08/19/2003 12:06:57 PM PDT by talleyman (E=mc2 (before taxes))
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To: Pharmboy
We are the only part of the primate order to be without fur, have (slightly) webbed fingers and toes, hugely developed brains, and a subcutaneous layer of body fat. All of these are characteristics of aquatic mammals (whales, dolphins, etc.).

I've always thought the fossils they keep digging up in Olduvai Gorge and elsewhere are basically what they seem, chimpanzee progenitors or other now extinct forms of primates. If they really want to find ancient homo sapiens, they need to look near ancient shorelines, which because of changes in sea levels are now far off shore. This in turn makes the chances of finding genuinely ancient (100,000 years BCE plus) human remains all but impossible.

This is at least what I've drawn from a lifetime of watching National Geographic specials and IMHO probably as valid as the conclusions of PhD carrying believers in current "scientific" dogma.

54 posted on 08/19/2003 12:25:59 PM PDT by katana
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To: talleyman
I thought that was 600,003 years ago!!


You forgot to take leap years into account. That's the 3-year difference.



I ALWAYS do that!
55 posted on 08/19/2003 12:29:29 PM PDT by WKB (3!~ ( You can hear it anywhere but only here can you tell the world what you think about it))
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To: Pharmboy
An Australopithecus, sporting full-bodied fur about four million years ago.

Someone help me out here please?

I missed any citation and documentation of the discovery or discoveries on which this statment is based.

56 posted on 08/19/2003 12:56:49 PM PDT by Publius6961 (Californians are as dumm as a sack of rocks)
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To: blam
So the quality, not the quantity changed.
57 posted on 08/19/2003 1:01:23 PM PDT by happygrl
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To: Pharmboy
Why Humans and Their Fur Parted Ways


58 posted on 08/19/2003 1:01:43 PM PDT by paws_and_whiskers
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To: Pharmboy
what about Robin Williams? now thats one hairy ape.
59 posted on 08/19/2003 1:08:56 PM PDT by southern cross forever
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To: katana
Click here for a good aquatic ape site. Elaine Morgan (from the UK) has written much about this subject.
60 posted on 08/19/2003 1:15:13 PM PDT by Pharmboy (Dems lie 'cause they have to...)
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