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Science Forum Index » Anthropology - Paleo Forum » Frizzy & straight hair: lice pathogens
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 Posted: Fri Mar 09, 2007 11:16 am |
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http://www.nytimes.com/2007/03/08/science/08louse.html?ex=1331010000&en=4792bff92e8a083d&ei=5088&partner=rssnyt&emc=rss
In Lice, Clues to Human Origin and Attire
Scientists believe they have figured out how and why the human pubic
louse,
right, and the gorilla louse, left, diverged 3.3 million years ago.
Nicholas Wade 8.3.07
http://www.nytimes. com/2007/ 03/08/science/ 08louse.html?
ex=1331010000& en=4792bff92e8a0 83d&ei=5088& partner=rssnyt& emc=rss
One of the more embarrassing mysteries of human evolution is that
people are
host to no fewer than three kinds of louse while most species have
just one.
Even bleaker for the human reputation, the pubic louse, which gets its
dates
and residence-swapping opportunities when its hosts are locked in
intimate
embrace, does not seem to be a true native of the human body. Its
closest
relative is the gorilla louse. (Don't even think about it.)
Louse specialists now seem at last to have solved the question of how
people
came by their superabundance of fellow travelers. And in doing so they
have
shed light on the two major turning points in the history of fashion:
when
people lost their body hair, and when they first made clothing.
Three kinds of louse call Homo sapiens their home, but each occupies a
different niche on the human body. The head louse, Pediculus humanus,
lives
in the forest of fine hairs on the scalp. Its cousin, the body louse,
lives
not on the skin but in clothes. And the exclusive territory of the
pubic
louse, Phthirus pubis, is the coarser hairs of the crotch.
Lice are intimately adapted to their hosts and cannot long survive
away from
the body's blood and warmth. If their host evolves into two species,
the
lice will do likewise. So biologists have long been puzzled over the
fact
that the human head louse is a sister species to the chimpanzee louse,
but
the pubic louse is closely related to the gorilla louse.
By comparing louse DNA, a team led by David L. Reed of the University
of
Florida has now reconstructed how this strange situation probably came
about. Dr. Reed's team collected pubic lice from a public health
clinic in
Salt Lake City. Samples of gorilla lice were obtained by members of
the
Mountain Gorilla Veterinary Project, which provides free health care
to
gorillas in the wild.
The number of DNA differences between the gorilla louse and the pubic
louse
indicates that they diverged some 3.3 million years ago, Dr. Reed and
colleagues report in today's issue of the journal Biomed Central
Biology.
Among people, the pubic louse is usually spread by sexual contact, but
the
gorilla louse could have been contracted in some other way.
"We'll never know if it was sex or something more tame," Dr. Reed
said. What
can be said about the transfer, he believes, is that it signals human
ancestors had already lost their body hair by 3.3 million years ago,
confining the human louse to the head and leaving the groin open to
invasion
by the gorilla louse.
Archaeologists contend that human ancestors lost their standard ape
body
hair when they left the shade of the forests for the hot, open savanna
and
needed bare skin for efficient sweating. Adaptation to the savanna was
well
in place by 1.7 million years ago. But loss of body hair could have
begun
earlier, and Dr. Reed's result suggests a time for when people first
became
naked.
If people first became nudists 3.3 million years ago, when did they
start to
wear clothes? Surprisingly, lice once again furnish the answer. Though
humans may long have worn loose garments like animal skin cloaks, the
first
tailored clothing would have been close-fitting enough to tempt the
head
louse to expand its territory. It evolved a new variety, the body
louse,
with claws adapted for clinging to fabric, not hairs.
In 2003, Mark Stoneking, a geneticist at the Max Planck Institute in
Leipzig, Germany, estimated from DNA differences that the body louse
evolved
from the head louse about 107,000 years ago. The first sewn clothes
were
presumably made shortly before this time.
Probing back even earlier in louse evolution, Dr. Reed and his
colleagues
report that the two species of primate lice, Pediculus and Phthirus,
probably diverged from each other on an ape host 13 million years ago.
The
divergence may have happened after the lice started to specialize in
different parts of the body.
Some seven million years ago, this ancient ape species split into
gorillas
and the ancestors of humans and chimps, with both lineages infected by
both
species of lice. But Pediculus then fell extinct in its gorilla hosts,
according to Dr. Reed's reconstruction, and Phthirus vanished from the
chimp-human ancestor. Next, chimps and humans diverged, and their
joint
louse diverged with them into Pediculus humanus and Pediculus
schaeffi.
The last event in this history of human-louse cohabitation was the
transfer
of the gorilla's Phthirus louse to people.
Dr. Stoneking said Dr. Reed's reconstruction was "pretty reasonable"
and
said he agreed that acquisition of the gorilla's louse indicated
people had
lost their body hair by then. "The transfer doesn't have to be
sexual," he
said, "but presumably it does require reasonably close contact." |
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| Posted: Fri Mar 09, 2007 1:06 pm |
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(Pediculus humanus humanus) This louse is the primary vector of
Rickettsia prowazekii which causes Epidemic typhus. Historically this
was one of the most significant diseases ever to infect humans, and is
still labelled today as a category B bioterrorism agent.
Body lice Phh attach to clothing. |
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| Rich Travsky |
| Posted: Sun Mar 18, 2007 11:37 pm |
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Marc Verhaegen wrote:
Quote:
"Rich Travsky" <traRvEsky@hotmMOVEail.com> wrote in message
news:45C3537F.4B96C6E8@hotmMOVEail.com...
Humans have never been selected for hydrodynamics.
Ah?
My boy, why don't you give us some arguments instead of producing such
fanatic statements?
Care to give us your opinion on why humans, as opposed to all other primates
& to other bipeds (except penguins etc.), have head+body+legs +-on 1 line?
Humans are obligate bipeds. Don't you know that? |
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| Marc Verhaegen |
| Posted: Sat Mar 24, 2007 11:33 am |
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Op 19-03-2007 05:37, in artikel 45FE139D.D21112D9@hotmMOVEail.com, Rich
Travsky <traRvEsky@hotmMOVEail.com> schreef:
Quote: Marc Verhaegen wrote:
"Rich Travsky" <traRvEsky@hotmMOVEail.com> wrote in message
news:45C3537F.4B96C6E8@hotmMOVEail.com...
Humans have never been selected for hydrodynamics.
Ah?
My boy, why don't you give us some arguments instead of producing such
fanatic statements?
No answer of course.
Quote: Care to give us your opinion on why humans, as opposed to all other primates
& to other bipeds (except penguins etc.), have head+body+legs +-on 1 line?
No answer of course.
Only some irrelevant blabla:
Quote: Humans are obligate bipeds. Don't you know that?
³While wading, the monkey (Nasalis larvatus) uses an upright posture, with
the females carrying infants on their hip. Troops have been filmed
continuing to walk upright, in single file, along forest trails when they
emerge on land, the only non-human mammal, with the exception of gibbons &
giant pangolins, known to use this form of locomotion for any length of
time²
http://en.wikipedia.org/wiki/Proboscis_Monkey
Try to be a bit relevant.
Why don't you inform??
http://groups.yahoo.com/group/AAT
http://allserv.rug.ac.be/~mvaneech/outthere.htm |
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