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Topic: RE: virus: What a Story Lice Can Tell (Read 927 times) |
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Blunderov
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"We think in generalities, we live in details"
  
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RE: virus: What a Story Lice Can Tell
« on: 2004-10-05 04:53:37 » |
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[Blunderov] Again, the whole article posted. This time to save Virions
the trouble of registering at the site in order to view it.
Good ammunition against creationists.
Best Regards.
http://www.nytimes.com/2004/10/05/science/05lice.html?th
What a Story Lice Can Tell
By NICHOLAS WADE
Published: October 5, 2004
In a finding that seems bound to inspire several science fiction
treatments, Dr. David Reed of the Florida Museum of Natural History in
Gainesville has reached the startling conclusion that some human lice
show signs of having evolved originally on a different human species.
In today's issue of the journal PLoS Biology, he and his colleagues
suggest that modern humans may have contracted this strain of lice from
an archaic human like Homo erectus.
Last year Dr. Mark Stoneking and colleagues ferreted out another fact
from lice, the date when humans first started to wear clothes - about
72,000 years ago according to their calculations. This date has long
eluded archaeologists because of the perishability of items like skins,
fabrics and the bone needles used to sew them.
Dr. Stoneking, who works at the Max Planck Institute for Evolutionary
Anthropology in Leipzig, Germany, hopes that lice may be coaxed to yield
a yet more intimate secret, the date when humans shed their ape-like
body hair and roamed naked across the scorching savannas of Africa.
This louse's eye view of human evolution rests on analysis of the DNA of
lice sampled from populations around the world.
It also depends on the natural history of lice, which have developed
some rather specialized habits.
The human body provides three different kinds of ecological niche, from
the louse's point of view, and a different type of louse inhabits each.
The head louse lives in the hairs of the head. The body louse is adapted
to live in clothing, since the human body lacks proper hair. And the
pubic louse dwells in the coarse hairs of the groin, a cramped habitat
but one that affords a convenient opportunity for switching abodes
whenever the host is intimately occupied with a partner.
Six million years ago, before the line leading to humans split from the
chimpanzee lineage, matters may have been much simpler. The joint
ancestor of humans and chimps had full body hair, like a proper primate,
and presumably a single kind of louse ranged freely from its head to its
toes.
That louse would have belonged to the genus Pediculus and evolved into
two sister species when the human and chimp lineages parted ways.
The human head and body lice are known as Pediculus humanus and the
chimpanzee louse is Pediculus schaeffi.
When humans lost their body hair, perhaps 1.8 million years ago, the
Pediculus louse would presumably have been restricted to the head,
leaving the rest of the body vacant.
This could have been the moment when the pubic louse began its long-term
relationship with its human host. Dr. Stoneking believes that if he
could establish when the pubic louse arrived, by assessing the amount of
genetic variation in today's pubic louse population, he might be able to
fix a minimum date for when people attained nakedness.
A perplexity that louse specialists have not yet resolved is that the
pubic louse belongs to a different genus from Pediculus, being known to
taxonomists as Phthirus pubis.
Bizarrely, its closest relative is Phthirus gorillae, the louse that
infects the gorilla.
How it got to humans from gorillas, if that is indeed its origin, is a
question that raises some dire possibilities.
But there may be less lurid explanations. Some experts believe that
Phthirus lice have infected the primate line for millions of years but
have somehow been evicted altogether by chimpanzees and confined to the
groin in humans.
"The acquisition of the pubic louse likely has nothing to do with when
we lost our body hair," Dr. Reed said.
Dr. Reed's new finding raises the intriguing possibility that humans
contracted one strain of the Pediculus louse from another host species.
He and colleagues gathered head and body lice from around the world and
analyzed their DNA.
When they tried to construct a family tree for the lice, based on
variations in a particular DNA segment, their computer spit out a tree
with two quite separate clusters.
One cluster of lice was found only in the New World, in samples from the
United States and Honduras. The other cluster occurred worldwide.
Since changes in DNA clock up at a fairly constant rate, geneticists can
often estimate the coalescence date - the age at which all branches of a
tree merge back into a single root.
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RE: virus: What a Story Lice Can Tell
« Reply #2 on: 2004-10-06 08:38:04 » |
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Sorry for remaining silent as long; I couldn't yet force myself to swallow the "eternal darkness"-thread (already overfed with social criticism...), but as to the lice, very entertaining.
Ah well, my bitter experiences from the christian front tell me, though, that there are no ARGUMENTS against creationism. It is as far as I know as assimilatingly-ad-hoc-hypothetical-reality-twisting as christianity itself (and besides, far more annoying due to its assumed scientific semblance) - wasn't it that they even refute the methods of chronometry in order to squeeze life on earth in their 10000 or so years' period?
From the battlefield,
Björn
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Othello. Thou dost conspire against thy friend, Iago,
If thou but think'st him wrong'd, and mak'st his ear
A stranger to thy thoughts.
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