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Science Forum Index » Anthropology - Paleo Forum » Epic of Human Migration Is Carved in Parasites’ DNA
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| Roger Lee Bagula |
 Posted: Thu Mar 15, 2007 1:32 pm |
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Not just the pubic lice...
http://www.nytimes.com/2007/03/13/science/13para.html?ex=1331438400&en=ec1e31fd869204f8&ei=5088&partner=rssnyt&emc=rss
Epic of Human Migration Is Carved in Parasites’ DNA
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By NICHOLAS WADE
Published: March 13, 2007
A human body is not the individual organism its proud owner may suppose
but rather a walking zoo of microbes and parasites, each exploiting a
special ecological niche in its comfortable, temperature-controlled
conveyance. Some of these fellow travelers live so intimately with their
hosts, biologists are finding, that they accompany them not just in
space but also in time, passing from generation to generation for
thousands of years.
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Josh Cochran
The latest organism to be identified as a longtime member of the human
biota club is Streptococcus mutans, the bacterium that causes tooth
decay. From samples collected around the world, Dr. Page W. Caufield and
colleagues at New York University have found that the bacterium can be
assigned by its DNA to several distinct lineages. One is found in
Africans, one in Asians and a third in Caucasians (the people of Europe,
the Near East and India), his team reported in last month’s Journal of
Bacteriology.
The geographical distribution of these lineages reflects the pattern of
human migration out of the ancestral homeland in Africa. If the tooth
decay bacterium spreads easily from person to person, any geographical
pattern would soon be blurred. But Streptococcus mutans is transmitted
almost entirely from mother to child, preserving its lineages over
thousands of years. The bacteria apparently infect the infant during
birth, beginning the work that provides the dentistry profession its
livelihood. “We’ve never seen father-to-child transmission,” Dr.
Caulfield said. Thanks, Mom.
Another faithful member of the human road show is Helicobacter pylori, a
bacterium that inhabits half the stomachs in the world. It is a usually
well-behaved guest, but gives its hosts ulcers when it acts up. Its
pattern of geographic distribution matches that of its host’s
migrations, Dr. Mark Achtman of the Max Planck Institute in Berlin and
colleagues reported in the journal Nature last month.
There are five ancestral populations of H. pylori — two in Africa, two
in Europe and one in East Asia. But all had a common origin, Dr. Achtman
said, in a bacterium that started to spread out from East Africa 58,000
years ago, give or take 3,000 years. This is the same time period in
which modern humans are thought to have begun their migration out of
Africa. The match in dates “implies that H. pylori was present in Africa
before the migrations, suggesting that Africa is the source of both H.
pylori and humans,” Dr. Achtman and colleagues conclude evenhandedly.
H. pylori seems to be transmitted within families but the exact route —
perhaps vomit — is unclear. “It’s amazing that any microbe’s
geographical distribution would parallel that of humans as well as
pylori’s does,” Dr. Achtman said. “You think of microbes as being easily
transmissible and they are carried all over the world on ships and
planes, yet some have not lost these signals of ancient migrations.”
DNA analysis has also shed light on the origin of the tapeworm, one of
the 400 or so nonmicrobial parasites that regard the human body as home.
The lifecycle of the tapeworm Taenia asiatica alternates between people
and pigs, an animal that the religious authorities of both Judaism and
Islam agree is unclean. It would be of interest to know just when these
filthy animals infected people with their parasites. But the answer is
not quite what had been expected.
Eric P. Hoberg, of the U.S.D.A.’s Agricultural Research Service in
Beltsville, Md., concluded in 2001 that people contracted tapeworms
millions of years ago in Africa, long before the emergence of
agriculture and domestic animals. It was humans who infected pigs with
tapeworms, not the other way around, Dr. Hoberg and colleagues reported.
Indeed, people infected pigs not only with Taenia asiatica but also with
a second species of tapeworm, Taenia solium, which humans seem to have
acquired either by eating each other or by eating dogs.
If pigs had a religion, it is pretty easy to guess which species they
would designate as unclean. |
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| Paul Crowley |
| Posted: Fri Mar 16, 2007 10:10 am |
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"Roger Lee Bagula" <rlbagulatftn@yahoo.com> wrote in message news:45F99141.5060908@yahoo.com...
Much the same, no doubt, applies to all other
species. The microbes and parasites would
each have their own history -- coming to their
present host species from other hosts.
In a few years, we should have a complex and
detailed map, showing tens of thousands of
inter-relationships and origins. All of this
will add up, enabling accurate accounts to be
given of the host species habitats and the
locations in their evolutionary history.
H.pylori, for example, will highly probably have
close relations in other hosts, and would have
come to humans from somewhere -- probably
from another animal in the same habitat in Africa.
So not merely are there distinct sets of animals
that occupy different habitats, there are (almost
certainly) distinct sets of microbes and parasites
living off them.
One thing for sure -- very few of the microbes
and parasites related to human ones will live off
savanna or near-desert species.
Paul. |
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| jllyz32248391350 |
| Posted: Fri Mar 16, 2007 5:49 pm |
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On 3ÔÂ16ÈÕ, ÏÂÎç11ʱ10·Ö, "Paul Crowley"
<slkwuoiutiuytciu...@slkjlskjoioue.com> wrote:
Quote: "Roger Lee Bagula" <rlbagulat...@yahoo.com> wrote in messagenews:45F99141..5060908@yahoo.com...
Not just the pubic lice...
http://www.nytimes.com/2007/03/13/science/13para.html?ex=1331438400&e....
A human body is not the individual organism its proud owner may suppose but rather a walking
zoo of microbes and parasites, each exploiting a special ecological niche in its comfortable,
temperature-controlled conveyance. Some of these fellow travelers live so intimately with
their hosts, biologists are finding, that they accompany them not just in space but also in
time, passing from generation to generation for thousands of years.
Much the same, no doubt, applies to all other
species. The microbes and parasites would
each have their own history -- coming to their
present host species from other hosts.
In a few years, we should have a complex and
detailed map, showing tens of thousands of
inter-relationships and origins. All of this
will add up, enabling accurate accounts to be
given of the host species habitats and the
locations in their evolutionary history.
H.pylori, for example, will highly probably have
close relations in other hosts, and would have
come to humans from somewhere -- probably
from another animal in the same habitat in Africa.
So not merely are there distinct sets of animals
that occupy different habitats, there are (almost
certainly) distinct sets of microbes and parasites
living off them.
One thing for sure -- very few of the microbes
and parasites related to human ones will live off
savanna or near-desert species.
Paul. |
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| Day Brown |
| Posted: Fri Mar 16, 2007 8:40 pm |
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On Mar 16, 9:10 am, "Paul Crowley"
<slkwuoiutiuytciu...@slkjlskjoioue.com> wrote:
Quote: One thing for sure -- very few of the microbes
and parasites related to human ones will live off
savanna or near-desert species.
True, but we dont need very many for devasting results. like a really
deadly virus in the SW on pack rats.
Kauffman, "The Origins of Order" comments that the immune systems of
the savannah herd animals are really robust, whereas relativly
isolated species, like the small hominid groups, have weak ones.
Then Hodder, in "The Leopard's Tale", his report on the dig at Chatal
Hoyuk, comments on the mouse problem in a densly populated community-
before the introduction of the house cat. OTOH, this led to the use of
plaster from local volcanic ash deposits to create grain bins the mice
could not chew their way into, and then the introduction of pottery.
But I can see also that a dense population of rodents could have
introduced pathogens leading to the abandonment of communities. |
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| jllyz32248391350 |
| Posted: Fri Mar 16, 2007 11:23 pm |
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Guest
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On 3ÔÂ17ÈÕ, ÉÏÎç9ʱ40·Ö, "Day Brown" <daybr...@hughes.net> wrote:
Quote: On Mar 16, 9:10 am, "Paul Crowley"<slkwuoiutiuytciu...@slkjlskjoioue.com> wrote:
One thing for sure -- very few of the microbes
and parasites related to human ones will live off
savanna or near-desert species.
True, but we dont need very many for devasting results. like a really
deadly virus in the SW on pack rats.
Kauffman, "The Origins of Order" comments that the immune systems of
the savannah herd animals are really robust, whereas relativly
isolated species, like the small hominid groups, have weak ones.
Then Hodder, in "The Leopard's Tale", his report on the dig at Chatal
Hoyuk, comments on the mouse problem in a densly populated community-
before the introduction of the house cat. OTOH, this led to the use of
plaster from local volcanic ash deposits to create grain bins the mice
could not chew their way into, and then the introduction of pottery.
But I can see also that a dense population of rodents could have
introduced pathogens leading to the abandonment of communities. |
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