Re: Link To Full Paper Re: Lice Evolution May Reflect sapiens/erectus Contact

From: richard01 (richardparker01_at_yahoo.com)
Date: 10/12/04 

Date: 12 Oct 2004 05:15:52 -0700

"firstjois" <firstjoisyike@hotmail.com> wrote in message news:<3JKdnWWzwru8CvfcRVn-pg@comcast.com>...
> Rich Travsky wrote:
> >> Rich Travsky wrote:
> >>>
> >>
> >>
> http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020340
>
> Nice references! I want to spend some time seeing if the articles online
> are freely available or just online if you subscribe to the journal in
> particular.
>
> Jois

Carl Zimmer wrote this on his weblog (The Loom)
http://www.corante.com/loom/ last week:

 
October 04, 2004
If These Lice Could Talk

Contempt is never wise in biology. The creature that you look down on
as lowly, degenerate, or disgusting may actually turn out to be
sophisticated, successful, and--in some cases--waiting to tell you a
lot about yourself. That's certainly the case for lice.

The human body louse, Pediculus humanus, has two ways of making a
living--either dwelling on the scalp, feeding on blood, or snuggling
into our clothes and come out once or twice a day to graze on our
bodies. For lice, we humans are the world. They cannot live for more
than a few hours away from our bodies.Only by crawling from one host
to the next does their species escape extinction.

A group of louse specialists recently decided to find out where human
lice came from. Have they been riding on our bodies since before we
were human? A comparison of the lice that live on different primates
shows that they certainly can be very loyal. If you draw an
evolutionary tree of primates, and then draw a tree of their lice,
they are almost identical. On the other hand, some lice can live on
more than one species. And a side-by-side comparison of trees reveals
that in some cases they don't form a perfect mirror. In other words,
sometimes lice can make an evolutionary leap.

As the researchers report today in Public Library of Biology, they
compared human lice to the lice of primates, looking at both their DNA
and their anatomy. As earlier research had shown, they found a major
split among lice species that live on apes and on monkeys and other
primates. That reflects an ancient split in the primates themselves:
our ape ancestors diverged from other primates 20-25 million years
ago. The variation in louse DNA turns out to act like a sort of
molecular clock, showing when they split into different lineages. The
molecular clock puts the split between lice that live on humans and
chimps at 5.6 million years ago--exquisitely close to the age that's
been estimated for humans from studies on both DNA and fossils.

The research suggested that we've carried our lice for millions of
years, since before the time of our common ancestor with chimpanzees.
But after we parted company with the chimps, the lice have a
remarkable story to tell. Human lice split into two lineages. One
lineages is found around the world. The second is found only in North
America. The worldwide branch all share a common ancestor that lived
540,000 years ago. The North American branch shares a common ancestor
that lived 150,000 years ago. And finally, the two branches share a
far older common ancestor, which lived a 1,180,000 years ago.

So how did these two strains of the same species become separated and
then wind up back on our bodies? The researchers argue that human
evolution holds the key. Paleoanthropologists and geneticists still
debate over the origins of modern humans, but the rough outlines are
becoming clear. The first hominids to emerge that were tall,
big-brained bipeds--that weren't just upright apes, in other
words--lived about 2 million years ago. They very quickly began to
spread out of their birthplace in Africa to other parts of the world.
They were in the Caucusus mountains 1.8 million years ago and China
1.66 million years ago. These hominids are generally called Homo
erectus, although they may well have consisted of several species,
rather than one. And the ranks of Asian Homo erectus may have been
boosted by fresh migrations of African hominids when ecological
conditions favored another journey out of Africa. But it does appear
that Asian populations became pretty isolated from African hominids.
The fossils of Homo erectus from a few hundred thousand years ago look
pretty distinct from both African hominids and Neanderthals, with very
thick skull walls and other peculiar anatomical details. Thirty years
ago, most paleoanthropologists would have told you that these Asian
hominids probably were the ancestors of living Asians. But that's not
what the evidence gathered since then suggests. Instead, it now looks
pretty clear that Homo erectus was a very distinct species than Homo
sapiens, and became extinct perhaps as recently as 30,000 years ago.

Our own roots can be found in Africa. The oldest clear cut examples of
Homo sapiens fossils, found in Ethiopia, date back 160,000 years. By
about 100,000 years ago, our species was beginning to diverge into
different populations, and these differences can still be found in the
DNA of various African groups, such as the Khoisan of Southern Africa
(sometimes called bushmen). By 50,000 years ago, humans were moving
out of Africa. In Europe, they moved into territory occupied by
Neanderthals and their ancestors for some 300,000 years. Neanderthals
disappeared by 28,000 years ago. They seem to have been driven into
mountainous refuges by the booming population of humans. The story in
Asia has always been a bit fuzzier. Humans appear to have gotten to
Australia by at least 40,000 years ago, and perhaps much earlier. By
15,000 years ago, some Asian populations of Homo sapiens made their
way into the New World through Alaska. Exactly where Homo erectus was
on their arrival in Asia, and how long they survived, has never been
clear. It hasn't even been clear whether the two species came into
contact or not.

You may be able to guess how the louse scientists interpret the data
from their parasitic charges. When Homo erectus moved into Asia and
became isolated from our own ancestors, their lice became isolated as
well. When our own ancestors burst out of Africa around 50,000 years
ago, they carried the African lice with them. The most sensational
part of the story comes when humans arrive in Africa. The researchers
argue that a population of humans encountered Homo erectus and picked
up their lice. Their descendants then passed into North America, where
they--and their lice--live today. One of the many intriguing
implications of this research is that the contact may have occurred in
one limited regions--the same region where Native Americans originated
in Asia.

This is not the first case where our parasites have preserved our own
hidden history. Our tapeworms, for example, can tell us about how our
ancestors began eating meat. Malaria reveals how agriculture brought
new diseases to humans over the past few thousand years. Helicobacter
pylori, the bacteria that trigger stomach ulcers, maps the spread of
modern humans. (I go into more detail on some of these examples in my
book Parasite Rex.) And the lice probably have more to tell us.

For example, the scientists can't say for sure how humans most likely
picked up Homo erectus's lice. The contact definitely had to be
intimate. But did it occur when humans drove Homo erectus away from
their kills? Or did these two species make love, rather than war?
Although the genetic evidence indicates that Homo erectus could not
have contributed a significant number of genes to our species, it's
possible that they contributed a few. The answer to this question may
help show how Homo erectus became extinct, leaving us as the sole
hominids left on Earth.

One way to test that possibility will be to look at the other species
of lice that live on humans--crabs, or Pthirus pubis. If our ancestors
got body lice from Homo erectus during sex, they probably got crabs as
well. Somehow, though, I'm guessing that putting together a global
collection of crabs may take a little bit longer than the body lice.
But it will definitely be worth the wait.

UPDATE: 10/4 9:50 PM: A question occurs to me: why didn't we pick up
Neanderthal lice?

Relevant Pages

  • Re: A skull that rewrites the history of man
    ... It has long been agreed that Africa was the sole cradle of human ... these early humans are far more primitive-looking than ... the Homo erectus humans that were, until now, believed to be the first ... "Their brain capacity is about 600 cubic centimetres. ...
    (talk.origins)
  • Re: Mitochondrial Eve a fact?
    ... Homo erectus to Homo sapiens sapiens. ... Africa and colonized the old world on the order of a million ... They can also reasonably argue that with such low populations of humans ... has only daughters is the end of that particular Y-chromosome lineage. ...
    (talk.origins)
  • Four times out of Africa
    ... prehistoric and modern human beings left Africa ... First, some millions years ago or so, some Homo Erectus left Africa and ... humans that left Africa all became extinct. ...
    (sci.bio.paleontology)
  • News: Gorillas Gave Pubic Lice to Humans
    ... Gorillas Gave Pubic Lice to Humans, ... the gorilla louse and the human pubic louse separated into distinct ... species, the research revealed. ...
    (talk.origins)
  • Re: Lice Evolution May Reflect sapiens/erectus Contact
    ... > Genetic Analysis of Lice Supports Direct Contact between Modern and ... > A phylogenetic analysis reveals that humans have two types of head ... > lice and that one must have switched from an ancient to a modern human ...
    (sci.anthropology.paleo)