[Paleopsych] ABC (au): "Out of Africa" in Asia
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"Out of Africa" in Asia
http://www.abc.net.au/science/news/stories/s293857.htm
[Now this is earlier than the piece about changing the rate of mutations. It
may be stale but perhaps worth revisiting. I append two other articles.]
Friday, 11 May 2001
The origins of man debate continues
The hotly-debated notion that modern humans arose from Africa and
replaced all other populations of early humans across the globe has
been bolstered by new research.
A genetic study lead by Yuehai Ke from Fudan University in China, of
more than 12,000 men from 163 populations in East Asia strongly
suggests the so-called "Out of Africa" theory of modern human origins
is correct, according to a report in today's [18]Science.
The "Out of Africa" model states that anatomically-modern humans
originated in Africa about 100,000 years ago and then spread out to
other parts of the world where they completely replaced local archaic
populations.
Among the evidence for this notion are recent DNA tests which ruled
out the contribution of primitive humans or Neanderthals to modern
Europeans.
But others argue that the distribution and morphology of ancient human
fossils found in China and other regions of East Asia support a
competing theory - that modern humans evolved independently in many
regions of the world.
Now Yuehai Ke and his team from China, Indonesia, the United States
and Britain, tested the Y chromosomes of 12,127 East Asian men for the
presence of three specific mutations - types of genetic markers. The
three mutations are derived from a single earlier mutation in African
humans.
The team found every individual they tested carried one of the three
later mutations and no ancient non-African DNA was found. They
therefore rule out even a "minimal contribution" from the primitive
East Asian humans to their anatomically-modern counterparts.
Dr Colin Groves, from the anthropology department at the Australian
National University, described the new data from such a large sample
of men as "absolutely decisive".
"I'm a supporter [of the Out of Africa model] but I can't for the life
of me think how any multi-regional model could fit this," he told ABC
Science Online.
The new data analysing male genes was "telling exactly the same story"
as previously-reported data analysing genes in cell structures called
mitochondria, passed from one generation to the next via females, he
added.
Dr Groves' ANU colleague and well-known opponent of the Out of Africa
model, Dr Alan Thorne, was not available to comment on the new
research.
Further controversy on human origins
Tuesday, 16 January 2001
Mungo man - analysis of DNA from this fossil announced last week
reignited a controversy over the origins of modern humans.
New research supports the theory that the ancestors of modern humans
came from many different regions of the world, not just a single area
-- but critics remain far from convinced.
The study, published in the current issue of [18]Science by University
of Michigan anthropologist Milford H. Wolpoff and colleagues, is the
second study in a week to fuel the debate on the origin of the human
species.
Australian researchers set off a storm last week when they announced
that their analysis of mitochondrial DNA from 'Mungo Man' also
supported the so-called 'regional continuity theory'. Their study is
due to be published this month in the Proceedings of the National
Academy of Sciences.
The study presented in this week's Science comes to the same
conclusion following a comparison of early modern and archaic fossil
skulls from around the world.
"Ancient humans shared genes and behaviours across wide regions of the
world, and were not rendered extinct by one 'lucky group' that later
evolved into us," says Wolpoff. "The fossils clearly show that more
than one ancient group survived and thrived."
The researchers analysed the similarities and differences between
fossil skulls from Australia and Central Europe, and peripheral
regions far from Africa, where according to the dominant "Out of
Africa" theory -- also known as the "Eve" or "Replacement" theory --
modern humans evolved.
"Basically we wanted to see if this comparison could disprove the
theory of multiple ancestry for the early European and Australian
moderns," said Wolpoff.
The researchers said they found that the most recent European and
Australian skulls shared characteristics with the ancient African and
Near Eastern population and with the older fossils from within their
own regions. They also found there were many more similarities than
could be explained by chance alone -- a finding which amounted to "a
smoking gun" for the regional continuity theory.
The findings are the latest evidence in the continuing scientific
controversy about the origin of modern humans (Homo sapiens). Most
scientists believe that all living humans can trace their ancestry
exclusively to a small group of ancient humans, probably Africans,
living around 100,000 years ago. If this theory was true it would mean
that all other early human groups, whose fossils date from this time
back to almost two million years ago, must have become extinct,
possibly wiped out in a prehistoric genetic holocaust.
Other scientists, including Wolpoff and Australian National University
anthropologist Dr Alan Thorne, maintain that there is little evidence
that a small group originating in a single geographic region replaced
the entire population of early humans.
"In asking the question a different way, and directly addressing the
fossils, this study provides compelling evidence that replacement is
the wrong explanation," says Wolpoff. "Instead, the findings support
the theory of multi-regional evolution. Modern humans are the present
manifestation of an older worldwide species with populations connected
by gene flow and the exchange of ideas."
Palaeoanthropologist Associate Professor Peter Brown of the University
of New England disputes the findings.
"I'm amazed that Science has published this article. If it had been
submitted to me by a third year student I would have failed them," he
told ABC Science Online.
Professor Brown said that Wolpoff and colleagues had chosen an
Australian fossil that was unrepresentative of the skulls of that
time.
"It's pathologically different. It has a skull as thick as a bike
helmet," he said. "They've just chosen a fossil that suits their
theory".
He said that the authors had also ignored literature that was contrary
to their theory.
Dr Alan Thorne, however, insists that the evidence is on his and
Wolpoff's side.
"What we've found is mitochondrial DNA in an Australian fossil that is
much more primitive than anything that's been found in Africa," he
said. "And there is no archaeological or physical evidence to support
the idea that Aboriginal Australians originated from Africa."
Anna Salleh - ABC Science Online
News in Science - Another blow for Out of Africa? - 23/02/2001 X-URL:
http://www.abc.net.au/science/news/stories/s250390.htm
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Another blow for Out of Africa?
Friday, 23 February 2001
Nanjing man
Nanjing man
Another Australian study - this time of Chinese fossils - has weighed
into the controversy over the origins of modern humans, supporting the
theory they evolved in many different regions of the world.
Dr Jian-xin Zhao and Professor Ken Collerson from the [18]University
of Queensland (UQ) have dated ancient human fossils in China as being
at least 620,000 years old - much older than previously thought.
The researchers from the Earth Sciences Department say the findings
support the theory that Asian populations evolved directly from Asian
Homo Erectus, rather than evolving from populations out of Africa.
A major argument against this regional continuity theory, Dr Zhao told
ABC Science Online, is that the age of Homo Erectus fossils found in
Asia did not allow enough time for Homo Sapiens to evolve.
"This new date gives plenty of time for Home Erectus to evolve into
Homo Sapiens," he says.
The researchers measured the decay of uranium into thorium in samples
of calcite flowstone directly above recently discovered Homo Erectus
fossils called Nanjing Man, in the Tangshan Cave 250 kilometres
northwest of Shanghai.
In the past this method has been used to date teeth and bones, however
the researchers say applying it to calcite flowstone samples has
provided much more accurate dates and challenged the reliability of
using fossil teeth for the purposes of dating.
"Age estimates derived from teeth or bones depend very much on how and
when uranium was taken up during fossilisation process, and are often
younger than the true ages," Professor Collerson says. "In contrast,
the University of Queensland dates were derived from dense and pure
crystalline flowstone that was closed to uranium and thorium mobility
and are therefore more reliable."
The findings, developed in collaboration with Dr Kai Hu and Dr Han-kui
Xu from Nanjing, were published recently in the international journal
Geology.
Anna Salleh - ABC Science Online
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