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Newsletter #5
Scientists in Nature Magazine
Challenge Out of Africa Thesis
An Asian perspective on early human dispersal from Africa
BY ROBIN DENNELLI and WIL ROEBROEKS
Dec. 22, 2005
Nature vol. 438, pp. 1099-1104
The
past decade has seen the Pliocene and Pleistocene fossil hominin record
enriched by the addition of at least ten new taxa, including the Early
Pleistocene, small-brained hominins from Dmanisi, Georgia, and the
diminutive Late Pleistocene Homo floresiensis from Flores, Indonesia.
At the same time, Asia's earliest hominin presence has been extended up
to 1.8 Myr ago, hundreds of thousands of years earlier than previously
envisaged. Nevertheless, the preferred explanation for the first
appearance of hominins outside Africa has remained virtually unchanged.
We show here that it is time to develop alternatives to one of
palaeoanthropology's most basic paradigms: 'Out of Africa 1'.
Study Suggests 'Y' the Male Chromosome Will Endure
By DAVID BROWN
The Washington Post
September 5, 2005
To paraphrase Mark Twain, reports of the impending death of the human Y chromosome have been greatly exaggerated.
Research
published last week revealed that the chromosome of maleness -- which
under the microscope looks as worn down and misshapen as a stubbed-out
cheroot -- is actually healthy and holding up fine against the ravages
of evolutionary time.
It turns out the human Y has barely
changed in the last 6 million years. All its important parts still
work. Predictions that it will cease to exist in another 10 million
years -- and with it, men as we know them -- may be wrong.
In Chimpanzee DNA, Signs of Y Chromosome's Evolution
By NICHOLAS WADE, The New York Times
Published: September 1, 2005
Scientists
have decoded the chimp genome and compared it with that of humans, a
major step toward defining what makes people human and developing a
deep insight into the evolution of human sexual behavior.
The
comparison pinpoints the genetic differences that have arisen in the
two species since they split from a common ancestor some six million
years ago.
Chimpanzees and people possess almost identical sets
of genes, so the genes that have changed down the human lineage should
hold the key to what makes people human.
Biologists suspect that
only a handful of genes are responsible for the major changes that
reshaped the apelike ancestor of both species into a human and that
these genes should be identifiable by having evolved at a particularly
rapid rate.
Dental DNA reveals our ancient roots
By Leigh Fenly
UNION-TRIBUNE STAFF WRITER
August 24, 2005
ASHLAND,
Ore. -- Paleontologist Timothy Heaton was used to finding
35,000-year-old remains of brown bear, black bear, hoary marmot and
antelope in On Your Knees Cave, a tight opening tucked in the dense
hemlocks of Alaska's vast Tongass National Forest. But on the last day
of excavation in 1996, as Heaton was filling a final bag of sediment,
he came upon something quite different.
A lower jaw. A pelvic bone. Obsidian worked into a spear point.
Unmistakable evidence of an ancient human.
Since,
the effort to tease clues from the 10,300-year-old remains, the oldest
ever found in Alaska or Canada, has involved myriad research
laboratories, most recently the Molecular Anthropology Lab at UC Davis.
A
tooth from On Your Knees Cave Man wrapped in cotton and shipped via
Federal Express arrived there in 2003. Brian Kemp, a Ph.D. candidate,
removed the tooth's crown and hammered out a quarter-gram portion of
root. He subjected it to bleach, a decalcifying chemical and a
protein-devouring enzyme. With a silica extraction, he got the tooth's
DNA to jump out of the solution.
With the same process forensic
scientists use to link DNA to criminals, Kemp tricked the purified DNA
into copying itself millions of times. The resulting sequences, the
oldest DNA ever extracted from human remains in the Americas, revealed
some of the old man's secrets.
Kemp's analysis, which he will
submit to Nature, confirmed the Ice Age remains as male and established
his maternal ancestry as Asian.
From differences in the genetic
sequences, Kemp is now able to argue that the cave man's DNA represents
a new ancient lineage in North America. Comparing that DNA to
modern-day sequences, he also is suggesting changes to some scientists'
estimates of the time of the first migrations to the New World.
In
the months to come, the results will likely be strenuously argued. Less
debatable is the fact that Kemp's work gets us closer to understanding
who first peopled North America and offers a glimpse at the tantalizing
future of genetic anthropology.
The human genome stores vast
amounts of information on the movements, relationships and adaptations
of past populations. In the last decade, after some embarrassing
missteps and exaggerated claims, DNA technology has begun to reveal
some of that dormant information.
The promise is huge, says Nina
Jablonski, an anthropologist at the California Academy of Sciences. "As
the early problems get solved, we're going to have the framework to
learn about relationships among ancient people. DNA is going to answer
all our questions about who is related to whom."
To follow this conversation for long you need a vocabulary word: mitochondrial DNA.
Most
people are familiar with nuclear DNA – our genes that come to us
courtesy of our mother and father, when the sperm fertilizes the egg
and both sets of genes mix.
As a tool for genetic
anthropologists, nuclear DNA is troublesome because all that
reshuffling of genes makes it tough to trace a direct genetic line from
individual to individual.
But the mitochondria, the cell's
energy-producing bodies, also have tiny genomes, and these are
inherited only from our mothers. Because there is no mixing with male
genes, Smith explains, mitochondrial DNA stays the same from generation
to generation, except when random mutations occur.
And
mitochondrial DNA is abundant in cells compared to nuclear DNA and
therefore more likely to be extracted. It will never be enough to clone
an early cave man, but for Kemp, Smith and other genetic
anthropologists, mitochondrial DNA is the mother lode.
"This is what's allowing us to construct a history where there is no written record," Smith says.
The
reason they can do this is because the rate of mutation in
mitochondrial DNA remains constant over time – in each individual, from
prehistory to modern-day, changes occur at the same rate. That rate of
change is used as a measuring stick for time known as the molecular
clock.
To make sense of all the mutations, scientists group
individuals with similar sets of mutations into families known as
haplogroups. Haplogroups are further divided into smaller groups called
haplotypes. OYKCM belongs to haplotype D, one of five founding lineages
that appear in North America. But his haplotype is rare.
"When I first saw it, I wasn't sure what I was looking at," Kemp says. "He was D-something else."
The
D-something-else genetic sequence is like a fingerprint of inherited
mutations. Kemp wanted to find out if anyone living today had anything
similar. From a genetic database of 3,500 Native Americans, he found 47
individuals living in North and South America who belong to the same
haplotype. These are the cave man's relatives, inheritors of his same
fingerprint of mutations.
The 47 are widely spread, from
California to Tierra del Fuego. Some belong to California's Chumash
tribe, Ecuador's Cayapa tribe and the Tarahumara in Mexico. This wide
dispersal is an important clue to the geographic reach of the cave
man's family and the migratory routes they might have taken.
Mitochondria can be inherited from both parents
* 17:01 23 August 2002
* NewScientist.com news service
* BY DANNY PENMAN
Mitochondria
may not be inherited solely through the maternal line, according to new
research that promises to overturn accepted biological wisdom.
If confirmed by other researchers, the findings could have huge implications for evolutionary biology and biochemistry.
Robert
Sanders Williams, from Duke University Medical Center in North
Carolina, says the findings are "remarkable and unanticipated. This is
more than a mere curiosity. It asserts the principle that it can occur
in humans. It could have significant implications for the study of
human evolution and the migrations of populations," he says.
DNA Machine May Advance Genetic Sequencing for Patients
By NICHOLAS WADE
Published: August 1, 2005
A
new kind of machine for decoding DNA may help bring costs so low that
it would be feasible to decode an individual's DNA for medical reasons.
The machine, developed by 454 Life Sciences of Branford, Conn., was
used to resequence the genome of a small bacterium in four hours, its
scientists report in an article published online today by the journal
Nature. Read the article in The New York Times.
Vive la difference!
By Charles Lee
Until
very recently, it was widely touted that the complete DNA sequences of
any two human beings were 99.9% identical. A new study refutes this
notion through a comprehensive comparison of two individual genomes
which detects hundreds of new structural genomic variants. The article
appears in Nature Genetics 37, 660 - 661 (2005).
Heart Drug for Blacks Endorsed
Racial Tailoring Would Be a First; Idea Stirs Debate
By Rob Stein
Washington Post Staff Writer
Friday, June 17, 2005; Page A01
Federal
health advisers yesterday endorsed the approval of a drug to treat
heart failure in African Americans, which would make the controversial
pill the first medicine targeted at a specific racial group. Read article.
mtDNA J and K Have Low Susceptibility to Parkinson's Disease
Confirming
previous studies, a new article finds that K and its related haplogroup
J have a a lower risk than other haplogroups for Parkinson's Disease.
D. Ghezzi et al., "Mitochondrial DNA haplogroup K is associated with a
lower risk of Parkinson's disease in Italians," European Journal of Human Genetics (2005) 13, 748-752.
DNA Study Yields Clues on First Migration of Early Humans
By NICHOLAS WADE, The New York Times
Published: May 13, 2005
By
studying the DNA of an ancient people in Malaysia, a team of
geneticists says it has illuminated many aspects of how modern humans
migrated from Africa.
The Orang Asli people, north of Kuala
Lumpur, Malaysia, were studied by geneticists who traced their
mitochondrial DNA from Africa.
The geneticists say there was
only one migration of modern humans out of Africa; that it took a
southern route to India, Southeast Asia and Australia; and that it
consisted of a single band of hunter-gatherers, probably just a few
hundred people strong.... Read more...