Source: National Post, Tuesday, October 31, 2000 (A16)

Genetics
------------

MALE GENE POOL BACKS THEORY ON OUR ORIGINS

Branches Of Family Tree

PARIS - The theory that Homo sapiens originated in
Africa before slowly spreading across the world has
been powerfully backed by new research into variations
in the male sex chromosome.

The so-called "Out of Africa" hypothesis, sketched in
1987, is based on mitochondrial DNA - scraps of genetic
tissue only inherited from the maternal side -- that
were found in ancient fossils.

This suggested that modern man first appeared in
eastern Africa about 150,000 years ago, leaving at
various times between 35,000 and 89,000 years ago and
eventually conquering the planet.

A major research effort from scientists in eight
countries, published yesterday in the November issue of
the journal 'Nature Genetics', has now validated the
theory -- and in so doing has devised a potent tool to
probe the very earliest origins of mankind.

The team drew up a genetic family tree of mankind
thanks to small variations in the genes of 1,062 men in
communities around the world.

They identified 167 markers: genetic sequences called
alleles in the Y chromosome, which only men carry.
(Women carry two X chromosomes, while men have both X
and Y.)

Variations in these markers corresponded astonishingly
to the regions where the men live.

In other words, the markers reflected the waves of
human migration that unfolded across the world over
tens of thousands of years. Each ripple caused a tiny
disturbance in the male gene pool as the species
intermingled and the Y chromosome adapted through
natural selection.

Samples were taken from men in 22 different regions, in
countries that included Pakistan and India, Cambodia
and Laos, Australia and New Guinea, America, as well as
Mali, Sudan, Ethiopia and Japan.

Their allele mutations were then assembled into 10
types, called haplogroups.

Like branches off a family tree, they show a migration
from eastern Africa into the Middle East, then southern
and southeast Asia, then New Guinea and Australia,
followed by Europe and Central Asia.

Among the findings:

* Some modern-day men in later-day Sudan, Ethiopia and
southern Africa are the closest lineal descendants to
the first Homo sapiens who set out on that great trek.
"A minority of contemporary East Africans and Khoisan
[southern Africans such as the Bushmen and Hottentots]
represent the descendants of the most ancestral
patrilineages of anatomically modern humans that left
Africa between 35,000 and 89,000 years ago," the team
write [sic];

* New Guinesa and Australia were settled early in the
process. This could be supported by the finding of a
Homo sapiens burial site in Australia believed to [sic]
60,000 years old;

* Japan has remained in remarkable genetic isolation.
The mutations are strikingly different from those of
surrounding populations and account by themselves for a
specific haplogroup;

* Native Americans have a common ancestry with
Eurasians and East Asians, raising intriguing questions
about the first peopling of North America.

The findings "takes historical population genetics, or
'archeogenetics,' a quantum leap forward," says a
commentary in 'Nature Genetics' by a team from the
McDonald Institute for Archeological Research in
Cambridge.

The research was especially important given that it
came from DNA of living populations rather than genetic
material teased out of rare fossils, they said. The
technique was to take samples of genetic tissues,
amplify them and then search for the markers using a
chromatographic analysis.

The study was led by Peter Underhill of Stanford
University in Palo Alto, Calif.


Agence France-Presse

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