By: Ivan Noble
Modern humans migrated out of
Africa into Central Asia before spreading both
east and west into North America and Europe, says
an international team of scientists who have used
modern DNA analysis to trace ancient migrations.
40-50,000 years ago, Central Asia was full of
tropical trees, a good place for hunting and
fishing," said Nadira Yuldasheva, of the
Institute of Immunology at the Academy of
Sciences, Tashkent, Uzbekistan.
desertification came in, some people moved west
into Europe and some moved into Siberia and on
into North America," she told BBC News
Professor Ruslan Ruzibakiev organised the
collection of thousands of blood samples across
Central Asia and the Caucusus.
They are now
working with Spencer Wells at the Wellcome Trust
Centre for Human Genetics, Oxford, UK, using
telltale mutations of the Y-chromosome to trace
the paths of the ancient travellers.
explained why the Y-chromosome holds the key to
tracking lines of descent.
thing about the Y-chromosome is that it doesn't
recombine," he said.
When a child
is created, its DNA comes from both its parents.
is shuffled like a pack of cards," Dr Wells
But if it the
child is a boy, his Y-chromosome can only come
from his father, since only men have
mutations to the Y-chromosome, which take place
naturally over time, are passed directly from
father to son without any shuffling.
like Dr Wells and Dr Yuldasheva have used these
inherited markers to trace a family tree of human
comparing this tree with known archaeological and
linguistic facts, they believe that they have
developed a more detailed understanding of how
anatomically modern humans moved around the world.
like Central Asia was settled really early, around
40,000 years ago, as humans came out of Africa. We
can trace back to regional 'Adams'," said Dr
regional Adam's descendants moved up to the steppe
lands - probably because of climate change and
then went west.
would have been the Cro-Magnons, the people who
correspond to our popular image of the cave
man," he said.
wave moved along the steppe belt well to the east
into the Americas," he added.
Dr Wells and
his colleagues believe that their work also traces
the expansion of the Indo-Iranian people known as
the Kurgan civilisation, or more popularly Aryans.
a diagnostic Indo-Iranian marker," he said,
referring to one of the Y-chromosome mutations.
shows the progress of the 'Aryans' into India and
beyond. These Indo-Iranians spoke a language which
is believed to be the forerunner of many modern
living high in the mountain valleys of Central
Asia still speak a form of Sogdian - the oldest
living Indo-Iranian tongue.
The study also
shows how successful emigrants from Central Asia
were able to spread their language further than
from Iran show far fewer Indo-Iranian markers in
the west of the country, despite an Indo-Iranian
language being dominant across the region.
explanation, said Dr Wells, could be that the
incomers were so successful that the original
inhabitants of the region began to adopt the
Asia's diverse genetic mix is explained by the
migrations that came much later, when the Silk
Road carried wealth and trade goods from China to
Europe and back.
migrations are reflected in the DNA, too, and it
is clear that despite the majority of modern
Central Asians speaking Turkic languages, they
derive much of their genetic heritage from the
conquering Mongol warriors of Genghis Khan.
Asia is revealed to be an important reservoir of
genetic diversity, and the source of at least
three waves of migration, leading into Europe, the
Americas and India," the researchers wrote in
the Proceedings of the National Academy of