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"On my part, I remain committed to the process of dialogue. It is my firm belief that dialogue and a willingness to look with honesty and clarity at the reality of Tibet can lead us to a viable solution."

Tibetans evolved rapidly to cope with high altitudes, study finds

July 5, 2010

Rachel Bernstein
Los Angeles Times
July 3, 2010

LOS ANGELES -- The Tibet plateau is a land of
yaks and sherpas -- and rapid evolution. Over a
mere 3,000 years -- a blink of an evolutionary
eye – Tibetan highlanders have developed a unique
version of a gene that helps them cope with life
at extremely high altitudes, according to a study
published Friday in the journal Science.

The research group, led by a biologist at the
University of California, Berkeley, Rasmus
Nielsen, found the gene by comparing DNA from 50
Tibetans and 40 neighboring Han Chinese. The two
groups are closely related, with one important
difference: The Tibetans live at an elevation of
at least 14,000 feet, while the Han population
lives relatively close to sea level.

"The change at this particular position in
Tibetan highlanders represents one of the most
dramatic examples of genetic change in recent
human history," said University of Nebraska
evolutionary geneticist Jay Storz, who was not
involved in the study. "It really is a great
story about how the human gene pool is still
being shaped by the forces of natural selection."

The researchers calculated that the Tibetan and
Chinese populations separated about 3,000 years ago.

"This is not the distant past," said John Hawks,
an anthropologist at the University of Wisconsin.
"This is stuff that's happened in 40 human generations."

It makes sense that the harsh environment of the
Himalayas promoted fast evolutionary adaptation.
The high altitude, where each breath of air has
40 percent less oxygen than the same breath at
sea level, is associated with reproductive
difficulties such as miscarriages and low birth
weight. In response, Tibetans have adapted in a
way that is remarkably effective: lower blood hemoglobin levels.

Scientists still don't know exactly how the low
hemoglobin levels help the Tibetans, but they do
know that too much hemoglobin makes the blood too
viscous, making oxygen distribution more
difficult. By maintaining lower hemoglobin
levels, the Tibetans have avoided this damaging effect.
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