Washington: Scientists have long wondered
why the people of the Tibetan Highlands can live at elevations
that cause some humans to become life-threateningly ill. Now a study claims to have finally found an answer to that mystery.
An international team has claimed that thousands of
years ago Tibetans developed 10 unique oxygen-processing genes to help them adapt to life at high elevations, the `Science Express` journal reported.
According to the study, Tibetan highlanders began
to genetically adapt to prevent polycythemia -- a process in
which the body produces too many red blood cells in response
to oxygen deprivation -- and other health abnormalities, like
swelling of the lungs and brain and hypertension of the lung
vessels, leading to eventual respiratory failure.
Even at elevations of 14,000 feet above sea level
or higher, where the atmosphere contains much less oxygen than at sea level, most Tibetans do not overproduce red blood cells and do not develop lung or brain complications.
The scientists from the University of Utah School of
Medicine and Qinghai University Medical School found evidence
that this might be related to the 10 genes, two of which are
specific genes strongly associated with hemoglobin, a molecule
that transports oxygen in the blood.
High-altitude lung and brain complications threaten
and even kill mountaineers who scale world`s tallest peaks.
Others who find themselves at elevations significantly higher
than where they normally live and work also can be stricken
with the condition.
But the Tibetans have evolved genes that others living
at similar elevations have not developed, according to Lynn B
Jorde, who led the study. "For the first time, we have genes
that help explain that adaptation," he said.
Added co-scientist Josef T Prchal: "What`s unique
about Tibetans is they don`t develop high red blood cells
counts. If we can understand this, we can develop therapies
for human disease."
The Tibetans also show higher levels of nitric
oxide, a molecule that may help get more oxygen to tissues and prevent polycythemia. "This might help make up for having fewer red blood cells," Jorde said.