The Telegraph, India[Monday, November 12, 2007 10:24]
By G.S. MUDUR

New Delhi, November 11 - Tibetans who were born and raised in India 
are taller and display other physiological changes that are not 
observed among original Tibetan highlanders, Calcutta-based 
scientists have found.

The changes are among the first signals that Tibetans - the world's 
longest-surviving high altitude residents - are adapting to the low 
altitude environment in India, anthropologists at the Indian 
Statistical Institute (ISI), Calcutta, said.

Their studies show that Tibetan men and women between the ages of 18 
and 40 who were raised at low altitudes in India are on an average 
about 4 to 5cm taller than their counterparts in high altitude regions.

"Among all human populations, Tibetans have adapted best to the high 
altitude environment," said Ranjan Gupta, head of the ISI's 
biological anthropology unit. "It's possible we're now looking at a 
reversal of this adaptation," Gupta told The Telegraph.

Gupta and researcher Vikal Tripathy studied body features of Tibetans 
in three settlements at different altitudes in India - Choglamsar in 
Leh at 3500m above sea level where the environment is similar to the 
high altitude regions of Tibet, a settlement in Chandragiri (Orissa) 
and another at Bylakuppe (Karnataka), both within 1000m above sea level.

The lower height of Tibetans at Choglamsar might be explained through 
low oxygen in the air and relatively poor nutrition in high altitude 
regions, the researchers said, presenting their findings in the 
American Journal of Human Biology. Populations at low altitudes have 
access to a greater diversity of vegetables and fruits in winter than 
people living at high altitudes.

"Everyone has genetic potential... when the different stresses 
associated with high altitude are removed, the genetic potential gets 
activated," said Gupta.

"This is very significant work. It's the first time anyone has 
systematically looked at Tibetans at different altitudes," said 
Charles Weitz, chairman of anthropology at Temple University, 
Philadelphia, in the US. Weitz is an authority on adaptation to high 
altitude environments, having studied populations in South America 
and China.

Archaeological evidence suggests that humans had settled in Tibet 
around 20,000 years ago, long before any other population had settled 
in high altitude zones around the world.

Scientists believe both the genetic make-up and the environment 
contribute to human growth and development. "This study is part of a 
broader effort to determine how much of human adaptation is driven by 
the genes and how much by the environment," Weitz said.

Gupta and Weitz are now writing a proposal for a joint study to 
pursue this line of research in finer detail. "India offers a unique 
natural environment for such a study," Gupta said. Some 80,000 
Tibetans fled their native land in 1959 and have settled in India 
where the environment is very different from that found on the 
Tibetan plateau.

The ISI study also found that Tibetans living at low altitudes had 
slightly higher values of weight, skin-fold thickness at the triceps, 
and upper arm circumference. The researchers believe greater physical 
activity may be causing Tibetans at low altitudes to gain more weight 
than Tibetans living at high altitudes.

"Some changes may also relate to body surface area. In extreme cold, 
a low surface area helps the body retain heat, but this is not 
necessary at low altitudes," Gupta said. "Better nutrition and the 
absence of high altitude stress - both might be driving the changes 
we're seeing," he said.