Q. How are Tibetans able to acclimatize so easily?
A. It's in their genes, of course, but the precise mechanics are still a mystery. This summer, researchers identified 30 genes with DNA mutations that are more prevalent in Tibetans (and presumably Nepali Sherpas) than in ethnic Han Chinese. Tibetans split off from the Han less than 10,000 years ago, a fact that allows scientists to determine which specific genes gave them a high-altitude advantage. Variants of one in particular, the so-called "super athlete" gene EPAS1, have already been linked to improved performance. "Tibetans have a mutation in that gene that is very, very rare," says University of California at Berkeley geneticist Rasmus Nielsen, who worked on the analysis of the Tibetan data. "Presumably, that is one of the particular variants that helps them perform well in a high-altitude environment." But how it all works isn't completely understood. When you or I head to the Himalayas, our bodies compensate for the thinner oxygen levels by producing more hemoglobin, increasing the blood's ability to transport oxygen. But more hemoglobin also thickens your blood, making it harder for the heart to pump and sometimes leading to acute mountain sickness. Tibetans produce less hemoglobin in their blood yet function well at altitude. Still, not having the gene mutation doesn't mean you should forget about climbing in the Himalayas. Good training can get you to the top, too.