Tibetans live at altitudes of 13,000 feet, breathing air that has 40 percent less oxygen than is available at sea level, yet suffer very little mountain sickness.

The reason, according to a team of biologists in China, is human evolution, in what may be the most recent and fastest instance detected so far. Comparing the genomes of Tibetans and Han Chinese, the majority ethnic group in China, the biologists found that at least 30 genes had undergone evolutionary change in the Tibetans as they adapted to life on the high plateau. Tibetans and Han Chinese split apart as recently as 3,000 years ago, say the biologists, a group at the Beijing Genomics Institute led by Xin Yi and Jian Wang. The report appears in Friday’s issue of Science.

If confirmed, this would be the most recent known example of human evolutionary change. Until now, the most recent such change was the spread of lactose tolerance — the ability to digest milk in adulthood — among northern Europeans about 7,500 years ago. But archaeologists say that the Tibetan plateau was inhabited much earlier than 3,000 years ago and that the geneticists’ date is incorrect.

When lowlanders try to live at high altitudes, their blood thickens as the body tries to counteract the low oxygen levels by churning out more red blood cells. This overproduction of red blood cells leads to chronic mountain sickness and to lesser fertility — Han Chinese living in Tibet have three times the infant mortality of Tibetans.

The Beijing team analyzed the 3 percent of the human genome in which known genes lie in 50 Tibetans from two villages at an altitude of 14,000 feet and in 40 Han Chinese from Beijing, which is 160 feet above sea level. Many genes exist in a population in alternative versions. The biologists found about 30 genes in which a version rare among the Han had become common among the Tibetans. The most striking instance was a version of a gene possessed by 9 percent of Han but 87 percent of Tibetans.

[NYTimes]

A little girl asked her mother, “How did the human race appear?”

The mother answered, “God made Adam and Eve and they had children, and so was all mankind made …”

Two days later the girl asked her father the same question.

The father answered, “Many years ago there were monkeys from which the human race evolved.”

The confused girl returned to her mother and said, “Mom, how is it possible that you told me the human race was created by God, and Dad said they developed from monkeys?”

The mother answered, “Well, dear, it is very simple. I told you about my side of the family and your father told you about his!”