22 July 2010

Just How Fast Is Human Evolution?

*** Find out how fast our bodies can adapt to new living situations and what's involved.





From Denny: Imagine you and your family were forced out of your homes and told to trek a few thousand miles and go live high up in the mountains. How high? Try 14,000 feet up high and breathe 40 percent less oxygen than you were used to breathing at a sea level altitude. This is exactly what has happened to the people who are now called Tibetans.

Some Chinese scientists decided to take a look at today's current Tibetans and analysis their DNA versus today's Han Chinese. It's speculated that the Han Chinese, the majority ethic group, split from China and went high up into Tibet about 3,000 years ago.

What the scientists found is that 30 genomes have evolved in this short time. They examined the genomes from 50 Tibetan villagers and 40 Han Chinese from today's Beijing, China. What they found is that a genome rare among 9 percent Han Chinese is common among 87 percent Tibetans.

Which mysterious gene is this that has scientists so excited with their find? The official name of the gene is hypoxia-inducible factor 2-alpha, or HIF2a. What this gene shows is that those persons with it have fewer red blood cells and, therefore, less hemoglobin in their blood.

Why is this important? Because when people who have been living well below such high altitudes try to live up high what happens is that their blood thickens. You see our bodies try to counteract those very low oxygen levels by manufacturing more red blood cells. Then this overproduction of red blood cells leads to chronic mountain sickness, or altitude sickness.

It also causes lesser fertility. The current day Han Chinese living in Tibet suffer three times the infant mortality rate of the Tibetans. China's displacement policy of the population to subdue Tibet by sending in communist Chinese to take away the land from the Tibetans seems to have backfired on them and now they have fallen into an evolutionary trap.

While scientists can account for why the Tibetans do not suffer from altitude sickness they still don't know how they compensate for living with much less oxygen. There are archaeologists who argue the 3,000 year fast evolution is not likely. They favor the argument for the Tibetan plateau being inhabited anywhere from the past 7,000 to 21,000 years. Anyway you look at it, such high altitude living so successfully is impressive!

For more details about the three reports, go here: Scientists Cite Fastest Case of Human Evolution



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