U. scientist says human evolution is going strong
In fact, he and others observe acceleration in rates of change
A team of researchers led by the U.'s Henry Harpending contends that humans are still evolving, the rate is accelerating and the changes differ markedly among some continents. The report, published online Monday in the Proceedings of the National Academies of Science, says change has been especially fast since the end of the last ice age about 10,000 years ago.
The scientists scanned gene sequences of 270 people from populations throughout the world. These sequences were posted on the Internet by the researchers, who often are required by funding rules to release their results quickly.
Harpending and associates found many regions of the human genome that had indications of recent changes.
"We've identified thousands of them," said Harpending, whose title is distinguished professor in the anthropology department. The next step was to check whether genes whose purposes are known are present in these regions.
One of the genes has a mutation that allows adults to digest milk sugar. "It's called lactose tolerance," he said in a telephone interview Monday.
Yet many residents of Asia and Africa don't have the mutation, and adults there aren't able to digest milk sugar. This intolerance will give them diarrhea after drinking milk.
Harpending added that he often works in southern Africa, and when people there see him pour milk on his breakfast cereal, it's a gut-wrenching experience for them.
But sometime in the past for certain populations, a mutation happened that prevents the switching off. The mutation is very common for people from Europe.
A recent study reported the results of gene sequencing on Danish skeletons dating to 8,000 years ago. These people did not have the mutation leading to lactose tolerance. That means genetic mutation must be newer than 8,000 years ago, he said.
Today, about 90 percent of Danes have the mutation. It quickly spread through the population because it is advantageous: If one person has to ferment milk to break down the milk sugar and then make cheese with the result, he has a digestive disadvantage compared to someone who can just drink the milk.
Other mutations concern "broken pigment genes," giving Europeans white skin, blond hair and blue eyes. The cause of this mutation is that after people moved out of Africa and into Europe, they needed a better way to get vitamin D.
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