Scientists have compared genes from different ethnic groups and found more recent genetic mutations are changing the way some people metabolize food, store fat, grow hair, and fight disease.
One new mutation that appears only in Asians may improve hearing and balance.
Some of the more recent changes have not spread through the world uniformly - affecting only those of European, African, or Asian ancestry. Would any future findings suggest that some group had traits that might be considered superior to others?
Already, for example, some scientists have theorized that recent genetic changes have endowed Ashkenazi Jews with higher average intelligence.
To deal with such potentially inflammatory ideas, the National Institutes of Health assembled a meeting in 2008 on the social and ethical implications of natural selection in humans. "There was a spirited debate about whether we should be engaged in this research at all," said Josh Akey, a geneticist from the University of Washington. Some argued that no good could come of it, he said.
Akey and other scientists who do this work say they hope to advance medicine by revealing why some people are more vulnerable than others to HIV, malaria, flu, autoimmune diseases, allergies, diabetes, alcoholism, and obesity.
The scientists argue that none of this work points to the superiority of one group or person over another. It's an old misconception that evolution is elevating humanity up some ladder of perfection, he said, or that one group could be more evolved than another.
"When we talk about natural selection, people think about survival-of-the fittest," Akey said, "but that's not really how it works."
Local environments bend the course of evolution. Traits that would make someone "fit" in one place could prove to be liabilities in another.
