http://www.sina.com.cn 2007年12月17日 13:45
People are evolving more rapidly than in the distant past, with residents of various continents becoming increasingly different from one another, researchers say. "I was raised with the belief that modern humans showed up 40,000 to 50,000 years ago and haven't changed," explained Henry C. Harpending, an anthropologist at the University of Utah. "The opposite seems to be true.Our species is not static." That doesn't mean we should expect major changes in a few generations, though, evolution occurs over thousands of years.
Harpending and colleagues looked at the DNA of humans and that of chimpanzees, our closest relatives, they report in this week's online edition of Proceedings of the National Academy of Sciences.If evolution had been proceeding steadily at the current rate since humans and chimps separated 6 million years ago there should be 160 times more differences than the researchers found. That indicates that human evolution had been slower in the distant past, Harpending explained.
"Rapid population growth has been coupled with vast changes in cultures and ecology, creating new opportunities for adaptation," the study says. "The past 10,000 years have seen rapid skeletal and dental evolution in human populations, as well as the appearance of many new genetic responses to diet and disease."