Explosive population growth is driving human evolution to speed up around the world, according to a new study.
The pace of change accelerated about 40,000 years ago and then picked up even more with the advent of agriculture about 10,000 years ago, the study says.
And while humans are evolving quickly around the world, local cultural and environmental factors are shaping evolution differently on different continents.
"We're evolving away from each other. We're getting more and more different," said Henry Harpending, an anthropologist at the University of Utah in Salt Lake City who co-authored the study.
For example, in Europe natural selection has favored genes for pigmentation like light skin, blue eyes, and blond hair. Asians also have genes selected for light skin, but they are different from the European ones.
"Europeans and Asians are both bleached Africans, but the way they got bleached is different in the two areas," Harpending said.
He and colleagues report the finding this week in the journal Proceedings of the National Academy of Sciences.
Snips of DNA
The researchers analyzed the DNA from 270 people in the International HapMap Project, an effort to identify variation in human genes that cause disease and serve as targets for new medicines.
The study specifically looked for genetic variations called single nucleotide polymorphisms, or SNPs (pronounced "snips"), which are mutations at a single point on a chromosome.
(See an interactive overview of human genetics.)
"We look for parts of chromosomes that are common in the population but are new, and if they are common but recent, they must have gotten to high frequency by selection," Harpending explained.
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