Scientific American has a remarkably interesting article about what a team of researchers have found through analyzing human genetic variation about the speed of our evolution. As SciAm reports:
Homo sapiens sapiens has spread across the globe and increased vastly in numbers over the past 50,000 years or so—from an estimated five million in 9000 B.C. to roughly 6.5 billion today. More people means more opportunity for mutations to creep into the basic human genome and new research confirms that in the past 10,000 years a host of changes to everything from digestion to bones has been taking place.
"We found very many human genes undergoing selection," says anthropologist Gregory Cochran of the University of Utah, a member of the team that analyzed the 3.9 million genes showing the most variation. "Most are very recent, so much so that the rate of human evolution over the past few thousand years is far greater than it has been over the past few million years."
"We believe that this can be explained by an increase in the strength of selection as people became agriculturalists—a major ecological change—and a vast increase in the number of favorable mutations as agriculture led to increased population size," he adds.
One quick note, the researchers did not analyze 3.9 million genes, but 3.9 million of the individual differences in genes called single nucleotide polymorphisms (SNPs). My favorite finding is:
"Ten thousand years ago, no one on planet Earth had blue eyes," Hawks notes, because that gene—OCA2—had not yet developed.
The University of Wisconsin press release adds some interesting observations from UW anthropologist John Hawks. To wit:
The findings may lead to a very broad rethinking of human evolution, Hawks says, especially in the view that modern culture has essentially relaxed the need for physical genetic changes in humans to improve survival. Adds Hawks: "We are more different genetically from people living 5,000 years ago than they were different from Neanderthals."
Humans alive today are as different from people living 5,000 years ago as they were from Neanderthals?! Fascinating.
Disclosure: My eyes are brown, but some of my best friends are blue-eyed and some others have green eyes.