Research shows that humans are still under selection, not just for things like disease resistance but for cognitive abilities

Annalee Newitz:

New evidence suggests humans are evolving more rapidly -- and more recently -- than most people thought possible. But for some radical evolutionists, Homo sapiens isn't morphing quickly enough.

"People like to think of modern human biology, and especially mental biology, as being the result of selections that took place 100,000 years ago," said University of Chicago geneticist Bruce Lahn. "But our research shows that humans are still under selection, not just for things like disease resistance but for cognitive abilities."

Lahn recently published the results of a study demonstrating that two key genes connected to brain size are currently under rapid selection in populations throughout the globe.

"The jury is still out on what this means because we aren't entirely sure what these genes do," said Lahn. "It's possible they just control size and shape of the brain, rather than cognition. But the data is pretty compelling that the brain is evolving."

Some radical thinkers suggest human evolution needs to move even faster, with a little help from science.

"Biological evolution is too slow for the human species," said Ray Kurzweil, futurist and author of The Singularity Is Near. "Over the next few decades, it's going to be left in the dust."

He may be right, and not just because biotech researchers are racing to rewrite our genomes. Old-school theories that painted evolution as a glacial process have recently come under fire from researchers who see human evolution as a fast-paced and ongoing process.

Their work flies in the face of popular Darwinian theories of human behavior such as those espoused by Harvard University scientist Steven Pinker, whose recent book The Blank Slate takes for granted the idea that Homo sapiens hasn't changed since its long trek out of Africa 100,000 years ago.

Chicago geneticist Lahn is most intrigued by the possibility that cultural factors are involved in brain evolution. "We think some of these new gene variants may be as young as a few thousand years, a period when human culture was changing dramatically," he said. "Maybe these genes are selected not for hunting but because of organized society." He cautioned that this is just a hypothesis, but "recent cultural evolution and biological evolution may be linked."

It may be hard to think of something a few thousand years old as "recent," but from the perspective of evolutionary biology, it's positively contemporary.

"The time scale for a strongly favored mutation to sweep through a population is about 5,000 years," said Jonathan Pritchard, a University of Chicago evolutionary biologist. "It's hard to get an exact estimate for rates of change, but we know that the lactase gene is evolving the fastest in humans. It was new 5,000 years ago and now it's in virtually everybody in Europe."

The lactase gene is what allows humans to metabolize dairy products as adults. It's widely believed to have evolved in response to humans' domestication of dairy animals -- individuals who could enhance their diet with dairy products had such a strong survival advantage that the gene spread at the speed of, well, several thousand generations.

A storm of publicity greeted Pritchard's recent paper on signals of selection across the human genome. The response came in large part because Pritchard and his colleagues had found such overwhelming evidence that many human genes are evolving: not just ones that govern the brain, but also ones associated with reproduction, disease resistance and the ability to process certain kinds of foods.

"I think my work is changing people's ideas about evolution, because now natural selection seems to have continued all the way up to the present day," said Pritchard. "There's no reason to think it stops now."

That's why futurists like Kurzweil are excited about Lahn and Pritchard's work -- it could lay the foundations for a new understanding of evolution that's more tolerant of the idea that humans should intervene in their own genetic transformation.

Lahn is comfortable with this idea. "If there's an evolutionary advantage to be had by using technology, then people will do it," he said. "People are going to start changing the game in evolution in ways Darwin never anticipated."

Trans-humanist pundit James Hughes, author of Citizen Cyborg, thinks it's time to speed up the evolutionary process.

"You can take what nature gave you, but there's no good reason to take nature as a guide for where you should go in the future," Hughes said.

"People are comforted by the slow pace of biological evolution," said Kurzweil. He predicted that "genetic reprogramming" will soon lead to "dramatic evolutionary changes."

Lahn, for his part, is a "moral relativist" on these issues, but does concede: "Human evolution could soon occur at a rate and with a set of rules that may be very different than what the Darwinian model has characterized so far."

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