CHICAGO — Could you use more brainpower?

Nature apparently thinks you can, according to two University of Chicago studies providing the first scientific evidence that the human brain is still evolving, a process that may increase people's capacity to grow smarter.

Two key brain-building genes, which underwent dramatic changes in the past that coincided with huge leaps in human intellectual development, are undergoing rapid mutations, evolution's way of selecting for new beneficial traits, Bruce Lahn and his University of Chicago colleagues reported in today's issue of the journal Science.

The researchers found that not everyone has these genes, but that evolutionary pressures are causing them to increase in the population at an unprecedented rate. Lahn's group is also trying to determine how smart these genes may have made humans.

One of the mutated genes, microcephalin, began its swift spread among human ancestors about 37,000 years ago, a period marked by a creative explosion in music, art, religious expression and tool-making.

The other gene, ASPM (abnormal spindlelike microcephaly-associated), arose about 5,800 years ago, around the time of writing and the first civilization in Mesopotamia, which dates to 7000 BC.

"People have this sense that as 21st-century humans we've gotten as high as we're going to go," said Greg Wray, director of Duke University's Center for Evolutionary Genomics. "But we're not played out as a species. We're still evolving, and these studies are a pretty good example of that."

Just as major environmental changes in the past, such as dramatic shifts in the climate, food supply or geography, favored the selection of genetic traits that increased survival skills, the pressures on gene selection today come from an increasingly complex and technologically oriented society, said Lahn, a professor of human genetics and a Howard Hughes Medical Institute investigator

"Our studies indicate that the trend that is the defining characteristic of human evolution — the growth of brain size and complexity — is likely still going on," he said.

"Meanwhile, our environment and the skills we need to survive in it are changing faster then we ever imagined," Lahn said. "I would expect the human brain, which has done well by us so far, will continue to adapt to those changes."

Evolutionary changes occur when a member of a species experiences a mutation in a gene that gives him a new skill, such as running faster, seeing farther or thinking better. The genetic mutation increases his likelihood of survival and having more children, thereby allowing the new mutation to spread quickly through the population.

That's what happened to the microcephalin mutation, which occurs in 70 percent of all people, and the ASPM gene mutation, which has spread to 30 percent of the world's people.

Other experts called the Chicago studies "stunning" but said that while the two genes appear to make people smarter by helping to engineer bigger brains, there are many more genes involved in brain building and human intelligence and cognition.

"It's very exciting but it's really just the beginning of a whole new phase of research," said Duke's Wray.

"These aren't going to be the only genes and these aren't going to be the only changes. We don't even really know exactly what these changes mean, but it's a glimpse into the future of our understanding of how the human brain came to be and function the way it does."