UW-Madison Anthropologist's Calculations Advance the Study of Evolution

Jan 06, 11:20 AM

Jan. 6--Like Hamlet contemplating the skull of poor Yorick, John Hawks sees a lot more than most of us when he peers at a skull, something he does frequently. In fact, it 's his job.

Hawks is a UW-Madison anthropologist. Last month, he and colleagues made headlines around the world with a study that showed evolution in humans is happening at a much faster rate than had been previously believed. Hawks studied changes in the human genome and then came up with a mathematical calculation that showed the bigger a population, the faster the rate of evolutionary change.

The work received widespread praise. Clark Larsen, chairman of anthropology at Ohio State University, was not involved in the study but has done his own research on evolution among humans in the last 10,000 years. He said the work by Hawks is "very important " and shows that evolution is happening "right before our eyes. "

Hawks supplemented his mathematical calculations linking genetic mutation and population size with supporting data from fieldwork. He studied, for example, 5,000-year-old skeletons in Germany that showed an adaptation within that 5,000-years that allowed humans to overcome lactose intolerance and drink milk.

It was his contemplation of human skulls that two years ago set Hawks on the intellectual journey that led to this most recent publication. From his studies of skulls, Hawks knew that a change in human brain size has taken place.While human brain size grew slowly over a long period of time, an analysis of skulls showed the size of the brain started shrinking about 10,000 years ago. Today, the brain is about an eighth of the size it was before this change.

Contemplating this change, Hawks thought about why such a major change would take place in such a relatively short period of time. He theorized that evolution was making the brain more compact and efficient and that the rapid change was driven by the dramatic growth in human population from an estimated 5 million people in 9000 B.C. to 6.5 billion today.

The idea of evolutionary change being linked to population size is not new. In his famous writings, Charles Darwin noted that in animal breeding, herd size "is of the highest importance for success, " because the larger the population, the more genetic variation.

But Darwin did not have access to the modern-day knowledge of genes. Hawks and co-author Gregory Cochran, an anthropologist at the University of Utah, were able to tap into the massive library of genes catalogued in the human genome project and actually find those sequences that showed evidence of adaptation. Then, working frequently at home while watching his children, Hawks did the math.

"We worked out the mathematics of the connection between population and genetics, " Hawks said. "This was entirely new. "

Hawks has been gratified by the response to his work. He is unusual in the science world in that he relishes communicating what he does to the general public. He 's extensively discussed his work on a very popular blog he started a few years ago; today the blog at http://www.johnhawks.net/weblog/ has 4,000 hits a day, more traffic than the American Anthropological Association.

The interest in the work, Hawks said, comes at least partly from an interest in evolution in general. This is an exciting time in the field, when science is catching up to theory.

"I think people have trouble thinking about such time scales, " Hawks said. "But when I can dig up a 5,000-year-old skeleton in Germany and see that there are genes that people in Germany don 't have today, that 's evolution. You can 't do better than that. "

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