The good news is that natural selection may yet correct some of those inefficiencies. A study published in the December Proceedings of the National Academies of Sciences found that not only are humans still evolving, but we are doing so at a faster rate than ever before, with genes that affect our diets and brains leading the race. “If humans had always evolved this rapidly, the difference between us and chimps would be 160 times greater than it actually is,” says the study’s lead author, University of Utah anthropologist Henry Harpending.

The findings have turned some traditional assumptions on their heads. For decades, biologists believed that human evolution had ground to a halt about 10,000 years ago, when the dawn of agriculture and technology gave us unprecedented control over our environments and made us masters of our own destiny. But rather than slow evolution down, those advances, Harpending says, enabled humanity to hit the accelerator. With better technology, our ranks have swelled from millions to billions. This has driven us to colonize more and different regions of the globe. More people mean more mutations, and more environments mean more things to adapt to. Migration into the Northern Hemisphere, for example, has favored adaptation to cold weather and less skin pigmentation for better sunlight absorption.

“History looks more and more like a science-fiction novel in which mutants repeatedly arose and displaced normal humans — sometimes quietly, by surviving starvation and disease better, other times as a conquering horde,” says study co-author Gregory Cochran. But what the next generation of mutants will look like is anybody’s guess. While Harpending and Cochran estimate that 7 percent of all human genes are undergoing rapid evolution, they concede that scientists haven’t a clue what most of those genes do — or what direction they’re moving in. One safe bet, they say, is that people from different regions of the world will be less alike than they are today. While malaria-resistant genes are evolving in Africa, genes that suppress body odor and make for coarser hair have emerged in Asia. Meanwhile, the ability to digest milk into adulthood has evolved in Europe, where dairy farming is common, but has yet to appear throughout China and Africa. “We are evolving away from one another,” says Harpending.

... contd.