“When I was in graduate school in the mid-’90s, the dogma was that culture had halted evolution,” Hawks told me. But he and his colleagues found genomic evidence that, on the contrary, culture has increased the pace of human evolution over the last 40,000 years, and especially over the last 10,000. What’s driven this acceleration, they argued in PNAS, is the global human population explosion that commenced 10,000 years ago, as a consequence of the agricultural revolution. Humankind invented agriculture, started eating different foods, and began dwelling in cities; populations expanded, allowing large numbers of mutations. Natural selection promoted the spread of beneficial variations.
According to Hawks, evidence indicates recent selection on more than 1,800 human genes. Beyond identifying a selected allele, he adds, analysis can often determine from its sequence something of what the allele does. Hawks believes that some of the new alleles confer new digestive capabilities, as with glucose and lactose tolerance; pathogen resistance, as against malaria; improved capacity for DNA repair, which may be associated with human longevity; and new neurotransmitter variations, like the dopamine variant DRD4‑7R, which was strongly selected for in some populations perhaps 40,000 years ago and is implicated in heightened tendencies toward impulsiveness, attention deficit disorder, and alcoholism. (More-conservative population geneticists argue that while humans are probably still evolving, it’s not clear that evolution is accelerating, and still less certain which alleles are of recent origin.)
Discussing differences in populations isn’t something our egalitarian society enjoys. But one of Hawks’s coauthors, Henry Harpending, a population geneticist and anthropologist at the University of Utah, thinks it should be: “Citizens should appreciate that evolution is ongoing, numerous real human differences exist, and we’re hurting many people by denying them.” Harpending notes, too, that life-sciences industries followed up on the paper, seeking opportunities for drug development and personalized medicine. “In the face of embarrassed silence from the world’s scientists, they’re not inhibited,” he says. “They want to make money and are on it like crows on roadkill.” If Harpending is right, we will learn new facts about human development whether we want to or not.
Mark Williams is a contributing editor to Technology Review.