Have humans stopped evolving? That question has been getting some rare media and blog attention this week ever since David Attenborough, the 87-year-old British naturalist and broadcaster, declared: “I think that we’ve stopped evolving.”
In an interview published this week in the magazine Radio Times, the influential Attenborough, host of numerous television documentaries on natural science, held forth on a number of topics. At one point, he explained that so many more babies survive childbirth now that natural selection, as proposed by Charles Darwin, cannot act on humans to favor infants with traits that are beneficial today or to weed out those with adaptations that impair survival. “We stopped natural selection as soon as we started being able to rear 95–99 per cent of our babies that are born. We are the only species to have put a halt to natural selection, of its own free will, as it were,” he said.
But his view doesn’t reflect scientific consensus. “Humans are most certainly still evolving, just not necessarily in ways we might expect,” wrote Catherine Woods of the Center for Neural Science at New York University in New York City in May in Science.
For example, millions of people in developing countries continue to live in poverty and to suffer from infectious diseases. Under these conditions, natural selection may be favoring genes that confer resistance to disease, such as AIDS and malaria, or enhance reproductive fitness in other ways, researchers said in a report in Science. “As long as some people die before reproducing or reaching reproductive age, selection is likely to be acting,” geneticist Chris Tyler-Smith of the Wellcome Trust Sanger Institute near Cambridge, U.K., told Science in 2005. And since that time, researchers have discovered a spate of human genes that evolution has strongly favored recently, such as mutations that help highland Tibetans survive at high altitude, Yupik Eskimos to stay warm efficiently, Europeans to thrive on cereal grains, and East Asians avoid alcoholism.