A massive new study (in Science) of human genetic diversity reveals surprising insights into our species' evolution and migrations—including support for the theory that the first modern humans originated in Africa—scientists said today. Researchers compared 650,000 genetic markers in nearly a thousand individuals from 51 populations around the globe—an unprecedented level of detail for a human genetic study. "You get less and less variation the further you go from Africa," said Marcus Feldman, an evolutionary biologist at Stanford University in California and a study co-author. Such a pattern fits the theory that the first modern humans settled the world in stepping-stone fashion after leaving Africa less than 100,000 years ago.