Humans, as an evolutionary group, are often said to be losing their sense of smell. “But our sense of smell is not simply declining,” says Lian Deng of the School of Life Sciences at China’s Fudan University. The genetic differences among the populations did not pertain only to smell. Even among modern humans, sense of smell varies widely from person to person, and much of that variation is thought to come from differences in odor-receptor genes, says Duke University molecular geneticist Hiroaki Matsunami, who was not involved in the work. To him, the study provides evidence that humans’ recent evolutionary history might have helped shape these genes.