The shapes and sizes of thousands of skulls from all over the globe point to a single origin in sub-Saharan Africa for modern humans, according to a recent study. University of Cambridge population biologist Andrea Manica examined data from more than 4,600 male and 1,500 female skulls—all less than 2,000 years old—from academic collections across the globe, each of which was measured for 37 different structural characteristics. The researchers found that the farther a population was located from Africa, the fewer variations in skull shape they displayed. The same loss of variation with increasing distance from Africa has been found in analyses of DNA. Manica argues that this strongly supports the idea that modern humans arose in Africa, probably around 200,000 years ago, and then spread to other locations around the world starting about 50,000 years ago, hardly or never mixing with other species of hominids. Whenever a group left the ancestral African population, they took with them only a fraction of the total variation present in the cradle of humanity. Each subsequent migration out of these departed groups would reduce variability in genes and skull shape. Genetic data support this hypothesis, so scientists of the “Out of Africa” school of thought are boasting of a slam dunk.

Still, a minority of anthropologists still insist that fossils tell adifferent story, with humans evolving from groups of hominids that werespread all over the world. The opposing team says that 2,000-year-old skulls cannot say much about our earliest ancestors. “You can look at the data another way,” says paleoanthropologist Milford Wolpoff of the University of Michigan. “Look at it specific to the environmental pressures. There would be more variability in an African population because Africa has a less stable climate and environment.”