Dr Manica's research uses methods and ideas from animal population biology to elucidate the origin of modern humans. Competing ideas have modern humans descending independently from different predecessors in different areas, or evolving from a relatively recent expansion from one population in Africa. If the latter idea is correct, such rapid movement should lead to a progressive loss of genetic diversity, because each new population would be founded by relatively few individuals. Andrea Manica has tested this idea and found an almost perfect fit with this predicted loss of diversity and the current worldwide patterns of genetic diversity. With anthropologists, he was then able to confirm this conclusion by repeating the analysis on variations in skull measurements. The identical pattern provided by molecules and bones provides a clear, unified picture of how modern humans came to occupy the whole world. These new insights on human origins have consequences, which he is now pursuing, for the ability of different populations to adapt to diseases; populations far away from Africa are expected to have less genetic variability and therefore have less ability to adapt.