Where did the first Homo sapiens live? How did humans colonize distant Pacific islands? When did people first arrive in North America? Questions such as these have been central to the modern discipline of anthropology. The answers paint a fascinating picture of the movements of human populations, which have been shaped in many cases by extreme climate events.Scientific consensus puts the earliest known ancestors of modern humans in East Africa, roughly 200,000 years ago. The first wave of humans to migrate out of Africa about 85,000 years ago followed the coasts through the Middle East, into Southern Asia via Sri Lanka, and eventually around Indonesia and into Australia. A subsequent wave of migration between 40,000 and 12,000 years ago brought humans northward into Europe. The frozen north limited human expansion in Europe, but also created a land bridge connecting Asia with North America. Ancestors of the Native Americans took this route, called the Bering land bridge, about 25,000 years ago.Scientists use a number of factors to rehash early human migration patterns, including archaeological evidence of human presence, such as tools and fossils, and more recently mitochondrial DNA (mtDNA). NOVA Online explains how mtDNA is inherited and how it is used by scientists in research