Mitochondrial DNA (mtDNA) is a useful molecule for comparing different human populations because people inherit mtDNA entirely from their mother and the differences between mtDNA from different individuals accumulate over time as a result of mutations. Comparison of mtDNA sequences from individuals representing different human lineages can therefore be used to infer information about the history of human migrations, including what is believed to be the early-migration out of Africa, where the human species originated.
Vincente Cabrera and colleagues from the University of La Laguna in Spain analysed the complete mitochondrial DNA sequence of 42 people, including representatives of all the major sequence related lineages in the Old World. Their data supports the notion that humans originated in Africa, from which they expanded eastwards between sixty and seventy thousand years ago. Ten to thirty thousand years later, the humans then in western Asia spread to many areas, including Europe and India, as well as going back to northern parts of Africa.
As human populations continue to migrate it is important that we analyse these ‘footprints’ now, before they are lost in the stampede of more modern human migration.