Mitochondrial genome variation and the origin of modern humans

Abstract
The analysis of mitochondrial DNA (mtDNA) has been a potent tool in our understanding of human evolution, owing to characteristics such as high copy number, apparent lack of recombination1, high substitution rate2 and maternal mode of inheritance3. However, almost all studies of human evolution based on mtDNA sequencing have been confined to the control region, which constitutes less than 7% of the mitochondrial genome. These studies are complicated by the extreme variation in substitution rate between sites, and the consequence of parallel mutations4 causing difficulties in the estimation of genetic distance and making phylogenetic inferences questionable5. Most comprehensive studies of the human mitochondrial molecule have been carried out through restriction-fragment length polymorphism analysis6, providing data that are ill suited to estimations of mutation rate and therefore the timing of evolutionary events. Here, to improve the information obtained from the mitochondrial molecule for studies of human evolution, we describe the global mtDNA diversity in humans based on analyses of the complete mtDNA sequence of 53 humans of diverse origins. Our mtDNA data, in comparison with those of a parallel study of the Xq13.3 region7 in the same individuals, provide a concurrent view on human evolution with respect to the age of modern humans.