Douglas Wallace: UC Irvine Department of Ecology and Evolutionary Biology

The investigation of human origins and migrations has been greatly advanced by the analysis of human genetic variation to determine the relationships between different human populations. Such studies have permitted demonstration of the recent African origin of humans, the reconstruction of ancient migrations, and the correlation of human genetic history with linguistic affiliations. The first component of the human genome to be used in these investigations was the maternally-inherited human mitochondrial DNA (mtDNA) which codes for key proteins involved in the conversion of dietary calories in into ATP to fuel work and heat to maintain our body temperature. Variation in the human mtDNA has been found to be encompassed in a single dichotomously branching tree with the different branches of the tree correlating dramatically with the geographic distribution of indigenous peoples from around the world. The mtDNA correlation with human populations is much greater than that seen for either the paternally-inherited Y chromosome or the biparentally inherited autosomes. We now believe that this correlation is because variation in the mtDNA permitted our ancestors to adapt to the increasingly cold environments that they encountered as they migrated out-of-Africa and into temperate Eurasia and arctic Siberia. Hence, selection has stabilized the geographic distribution of mtDNA variation such that mtDNA variation has sustained the distribution of the earliest human incursions around the world. This unique aspect of the mtDNA now makes mtDNA variation a particularly valuable tool for the analysis of deep cultural associations and origins. This is currently proving to be the case in studies on the origins and radiation of Native America languages and myths.
http://www.bec.ucla.edu/papers/Wallace_23.5.05_1.pdf