THE ROOT OF THE PHYLOGENETIC TREE OF HUMAN-POPULATIONS

Although African populations have been shown to be most divergent from any other human populations, it has been difficult to establish the r oot of the phylogenetic tree of human populations since the rate of ev olutionary change may vary from population to population owing to the fluctuation of population size and other factors. However, the root ca n be determined by using the chimpanzee as an outgroup and by employin g proper statistical methods. Using this strategy, we constructed phyl ogenetic trees of human populations for five different sets of gene fr equency data. The data sets used were two sets of microsatellite loci data (25 and 8 loci, respectively), restriction fragment length polymo rphism (RFLP) data (79 loci), protein polymorphism data (15 loci), and Alu insertion frequency data (4 loci). All these data sets showed tha t the root is located in the branch connecting African and non-African populations, and in the four data sets the root was established at a statistically significant level. These results indicate that Africans are the first group of people that split from the rest of the human po pulations.