Chromosomal evolution of the great apes and man.

A study of all the chromosomal changes that have occurred during evolution of the great apes and man gives an indication of the phylogeny of these species. Their karyotypes differ from one another by a dozen chromosomal changes. The karyotype of their ancestor was very similar to that of living orangutans. Reconstruction of the sequence of the chromosomal changes indicates that, after the isolation of the orang-utan, a common ancestral population existed for the other species. Then, each branch leading to the living genera was independently isolated. The karyotype of the chimpanzee is an intermediary stage between that of man and the gorilla for some chromosomes. The human karyotype is less differentiated than that of the chimpanzee or the gorilla.