Chromosomes and the origins of Apes and Australopithecines

International audienceComparison of molecular data suggests that the higher apes (Gorilla, Pan) and humankind (Homo) are closely related and that they diverged from the common ancestor through two speciation events situated very closely together in time. Examination of the chromosomal formulas of the living species reveals a paradox on the distribution of mutated chromosomes which can only be re-solved by a model of trichotomic diversification. This new model of divergence from the common ancestor is characterized by the transition from (1) a monotypic phase to (2) a polytypic phase of three sub-species - pre-gorilla, pre-chimpanzee and pre-australopithecine. The quadruped ancestors of Australopithecus appear to have been one of the three components of the common ancestor- The question is whether ramidus is an auslralopithecine or a pre-australopithecine representative of the common ancestor. The new model of diversification of the common ancestor is resituated in the paleogeographic and paleoclimatic context which, through the north-south pattern of extension of aridity, provides a coherent scenario for the formation of extant species and sub-species of the Gorilla and Pan genera