"Robert Karl Stonjek" <[email protected]> wrote > But Haile-Selassie and his collaborators suggest that the > teeth of these specimens indicate that they are very > similar to A. kadabba. On the basis of the available > evidence, they contend, all three may belong to the same > genus or even species. > > A contrary view comes from David R. Begun of the > University of Toronto, who counters that the A. kadabba, > Sahelanthropus and Orrorin dentitions differ in important > ways. "Rather than a single lineage, the late Miocene > [hominid] fossil record may sample an adaptive radiation, > from a source either in Eurasia or yet undiscovered in > Africa, the first of several radiations during the course > of human evolution," The base of the cladistics tree of human evolution is always going to be/appear bushy. This is a direct consequence of the fact that human evolution began when our chimpanzee-like ancestors began to settle down into relatively separate and geographically isolated communities which itself was a direct result of the onset of the dry season of the monsoon habitat, which began about 8 mya. This geographic isolation dictated reduction in gene flow which shows up in the fossil record as higher degrees of morphological variation between members of the same species, similar to what we see with respect to different breeds of dogs. And just as we don't consider the morpholgical differences between a great dane and a miniature terrier to be indicative of them being members of different species we should not consider the differences between different early hominid fossils to be indicative of different species. Jim
