The History of Our Tribe Hominini Textbook Part IV Pleistocene Epoch Chapter 22 Genus Homo

22 . Genus Homo It is generally thought that by , there were at least two species of Homo in East Africa , Homo and Homo . The inclusion of those fossils in our genus is not accepted by all and is somewhat arbitrary . Some argue that habilis does not differ enough from to warrant different genus designation . Its inclusion in Homo was prompted by the fact that they are thought to have made and used tools and thus to have been cognitively advanced . habilis was more than the , and the skull vault is flexed as in Au . and later species of Homo . There is debate as to whether or gave rise to Homo ( African form of the ) and hence should be included in our lineage . Both species overlap the more derived in time and geographic space . The size and architecture of the brain of habilis make it a tender in the minds of some researchers . However , their limb proportions , retention of long arms and short legs , do not resemble . According to some researchers , possessed more femora ( plural of femur ) limb proportions , and a more orthognathic face , thus making them a better candidate for the ancestor of . However , it has not been determined that remains can be definitively assigned to the species , because are rarely found in association with cranial material ( from which species designation derives ) In addition , the claim to a more orthognathic face has been called into question based upon biometric reconstruction of the face is impossible in terms of the relative positioning of key features ( et al . 2008 ) While some claim that sis were more than , others believe that their relative brain size ( ie brain size taking into account body size ) was lower and the temporal region , which is a conservative region of the skull , was more primitive . They also had more robust faces and teeth , unlike . 143