Wakeley (2008) rejected these hypotheses; he suggested alternative explanations, including selection pressure on the X chromosome in the ancestral populations prior to the chimpanzee–human last common ancestor (CHLCA). Most DNA studies find that humans and Pan are 99% identical, but one study found only 94% commonality, with some of the difference occurring in non-coding DNA. It is most likely that the australopithecines, dating from 4.4 to 3 Mya, evolved into the earliest members of genus Homo. In the year 2000, the discovery of Orrorin tugenensis, dated as early as 6.2 Mya, briefly challenged critical elements of that hypothesis, as it suggested that Homo did not in fact derive from australopithecine ancestors. All the listed fossil genera are evaluated for: probability of being ancestral to Homo, and whether they are more closely related to Homo than to any other living primate—two traits that could identify them as hominins. Some, including Paranthropus, Ardipithecus, and Australopithecus, are broadly thought to be ancestral and closely related to Homo; others, especially earlier genera, including Sahelanthropus (and perhaps Orrorin), are supported by one community of scientists but doubted by another. List of known hominin species Extant species are in bold. Sahelanthropus tchadensis Orrorin tugenensis Ardipithecus kadabba Ardipithecus ramidus Australopithecus anamensis Australopithecus afarensis Australopithecus deyiremeda Australopithecus garhi Kenyanthropus platyops Australopithecus africanus Australopithecus sediba Paranthropus aethiopicus Paranthropus boisei Paranthropus robustus Pan troglodytes Pan paniscus Homo habilis Homo rudolfensis Homo ergaster Homo erectus Homo antecessor Homo heidelbergensis Homo naledi Homo neanderthalensis Homo denisova Homo sapiens Homo floresiensis Homo luzonensis See also History of hominoid taxonomy Human evolution Human taxonomy Human timeline List of human evolution fossils References External links Human Timeline (Interactive) – Smithsonian, National Museum of Natural History (August 2016). Homininae Human evolution Mammal tribes Taxa named by Camille Arambourg Taxa described in 1948