Scientists who believe Australopithecus is a human ancestor see in its fossil bones signs of upright walking ability and other human features. But Oxnard’s studies show a creature just as likely to be found swinging through the trees like a gibbon or orangutan as walking upright on the ground.
Even among scientists who do accept Australopithecus as a human ancestor, there is a great deal of disagreement. On one side, we have Donald Johanson, and his colleagues and supporters, who believe that the australopithecines walked upright on the ground just like modern humans. This would, according to this group, be especially true of Lucy, the specimen of Australopithecus afarensis that Johanson himself discovered in Ethiopia during the 1970s (Johanson and Edey 1981). But Johanson’s critics, and there are many, say that the long curved fingers and toes of Lucy and her relatives, along with many other anatomical features, show that these creatures spent a lot of time in trees (Stern and Susman
1983, pp. 282–284; Susman et al. 1984, p 117; Marzke 1983, p. 198). Here they would be in agreement with Oxnard. Some scientists think that Johanson and his coworkers have mistakenly combined the fossils of two or three kinds of creatures into the single species Australopithecus afarensis.
During the 1970s, Johanson put forward the idea that Lucy was the oldest known human ancestor, and that starting with her all the other hominids could be arranged in a definite evolutionary progression. The several species could be arranged in two branches coming from the trunk of Australopithecus afarensis. One branch would be composed of the Homo habilis, Homo erectus, and then Homo sapiens. On the second branch would be the remaining australopithecines. First comes Australopithecus africanus, then Australopithecus robustus, then Australopithecus boisei. The trend among these is toward greater robustness. In 1985, the Black Skull, designated Australopithecus garhi, was discovered. This was a robust australopithecine specimen even more robust than A. boisei. If the Black Skull had been younger than A. robustus and A. boisei , there would have been no problem. It would have fit nicely into the progression of robust australopithecines. But instead the Black Skull was older than the oldest specimens of A. robustus. This completely messed up the neat little diagram drawn by Johanson.
As it stands now, there is no agreement at all about the relationships between the various species of Australopithecus. As physical anthropologist Pat Shipman (1986, p. 92) put it, “The best answer we can give right now is that we no longer have a very clear idea of who gave rise to whom.” Shipman said that in 1986, but the situation has not changed much since then. In fact, the situation has become even more complicated with the addition of discoveries of new species of Australopithecus such as Australopithecus anamensis and Australopithecus aethiopicus. The confusion extends not only to the evolutionary relationships among the australopithecines but also to the relationship between Australopithecus and Homo habilis, the first member the genus to which modern humans belong. Shipman, considering all the alternatives, said, “We could assert that we have no evidence whatsoever of where Homo arises from and remove all members of the genus Austra-lopithecus from the hominid family.” In other words, Australopithecus is not a human ancestor, which is exactly what Zuckerman and Oxnard have always said. But Shipman hesitated, noting, “I’ve such a visceral negative reaction to this idea that I suspect I am unable to evaluate it rationally. I was brought up on the notion that Australopithecus is a hominid” (Shipman 1986, p. 93).
And here is one more problem with Australopithecus—mainstream scientists say Australopithecus lived only in Africa. But other scientists have reported australopithecines from China, Indonesia, and Southeast Asia (Robinson 1953, Jian et al. 1975, Franzen 1985, and Chen 1990). If accepted, this would make a mess of most current schemes of hominid evolution, making an Asian origin for the hominids as likely as an African origin.
Up until 1987, Homo habilis was depicted as a marked evolutionary advance from Australopithecus toward the human condition. Both in the scientific literature and popular presentations, Homo habilis was shown as larger than its australopithecine ancestors, and with a more humanlike body, although the head still had some apelike features. In 1987, Tim White and Donald Johanson (Johanson et al. 1987) reported the discovery of a fairly complete Homo habilis skeleton at Olduvai Gorge. Homo habilis turned out to be a very small creature with long apelike arms, not very different from Australopithecus in size and body proportions. As in the case of Australopithecus, some researchers think that Homo habilis has been mistakenly put together from the fragmentary fossil bones of two or more species (Wood 1987).
The new picture of Homo habilis has made the supposed evolutionary transition to Homo erectus more problematic. In 1984, a team of scientists including Richard Leakey found an almost complete Homoerectus skeleton (Brown et al. 1985, p. 788). Up until this time, scientists had never found any limb bones that could be positively connected with a Homo erectus skull. Yet for decades, scientists had been making fullscale models of Homo erectus, as if they really knew the correct relative sizes of the head and limbs. Strikingly, the newly found skeleton was that of an adolescent youth who would have been over 6 feet tall when fully grown. Furthermore, at about 1.6 million years old, this was the oldest Homo erectus individual found up to that time. The OH 62 Homo habilis individual found by Johanson and White was only 200,000 years older, but was quite small and apelike in comparison. An evolutionary transition so great in so little time seems quite improbable, although it is accepted by evolutionists as a matter of faith. Even some evolutionists have doubts about it. The relationship between the early varieties of the genus Homo is further complicated by African fossils designated Homo rudolfensis and Homo ergaster.
At the more recent end of its existence, Homo erectus is thought by most scientists to be the direct ancestor of Homo sapiens. Louis Leakey (1960, pp. 210–211; 1971, pp. 25, 27), however, never accepted this. In his books, he gave many anatomical reasons why neither Homo erectus nor the australopithecines should be considered ancestral to modern humans. His dissenting view is rarely, if ever, mentioned in modern textbooks about human evolution.