Forbidden Archeology: The Hidden History of the Human Race

This leaves us with a three-branched family tree. Down at the bottom we still have Australopithecus afarensis. Above are three branches—the Homo line on the first, Australopithecus boisei and the Black Skull on the second, and then Australopithecus africanus on the third, leading to Australopithecus robustus.

But Shipman pointed out that it then becomes difficult to account for the fact that Australopithecus boisei and Australopithecus robustus are so similar. If Australopithecus robustus came from Australopithecus africanus and Australopithecus boisei from Australopithecus afarensis, then Australopithecus boisei and Australopithecus robustus would have had to develop their robust similarities independently by parallel evolution, something that is possible but unlikely.

According to Shipman, another way to explain the similarities between Australopithecus boisei and Australopithecus robustus is to propose that Australopithecus robustus was not descended from Australopithecus africanus and that Australopithecus robustus and Australopithecus boisei had a common ancestor besides Australopithecus africanus—perhaps Australopithecus afarensis.

So now we have a four-branched tree, with Australopithecus afarensis at the bottom. Above are the Homo line, Australopithecus africanus, Australopithecus robustus, and Australopithecus boisei, all separate from each other.

Shipman found it very hard to believe that a single species, Australopithecus afarensis, could have given rise to four separate lineages. So where did the four new species come from?

Shipman suggested that one should take a very hard look at the idea that Australopithecus afarensis represents just one sexually dimorphic species. She pointed out, as we have discussed in Section 11.9.8, that some scientists have concluded that “at least two species of Australopithecus and possibly Homo are mistakenly lumped together into afarensis” (Shipman 1986, p. 90).

Walker said it is likely that “the specimens identified as Australopithecus afarensis include two species, one of which directly gives rise to Australopithecus boisei” (Walker et al. 1986, p. 522).

How did Johanson respond to the discovery of the boisei-like Black Skull? He admitted that the Black Skull complicated things, making it impossible to arrange Australopithecus africanus, Australopithecus robustus, and Australopithecus boisei in a single line of succession coming from Australopithecus afarensis. Johanson proposed 4 possible arrangements of these species, along the lines we have been discussing, without suggesting which one was correct (Johanson and Shreeve 1989, p. 126). There was, he said, not yet enough evidence to decide among them.

The uncertainty about the number of species at Hadar, combined with the confused relationships among the successor species (Australopithecus africanus, Australopithecus robustus, Australopithecus boisei, and Homo habilis), create problems for evolutionists attempting to construct a phylogenetic tree for these hominids. Shipman (1986, p. 92) stated: “the best answer we can give right now is that we no longer have a very clear idea of who gave rise to whom.” Walker warned that the discovery of KNM 17000 suggested “that early hominid phylogeny has not yet been finally established and that it will prove to be more complex than has been stated” (Walker et al. 1986, p. 522).

In the midst of the new complexity, one question is especially important— the origin of the Homo line. Shipman told of seeing Bill Kimbel, an associate of Johanson, attempt to deal with the phylogenetic implications of the Black Skull. “At the end of a lecture on Australopithecine evolution, he erased all the tidy, alternative diagrams and stared at the blackboard for a moment. Then he turned to the class and threw up his hands,” wrote Shipman (1986, p. 93). Kimbel eventually decided the Homo line came from Australopithecus africanus ( Willis 1989). Johanson and White continued to maintain that Homo came directly from Australopithecus afarensis.