In their recent article “Gorilla-like anatomy on Australopithecus afarensis mandibles suggests Au. afarensis link to robust australopiths” (Proceedings of the National Academy of Sciences [USA] 104 (2007):6568-6572) the authors Y. Rak, A. Ginzburg, and E. Geffen point out that a fossil skull of Australopithecus afarensis (same species as “Lucy”) reveals a morphological link with the robust australopithecines instead of the genus Homo. The fossils’s mandibular ramus, where the lower jaw attaches to the skull, is nearly identical to that of the gorilla and the robust australopithecines and quite different from other primates. A similar morphology is apparent in a specimen of Australopithecus africanus. This discovery removes Australopithecus afarensis from the direct ancestry of humans. Another fossil species, Ardopithecus ramidus, has the same type of mandibular ramus as humans and many other primates.

Comment: Removal of Australopithecus afarensis, and probably all members of the genus Australopithecus, from the ancestry of humans, is not unexpected. Although the humans and australopithecines have numerous similarities, there are enough anomalies in the data to suggest they are not as closely related as generally thought.