Let’s return to my favorite group (though I think they’re not terribly closely related) in the human fossil record, the robust australopithecines. They have popped fairly frequently in the news this year, most recently regarding their possible use of bone tools (Backwell and d'Errico, in press). This group is funny. They first appeared probably some time around 2.7 million years ago, in the controversial form of Australopithecus aethiopicus. No one knows where exactly this enigmatic group came from, save for that the only known, fairly complete cranium (KNM WT 17000) has many primitive features, and is largely similar to the earlier A. afarensis. Around 2.3 million years ago or so, A. aethiopicus appears to be ‘replaced’ by A. boisei, whose face is less protruding, has smaller anterior teeth, and has a derived P3 morphology. This is all in East Africa, mind you. Then, some time probably around 2 million years ago, or a little later, a robust form (A. robustus) appears in South Africa, where erstwhile the only hominin was A. africanus (some argue that there are 2 species in the A. africanus hypodigm). Personally, A. robustus looks like a more ‘robust’ A. africanus: larger posterior teeth, more anteriorly placed cheeks—but there is much overlap in many of traits between these two taxa. And much to the chagrin of many cladists, the South and East African robusts appear fairly different morphologically; a recent study (Gonzalez-Jose et al. 2008) that examined hominoids morphometrically (that is, in terms of aspects of cranial shape) found the two robust taxa to be distinct (but that’s a topic for another post . . .). And all the while these buggers lived right alongside Homo, our ancestors! That’s some effed up stuff.
Backwell L, d'Errico F Early hominid bone tools from Drimolen, South Africa. Journal of Archaeological Science In Press, Accepted Manuscript
Gonzalez-Jose R, Escapa I, Neves WA, Cuneo R, Pucciarelli HM (2008) Cladistic analysis of continuous modularized traits provides phylogenetic signals in Homo evolution. Nature 453(7196):775-778
Lockwood CA, Menter CG, Moggi-Cecchi J, Keyser AW (2007) Extended male growth in a fossil hominin species. Science 318:1443-1446
Moyà-Solà S, Köhler M, Alba DM, Almécija S (2008) Taxonomic Attribution of the Olduvai Hominid 7 Manual Remains and the Functional Interpretation of Hand Morphology in Robust Australopithecines. Folia Primatologica 79(4):215-250
Wood B, Collard M (1999) The changing face of genus Homo. Evolutionary Anthropology 8(6):195-207