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K. Kris Hirst

A Plant Eating Ancestor: Australopithecus bahrelghazali

By November 12, 2012

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The 3.0-3.5 million year old hominin called Australopithecus bahrelghazali made news today, when the journal Proceedings of the National Academy of Sciences reported solid evidence that this ape-like fellow from Koro-Toro Locality KT12 in the central African Djurab Desert of modern day Chad was a plant-eater.

Papyrus Swamp near Kabarole, Uganda
Dinner at the Papyrus Swamp near Kabarole, Uganda AnSchieber

That's pretty weird: up to now, the earliest of our ancestors to have been determined plant-eaters are Australopithicus boisei, a species from the Rift Valley of east Africa, half a continent away and 1 million years or more later.

Premolar from Koro-Todo K12 Australopithecus bahrelghazali
Premolar from Koro-Todo K12 Australopithecus bahrelghazali. Julia Lee-Thorp of Oxford University

The evidence is based on laser ablation of fossil teeth such as the premolar above and analysis of the material using the robust science of stable isotope analysis, which seems to suggest that the hominin nicknamed Abel may well have munched on some early ancestor of papyrus.

Lee-Thorp JA, Likius A, Mackaye HT, Vignaud P, Sponheimer M, and Brunet M. 2012. Isotopic evidence for an early shift to C4 resources by Pliocene hominins in Chad. Proceedings of the National Academy of Sciences Early Edition.

Comments

July 28, 2013 at 3:42 pm
(1) marc verhaegen says:

That the australopiths, esp.those from E.Africa, were predom.plant eaters (the S.African ones were more omnivorous apparently) has often been argued. They often fossilised in papyrus swamps, and independent lines of evidence suggest many of the E.African australopiths might have fed partly on papyrus sedges (google “aquarboreal” & “greg laden guest post verhaegen”).
But that the australopiths were human ancestors has never been proven. There’s no evidence that the humanlike features in austrlopiths are primitive. In my Hum.Evol.papers (1990s) I morphologically & embryologically compared australopiths with extant humans & apes, and concluded: ‘humanlike’ is not necessarily ‘derived’, and ‘apelike’ is not synonymous with ‘primitive’; the australopiths did not have apelike ancestors, but most of their humanlike features might have been primitive; both African apes & humans were derived (in divergent directions) from more australopith-like ancestors; and the Homo-Pan LCA was probably a partially bipedal, gracile australopith-like form “with chiefly a mosaic of human & chimp (esp. bonobo) features: low sex.dimorphism, minimal prognathism, slightly enlarged canines, non-protruding nasal skeleton, smooth ectocranium without crests, “small” brain with ape-like sulcal pattern, rel.non-flexed basicranium, intermediate position of foramen magnum, “short” forelimbs without knuckle-walking features, very wide pelvis, low ilia, (very) long femoral necks, “short” legs, (very) valgus knees, full plantigrady, longer & not very abductable halluces …” (Verhaegen 1994). The newly discovered Au.sediba fossils (Berger 2013), with a mix of ape- & human-like features, confirm their mosaic-like evolution, but instead of “bipedal” I’d now prefer the more correct term “orthograde” (with habitually vertical lumbar spine). Their predom.vertical locomotions were probably not confined to upright walking or even wading. Refs, eg, in my guest post at Greg Laden’s blog.

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