Wednesday, February 25, 2009

Australopithecus Africanus Were Nutcrackers

Large and heavy premolars from fossil hominins are traditionally viewed as indications of a diet consisting of small, hard objects or massive amount of food.

Using finite element analysis in conjunction with comparative, imaging, and experimental methods, Strait et al. (2008) came up with a modified conclusion: these large and heavy premolars served as nutcrackers to break open hard nuts and seeds. A shift to nuts and seeds diet may explain that A. africanus were exploring new food resources, possibly due to a scarcity of preferred food source. Early Humans Had Nutcracker Jaws.

What are the implications of this research?

Does it mean that our hominin ancestors (A. africanus) were forced to exploit new food resources earlier than we had thought?

Were there environmental changes that lead to lower production of preferred food sources (possibly fruits)?

Exponential increase of Australopithecine population in a shrinking forested habitat forced some individuals with larger and heavy premolars to exploit new food resources (nuts and seeds)?

Cranial facial morphology A. africanus. Photo from PNAS

Computer simulations showed the compressive stress of biting in the cranium of A. africanus. Bright colors indicate high stresses, and show that a bone running alongside the opening of the nasal cavity acts as a strut to reinforce the face against premolar loads. Credit: Arizona State University and the Hominid Feeding Biomechanics research team. Photo from

Strait DS. Weber GW. Neubauer S. Chalk J. Richmond BG. Lucas PW. Spencer MA. Schrein C. Dechow PC. Ross CF. Grosse IR. Wright BW. Constantino P. Wood BA. Lawn B. Hylander WL. Wang Q. Byron C. Slice DE. Smith ML. 2008. The Feeding Biomechanics and Dietary Ecology of Australopithecus africanus. Proceedings of the National Academy of Sciences of the United States of America 106 (8) 2124-2129.

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