User:Kleaslemon/Australopithecus

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In January of 2009, four fossils were discovered through the efforts of the Dikika Research Project working in the Lower Awash Valley in north central Ethiopia. Two of the fossils displayed traces of cut marks (DIK-55-2, a right rib fragment of a large ungulate & DIK-55-3, a femur shaft fragment of a young bovid). Research team members stated that fossilization dated after the formation of cut marks, evidence proved by the Secondary electron imaging (SEI) and energy dispersive X-ray (EDX) spectrometry data. Through the optical and environmental scanning electron microscopy (ESEM) observations, the research team also claimed that they could limited the possibility of trampling and biochemical causes, and attributed the cut marks to the effect of cutting and percussion, which indicating the use of stone tools. Considering the contemporaneity and the discovery of Australopithecus afarensis specimen on the same site (e.g. DIK-1-1), most of the paleoanthropologists attributed this behavior to Australopithecus afarensis.

In 2015, another research team published a paper stating that the ability of tool use of Australopithecus afarensis could be confirmed by its trabecular bone pattern. This research team argued that there had been too much dependence on the examination of external morphology in the study of paleoanthropology and that sometimes evidence from external morphology could be ambiguous. Some traits could be ancestral and no longer serve a purpose. In the case of the trabecular bone, it changes through life according to mechanical loading, therefore it could be a good hand morphology reference for Australopithecus afarensis on the matter of appropriate hand postures for tool use. After the comparison of Hylobatids, Pongo, Gorilla, Pan, recent H. sapiens and early H. sapiens, this team concluded that a complete suite of derived later Homo-like hand morphology was not necessary for using tools, and the trabecular orientation of Australopithecus afarensis metacarpals was clearly shaped by the use of tools.

There are debates, however, regarding whether the Australopithecus afarensis was simply a tool user or a craftsman. One research team in 2017 claimed that the Australopithecus afarensis did not have a forceful and precise grip that was adequate for tool making. This team focused their study on the 5th ray of Australopithecus afarensis, a trait which is important for the ability of hand to grip. The morphology of hamate-metacarpal V joint (CMC-V) could determine the flexibility of the 5th ray and the formation of a powerful grip, through the simulation of musculoskeletal models (with the presence of certain technical and informational limitations), evidence showed the pulp of the 5th ray did not provide the necessary conditions for the maintenance of a large-sized object, thus making the hypothesis of tool maker Australopithecus afarensis questionable.

Reference:

Domalain, Bertin, A., & Daver, G. (2017). Was Australopithecus afarensis able to make the Lomekwian stone tools? Towards a realistic biomechanical simulation of hand force capability in fossil hominins and new insights on the role of the fifth digit. Comptes Rendus. Palevol, 16(5-6), 572–584. https://doi.org/10.1016/j.crpv.2016.09.003

McPherron, Alemseged, Z., Marean, C. W., Wynn, J. G., Reed, D., Geraads, D., Bobe, R., & Béarat, H. A. (2010). Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia. Nature (London), 466(7308), 857–860. https://doi.org/10.1038/nature09248

Skinner, Stephens, N. B., Tsegai, Z. J., Foote, A. C., Nguyen, N. H., Gross, T., Pahr, D. H., Hublin, J.-J., & Kivell, T. L. (2015). Human-like hand use in Australopithecus africanus. Science (American Association for the Advancement of Science), 347(6220), 395–399. https://doi.org/10.1126/science.1261735