Australopithecines

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Africa is the supposed birthplace of the human race. It is here that the Australopithecines, a group of hominins including Australopithecus and Paranthropus, lived from 4.2 to 1.2 million years ago. In the same area but from 1.9 to 0.027 million years ago, Homo ergaster also roamed around. Even though they shared the same geographic location, they each represent very different phases of the evolution to what we are today. It would therefore be interesting to see how they differed, based on the physical traits of certain representative fossils, when it comes to body size, bipedalism and other cranio-dental features.

Height is one of the most explicit physical differences between the Australopithecines and H. ergaster. The Australopithecines
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ergaster on the contrary is a fully habitual bipedal species, implying that its morphology differs greatly from that of the Australopithecines. Not only is it much taller than the australopithecine species, which helped with the heat dispersal on the body, the long distance walking and the long stride length, but the way this species walked is very different. The elongation of the hind limbs compared to australopithecines, represents one of the most important evolutionary changes and is observable in the morphology of H. ergaster (Jungers, 1982). This would perhaps lead to a change in gait: more efficient fully erect walk instead of a ‘bent-hip bent-knee’ gait (Wang, 2004).Another important feature that heavily influences haw the species walks is the shape of the pelvis. It seems to be narrower than even modern humans, indicating a far more efficient upright walk. A H. ergaster male partial hip bone, KNM-ER 3228 is an example of this. “In most of its features this specimen resembles modern human male hip bones. This is especially true for functional features related to weight transfer from the trunk to the pelvis and within the pelvis, and to the effective action of musculature arising from the pelvis during the performance of the modern human type of bipedalism” (Rose, 1984, p 371). An additional indication to a more fully developped bipedalism is the lumbar and thoracic curvature of the spine, as well as the shape of the ribcage as seen in KNM-ER 15000 (Latimer et al, …show more content…
This is visible in the comparison between australopithecine cranial capacity which lies between 340 and 600cc while the H. ergaster cranial capitity is round 880cc. This can even be more when looking at OH 9 or ‘Chellean Man’ whose cranial capacity was approximately 1067cc (Rightmire,1979). When looking at KNM-ER 406, robust Australopithecine Paranthropus boisei, one observes that presence of a sagittal crest, used to anchor large chewing muscles, indicting a hard diet of nuts and seeds. This is supported by the existence of large premolars, molars and thick enamel. H. ergaster had a softer diet which is reflected by the lack of sagittal crests and smaller molars as well as thinner enamel (Larsen and Repcheck, 2008). Overall, the more recent species have a less robust cranio-dental

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