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Unformatted text preview: Chapter 13: F rom Hominin to Homo- Homo ergaster appeared 1.8 million years ago o They were much more like modern humans They developed slower and their infants were helpless at birth They were also fully committed to a lire on two legs; they had short arms and long legs There was reduced sexual dimorphism o However, they had smaller brains and their subsistence technology was not as flexible as ours Hominins of the Lower Pleistocene: Homo ergaster- The Pleistocene epoch began 1.8 million years ago and saw a cooling of the worlds climate o The Pleistocene is divided into three parts Lower Began 1.8 mya when the climate cooled Middle Started with increased fluctuations in temperature and the first continental glaciers in northern Europe Ended with the termination of the penultimate glacial period about 130 thousand years ago Upper Ended about 12 thousand years ago when a warm interglacial phase of the world climate began- Homo ergaster appears in the African fossil record about 1.8 mya and disappears about 0.6 mya o They are similar to fossils of Homo erectus found in Indonesia and were originally classified with them, but scientists decided that there was enough difference between them to assign them a new species- Homo ergaster appeared in Eurasia about the same time it was first known from Africa o I t was the first species out of Africa about 1.7 mya and they took their toolmaking skills with them o Their fossils are associated with Oldowan tools Morphology- Skull of Homo ergaster differ from those of both earlier hominins and modern humans o Similar to hominin skulls because they narrowed behind the eyes, had a receding forehead, and no chin o However, they had a smaller, less prognathic face, a higher skull, and smaller jaws and teeth like modern humans o They also had traits that didnt belong to either group They had a horizontal ridge at the back of the skull (occipital torus), giving it a pointed appearance form the side and large browridges These adaptations were probably related to their diet- The postcranial skeleton of Homo ergaster is much more similar to the skeleton of modern humans than to that of earlier hominins, but it still differs from outs in interesting ways o They have the same body proportions as people who live in tropical savannas today: long legs, narrow hips, and narrow shoulders and short arms o They were pretty tall and their infants matured slowly and were probably dependent on their mothers for an extended period of time o Sexual dimorphism was reduced o They might not have had a spoken language they had less control over the muscles in their rib cage and diaphragm o Homo ergaster was the first hominin that could run for long distances which was useful in long-distance scavenging and hunting in open country- Homo ergaster may have developed more rapidly than modern humans o This suggests that learning did not play such an important role in the lives of these...
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- Fall '07