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13 Cards in this Set
- Front
- Back
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What makes a Hominin a Hominin? |
Bipedalism -Foramen Magnum -S shaped spine -Short Pelvis -long legs -knees angle toward midline -non opposable thumbs -Double Arched Foot Non Honing Chewing -Blunt, nonprojecting canine -Small canine relative to size of other teeth -No Diastema -Wear on tips of canines and of premolars -Cusps on lower third premolar equal size |
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Differences of Darwin and Lovejoy:Bipedalism |
Darwin -> hunter theory, free hands for tools LoveJoy ->provisioning, freehands for caregiving of children |
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Pre-Australopithecine->Australopithecine |
Teeth (modified honing->nonhoning) Bones (Vestiges of apelike arboreal traits->Loss of traits) Brain (small-> slight increase) |
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Raymond Dart |
Found Tuang site, africanus |
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Late Australopithecines -> Early Homo |
Brain smaller->bigger Face bigger->smaller Teeth bigger->smaller |
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What is Hominin |
primarily defined by two obligate behaviors, bipedlism and nonhoning chewing |
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Theories of hominin evolution |
The first hypothesis is known as Darwin’s hunting hypothesis, which suggests that hominids were bipedal because it freed their hands to carry weapons. He believed that their greater intelligence due to large brains enabled them to make and use tools. However, it is now known that bipedalism occurred long before brain size increase and the first stone tools. The second hypothesis is the patchy forest hypothesis. Originally developed by Peter Rodman and Henry McHenry, it suggests that bipedalism arose because it was more energy-efficient in certain environments, especially those with few trees. When the forests became patchier and food more dispersed, hominids more efficiently used their energy by walking upright and could carry the collected food with their now-freed hands. The third hypothesis is the provisioning hypothesis of Owen Lovejoy. This hypothesis suggests that bipedalism arose due to monogamous males provisioning females with food and protection from potential predators. By providing females with food, the females would potentially be able to care for more than one dependent offspring at a time, reducing the time between births. Males would need to have freed hands in order to carry food to the female and, thus, bipedalism originated. |
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What were the first Hominins? |
-Pre-Australopithecines, earliest fossil hominins, 7-4mya -Next, Austalopithecines, 4-1mya -early stone tools of Olduwan, dental microwear, craniofacial anatomy and stable isotopes suggest a transition in diet from meat to grass. -first hominins show a lot of diversity in all anatomical characteristics (ex. some were terrestrial some were arboreal) |
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Fate of the first hominins |
-increased robsuticity of the chewing complex minimal change in brain size which reflected eating hard tough foods like plants and grasses. -by 2.5 one early hominin fave rise to the genus Homo, 2 other australoppithecine lineages (e and S Africa) when extinct around 1 mya |
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Advantages to bipedalism |
being able to see farther, carry food and/or children, and run long distances. Eventually, freed hands would enable hominids to create and use tools; however, this feature would require increased brain size, which occurred millions of years after bipedalism arose. |
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Disadvantages of bipedalism |
-greater exposure to potential predators. -Potential back injuries, including slipped disks and arthritis, ( walking upright, lifting heavy objects, and carrying heavy items put substantial strain on the lower back.) -Varicose veins... circulatory system has to move blood from the legs to the heart. -injury occurs to one foot or leg, the individual is unable to move. For early hominids without cultural adaptations, such as crutches, this would have drastically affected their ability to survive. |
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Pre-Australopithecines |
The oldest species is Sahelanthropus tchadensis, a fossil found in central Africa, dating between seven and six million years ago. It had a small brain, roughly the size of modern apes. Orrorin tugenensis was discovered in East Africa and dates to six million years ago. It had curved phalanges, which suggest that while bipedal, Orrorin continued to use the trees. Ardipithecus kadabba and Ardipithecus ramidus were found in East Africa and date between 5.8 and 4.4 million years ago. These fossils also had curved phalanges, indicating continued use of the trees. All of the preaustralopithecines were found in wooded environments, were diverse, and were morphologically primitive. |
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Who are the australopithecines? |
The fossils have been found in both East Africa and South Africa and are clearly bipedal with nonhoning chewing. They also have a range of variation in size and robusticity. The oldest australopithecine is Australopithecus anamensis, ancestor to Australopithecus afarensis. Australopithecus afarensis was ancestral to several other species, including Australopithecus africanus from South Africa and Australopithecus garhi, who made and used the first stone tools. Australopithecus platyops existed at the same time as Australopithecus afarensis, but had a much flatter face, a derived feature. A special group of australopithecines, the robust australopithecines, possessed a number of robust cranial and dental traits such as a sagittal crest and large posterior teeth. The robust australopithecines include Australopithecus aethiopicus, Australopithecus boisei, and Australopithecus robustus, a South African descendant ofAustralopithecus africanus. |
