BIO Lecture Outline 5

BIO Lecture Outline 5 - ANT 100Y Lecture #5 Outline Whats a...

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ANT 100Y Lecture #5 Outline 1 What’s a Hominin Modern humans, chimpanzees, and fossil species more closely related to each other than any other living species. Quadrupedalism vs. Bipedalism Changes in Hominin Brain Size Hominin Fossils Sahelanthropus tchadensis Chad, Africa, Dated to ca. 7.0-6.0 MYA. Important: Distance from East Africa, & great antiquity of fossils, suggest earliest members of hominin clade more widely distributed than has been thought. Divergence between human & chimpanzee lineages earlier than indicated by most molecular studies. Orrorin tugenensis Tugen Hills of Kenya. Dated to ca. 6.2-5.6 MYA. May be one of oldest known hominins yet discovered. Small teeth retain thick enamel like all australopithecines & species in genus Homo. Important: Postcrania evidence of bipedal locomotion, but not obligate bipedalism; woodland setting rather than savanna; adaptive trend emphasizing powerful mastication. Ardipithecus ramidus Found Aramis & Middle Awash, Ethiopia. Dates to ca. 4.4 MYA. May have been obligate biped. Powerful arms & forearms were not used to support body weight (not quadraped), but do indicate used in climbing. Australopithecus anamensis Turkana region of Kenya, Dated to 4.1-3.9 MYA. Possesses mix of advanced & primitive traits. Teeth covered with enamel much thicker than that of A. ramidus . In size and shape, however, teeth of A. anamensis were primitive relative to later hominins. Australopithecus afarensis Eastern Africa 3.9 to 3.0 MYA. Pelvis and leg bones resemble those of modern humans in some ways. Sexual dimorphism in body size. Laetoli Footprints (3.6 MYA) demonstrate early hominins were bipedal. Big toes hardly diverged from the rest of foot, unlike in chimpanzees. Gait was "heel- strike" followed by "toe-off"; the way modern humans walk. Australopithecus bahrelghazali
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BIO Lecture Outline 5 - ANT 100Y Lecture #5 Outline Whats a...

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