Lecture 7 Ch 9 - Lecture 7 Early Hominid Origins And...

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Unformatted text preview: Lecture 7 Early Hominid Origins And Evolution Chapter 9 Hey! Look!. .. No hands! Early Hominids What is a hominid? Who were the first hominids? The Pre-Australopithecines Who were the Australopithecines? Why did bipedalism develop? locomotion the way we move/walk quadrupeds = creatures that walk on four feet hominoids = ancient apes, modern apes and hominins (including modern humans). bipeds (two feet) = hominids (exception: birds) terrestrial ground-living arboreal tree-living (climbers and leapers and brachiators/arm-swingers) Hominid traits esp. reflect: Locomotion (acquiring and transporting food) and Chewing food (mastication) Bipedal locomotion changes in pelvis and long bone lengths towards habitual AND obligate bipedalism the most efficient locomotion for us more central position of foramen magnum in skull base Big toe is non-divergent (non-grasping or opposable) in hominids (versus Great Apes) This sort of big toe (hallux) is one key rearrangement for bipedalism and should also be an early trait of the hominids. Seen in footprints of Laetoli, Tanzania Evidence for bipedalism from foot bones and footprints: round heels double-arches nondivergent big toes Nonhoning chewing Technically, A. robustus illustration emphasis on crushing foods emphasis on slicing esp. plant foods esp. seeds and nuts (hard foods) esp. plants and soft fruit Hominids and orangutans Pongids (excluding Orangutan) NOTE: Rapid or sudden or early brain size increase is not an early hominid trait Cranial capacities of selected hominoids Sahelanthropus 350cc Some hominid find sites Sahelanthropus tchadensis (7-6mya) skull found in Chad in 2002 by M. Brunet teeth show nonhoning chewing Foramen magnum is central Derived traits (not original, but stemming from adaptation or mutation) Sahelanthropus tchadensis Sagittal crest Small braincase Massive brow ridges Primitive traits (more apelike, not yet modified) Orrorin tugenensis 6 mya, jaw, teeth, arm and leg bones, Kenya, 2001 by Haile-Selassie Ardipithecus 2 species now recognised Ardipithecus kadabba 5.5-5.6 mya, teeth only Late Miocene (c. 5.8-5.6mya) - Non-honing chewing, but some polishing on outside of lower P3 suggests intermediate ( perihoning ) Ardipithecus ramidus from Ethiopa , 4.4 mya Early Pliocene (c. 4.4mya) -Both species have thin enamel (the only ones in the hominid range)-Curved foot phalanges (toes) indicate continued arboreal activity, but femur and pelvis show bipedalism Recovery of remains of arm bone fragments of one Ardipithecus ramidus (c. 4.5 mya) individual at Aramis, Ethiopia So, Sahelanthropus , Orrorin and Ardipithecus all appear to have lived in wooded settings, based on other ancient fossil plants and animals....
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Lecture 7 Ch 9 - Lecture 7 Early Hominid Origins And...

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