A101 - Chapter 10 Reviewer.docx

CHAPTER 10: REVIEWER I. Bipedalism in a Nutshell  Bipedalism as an efficient form of locomotion  Morphological changes partly as a result of maintaining center of balance  Hominins as both habitual and obligate bipeds  Early hominins were semi-arboreal and was not as efficient bipedally than more recent hominins with more derived traits II. Morphological Evidence of Bipedalism  Main changes: 1. Repositioning of foramen magnum to the base of the skull 2. Emergence of spinal curves 3. Shortening and broadening of pelvis  Improved weight distribution and balance  Basin shape supports internal organs  Repositioning of the gluteus maximus from side of the body to the posterior aspect of the body  Supports walking, running, and climbing 4. Lengthening of hind limbs  Increases stride length 5. Angling of the femur inwards 6. Restructuring of the foot  Arches  Big toe realigned to other toes; not divergent anymore  Sterkfontein fossils provided evidence for early hominin foot structure III. Early Hominins  Main Periods 1. Pre-Australopithecus  6 – 4.4 mya (late Miocene to early Pliocene)  Most primitive of hominins 2. Australopithecus  4.2 5 - 1.2 mya (Pliocene to early Pleistocene)  Had diverse forms of hominins – some primitive and some derived 3. Homo  2.8 – 1.4 mya (Pleistocene)  First members of genus Homo IV. Pre-Australopiths  Key Fossils 1. Sahelanthropus tchadensis (7 – 6 mya)  Site: Chad  Characteristics  Foramen magnum occupied intermediate position  Oldest and earliest recorded hominin  Pronounced brow ridges  Reduced canine; lacks honing complex

 Small braincase  Vertical face; tucked into brain case 2. Orrorin tugenensis (6mya)  Site: Tugen, Kenya and Awash, Ethiopia  Characteristics:  Post-cranial indicates bipedalism 3. Ardipithecus (5.8 – 5.2 mya)  Site: Middle Awash, Afar Triangle of Ethiopia  toe bone indicates bipedalism  Ardi  Competent biped, but had difficulty running  Earliest hominin with different body parts represented  Found in Aramis in Middle Awash  Grasping foot with divergent big toe  Ilium is short and broad  Small cranial capacity V. Australopiths Overall  Main characteristics: 1. Clearly bipedal 2. Small braincase in relation to Homo 3. Large teeth with thick enamel  2 Main Genera 1. Paranthropus  Considerable sexual dimorphism in terms of robustness  deep lower jaw for chewing  flat face and broad flaring cheekbones  largest teeth and premolars  most derived  sagittal crest 2. Australopithecus Breakdown of Genera  Australopiths 1. A. anamensis (4.2 – 3mya)  Site: Middle Awash, Ethiopia and Kenya, East Africa  Characteristics:  Evidence for bipedalism  Sharp and large canine, sectorial first premolar 2. A. afarensis  Site: Hadar, Ethiopia and Laetoli, Tanzania  Characteristics:  Bipedal but with short stride and with cadence  Longer upper limbs with scapula indicating mixed locomotion  Most primitive australopith than any other later australopith fossils in South or East Africa

 Presence of crest  Sharp canine, first premolar is semisectorial, parallel tooth rows  Short in stature  Small brain  Key Fossils:  Lucy, Dikika fossil 3. A. africanus (3 – 2 mya)  Site: South Africa  Characteristics:  Improved brain development  Large teeth  Small brain  Key Fossils: Taung child, Mrs. Ples 4. A. sediba (2- 1.5 mya)  Site: Malapa Cave, South Africa  Characteristics:  Diet closer to chimpanzees (fruit, bark, leaves) than other australopiths that fed on grasses and meat  More flexible lower spine  Reorganization of the brain  Short but curved fingers  Strong upper body indicating arborealism  Vertebrae follows 5 lumbar pattern 

Paranthropus 1. P. aethiopicus (2.5 mya)  Site: Lake Turkana, Kenya  Characteristics:  Known as black skull due to manganese rich deposits in site  Sagittal crest  Upper face projects  Dental row converges at back  Broad face with large palate 2. P. boisei (2 mya)  Site: Olduvai and East Turkana, East Africa  Characteristics:  Very robust in teeth and jaws  Body size typical of other australopiths 3. P. robustus (2 – 1.2 mya)  Site: South Africa  Similar to boisei but not as dentally robust

VI. Homo Genera of the Plio-Pleistocene 1. H. habilis (1.8 mya <)  Site: Olduvai and Turkana Basin  Characteristics:

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Significant ecephalization Large back teeth Robust face Coexisted with H. erectus Considered as Olduvai toolmakers by Leakey

VII. Summary/Comparison

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All have a limited range Small niche, small population and easily separated = allowing genetic drift to transpire rapidly, resulting in speciation Paranthropus likely to be less arboreal to explore another niche Except for Homo, there is little evidence for encephalization and increase in body size o Hypothesis: lack of tool manufacture All demonstrate accelerated growth and development pattern (similar to African apes)