Australopiths 1

Australopiths 1 - Early Hominids Chapter 11 Chapter Three...

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Unformatted text preview: Early Hominids: Chapter 11 Chapter Three major groups of early hominids: hominids: 1. Pre-australopiths-earliest and most -earliest primitive possible hominids (7.0-4.4 Ma.) Ma.) 2. Australopiths-diverse forms, some -diverse more primitive, others more derived. First definitive hominids. (4.2-1.2 Ma.) First 3. Early Homo-the first members of our -the genus (2.4-1.4 Ma.) genus Australopiths Australopiths Two closely related genera: Australopithecus (Gracile Australopithecus australopiths) australopiths) Paranthropus (Robust Paranthropus australopiths) australopiths) Gracile Australopiths (2.5-4.2 Ma.) Ma.) Australopithecus Australopithecus afarensis (East afarensis Africa) Africa) Australopithecus Australopithecus africanus (South Africa) Africa) A. afarensis A. africanus Features of Australopiths Features 1. 2. 3. 3. They are all clearly bipedal (although not necessarily They identical to Homo in this regard). identical They all have relatively small brains (i.e., at least They compared to Homo). They all have large teeth, particularly the back teeth, They with thick to very thick enamel on the molars. with Australopithecus afarensis Australopithecus (East Africa) A.L. 288 “Lucy” A. afarensis Primitive Characteristics Primitive Small Brain Small Brains a little larger Brains than Pan: 400-500 Pan 400-500 cubic centimeters Projecting face Projecting Chimpanzee, A. afarensis, Human A. U-shaped U-shaped Parabolic Flat jaw joint Flat “Lucy” and H. sapiens female Small stature, Small between 3-5 feet. between Still a tree climber? Still Limb Limb proportions intermediate between Pan and Pan Homo Homo Long curved Long fingers and toes toes Derived Traits Derived Primitive traits shared with living apes apes Brains 400-500 cubic centimeters (cc) (Ape-like) Projecting face Dental arcade U-shaped Diastema Canines larger, more sexually dimorphic than in Canines humans humans Asymmetrical premolars, not strongly bicuspid Broad cranial base, flat jaw joint Limb proportions intermediate between Limb chimpanzees and humans (long arms, short legs) chimpanzees Long, curved fingers and toes Derived Traits Derived Canine reduction: canines are intermediate Canine in size between Pan and Homo Pan Homo Premolars show slight development of Premolars second cusp second Very large cheek teeth, thick enamel: More Very large thick grinding, dietary shift towards harder to process foods process Bipedal (not like a modern human) A. afarensis A. Modern Human Derived Postcranial Features (Bipedality) Derived 1. Foramen magnum underneath skull 1. (to balance head on vertebral column) column) 2. Vertebrae are wedge-shaped, giving 2. spine shock-absorbing curves spine 3. Short, broad pelvis --but lesser but gluteal muscles not wrapped around hip joint as much as in humans; pelvis balancing mechanism may not be fully developed be 4. Femur is angled towards midline, 4. maintains balance over one foot maintains 5. 6. Non-opposable big toe, arches in 5. foot foot Laetoli, Tanzania: 3.6 Ma footprints Laetoli, Arches in the Foot: shock absorption Australopithecus Human Arch Laetoli footprint A. afarensis males>>females Male average 4’ 11”, 99 lbs Female average 3’ 5”, 64 lbs ...
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