Bio Anth Week 10 of Notes
Bio Anth Week 10 of Notes Anth 1001
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This 3 page Class Notes was uploaded by Jaimee Kidd on Wednesday April 6, 2016. The Class Notes belongs to Anth 1001 at George Washington University taught by Shannon C. McFarlin in Spring 2016. Since its upload, it has received 7 views. For similar materials see Biological Anthropology in anthropology, evolution, sphr at George Washington University.
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Date Created: 04/06/16
Early Homins • Geographical location of possible stem hominins ◦ Fossils come primarily from East and Central Africa—the Great Rift Valley ◦ East Africa Rift System ▪ 3 Continental Plates ▪ Indian, Arabian, and African/Nubian Plate ▪ Area of active drifting of the continental plates, very active volcanic areas along the boundaries ▪ Created a stream of lakes down the East African Rift Valley ▪ These lake environments probably would have been very important for early hominids because of different vegetation and areas of congregation ▪ Sediments on the high portions of the rifts are eroding exposing boulder rock layers, many of which contain the remains of old vertebrates that are now extinct ▪ Because of the very active geology in this region allow for the exposure of a lot of hominid and vertebrate species ▪ Many of these volcanoes have spewed out ash layers allowing for chronometric dating • What Makes a Hominid? ◦ Major Evolutionary Novelties of Humans ▪ Habitual upright walking (bipedalism) ▪ Characteristics of the dentition ▪ Elaboration of material culture ▪ Significant increase in brain size ▪ Long developmental period and long lifespan ◦ Adaptive explanations for the origin of bipedalism ▪ Social Factors: ▪ Ability to provision for the family in the context of evolution of monogamous systems ▪ This is tied to the assumption that early hominins resided in open savana like environments ▪ Problems: other hominids do this as well such as Chimpanzees who carry things and walk for short periods of time ▪ Ecological Factos ▪ Moving across forested patches with high energetic efficiency ▪ Finding food and spotting predators • Sahelanthropus tchadensis ◦ 7-6 million years ago ◦ Digitally reconstructed —> more vertical face, higher skull vault ◦ Smaller canines, no CP-3 honing complex ◦ BIped? - position of foramen magnum ▪ More directly under the skull than what we see in modern apes ▪ Slightly more human-like position ◦ But primitive in other respects (brain size, U-shaped dental arcade) • Orrorin tugenensis ◦ 6 million years ago ◦ Fragmentary evidence primarily post cranial ◦ Femoral morphology is indicative of bipedal locomotion ◦ Dental morphology is ape-like (large canines) • Ardipithecus radius and Ar. kadabba ◦ 4-6 million years ago ◦ Intermediate canine size between apes and later hominins ◦ relatively small brain, prognathism as in apes ◦ More forwardly-placed foramen magnum—consistent with bipedalism ◦ Significantly reduced canine size ◦ Loss of CP-3 honing ◦ Minimal sexual dimorphism ◦ Pelvis—Evidence for bipedalism? ▪ Mosaic characters for both bipedality and climbing ▪ Short and broad ilium (unlike chimps) ▪ Ischial surface is primitive ◦ Foot retains a divergent big toe ▪ Lacked other features for suspension/vertical climbing and knuckle walking seen in apes ◦ Combination of primitive and derived traits ◦ Evidence of its ancestral position for the hominid clade for Ardipithecus discovers ◦ Evidence of the position of A. radius as an early ape or an evolutionary side branch for others • Before Australopithecus ◦ Several taxa, based on very fragmentary and incomplete remains (except Ar. radius) ◦ While they possess some derived human-like traits (e.g. reduced canines & CP3 honing) their hominid status is debated • Major trends in Australopiths (Australopithecus and Paranthropus) ◦ Dentition ▪ Reduced canine size ▪ Larger cheek teeth ▪ Thicker enamel ▪ Paranthropus chewing adaptation, post canine megadontia ◦ Locomotion/posture ▪ Adaptions for bipedalism ◦ Relative brain size ▪ not substantially enlarged compared to apes ◦ Body size ▪ Smaller than modern humans, more sexual dimorphism ◦ Geographic location ▪ Two morphs or types of bipedal ancestors with large teeth and small brains known from East and South Africa ▪ Australopithecus (gracile) ▪ Paranthropus (robust) ▪ Gracile from now also found in Central Africa