Early Hominids January 31, 2005 Part I: Hominid Phylogeny Australopithecus africanus afarensis robustus Homo habilis erectus sapiens Hominid Phylogeny Australopithecus A. africanus Raymond Darts Taung Child mya Bipedal Small brain Sexual dimorphism suggests polygyny Partially arboreal Worked in groups Australopithecus A. afarensis Lucy Fan shaped pelvis mya Australopithecus Gracile A. afarensis A. africanus? Robust A. robustus A. boisei A. africanus? Folivore: large molars and sagittal crest Small canines Little sexual dimorphism Part II: When did this happen? Geologic time scale: How do we know? Relative Dating Statigraphy Glaciations Fluorine analysis Dendrochronology How do we know? Absolute Dating Carbon 14 (organics, up to 40,000 years) Potassium Argon (volcanic, over 500,000) Uranium Series (minerals b/w 1k and 1m) Thermoluminescence (rocks & minerals b/w 5k and 1 mya) Electron Spin Resonance (rocks & minerals b/w 1k and 1mya) How do we know? Calendars Historical accounts Part III: Why did this happen? Ecology: 1) Relationships between organisms and environment. 2) Relationships between human groups and their physical and social environments. Climactic Shifts Bipedalism Energy efficient locomotion Food gathering Avoiding predators Provisioning offspring Free hands (tools) Tracking prey Skeletal Comparison Brain Size Homo sapiens sapiens: 1,200-1,350 Modern Chimpanzee: 390 A. afarensis: 430 A. africanus: 490 A. robustus: 540 A. boisei: 490 (Measured in cubic centimeters) Skeletal Comparison Human Chimp Skeletal Comparison Robust Australopithecus Gracile Australopithecus Dental Comparison Modern Chimp A.afarensisH. sapiens Upper jaw Part IV: What does it mean? Killer Ape Osteo-donto-keratic tools Man the scavenger Probably vegetarian or omnivorous What does it mean? Savannah hypothesis Variable selection Phenotypic plasticity What does it mean? Bipedalism or Intelligence? Piltdown hoax What does it mean? Piltdown hoax