Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Models for Evolution of BipedalismSlide 8Slide 9Slide 10The First Humans(hominids)The first physical characteristic that sets humansapart from other primates isBIPEDALISMThese earliest hominids are found where?in east Africa and central AfricaIn looking at the first hominids (humans),What are the major issues?1. What did the last common ancestor between human and chimpanzee lineages look like?2. When did the split occur?3. What factors favored the development of bipedalism? What natural selective forces?4. HOW? Was bipedalism the result of a macromutation?5. Were there separate lineages of early hominids, of which only one survived to lead to us, or were they all part of the same lineage?Physical changes associated with bipedalismLocation of foramen magnum more centered under craniumShape of spinal columnShape of pelvisLengths and attachments of leg musclesAngle of femur and shape of kneeShape of footRelative lengths of arms vs legsThus, you could find any of these body partsand perhaps figure out if the creature was bipedalWHERE are theearliest hominids found?Central AfricaEast AfricaBipedal HominidsWhat factors played a role in the shift to bipedalism?The first hominids (humans) appear during theTerminal Miocene EventThe period when African forests gave way toextensive grassland savannas with scattered treesOne long-held hypothesis is that this changein vegetation favored bipedalismA new hypothesis this year posits that it wasan attraction to rough terrainBIPEDALISMLong-held view: environmental changes favored itTerminal Miocene Event: cooling and drying trendForests of Africa shrank, more grasslands with scattered treesMore of a mosaic of vegetation: woods vsgrasslandsModels for Evolution of Bipedalism1. Carrying Model2. Vigilance Model3. Heat Dissipation Model4. Energy Efficiency Model5. Foraging/Bipedal Harvesting Model6. Display Model7. Complex Topography ModelHowever, new information that waspublished in October 2009 is challengingour understanding of the earliest hominidsWhat was found?A bipedal hominid that lived in a forested areaArdipithecus ramidus 4.4 myaNow we know the last common ancestor betweenhumans and chimpanzees looked neither like ahuman nor like a chimpanzeeAnd now that more early hominid fossilshave been found and analyzed,we know that a wide variety of bipedaladaptations were taking place, withdiffering mixes of bipedal and arborealcharacteristicsToday, a movie on the first nearly completeskeleton of an early hominid“Lucy”Australopithecus afarensisWhy they know her to be bipedalHow closely they study her anatomyHow they can date her to 3.2 myaHow controversial her find was when presented at the national professional
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