The First Humans hominids The first physical characteristic that sets humans apart from other primates is BIPEDALISM These earliest hominids are found where in east Africa and central Africa In 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 bipedalism Location of foramen magnum more centered under cranium Shape of spinal column Shape of pelvis Lengths and attachments of leg muscles Angle of femur and shape of knee Shape of foot Relative lengths of arms vs legs Thus you could find any of these body parts and perhaps figure out if the creature was bipedal WHERE are the earliest hominids found Central Africa East Africa Bipedal Hominids What factors played a role in the shift to bipedalism The first hominids humans appear during the Terminal Miocene Event The period when African forests gave way to extensive grassland savannas with scattered trees One long held hypothesis is that this change in vegetation favored bipedalism A new hypothesis this year posits that it was an attraction to rough terrain BIPEDALISM Long held view environmental changes favored it Terminal Miocene Event cooling and drying trend Forests of Africa shrank more grasslands with scattered trees More of a mosaic of vegetation woods vs grasslands Models for Evolution of Bipedalism 1 Carrying Model 2 Vigilance Model 3 Heat Dissipation Model 4 Energy Efficiency Model 5 Foraging Bipedal Harvesting Model 6 Display Model 7 Complex Topography Model However new information that was published in October 2009 is challenging our understanding of the earliest hominids What was found A bipedal hominid that lived in a forested area Ardipithecus ramidus 4 4 mya Now we know the last common ancestor between humans and chimpanzees looked neither like a human nor like a chimpanzee And now that more early hominid fossils have been found and analyzed we know that a wide variety of bipedal adaptations were taking place with differing mixes of bipedal and arboreal characteristics Today a movie on the first nearly complete skeleton of an early hominid Lucy Australopithecus afarensis Why they know her to be bipedal How closely they study her anatomy How they can date her to 3 2 mya How controversial her find was when presented at the national professional conference
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