Introduction to the Great Rift Valley of Africa Early humans arose in eastern africa - Exposure of rock formation in hominan evolution Tells us about lifestyles and environments Species in the fossil record Why are species bounded from each other? Darwin's ideas of gradual evolution Gradual changes in fossil record Gradual gradations among living organisms Shouldn't see distinct types from place to place but rather a continuous range Darwin: as gradual changes happened among species and they become more adapted to small habitats, those gradations would give rise to larger populations in some
The variation within larger species would be continually giving rise to more and more favorable variations so that the larger species would continually replace the smaller ones Gradual change of time in a single geographic region is the evolutionary trajectory from Australopithecus anamensis to Australopithecus afarensis 4.2 and 2.9 mil years ago - We don't know if they are the only descendant diversity Morphology: the study of the size and shape of anatomical features Seeing variation - gave them names Human origins/variation Should different groups of humans be in different species Species or geographical races? Naming species - different biological groups or not? The evidence used to decide whether species have a close evolutionary relationship is not close by hand When talking about living primates -- biological species concept A species is a population that includes all of the populations that can actually or
Focuses on reproduction - not how different they look
Have evidence on variation among populations of great apes (chimps - 4 subpops and bonobos) Chimp subspecies - .5mil years Difference between species and subspecies is arbitrary Interview with Carol Ward about the origin of bipedalism Professor of anatomy at the university of missouri in columbia Working in field of kenya - kanapoi on south side of Lake Turkana Lab work on post-cranial anatomy - form of bones and skeleton about how ancient creatures moved and lived
Morphology - changes in early hominins Australopithecus anamensis to Australopithecus afarensis Bipedal locomotion Bipeds: hominins whos primary mode of locomotion is upright walking on 2 feet What adapted to, selection Why they were the way there Fossil - what did selection tell them to do Australopithecus afarensis 3.6 to 3.0 mil 2 feet - move around Lost grasping big toe - useful to climb trees They couldnt - 2 feet is so important that it gave up ability to climb trees - sacrifice Aust ramidus - 4.4 mil Terrestrial bidedality- walking on 2 feet on the ground rather than in trees Micone apes - 23 to 5mil Arboreal orthography - using upright posture to move in trees Natural selection in variation of population - vector of chance (magnitude and direction) Compared to living Austa anamensis - 4.2 to 3.8 mil Jaws and teeth - heavy chewing (adaptation) better and changing in diet - Leg is vertical - like humans Dont know about big toe, dont know about bone Hand - shift - long fingers, thumb