PS240 Midterm 1 Review - PS240 Midterm 1 Chapter 2 2.1 Human Evolution Humans didnt evolve from chimpanzees(our nearest relative but rather shared

PS240 Midterm 1 Review - PS240 Midterm 1 Chapter 2 2.1...

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PS240 – Midterm 1Chapter 22.1 – Human Evolution -Humans didn’t evolve from chimpanzees (our nearest relative) but rather shared a common ancestor 5-6 millions years ago-Earliest fossil hominin (human like ancestor) uncovered in Ethiopia is the Ardipithecus ramidus (“ground ape”) and dates back to 4.4 million years agooAble to walk upright oIntermediate between humans and chimpsoShows that bipedal locomotion predates evolution of a large brain in our ancestry-Next stage of evolution was the Australopithecus (“southern ape”) which dates back to 4.2 million years ago oOpen savannah dwelling creature oTwo main forms – a robust (strong and full-bodied) and a gracile (more delicate) form-Around 2.5 million years ago the first of the Homo line – Homo habilis (“handy man”) evolved from the gracile form of Australopithecus oFirst of our ancestors to make use of primitive stone tools; i.e. scrapers to removemeat from the bone oLarger brain capacity than H Habilis at 600 cc which suggests that tool use requires a larger brain -1.8 million years ago Homo habilis gave rise to Homo erectus (“upright man”) o850 cc brain capacity oengaged in hunting so therefore developed more sophisticated tools oable to make use of fireofirst of the species to leave Africaofirst of our ancestral species to live in small hunter-gatherer societies, where the old and infirm are provided for-Around 400,000 years ago H erectus gave rise to early Homo sapiens (“thinking man” – sometimes called “archaic humans”) oBrain capacity of around 1000 cc oNumber of subspecies evolved from early H. Sapiens, such as NeanderthalsShort and stocky, heavy eyebrow ridges and huge noses Successful subspecies Robustness was an adaptation to Ice-Age conditions rather than a throwback to our more ancient anthropoid (ape) ancestors Brains were on avg. 1450 – 1500 cc-Two main hypotheses to explain the emergence of Homo sapiens sapiens – the multiregional and the Out-of-Africa Replacement
oMultiregion hypothesis: Hss evolved from H erectus in a number of different geographical locations around EurasiaoOut-of-Africa Replacement hypothesis: all modern human populations are derived from a small number of individuals that lived in Africa around 150,000 years ago and rapidly replaced earlier populations, such as Neanderthals More likely Suggested that all present living humans can trace their ancestry back to one female living in Africa around 150,000 years ago – Mitochondrial Eve-Mitochondrial Eve: the most recent female ancestor of all living humans, lived in East Africa approx. 190,000 – 200,000 years ago-Evolution of Homo sapiens is characterized by the development of a number of features that distinguish us from the great apes, such as bipedal locomotion, great reduction in the growth of body hair and most importantly a greatly enlarged brain oAll of these changes are adaptive (came about thru Darwinian selective forces to provide us with survival and reproductive advantages)2.2 – Evolution of brain size and intelligence

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