human evolution - california state university, northridgedgray/evol322/chapter20.pdf · 2008. 5....
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Human Evolution
“ light will be thrown on the origin of man and his history”
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Humans and primates• Prosimians
– Lemurs, bushbabies
• Simians aremonkeys– New world monkeys
(platyrhini)
– Old world monkeys(catarrhini)
• Apes– Hominidae
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Humans closely related toAfrican great apes
• Sarich and Wilson 1967
• Serum albumin reaction
– Rabbit antibodies
• Dated with fossils
– Old world monkeys and apes 30 mya
• Humans and African great apes last shared a commonancestor 5 mya
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Humans more closely related tochimps than gorillas
• 3 molecular phylogenies– mtDNA (maternal)
– Y-linked gene (paternal)
– Autosomal genes
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Importance of concordance• Concordance means
agreement– Results with those three
different data sets agree
– Important because molecularphylogenies trace history ofgenes
– Of 14 separate independentdata sets
• 11 show humans and chimps
• 2 show gorillas and chimps
• 1 shows humans and gorillas
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Species trees and gene trees
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Concensus, conclusion?
• Humans and chimps shared recent commonancestry– About 5 mya
• Gorillas likely the next most closely related– orangutan
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Recent Human Ancestry
• Ok, so humans and chimps split 5 mya• What might the common ancestor have been
like?– Parsimony: limited tool use, broad diet,
cooperative group living• Hunting, warfare, cannibalism, social alliances,
status
• What evidence is there of the lineage ofhumans AFTER that split– I.e., the recent ancestry of the human lineage
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Gracile Australopithecines
• small braincases
• 400 to 500 cc
• walked on two legs
• female 1 meter tall
• males 1.5 meter
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bipedalism
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Robust Australopithecines
• Small brained– larger than gracile
Australopithecus
• Large bony crest– Jaw muscle
attachments
• Bipedal• Similar size to
gracileAustralopithecus
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Archaic humans, Genus Homo
• All African
• H. habilis– 600 cc brain
• Teeth and jawssmaller than inAustralopithecus
• Taller
• Less sexuallydimorphic in size
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Modern humans• Last 100,000 years• Biggest brain
– 2000 cc Cro-Magnon– Today about 1200 cc
• Higher foreheads• Flatter faces with
prominent nose• Culture?
– Cro-magnon I buried ingrave with 2 men 1woman and infant
– Animal bones, jewelry,stone tools
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The last survivor
• Modern Homo sapiens only descendent ofmultispecies radiation of African hominids
• Many species co-existed at one time– Up to at least 5 species
• origin and spread of modern Homo sapiens?
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Paleontological agreement on this:
• H. sapiens are descendents of some or all ofthe H. ergaster/H. erectus group of species.
• How and where did modern humans arise?– Archaic humans certainly in Africa
– Recent humans more widespread
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Geographic range
• Oldest H. ergaster/erectus fossils (1.6 to 1.9 mya)
– Koobi Fora (Africa)– Dmanisi (Caucasus Eastern Europe)– Longgupo Cave (China)– Sangiran and Mojokerto (Java)
• Oldest H. sapiens 100,000 years ago– Africa and western middle-east
• Bit later through Europe and Asia
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Some results
• mtDNA, 189 people
• ‘Mitochondiral Eve’ not single person• Likely was African
– But when?
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Nested genetic variation
• Founder effects predict– Descendent populations
have subset of geneticvariation found in originalsource population
• 12 alleles of TTTTCrepeats