Bio1B Evolution 12 Last lecture Fossil record cont Mass extinctions the K T boundary asteriod hypothesis dinosaue extinctions radiation of mammals Transitional forms tetrapods birds exaptation Evolution of developmental programs deep homology eg vertebrate limbs animal eyes Today Evolutionary origins of Homo sapiens fossils molecular evidence Recent evolution of humans eg lactose tolerance in adults Evolutionary medicine basic concepts and examples Pathogen evolution eg HIV evolution within single hosts Metabolic diseases thrifty gene hypothesis obesity type 2 diabetes Further courses in Evolution at UC Berkeley 1 Evolution of hominins fossil evidence II Homo key features increasing brain size lower sex dimorphism more terrestrial African origins H erectus europe 1 8Myr Indonesia Java man Extinct 200 Kya H floriensis 1M 12Kya Related to H erectus Neanderthals Europe and near east 200 24Kya Fig 34 40 3 Evolution of hominins fossil evidence I Hominins split from common ancestor with chimps about 7Myr African origins diversity expands 4 2Myr Key features bipedalism smaller canines large brain later A ramidus neither chimp nor human see display in VLSB Australopiths probably paraphyletic with Homo Robust anthropoids Lucy Fig 34 40 2 Evolution of hominins fossil evidence III H floriensis Possibly persistent relative of H erectus or malformed H sapiens Exemplifies humans evolve as other species dwarfing of large mammals on islands eg Stegodon pygmy elephants huge lizards Varanus Putative tools 1Myr fossils to 12Kya overlapping H sapiens H floriensis Microcephalic H sapiens 4 Migration of H sapiens Modern humans related species hybridization or replacement Out of Africa about 100Kya Rapid spread across Sth Asia to Australia central Asia One or 2 colonizations across Bering bridge during last ice age rapid spread to Sth America Polynesian migrations across Pacific are recent 1500 BC to 1000 AD New Zealand Genetic evidence largely supports single origin outof Africa over independent origins from different populations of H erectus multi regional 5 Recent evolution in humans lactose tolerance in adults Tolerance of lactose in adults is a recently evolved trait in humans Molecular analyses show independent origins from different mutations in lactase gene in Africa and Nth Europe The mutations are absent from fossil neolithic farmers 65Kya Lactose intolerance is the norm not a disease 7 But did modern humans hybridize with or simply 6 replace neanderthals Principles of Evolutionary Medicine see Zimmer pdf also new course in IB Tom Carlson Understanding evolutionary basis of disease risk can improve diagnosis and prevention Variation in human phenotypes results from genetic variation and environmental influences on development Selection operates to maximize inclusive fitness not health and longevity This can result in trade offs 8 Evolutionary mismatches constraints Rapid evolution of pathogens HIV an RNA virus within hosts see Zimmer pdf Thrifty genes hypothesis Native American and others selected for efficient metabolism because of history of famine with obesogenic food types very prone to obesity type II diabetes Rapid life history evolution aging and late onset diseases Tradeoff between selection for genes important prereproduction growth and post reproduction repair From Zimmer 2009 9 Hygiene hypothesis reduced exposure to pathogens in children increase in autoimmune disease athsma etc Evolutionary constraints appendix detached 10 retina small birth canal cf brain size etc
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