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MSU ISS 210 - Evolution and Human Origins

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ISS 210 1st Edition Lecture 4 Outline of Last Lecture I. Louis and Mary LeakyII. “Virtual Anthropology”III. Taphonomists and DepositionIV. A Leopards PrayV. StratigraphyVI. Vulcanic TuffsVII. ChronometricsVIII. “Trapped-Charge” DatingIX. Species: Where do you draw the line?X. CatastrophismXI. UniformitarianismXII. Phyletic GradualismXIII. Punctuated EquilibriumXIV. Allopatric SpeciationXV. Homosapiens Sapiens XVI. Cladistics Vs. Evolutionary TreeXVII. The Disadvantages of BipedalismXVIII. Dentition and SkullsXIX. Tooth Enamel Wear PatternsOutline of Current Lecture =I. The BasicsII. EvolutionIII. Malthus and PopulationIV. Natural SelectionV. Origins of Genetic VariationVI. Chimps and HumansVII. Chimp/Human DifferencesVIII. Genomic ChangeIX. Genetic DrifX. Founder Effect XI. Natural Selection (2)XII. Malarial Resistance in NepalXIII. Sickle-Cell AnemiaXIV. A. africanus: STSXV. Paranthropus: Vegetarian ExtraordinaireXVI. Paranthropus RobustsXVII. Horn Core Tool from Swartkrans, South AfricaXVIII. P. aethiopicus “Black Skull”XIX. The Panglossian Paradigm or the Calvin Effect XX. Necrolemur and Tarsier (Tarsi)XXI. Distinctive Features: MonkeyXXII. Distinctive Features: ApeXXIII. Chimpanzee Bipedal MovementCurrent LectureI. The Basics– Evolution is the change of frequency of genes over time– Individuals don’t evolve, populations do – Natural Selection is:Subject to random events ex) genetic drifIs not an optimization mechanism in the engineering senseDifferential reproduction of better suited traitsII. Evolution– Darwin demonstrated what Linnaeushad proposed that species are the work of time– For what?– Forces guiding process toward a predetermined goal?– Chardin’s teleological functionalism– Is change and variation simply the result of random events?– Stephen Gould looking out a starry but silent sky– How?– Underlying life principle that strives for perfection – Product of natural selection operating on existing genetic variabilityIII. Malthus and Population– In an Essay on the Principles of Population (1797) Malthus observes that– Population increases geometrically doubling every 25 years but it doesn’t because the food supply increases arithmetically– Population growth is thus limited by poverty, disease, and famine, which are natural and inevitable– The weak and the improvident are weeded out; the strong and wiser survived. Crudely, expressed as “survival of the fittest”IV. Natural Selection– Darwin observedAll individuals in a population differ slightly from each other and the differences are inheritedBy winnowing, their advantages heritable traits will tend to become more common with each generationVariation will allow selection to drive the lineage in a different directionDarwin observed the variation but didn’t understand its underlying cause– Natural Selection then is nothing more than the differential reproductive success of individuals within populations, mediated by the environmentV. Origins of Genetic Variation– Lack of genetic model to explain change– Gregor Mendel’s described how traits were inherited in a short monograph on peas published in 1866– Darwin was unaware of the Mendel’s work, which was largely ignored until it was “rediscovered” in 1900.– Change was attributed to a supposed “life principle” (entelechy) a directly force which strove for perfection within each individual – Implicitly a reflection of the social model of capital accumulation (families build wealth and pass it on) – The physical achievements/gains of parent passed to the offspring– Natural selection Is nothing more than the differential reproductive success of individuals within populations, mediated by the environment– Is a blind, mindless mechanism that lacks any intrinsic directionVI. Chimps and Humans– Share 98.7% DNA in common– Differ on 30,000,000 nucleotides– Very few had anything to do with speciation – the process that separated our species 6 to 7 million years ago – Most of these happened since separation, it is hard to know which ones– Hard to pin down the point at which two species diverge– Microevolution is the study of populations within species to examine and quantify processes of evolutionary change using population genetics– Macroevolution is the study of higher categories into which species are grouped to examine and quantify the patterns of evolutionary change using systemicVII. Chimp/Human Differences– Cranial properties (brain case and face)– Ape thumbs are longer– Relative brain size– Length of fingers– Chin present or absent– Knuckle – walking/bipedal– Spine- s-shaped or not, seen from side– Relative limb length (arm length: leg length)– Relation of skull to vertebral column VIII. Genomic Change– Individuals participate in the evolutionary process through reproduction, they do not themselves evolve. Species change with descent– Five ways genomes can change with time: Natural selection migration, genetic drif, altered mating patterns, such as inbreeding, and mutation– Mutation is source for new genetic material– Mistakes occur in about 1 in 50,000,000 bases or between 10 and 100 in every new egg or sperm cell– The majority of these “mistakes” have not effect on the health of the organism– Sexual reproduction means you get one “allele” from your mothers genome and one from your fathers which means you get two chances to get it rightIX. Genetic Drif– Result of “sampling error” related to population size– The larger the population, it is more likely you will get the frequencies you expect (500 organisms)– The smaller population, the more likely you will not get the frequencies you expect (4 organisms)– If you have an allele (Big A little a) of a gene and they are passed randomly– In a population of 500, there should b 250 A and 250 a in each generation– In an isolated population of four– You have a “bottle neck” and a higher probability that one or other allele will be eliminated– The allele that gets eliminated by chance may be a “better” and more fit allele– The ‘founder effect” is an especially severe form of bottle neckingX. Founder Effect – Natural disasters– Population of Pingalap decimated by Typhoon Lengkieki in 1775, one survivor had gene for color blindness: today 3,000 people do– Migration/isolation (endogamy)– Chinese immigration to South Africa had a dental disease and 7 wives


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MSU ISS 210 - Evolution and Human Origins

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