ISS 210 1st Edition Lecture 4 Outline of Last Lecture I Louis and Mary Leaky II Virtual Anthropology III Taphonomists and Deposition IV A Leopards Pray V Stratigraphy VI Vulcanic Tuffs VII Chronometrics VIII Trapped Charge Dating IX Species Where do you draw the line X Catastrophism XI Uniformitarianism XII Phyletic Gradualism XIII Punctuated Equilibrium XIV Allopatric Speciation XV Homosapiens Sapiens XVI Cladistics Vs Evolutionary Tree XVII The Disadvantages of Bipedalism XVIII Dentition and Skulls XIX Tooth Enamel Wear Patterns Outline of Current Lecture I The Basics II Evolution III Malthus and Population IV Natural Selection V Origins of Genetic Variation VI Chimps and Humans VII Chimp Human Differences VIII Genomic Change IX Genetic Drif X Founder Effect XI Natural Selection 2 XII Malarial Resistance in Nepal XIII Sickle Cell Anemia XIV A africanus STS XV Paranthropus Vegetarian Extraordinaire XVI Paranthropus Robusts XVII Horn Core Tool from Swartkrans South Africa XVIII P aethiopicus Black Skull XIX The Panglossian Paradigm or the Calvin Effect XX Necrolemur and Tarsier Tarsi XXI Distinctive Features Monkey XXII Distinctive Features Ape XXIII Chimpanzee Bipedal Movement Current Lecture I 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 drif Is not an optimization mechanism in the engineering sense Differential reproduction of better suited traits II 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 variability III 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 observed All individuals in a population differ slightly from each other and the differences are inherited By winnowing their advantages heritable traits will tend to become more common with each generation Variation will allow selection to drive the lineage in a different direction Darwin 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 environment V 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 direction VI 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 systemic VII 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 right IX 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 necking X 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 shared by 100 of his 400 descendents XI Natural Selection 2 Populations evolve not individuals as gene frequencies change in the population Individuals vary in their physical and behavioral characteristics most of which are heritable Those who survive to reproduce will be fitter or better adapted to prevailing circumstances Their alleles will be