ANT 102 1st EditionLecture 11Outline of Last Lecture I. CladogramII. What makes us humanIII. Bipedalism Outline of Current Lecture I. RaceII. Human variation and natural selectionCurrent LectureHuman Grips:PrecisionPowerDexterityRace: way to describe different groups of people with different physical characteristicsBiological definition of race: subspecies; populations that are capable of variable reproduction but still significantly different genetics**remember the biological species conceptDoes this definition apply to humans?Nope! From a biologic standpoint, race does not exist in humansNon-existence of a biological raceNo reproductive isolation—plenty of gene flow“racial” characteristics are not discreteEven racists cannot agree on the number of races due to the absence of correlated allele clustersThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Lewontin 1972 study of modern human populations: more genetic variation within geographical populations (85%) than between populations (15%)Variation between human populations is HALF as large as the variation between chimpanzee populations **the lack of genealogical foundation for race does not mean that race lacks significance to social identitiy or that populations do not have a specific genetic history**this does not mean that racism doesn’t exist in the world, it means that racist propaganda ultimately lacks any real basis to go off ofNatural selection and sexual selectionMany phenotype differences are due to tiny fractions of overall genetic diversityMany of these due to social preferencesHuman variation and natural selectionSun exposure/ solar radiation (skin color)Closer to the equator, darker skinMost variation in Africa than any other continent Melanin levels (control for how much ultraviolet radiation you will retain)Eumelanin: brown/blackPhaeomelanin: red/yellowAcclimatization: getting a tanGenetic variation in a production of melanin plus hemoglobin and caroteneVitamin D is necessary for healthy bone growthRickets was a huge problem in the late 1800’s and early 1900’s in AmericaEskimos, Aleuts, etc.:Sun reflects off the snow, that’s why they have such dark skinDiet consists of a lot of cold water fish (high is vitamin D)Albinism: inability to produce melaninHeat/cold stress (body shape and size)Generation and retention of heat is a function of body volumeDissipation of heat is a function of surface area (interaction between skin and air)The skinnier you are, the cooler you’ll remain and vice versaConsider a balloon: as the balloon expands, its volume expands faster than its surface area (its capacity to generate and retain heat increases more quickly than it is able to lose heat)Bergmann’s Rule: hot and fatRelationship in mammals between body mass and surface areaGreater mass allows greater heat retentionPredicts selection for increased volume in cold climatesAllen’s rule: Relates to shape of body and appendagesIn colder climates, shorter appendages are better at preventing heat loss due to higher mass to surface ratio and vice versaHigh altitude stress (oxygen in the blood)Tend to have larger hearts Living in higher altitude environments have genetic markers for higher saturation in their bloodDevelopmental plasticity and acclimatizationSun exposure: tanningHeat/cold stress: shivering, sweating, vasodilation (veins expand), vasoconstriction (veins shrink)High altitude: blood oxygen