ANT1Lecture8

ANT1Lecture8 - Midterm exam Next Thursday, February 7...

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Unformatted text preview: Midterm exam Next Thursday, February 7 Covers material through next Tuesday Will post example questions by tomorrow morning Discussion sections next week for the asking questions about material on midterm exam you still are required to attend section Anthropology 1 Winter 2008 Human Evolutionary Biology Common assumptions about race 1. Human biological variation can be divided into a small number of discrete categories 2. Knowing a person's race gives you important information about their genotype or ancestry Common assumptions about race 1. Human biological variation can be divided into a small number of discrete categories 2. Knowing a person's race gives you important information about their genotype or ancestry Short history of attempts to classify humans into races Linnaeus (1738) classified people into 4 sub-species by continent 1. Homo sapiens americanus 2. Homo sapiens europaeus 3. Homo sapiens asiaticus 4. Homo sapiens afer Short history of attempts to classify humans into races Blumenbach (1775) argued for 5 races Caucasian, Mongolian, Ethiopian, American, Malayan Defined primarily on skin color Short history of attempts to classify humans into races 19th and 20th centuries, profusion of racial classifications Deniker (1889) 29 races von Eickstedt (1937) 3 races, 18 subraces Coon, Garn, and Birdsell (1950) 30 races As many racial classifications as people trying to classify! Classifications failed 1. Most variation is found within groups 2. Variation can be due to environmental rather than genetic factors 3. No sharp boundaries in human variation (clinal variation) 4. Different traits result in different classifications Classifications failed 1. Most variation is found within groups 2. Variation can be due to environmental rather than genetic factors 3. No sharp boundaries in human variation (clinal variation) 4. Different traits result in different classifications Genetic distance Sharp boundary Geographic distance Genetic distance Smooth Geographic distance No sharp boundaries in human genetic variation Genetic distance Geographic distance erplot of FST and geographic distance. Red dots denote within-region comparisons, green triangles indicate comparisons between p asia, and blue diamonds represent comparisons with America and Oceania. (A) The relationship between FST and geographic distan cle distances. R2 for the linear regression of genetic distance on geographic distance is 0.5882. (B) The correction for large bodies of wat ^ erplot (R2 0.7835). The regression line fitted to the data [FST 4.35 10 3 (6.28 10 6) (geographic distance in kilometers)] is d et al. PNAS November 1, 2005 vol. 102 no No sharp boundaries in human genetic variation Suppose you parachute into Copenhagen You know you are not in Cape Town Race seems real But imagine you bike from Cape Town to Copenhagen Boundaries hard to detect Sampling makes race look real in the USA Racial classification in Brazil Racial classification in Brazil Racial classification in Brazil People are classified as "black," "Color" is assessed by Skin color Hair type Eye shape Lip shape "white," "intermediate" by their "color" Racial classification in Brazil "White" individuals are assumed to have Portuguese ancestry "Black" individuals are assumed to have West African ancestry Genetic classification Genetic distance W. African 10 genes found that distinguish Portuguese and West African individuals Portuguese Different classifications don't match Genotypes W. African Portuguese Black White Intermediate Different classifications don't match Genotypes W. African Portuguese Black White Intermediate Mendel's 2nd law explains why classifications don't match "Particles" for different traits are independently inherited = independent assortment Genes for "color" are inherited independently from other genes "Color" only gives information about genes influencing skin color, etc., and not about any other genes a person carries What explains human phenotypic variation? 1. Natural (sexual) selection? 2. Neutral evolutionary forces? Mutation Genetic drift Gene flow 3. Environmental (non-genetic) factors? What explains human phenotypic variation? 1. Natural (sexual) selection? 2. Neutral evolutionary forces? Mutation Genetic drift Gene flow 3. Environmental (non-genetic) factors? Cranial Form Genetics vs. cranial Form 85-95% 86-89% Cranial distance vs. geographic distance Cranial similarity Summary Patterns of variation for cranial form match those for genetic loci Suggests that cranial form was shaped by neutral evolutionary forces Climate differences Trends in body proportions and size Arctic hare Desert jackrabbit Human body proportions "Coldadapted" "Warmadapted" Surface Area Mass 260 301 Human body proportions Leg Length : Trunk Height 105 95 85 Europeans North Africans Sub-Saharan Africans 290 Human body proportions M.J. Tilkens et al. / Journal of Human Evolution 53 Standardized leg length Fig. 2. Residuals of the regression of lower limb length on lean mass exhibit a statistically significant relationship with the residuals of resting metabolic rate on lean mass (p 0.018 and R2 0.274). Epstein, Y., Sha work efficie Franciscus, R.G Homo erect Frayer, D.W., W Theories o Anthropol. 9 Hanna, J.M., L Little, M.A. plinary Scie Heglund, N.C., and mechan changes as J. Exp. Biol Holliday, T.W., modern hum Holliday, T.W., Neandertals Holliday, T.W., Paleolithic a Holliday, T.W., and early a 93e94. Hrdlicka, A., 19 Standardized resting metabolic rate Genetics vs. skin color 85-95% 12% Skin color geographic distribution Skin color vs. latitude Correlation latitude and skin color may be even stronger if one accounts for recent migrations Amount of melanin in the skin is the primary cause of skin color variation Melanin Sunlight has harmful effects UV radiation damages DNA and causes skin cancer Destroys vitamin B folate, which is important in preventing birth defects Sunlight has beneficial effects Sunlight necessary to catalyze the production of vitamin D Vitamin D necessary for absorption of calcium Vitamin D deficiencies can cause rickets Melanin is a natural sunscreen Skin color reflects a balance of the harmful and beneficial effects of sunlight in different geographic regions Summary More variation between groups for some phenotypic traits Result of adaptation by natural selection to different environments are unusual in their These traitsvariation within and patterns of between groups ...
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This note was uploaded on 04/15/2008 for the course ANT 001 taught by Professor Mchenry during the Winter '08 term at UC Davis.

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