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Chapter 4

Chapter 4 Anthro Textbook.doc
Chapter 4 Anthro Textbook.doc

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University of Toronto Mississauga
Kenneth Derry

 WEEK FIVE – January 21    , 2013  Chapter #4: Modern Human Variation & Adaptation HISTORICAL VIEWS OF HUMAN VARIATION • 1350 B.C – ancient Egyptians classified humans based on their skin color • Linnaeus – taxonomic classification o First attempt to describe variation among human populations o 4 separate categories o Least complimentary descriptions = sub-Saharan, dark-skinned Africans • Blumenbach o Classified humans into 5 races o Acknowledged limitations • If Europeans were Christian = uncivilized o Biological Determinism – this view was rooted in it, an association bw physical characteristics and such attributes as intelligence, morals, values, abilities, and even social and economic status THE CONCEPT OF RACE • All contemporary humans are members of the same polytypic species = HOMOSAPIENS • Races – people who have particular combinations of various characteristics and other traits have been placed together under this category • Phenotypic expressions that contribute to social identity = racial traits, sex, age, ethnicity • 1950s, Ethnicity – designed to avoid emotionally charged term race o Refers to cultural factors, but the fact that the words ethnicity and race are used interchangeably reflects the social importance of phenotypic expression and demonstrates once again how phenotype is mistakenly associated w culturally defined variables • Different in expression of one or more traits = species occupying different land • Anthropologists recognize that outdated conceptions of race are no longer valid B/C the amount of genetic variation accounted for by differences bw groups is vastly exceeded by the variation that exists within groups • Limitation of traditional classification  categories are distinct and based on stereotypes or ideals that compromise a specific set of traits (typological nature) CONTEMPORARY INTERPRETATIONS OF HUMAN VARIATION • 1950s  studies of modern human variation focused on various components of blood and other body chemicals • Thus  directly sequence DNA & identify entire genes and even larger DNA segments to make comparisons bw groups/populations • Human Polymorphisms • Loci w more than allele • Expressed in the phenotype • Traits that differ in expression bw populations and individuals • Main focus of human variation studies • Used to compare allele frequencies bw different populations  reconstruct evolutionary events linking human population w one another • Polymorphisms at the DNA Level • Single-Nucleotide Polymorphisms – point mutations w coding regions in DNA • Whole-Genome Analysis – 3 studies have evaluated molecular info for the entire genome in more than 1000 total individuals HUMAN BIOCULTURAL EVOLUTION • Culture – human strategy of adaptation • Evolution in a cultural context  humans live in cultural environments that are continually modified by their own activities • Natural selection  operated by specific environmental settings  environment dominated by culture • Lactase Persistence – in adults, the continued production of lactase, the enzyme that breaks down lactose o It allows adults in some human populations to digest fresh milk products o The discontinued production of lactase in adults leads to lactose intolerance and the inability to digest fresh milk POPULATION GENETICS • Used to interpret micro evolutionary patterns of human variation • The area of research that examines allele frequencies in populations and attempts to identify the various factors that cause allele frequencies to change over time • Factors that determine mate choice: (1) geographical (2) ecological (3) social • To determine whether evolution is taking place at a given locus, population geneticist measure allele frequencies for specific traits and compare these observed frequencies with a set predicted by a mathematical model: • Hardy-Weinberg Equilibrium – the mathematical relationships expressing the predicted distribution of alleles in populations; the central theorem of population genetics THE ADAPTIVE SIGNIFICANCE OF HUMAN VARIATION • Physiological response to environmental change is influenced by genetic factors • Adaptation – long-term evolutionary changes that characterize all individuals within a population • Acclimatization – another kind of physiological response to the environmental conditions, short-term, long-term or even permanent o Factors: genes, severity of exposure, technological buffers (shelter, clothing), individual behaviour, weight, body size • Developmental Acclimatization – irreversible and results from exposure to an environmental challenge during growth THE THERMAL ENVIRONMENT • Mammal  have pshyiological mechanisms that increase/reduce the loss of body heat • Reptiles  rely on exposure to ext
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