Modern Human Biological Variability Concept of Race Physical Anthropology Sub field of Anthropology concerned with human biology and evolution Developed to explain the extent of physical variation among living peoples Human Biological Variability POLYGENIST S SCHOOL Different groups encountered were in fact different species different creations variability solved MONOGENIST S SCHOOL We are all one species Development of the concept of Race Biological Races Variability seen in typological terms that is types or varieties of humans Physical anthropology became involved in developing the correct racial taxonomy Classification of Human Groups Folk Taxonomies classification of some class of phenomenon based on cultural traditions Do not always correspond to reality Folk Taxonomies of Race in American Culture European African Asian American Indians Hispanics Are these categories reflections of reality Yes and No Folk Taxonomies of Race in American Culture Yes Social Race Social reality reflected in many forms of behavior No Biological Race No biological reality No racial classification scheme has any more scientific merit than any other Ethnocentric ideas Biological Race A population differing in the FREQUENCY OF CERTAIN ALLELES from other populations within the same species Genetic definition Since we cannot determine allele frequency we rely on PHENOTYPIC characteristics ex Skin color Problems with Race Classifications Typologies are seen as static stable divisions in humankind Based on folk taxonomies of cultural tradition Problems with Race Classifications Gene flow reduces variation There are no and never have been pure races Gene Flow is the Rule Problems with Race Classifications White Americans have about 5 African genes 3 native American gene Black Americans have about 20 European genes 3 Native American Native Americans have about 30 European genes 5 African genes Problems with Race Classifications Early anthropologists were looking for statistical averages to define racial groups However they ignored 1 Range of Variation 2 Adaptation to the Environment Traits existed because of Natural Selection Problems with Race Classifications Physical traits evidenced in people around the world were NOT aspects of a TYPE But GENETIC ADAPTATIONS TO ENVIRONMENTS Skin color Dark skin advantageous near the equator greater degree of ultraviolet radiation Light colored skin advantageous away from the equator protection from cold Vitamin D regulation Folic Acid ex neanderthals Clinal Distributions Continuous change in a biological trait or trait frequency over time and space expressed in GRADATIONS Geographic generalizations do exist but there are no boundaries between one expression of a trait and another ex Blood types skin color Clinal Distributions Trait boundaries are ARBITRARY Different traits give different divisions No concordance Cluster of traits are useless as criteria Problems with Racial Types Biological traits show no concordance clusters of traits useless Maybe more variation within defined racial groups than between CULTURE Major adaptive mechanism products of cultural ability social systems technology etc GENETICS Basis for human biological variability All populations are constantly evolving gene frequencies are constantly changing each generation gene frequency cannot be displayed in an individual Human biological races Are at best a statistical abstraction Based on frequency of certain allele characters observed in small populations No stable divisions of humans Human races do not exist in nature as units of study in science Important Points to Remember Biological variation DYNAMIC EVOLUTIONARY PROCESSES As social barriers are erected broken down gene flow patterns change Environmental conditions alter natural selection shifts Mutations are always occurring Human Morphology Behavior Are the products of the dynamic interaction between CULTURAL BIOLOGICAL ENVIRONMENTAL VARIABLES Interests of Science Today HOW human biological variation came about in terms of the EVOLUTIONARY PROCESSES which created it WHAT biological traits are POLYMORPHIC determine their GENETIC BASIS WHY is a trait polymorphic POLYMORHPIC TRAITS SIMPLE controlled by a single gene of alleles stable throughout life COMPLEX controlled by many genes traits are unstable environment developmental changes ex Blood groups ex Skin color stature Example of SPT large set of SPT 30 or more blood groups ABO System I gene Ia Ib Io ABO Blood System 6 GENOTYPES 4 PHENOTYPES AA AO BB BO AB OO type A type A type B type B type AB type O Simple Polymorphic Trait Use blood types in Paternity Cases Punnett Square Simple Polymorphic Traits Important easy to trace useful for purposes of comparing populations at the genetic level Complex Polymorphic Traits More difficult to trace multiple genes are involved inability to determine exact number they undergo environmental and developmental influences CPT SKIN COLOR varies with regard to amounts of sunlight striking the earth s surface at different latitudes NOSE FORM relationship with the temperature and moisture content of the air BODY BUILD selected to some extent according to ave temperature in an area Complex Polymorphic Traits Important in reconstructing the evolutionary history of human polymorphic traits Why are there genetic differences We don t know completely All we can do is indicate traits and genes that seem to be distributed because of ADAPTATIONS to environments And carried along by the movements of people and reflect ANCESTRY ADAPTATION ANCESTRY HUMAN POPULATION DIFFERENCES Both processes may act together