Modern Homo Sapiens: Contemporary Problems


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Addresses the issue of race definitions, the souces of modern human variaton, and the Hardy-Weinberg Equilibirum

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Modern Homo Sapiens: Contemporary Problems

  1. 1. Modern Homo sapiens Contemporary Populations
  2. 2. Migration of Homo sapiens <ul><li>After peopling the Old World, others migrated to new worlds. </li></ul><ul><li>H. sapiens migrated to the </li></ul><ul><li>Near East by 90,000 BP </li></ul><ul><li>East Asia by 50,000 BP </li></ul><ul><li>Europe and Australia by 40,000 BP </li></ul><ul><li>New World by 15,000-30,000 BP </li></ul>
  3. 3. Polytypic Traits <ul><li>When populations migrate </li></ul><ul><li>They may become reproductively isolated </li></ul><ul><li>The potential for speciation exists </li></ul><ul><li>This is mitigated by gene flow, no matter whether </li></ul><ul><li>we all came out of Africa </li></ul><ul><li>whether we all evolved in different regions </li></ul>
  4. 4. Culture and Race: Pop Quiz <ul><li>What is the race of each student? </li></ul><ul><li>What is the cultural background of each student? </li></ul><ul><li>Am I asking the right questions? </li></ul>
  5. 5. Culture and Race: The Answers <ul><li>The first student is Angela Corbett : </li></ul><ul><li>An African American, Native Indian </li></ul><ul><li>“Caucasian” (actually Irish), Hispanic </li></ul><ul><li>The second student is Ethan Hernandez: </li></ul><ul><li>A Latino and Caucasian </li></ul><ul><li>The third student is Roxanne Cnudde : </li></ul><ul><li>Of American Indian, Spanish, Mexican </li></ul><ul><li>And Belgian “heritage.” </li></ul>
  6. 6. Defining Race <ul><li>What is race? </li></ul><ul><li>Skin color? </li></ul><ul><li>Hair texture? </li></ul><ul><li>Race is </li></ul><ul><li>Inherited genetically </li></ul><ul><li>Polytypical outcome of speciation </li></ul><ul><li>Too often confused with culture </li></ul>
  7. 7. Defining Culture <ul><li>Culture is </li></ul><ul><li>Based on learned behavior </li></ul><ul><li>Shared by a group </li></ul><ul><li>Conveyed by symbolic behavior, principally language </li></ul><ul><li>Patterned or Integrated </li></ul><ul><li>Too often confused with race </li></ul><ul><li>Chicanos: self-reference as la raza: </li></ul><ul><li>“ Race” and “ethnicity” used interchangeably in that term </li></ul>
  8. 8. Race and Culture: Related but Different <ul><li>Capacity for culture is inherited through the genes </li></ul><ul><li>Capacity for language </li></ul><ul><li>Capacity for tool making and use </li></ul><ul><li>Genes do not determine the </li></ul><ul><li>Language we speak: English, French, Mandarin </li></ul><ul><li>Tools we make and use: handaxes, pneumatic hammers or drills, computers </li></ul><ul><li>East Indians are as competent English speakers or computer users as North Americans are </li></ul><ul><li>How do we know? They’re taking our jobs! </li></ul>
  9. 9. Why the Confusion? <ul><li>Scientific versus Folk Taxonomy </li></ul><ul><li>Scientific taxonomy: </li></ul><ul><li>Race has no validity </li></ul><ul><li>There is greater variation within groups than between groups </li></ul>
  10. 10. Folk Taxonomy <ul><li>Opinion polls: Caucasian, Negroid, Mongoloid </li></ul><ul><li>Ignores other variants too long to list </li></ul><ul><li>Ignores complexities of the following: </li></ul><ul><li>Skin color: Shades throughout the spectrum </li></ul><ul><li>Hair texture: Straight to curly to kinky </li></ul><ul><li>Blood type: No correlation with other attributes </li></ul>
  11. 11. Clines and Discontinuous Traits <ul><li>Definition of Clinal Distribution (Clines) </li></ul><ul><li>A geographic continuum In the variation of a particular trait </li></ul><ul><li>What are these particular traits? </li></ul><ul><li>Skin color (by melanin content, white to very dark brown) </li></ul><ul><li>Body build (by weight and surface area) </li></ul><ul><li>Discontinuous Variation : Traits with little or no variation </li></ul><ul><li>Example: red hair in United Kingdom </li></ul>
  12. 12. What Can We Conclude About Race? I <ul><li>Race is a product of </li></ul><ul><li>genes --microevolution (polytypic) </li></ul><ul><li>Culture is the product of learning in a shared linguistic context </li></ul><ul><li>Can we ignore race? </li></ul><ul><li>As a purely biological concept, yes </li></ul><ul><li>“ Race is unsupported by scientific evidence </li></ul><ul><li>We cannot ignore biological variations, such as sickle cell anemia blacks </li></ul><ul><li>Or Tay-Sachs disease among Eastern European Jews </li></ul>
  13. 13. What Can We Conclude about Race <ul><li>As a cultural construct, </li></ul><ul><li>Visible differences are always addressed sociologically </li></ul><ul><li>Folk taxonomies persist—including la raza </li></ul><ul><li>A person I know is half-Armenian </li></ul><ul><li>On a form asking race/ethnicity, she writes “Human” </li></ul><ul><li>Lately, she has written “Person of Color, Medium Beige” </li></ul><ul><li>How do I know all this? She’s my wife. (I’m person of no-color myself.) </li></ul>
  14. 14. How did we become all one species? <ul><li>Skin color and hair texture are both products of several genes— polygenic --so we can expect variation </li></ul><ul><li>We move around a lot </li></ul><ul><li>Caribou and reindeer stayed put </li></ul><ul><li>Over 10,000 years evolved into separate subspecies of Rangifer tarandus : reindeer in Eurasia, caribou in North America (see text, pp. 293-295) </li></ul><ul><li>We’ve been around up to 130,000 years, maybe more </li></ul><ul><li>We’re always in search for better resources for food, clothing, and shelter </li></ul><ul><li>Transportation improvements also helped </li></ul>
  15. 15. Adaptation: Skin Pigmentation <ul><li>Skin color may be adaptive: </li></ul><ul><li>Gloger’s Rule : Within a species, more pigmented populations live near the Equator (map, upper left) </li></ul><ul><li>Lighter populations live further away from the Equator </li></ul><ul><li>Rationale: melanin serves as protection against ultraviolet rays of sun </li></ul><ul><li>Applies to all mammals and even birds (sparrows, lower left) </li></ul>
  16. 16. Adaptation: Weight <ul><li>Bergmann’s Rule : Within same species, average (mean) weight of individuals in a population </li></ul><ul><li>increases as the average environmental temperature decreases </li></ul><ul><li>Rationale: </li></ul><ul><li>More storage needed for energy required to survive in cold climates </li></ul><ul><li>See distribution of house sparrows on map (above left) </li></ul><ul><li>Compare white tailed deer in Michigan and Nicaragua (below) </li></ul>
  17. 17. Adaptation: Surface Area <ul><li>Allen’s Rule: Within same species, the relative size of protruding parts of the body (nose, ears), and the relative length of arms and legs increase, as the average environmental temperature increases </li></ul><ul><li>Rationale: </li></ul><ul><li>The greater the surface area, the greater the heat loss (Masai warriors, western Keny, upper left) </li></ul><ul><li>The lesser the surface area, the lesser the heat loss (Athabaskan peoples, near arctic, lower left) </li></ul>
  18. 18. Testing the “Rules” <ul><li>Some populations do conform to the “rules” </li></ul><ul><li>Lighter skin is usually found in the north (Gloger’s Rule) </li></ul><ul><li>Greater fat is found among Inuit, other circumpolar peoples (Bergmann’s Rule) </li></ul><ul><li>Limbs tend to be shorter among northern peoples (Allen’s Rule) </li></ul><ul><li>Darker skin is found among equatorial peoples </li></ul><ul><li>Thinner and long-limbed populations are also found among equatorial populations </li></ul>
  19. 19. Exceptions: Biological Features and Why Culture Matters <ul><li>Dark skinned populations also found in the north (Inuit, East Asians), contrary to Gloger’s Rule </li></ul><ul><li>Northern Europeans (Scandinavian) are long-limbed and thin, contrary to Allen’s Rule </li></ul><ul><li>Cultural adaptations are more important than biological ones </li></ul><ul><li>Culture separates us from direct pressures of natural selection </li></ul><ul><li>Question: How do tropical animals survive in extremely cold climates—like the Inuit (Eskimo)? </li></ul>
  20. 20. Cultural Adaptations: The Igloo <ul><li>How Inuit adapt to the north; the igloo, for one </li></ul><ul><li>Basic Design (see left, and p. 262 of Park text) </li></ul><ul><li>The entrance tunnel keeps out snow and wind </li></ul><ul><li>Entrance chamber face south or east, facing away from prevailing winds and maximizing use of sunlight </li></ul><ul><li>Removable door adds to the insulation </li></ul><ul><li>Ice window and snow block to reflect light from window </li></ul><ul><li>Sleeping platform located where heat rises </li></ul><ul><li>Geodesic dome minimizes wind resistance </li></ul>
  21. 21. Cultural Adaptations and Evolution <ul><li>Subsistence strategies is another cultural adaptation </li></ul><ul><li>Hunting and gathering involves heavy dependence on nature (!Kung hunters, upper left) </li></ul><ul><li>Horticulture: affords greater control of food sources, encourages settlement </li></ul><ul><li>Agriculture: leads to complex societies </li></ul><ul><li>Agriculture, such as this subak irrigation system, allows an unprecedented productvity </li></ul><ul><li>This Balinese system kept the land producing for more than 1,000 years (lower left) </li></ul>
  22. 22. Racism: A Cultural Phenomenon <ul><li>Folk taxonomy </li></ul><ul><li>Misinterpretation of biological attributes that involve an </li></ul><ul><li>unwarranted connection between biological attributes with culture </li></ul><ul><li>Example: Eugenics, or breeding a “superior race” that Francis Galton, a cousin of Darwin, founded </li></ul><ul><li>Example: “Intelligence”: Abilities come in several forms, and there are several kinds of intelligence. </li></ul><ul><li>The threefold category of “Negroid,” “Caucasoid,” and “Mongoloid” has long been refuted, yet this term is still used in police work and even among some sociologists </li></ul>
  23. 23. Measuring Population Stability: Hardy-Weinberg Equilibrium <ul><li>To understand change, we need to examine factors of stability. </li></ul><ul><li>Hardy-Weinberg Equilibrium is a contrary-to-fact formula of population stability </li></ul><ul><li>This formula shows how genotypic frequencies predict static populations with no evolutionary change </li></ul><ul><li>In othr words, mating is random—no partner preference—no mutation occurs, no migration or gene flow, and no genetic drift </li></ul><ul><li>This formula is named after Godfrey Hardy, a mathematician and Wilhelm Weinberg, a physicist, who developed it </li></ul>
  24. 24. Seven Conditions of the Hardy-Weinberg Equilibrium <ul><li>These are the seven conditions, none of which exists in the real world </li></ul><ul><li>1 .  mutation is not occurring </li></ul><ul><li>2.   natural selection is not occurring </li></ul><ul><li>3.   the population is infinitely large </li></ul><ul><li>4.   all members of the population breed </li></ul><ul><li>5.   all mating is totally random </li></ul><ul><li>6.   everyone produces the same number of offspring </li></ul><ul><li>7.   there is no migration in or out of the population </li></ul>
  25. 25. Sickle Cell Anemia as Example, I <ul><li>Refresher on Sickle Cell Anemia </li></ul><ul><li>A – hemoglobin free of sickle cells </li></ul><ul><li>S – hemoglobin with sickle cells </li></ul><ul><li>AS – sickle cell/non-sickle cell heterozygotes </li></ul>
  26. 26. Sickle Cell Anemia as Example, II <ul><li>Conditions of homozygotes/ heterozygotes </li></ul><ul><li>AA – Normal but subject to malaria </li></ul><ul><li>SS – Subject to sickle cell anemia </li></ul><ul><li>AS – Subject to neither sickle cell anemia nor to malaria </li></ul>
  27. 27. Hardy-Weinberg Equilibrium: 2 X 2 Table <ul><li>A Null Hypothesis: the assumption that nothing is happening </li></ul><ul><li>Basic Table (A-normal; S-sickle cell anemia) </li></ul><ul><li>Genotype Product of Frequencies </li></ul><ul><li> AA p X p = p2 </li></ul><ul><ul><li>AS p X q = pq </li></ul></ul><ul><ul><li> = 2pq </li></ul></ul><ul><ul><li>SA q X p = qp </li></ul></ul><ul><ul><li>SS q X q = q2 </li></ul></ul>
  28. 28. Hardy-Weinberg Equilibrium: The Formula <ul><li>p2 + 2pq + q2 = 1 (100%) </li></ul><ul><li>The frequencies are percentages </li></ul><ul><li>The percentages can be any proportion </li></ul><ul><li>This predicts that </li></ul><ul><li>Through the generations </li></ul><ul><li>The percentages of traits remain the same </li></ul>
  29. 29. Hardy-Weinberg Equilibrium: Indications of Evolutionary Change <ul><li>If the percentages change, some evolutionary change has occurred </li></ul><ul><li>Mutation </li></ul><ul><li>Nonrandom mating </li></ul><ul><li>Migration (gene flow) </li></ul><ul><li>Change by chance (genetic drift—if a frequency is very low) </li></ul>
  30. 30. Use of the Hardy-Weinberg Equilibrium <ul><li>Presence of diseases, such as AIDS/HIV </li></ul><ul><li>Impact on population </li></ul><ul><li>Relations with disease-causing species, such as the green monkey </li></ul><ul><li>Genetic diseases impact </li></ul><ul><li>Demographic changes, such as migration (blood types have been used) </li></ul>
  31. 31. Conclusion <ul><li>What we have covered: </li></ul><ul><li>The fallacy of race </li></ul><ul><li>The confusion between race and culture </li></ul><ul><li>Explanations of human physical variations </li></ul><ul><li>The Hardy-Weinberg Equilibrium to anticipate the changes that do take place. </li></ul>