ANTH1102 Lecture 11 Outline of Last Lecture I Evolution A Theories B Darwinian Evolution II Genetics and Evolution III Biochemical Genetics IV Population Genetics A Four Forces of Microevolution Outline of Current Lecture I Evolution continued II Human Variation and Adaptation A Human Biological Diversity i Skin Color ii Blood Type and Disease iii Adaptation B Allen and Bergman s Rules C High Altitude Biological vs Cultural Adaptation Current Lecture Forces of Microevolution continued gene flow exchange of genetic material through interbreeding direct and indirect decreases speciation Punctuated equilibrium Stephen Jay Gould and Niles Eldridge 1972 long periods of stability with occasional evolutionary leaps extinction and succession replacement mutations speed up evolution HUMAN BIOLOGICAL DIVERSITY clinal distribution gradual shift in allele frequencies between neighboring populations forces of microevolution affect geological distribution of varied human traits two types of natural selection directional selection a trait is selected for again and again and sexual selection particular trait s attract more mates Skin Color based on melanin and vitamin D synthesis darker skin within tropics advantages screens out UV radiation protects against skin cancer and sunburn folate destruction and neural tube defects spina bifida outside tropics disadvantages reduces UV absorption increases susceptibility to rickets and osteoporosis lighter skin outside tropics advantages absorbs UV more vitamin D production prevents rickets and osteoporosis within tropics disadvantages susceptible to skin cancer folate destruction neural tube defects and impaired spermatogenesis Skin color is relative to proximity to equator Blood Type and Disease ABO types A type Europe Bubonic plague resistant smallpox susceptible B type Asia smallpox resistant O type the New World syphilis resistant smallpox Bubonic plague cholera susceptible Sickle Cell Anemia and Malaria tend to be simultaneously common in many parts of Africa stabilizing selection and balanced polymorphism HbA HbS Adaptation lactose in tolerance lactose enzyme ability to digest milk biological plasticity ability to change biology or behavior to adjust to environmental changes tolerance in traditionally herder groups 90 Northern Europeans 80 Tutsi and Fulani Africa are lactose tolerant scientist speculations mutation occurred in Turkey 8 000 years ago Mark Thomas 3 different mutations occurred in Africa 6 800 2 700 years ago Sarah Tishkoff There may have been strong selective pressure over short periods of time Hypotheses famine contaminated water sources fertility advantage social prestige and health advantage Allen and Bergman s Rules climate temperatures hot tall thin body types common cold short stocky body types common This is because greater surface area leads to greater heat loss in hot climates people need to cool off more than those in cold climates who need to retain heat High Altitude Biological vs Cultural Adaptation Quechua Southern Peru and Sherpa Nepal are cultures that live at high altitudes hypoxia when lowlanders find it hard to breath in high altitudes biological adaptations rapid physiological responses to stressful conditions timeframe minutes hours e g shivering increased heart rate and red blood cells and elevation of basal metabolic rates developmental adaptations physiological characteristics adapted over time to help survival timeframe years e g increased lung volumes Quechua and greater lung volumes Quechua and Sherpa cultural adaptations clothing housing diet and behavior