ANTH 1013 1st Edition Lecture 8 Outline of Last Lecture I. Microevolution vs. MacroevolutionII. What is a species?III. Biological Species ConceptIV. How do new species form?V. MacroevolutionVI. Evolutionary Species ConceptOutline of Current Lecture I. Phenotypic variationII. Biocultural evolutionIII. Big pictureCurrent LectureI. Phenotypic variationi. Biological evolution: a change in allele frequency over timea. For evolution to occur we need allelic variation and that variation has to be heritable1. Alleles are constantly being created by mutations2. Once variation is present, genetic drift, gene flow, and natural selection take overb. Modern humans are phenotypically variable1. There are multiple reasons for this variation: a. Biological adaptationi. Natural selectionii. Biocultural evolutionb. Genetic driftc. Gene flowd. Acclimatione. Acclimatization2. Skin color: the amount and distribution of melanin, a pigment, causes the variation we observe in skin tones3. UV radiationa. Latitudinal gradient: most intense at equator, weakest at polesb. Elevational gradient: more intense at higher altitudesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.c. Dark skin acts as a natural sunblock4. Folate destructiona. UV radiation causes mutations, which lead to skin cancerb. But that’s not the only harmful effect of UV radiation. It alsodestroys folate, which is an important chemical for cells when they are rapidly dividingc. Sunlight and vitamin D production1. One benefit associated with exposing your skin to the sun is vitamin D production2. Vitamin D deficiency can lead to:a. Bone painb. Osteoporosisc. Muscle weaknessd. Muscle twitching3. If dark skin reflects radiation more effectively than light skin, then light skin manufactures vitamin D more readilya. African-American men living in the northern third of the US are 3.5 times more likely to be vitamin D deficient than light-skinned men4. What about before vitamin D supplements were available?a. Fish!d. Skin color: the big picture1. Skin color is a balancing act between the evolutionary demands of photo-protection and the need to create vitamin D in the skin2. Plus, we buffer vitamin D deficiencies with our dietii. Natural selection: human body size and shapea. Bergmann’s rule: endotherms in cold regions tend to be larger in body size than those from warmer regionsb. Allen’s rule: endotherms from cold regions have shorter limbs than populations from warmer regions1. In tropical climates, human body shape is adapted for losing heat2. In cold climates, human body shape is adapted to retain heatII. Biocultural evolutioni. The interaction between biology and culture in human evolutiona. Biocultural evolution is the coevolution of genes and cultureii. Lactose digestiona. Lactose (milk sugar) is broken down by the enzyme lactaseb. The typical adult human (and other mammals) phenotype is to not be able to digest milk sugar (lactose intolerance)c. Typically adults gradually stop manufacturing lactase after we are weanediii. Sickle cell and malariaa. According to some estimates, malaria has been the number one infectious killer of humans throughout our evolutionary historyb. As recently as 2004, 1.8 million people are estimated to have died from malarial infectionc. Sickle-cell hemoglobin protects from malarial infection1. Heterozygote advantage: the heterozygotes have a higher fitness than either homozygote2. Balanced polymorphism: stable frequencies of allelesiv. Genetic drifta. Old order Amish trace their ancestry to as few as 200 German immigrants, and they do not practice exogamy with other groups. As a result, they have experienced lots of genetic drift and rare traits elsewhere are now common.1. Ellis-van Creveld syndrome: causes polydactyly, congental heart defects, natal teeth, dwarfism, cleft palate, and other conditions2. PKU – 10x more likely to have it if you are born in the Amish community – inhibits brain growthb. The colony of Tristan de Cunha was founded by 15 people in 1814. One of them was heterozygous for a recessive disorder called retinitis pigmentosa1. Today the frequency of that allele in the descendants is 10x higher on Tristan than in the UKc. Ashkenazi Jews formed a fairly isolated gene pool in Europe with little exogamy. As a result, their descendants have elevated frequencies of some rare traits.1. Tay-sachs syndrome: 1/25 Ashkenazi Jews are estimated to be carriers of the recessive allelev. Gene flowa. African American populations have rates of European admizture of up to 25% in the United statesb. Because of gene flow among populations, we tend to see a spatial patterning of allele frequencies1. The gradual change in allele frequency across space is called a clinec. Variation that isn’t adaptive1. Humans are also variable because they respond to their environment2. Acclimation: immediate physiological response to environmental stressa. Shivering in cold climates; taking deep breaths in low oxygen environments3. Acclimatization: a change of an individual’s phenotype in response to changing environmental conditionsa. Adjusting to high altitudes. In response to decreasing partialpressure of oxygen at high altitudes your body responds by producing more red blood cellsIII. Big picturei. Physiological changes due to acclimation and acclimatization are not heritableii. Adaptation: the outcome of natural selection, the population’s gene pool evolves to meet the demands of the environmentiii. Humans as a species are ridiculously varieda. Some of this variation is adaptive and can be linked to natural selection, and some to interactions between culture and biologyb. Some variation is best explained via gene flow and genetic driftc. And some variation is not adaptive, and is only short termiv. Categorize human populations and understanding