Are traditional human race definitions biologically defensible?
1. No, because there is more genetic variation within than between different human races. 2. Yes, because skin color is genetically-influenced. 3. No, because speciation has occurred without reproductive isolation. 4. Yes, because they are the result of natural selection. Why do human populations differ? 1. 2. Natural selection: Example 1 (Fig 11.20): Example 2 (Fig 11.21): Example 3 (Fig 11.23): Why do darker-skinned people have higher fitness in high UV environments (Fig 11.24)? Why do lighter-skinned people have higher fitness in low UV environments? Some people have lighter skin than others, because they need to 1. Produce more folate. 2. Let more UV light in to make vitamin D. 3. Block harmful UV light from destroying vitamin D. 4. Protect folate from destruction due to UV light. Genetic drift: Due to founder effect (Fig 11.25): The red allele has increased frequency in the new population, is it adaptive? Due to bottleneck (Fig 11.25): The red allele has increased frequency in the
