14.6: Human Skin Color Variation - Part II (Worksheet)

Step Two: Understanding the Evolutionary Pressures of Skin Color

Begin this step after completing step one in part one of this activity. Now, watch the film The Biology of Skin Color produced by HHMI BioInteractive. This film explores the hypothesis that different tones of skin color in humans arose as adaptations to the intensity of ultraviolet radiation in different parts of the world. Then, answer the following questions.

1. What color skin do chimpanzees have under their fur?
2. What type of melanin do lightly pigmented people have?
3. What type of melanin do more darkly pigmented people have?
4. What other body parts does melanin color? What does melanin do for other species?
5. What kind of raw data helped Dr. Nina Jablonski find the answer to her questions about the relationship between UV radiation and human skin pigmentation?
6. In general terms, how is UV radiation intensity distributed throughout the world?
7. How do scientists measure skin color?
8. Why are folate and vitamin D important nutrients?
9. Describe the selective pressures for the production of darkly pigmented skin in areas with high UV radiation intensity.
10. Describe the selective pressures for the production of lightly pigmented skin in areas with low UV radiation intensity.
11. Describe the evolutionary interplay between folate and vitamin D.
12. What do scientists infer from the lack of variation in the MC1R gene among African populations?
13. Why are light skinned people at greater risk for skin cancer than dark skinned people?
14. Why might dark skinned people living in high latitude environments need to take a vitamin D supplement? (Note: please always consult your doctor before starting any supplement regimen).
15. Now design a diagram that illustrates the positive and negative selective factors that account for the differences in skin colors among human populations.

Step Three: Bringing it all Together

As Michael Rivera discusses in chapter 13, most human traits, including skin color, are non-concordant. That is, skin color is inherited independently of other genetically controlled traits. Imagine that you are talking with a friend who knows very little about this topic. In one or two paragraphs, summarize in your own words what you have learned in this activity. Explain to your friend how skin color is one piece of evidence for the biological fallacy of race. Describe to them how skin pigment is produced and why it varies between people throughout the world.