A Rainbow of Sepia
The Evolution of Human Skin Color
Continuing Studies and Executive Education
This flipped case study examines the selective pressures that have affected the evolution of diverse human skin pigmentations. To prepare for the case, students begin by watching videos and doing research on their own. In class, students use the information they have learned to answer questions that follow the research of Penn State anthropologist Nina Jablonski. As students work through the case they alternate between reading sections of the case study handout and viewing short video segments that reinforce concepts and engage students in the story of the real-world protagonist. At the end of the 90 minutes, students realize that several opposing pressures can act on one trait and that evolution can be a balancing act. This case is appropriate for AP and freshmen biology students who are completing a unit on evolution. It is adapted from an earlier case by the same author, “The Evolution of Skin Color.”
- Describe the evidence that human skin pigmentation is subject to natural selection.
- Explain how UV radiation impacts folate and vitamin D levels.
- Describe how skin color is a compromise between two evolutionary pressures.
- Predict the level of skin pigmentation of a population, if given information about the location where they evolved and their diet.
- Develop strategies to maximize their vitamin D and folate levels based on their skin pigmentation and where they live.
- Analyze graphical information.
KeywordsEvolution; skin color; melanin; natural selection; fitness; selective pressure; UV; ultra violet radiation; folate; vitamin D;
Educational LevelHigh school, Undergraduate lower division
Type MethodsInterrupted, Flipped
Subject HeadingsBiology (General) Evolutionary Biology Anatomy Biochemistry Cell Biology Genetics / Heredity Medicine (General) Molecular Biology Nutrition Physiology Public Health Science (General)
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The following video(s) are recommended for use in association with this case study.
- The Making of the Fittest: Natural Selection and Adaptation
This video focuses on the rock pocket mouse to show how quickly a trait can spread through a population when natural selective pressure is strong. Running time: 10:31 min. Produced by HHMI Biointeractive, 2011.
- How We Get Our Skin Color
This animation shows how human skin cells produce the pigment melanin and how a person’s unique skin color is determined by three primary factors: the type of melanin produced, how much of it is produced, and how it is distributed in skin cells. Running time: 3:32 min. Produced by HHMI Biointeractive, 2015.
- The Biology of Skin Color
Anthropologist Nina Jablonski presents the evidence in support of the hypothesis that the different shades of skin color among human populations arose as adaptations to the intensity of ultraviolet radiation in different parts of the world. Running time: 18:57 min. Produced by HHMI Biointeractive, 2015.