This simulation is based on Nina Jablonski and George Chaplin’s research into the evolution of human skin coloration. They found two selective pressures shaping the variation seen in skin pigmentation. In latitudes with high amounts of UV radiation (UVR) year round, there is a selective pressure for dark skin to protect folate from being degraded by UVR. Alternatively, in latitudes with low levels of UVR throughout the majority of the year, there is a selective pressure for lighter skin pigmentation to allow for photosynthesis of vitamin D.
For this simulation, I created a simple two-gene system for skin pigmentation, with one gene producing eumelanin (a brown-black pigment) and the other creating pheomelanin (a red-brown pigment). There were two alleles for each of these genes, one allele producing a high level of pigment and the other producing a low level. I matched the possible genotype combinations with skin color paints and painted wooden figures for the simulation. This took quite a bit of time, but was worth it. One lesson I learned from my research advisor was to never underestimate the power of representation. By working with a population of little ‘people’, students appeared to have a stronger learning experience with the simulation.
Students determined the possible genotypes of that generation’s children by working out Punnett Squares. If they did so correctly, they ‘unlocked’ a cheat sheet for all other possible genotype combinations. Then, students determined the next generation’s parents based on fitness proportionate selection for their particular latitude. Over time they saw a lightening of skin color in the population in polar latitudes and a darkening of skin color in equatorial regions.
By working through this simulation, students experienced the evolutionary causes of human skin coloration by seeing how skin pigmentation was a response to the environment in which their ancestors lived.
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