e- This question may be completed independently or as a group discussion. Variou

Question

e- This question may be completed independently or as a group discussion. Various cultures design gories differently, and they often base these categories on very different traits. For example, some cuitures nose shape as one of the defining traits for a racial group. Other cultures do not use nose shape in cial groups, but use hair color instead. What do differences in racial classification such as these s the universality of race and racial groupings? defining ra uggest abou 2. This question may be completed independently or as a group discussion. Review Figure 8.2. Note that skin might this be the ors are a little lighter in equatorial parts of the Americas than they are in equatorial Africa. Why case? (Hint: Think about the possible impact of evolutionary forces other than natural selection.) bution. This 3. This question may be completed independently or as a group discussion. Skin color has a clinal distri is true for many of our other traits as well. Describe one huma think has a clinal distribution n trait, other than those discussed here, that you 4. This question may be completed independently or as a group discussion. In Exercise 3, you considered the adaptations of people living in the Andes Mountains. What other adaptations do you think would be beneficial to indigenous people who live in similar high-altitude environments? Are there any other places in the world where you might expect to find populations with these adaptations to high altitude? (Use material in your classroom, in books, or online to help you.)

Explanation / Answer

3) There is a direct correlation between the geographic distribution of UV radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Areas that receive higher amounts of UVR, generally located closer to the equator, tend to have darker-skinned populations. Areas that are far from the tropics and closer to the poles have lower intensity of UVR, which is reflected in lighter-skinned populations. Researchers suggest that human populations over the past 50,000 years have changed from dark-skinned to light-skinned and vice versa as they migrated to different UV zones, and that such major changes in pigmentation may have happened in as little as 100 generations through selective sweeps. Natural skin color can also darken as a result of tanning due to exposure to sunlight

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