Anthropologists have been interested in evolution of skin color for a long time, but I believe that anthropologists and other scientists should study about it for many reasons. Here is one of many reasons.
Boyle (1970) and others observed association between skin color and high blood pressure among African Americans long time ago, and in these studies, skin color was used as a proxy for admixture and Africa ancestry. However, subsequent studies demonstrated complex relationship between skin color, socioeconomic status, and blood pressure.
For example, Klag et al. (1991) observed the association between skin color and blood pressure in African Americans, and they showed that darker-skinned African Americans tend to have increased blood pressure. They also show that this association depends on the socioeconomic status. Among African Americans in the lowest socioeconomic status, darker-skinned African Americans had considerably higher blood pressure level than lighter-skinned African Americans, but they did not observe the same pattern among the African Americans in the higher socioeconomic status. In their multivariate regression analysis, they observed significant interaction between skin color and socioeconomic status associated only with diastolic blood pressure. Moreover, they showed that whether African Americans completed high school education or not had a significant effect on blood pressure and again they observed statistically significant interaction between skin color and education (please note that survey data was collected between 1972-1974).
More recent study by Sweet et al. (2007) reported similar findings. They also found that darker-skinned African Americans have higher blood pressure in the CARDIA study, and they found the significant interaction between skin color and income. In a similar study of blood pressure, Gravlee at al. (2005) have shown that skin color is not associated with blood pressure in Puerto Ricans, but social classification based on skin color is associated with blood pressure in Puerto Ricans.
These studies show that both genetic/biological factors and socio-environmental factors have a great impact on blood pressure in African Americans. The effects of both of these factors on blood pressure, and maybe on other disease phenotypes, should be examined simultaneously.