Biology Problem: Correlating Skin cancer to Skin Color

[bambamm]

Background info: The Canadian Cancer Society provides some statistics about the incidence of skin cancer in Canada. In 2009, there were 5,000 new cases of malignant melanoma diagnosed, and 940 people died of this dangerous form of skin cancer. During 2009, there were 75,100 Canadians diagnosed with non-melanoma skin cancer, and 270 people died of this disease. The median age of diagnosis is 59 for malignant melanoma and 60 for non-melanoma skin cancer. Skin cancer risk increases with UV light exposure, and light skinned Caucasians have a higher incidence of skin cancer than other ethnic groups in Canada.

Q. With reference to the information provided above, explain why skin cancer alone may not have a sufficient impact on fitness to explain variation in human skin colour.

I'm really confused by this question. I'm thinking it is because variation in skin color is influenced by other factors like lifestyle choices and different exposures to UV radiation. But how does this relate to fitness and the above background info? Thanks in advance.

[canalon]

Age, size of population, incidence of the disease should be considered

[Darby]

And your skin does other things that require a certain amount of light penetration.