People living in equatorial countries have a darker skin tone than others. what would be the reason for this change in skin tone?
a. the ancestors of the people living in equatorial countries must have undergone a mutation for protection from malarial parasites and therefore evolved a darker skin tone.
b. the ancestors of the people living in equatorial countries must have undergone evolutionary adaptation for protection from harmful uv rays that fall straight on the equator.
c. people living in equatorial countries develop a darker skin tone due to the exposure to harmful ir rays falling straight on the equator, which damages their skin.