Why do we have different skin colors?

People have different skin colors because of melanin and Ultra violet radiation. Millions of years ago, people live in  equator region receives more sunlight and hence they receive more UV radiation. Their skin absorbs these UV radiations to produce Vitamin D. But excess radiation can cause damage to the body. Hence, in order to prevent their body from the over exposure of UV radiation, their body secretes melanin pigment. Thus, these people and their succeeding generations adapted more melanin in their skin and hence their skin looks black in color. In case of polar regions like Artic and Antartic, people receive lesser UV radiation as compared to equator. Hence, in order to absorb more UV radiation to produce vitamin D, these people and their following generations adapted to have a lower level of melanin. Thus, making their skin lighter.