What does it mean for a trait such as light skin coloration to be under negative selection in equatorial Africa?

What does it mean for a trait such as light skin coloration to be under negative selection in equatorial Africa?

11. What does it mean for a trait, such as light skin coloration, to be under negative selection in equatorial Africa? Relate negative selective pressure to what we know about MC1R allele diversity among African populations. It means that there is selection against that trait.

How has skin pigmentation evolved over time?

Pigmentation, (skin color), in humans has evolved under selection pressure from the duration and intensity of sunlight. Ancestral populations near the equator were selected for dark skin, while those living in higher northern latitudes were selected for lighter skin.

How is skin color affected by the environment?

The world-wide distribution of human skin color is highly correlated with the intensity of incident UV radiation. Thus, in places where the irradiation is very high, darker colors have been favoured, while at higher latitudes, where the irradiation is lower, lighter skins are predominant (Figure 2).

What two factors influence the shade of a person’s skin?

A person’s skin color is determined primarily by the proportion of eumelanin to pheomelanin, the overall amount of melanin produced, and the number and size of melanosomes and how they are distributed. People with naturally darkly pigmented skin have melanosomes that are large and filled with eumelanin.

What is the relationship between skin coloration and proximity to the equator?

For both males and females, skin reflectance (\%) is lowest at the equator (darkest skin). Among males, skin reflectance increases roughly 8.2\% for every 10 degrees of latitude in the Northern Hemisphere but only 3.3\% for every 10 degrees of latitude in the Southern Hemisphere.

What major problems did early humans face because of the environment?

Our ancestors met astonishing challenges in their surroundings, and were susceptible to disease, injury, and predators. Environmental change – one of the ongoing challenges to survival – created both risks and opportunities in the lives of early humans.

Why are skin colors different?

People have different skin colors mainly because their melanocytes produce different amount and kinds of melanin. The genetic mechanism behind human skin color is mainly regulated by the enzyme tyrosinase, which creates the color of the skin, eyes, and hair shades.