Black and White: an adaptation Why are people different colors?

The short answer is: different amounts of melanin The short answer is: different amounts of melanin. Melanin is a pigment that absorbs UV light

4.5 – 2 million years ago people lived in the savanna. The savanna is hot … and sunny

Advantages of being black or: natural selection pressures for black skin Dark skin blocks more UV radiation Too much sunlight decreases the amount of vitamin B (folate) in the body. In pregnant women, low vitamin B can cause infants to be born without a full brain or a spinal cord.

When people started to move to less sunny areas When people started to move to less sunny areas... Evolutionary pressures changed

Advantages of being brown or: natural selection pressures for lighter skin Lighter skin absorbs more UV radiation. The body needs sunlight to produce vitamin D. Without vitamin D, the body cannot store calcium in the bones and people develop rickets.

But skin too light may mean too much UV radiation, excess vitamin D and excessive calcium build up... calcification of soft tissues

So: Where are white people So: Where are white people? Skin color of indigenous people around the world

White are de-pigmented (with no melanin) people that originated in Scandinavian countries.

Typology: pre-scientific idea that there are different “types” of people.