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The Evolution of Skin Color

Middle school learnscience.org

Name Date

Predict

Human skin comes in many shades, from light to dark. Sunlight carries ultraviolet (UV) light, the part of sunlight that causes sunburn. Could the sun be part of the reason human skin comes in different colors?

Circle one. Yes / No

Why?

Watch

  1. The Evolution of Human Skin Coloryoutube.com/watch?v=-KkydZWlF3Y

Word of the day

Adaptation (ad-ap-TAY-shun). A trait that helps a living thing survive and have babies in its environment. An adaptation spreads through a group of living things over many generations.

Word partComes fromMeaning
ad-Latin ad-to, toward
apt-Latin aptāreto fit
-ationLatin -ātiōmakes the word a noun
  • An adapter helps a plug fit an outlet with a different shape.
  • Migration, moving from one place to another, ends in the same -ation.

Bonus word. Ultraviolet (uhl-truh-VY-uh-lit). Ultraviolet light, or UV light, is a part of sunlight that human eyes can’t see. Ultra- comes from the Latin word for “beyond.” Ultraviolet means beyond violet, the last color of the rainbow people can see.

Questions

  1. Melanin is a dark pigment, or coloring, in your skin. Melanin absorbs, or soaks up, UV light. How does melanin protect your skin from UV light?

    Hint. Think about what happens to UV light that melanin soaks up near the surface of the skin.

  2. Charles Darwin sailed around the world on a ship called the HMS Beagle. He wrote down that people’s skin was darker near the equator and lighter toward the poles. The equator is the imaginary line around the middle of Earth. Much later, NASA satellites measured the sun’s UV light all over Earth for years. Where did Darwin see the darkest skin? And what did the NASA UV map show in that part of the world?

    Hint. On the UV map in the video, hot pink and red show the most UV. Where are those colors?

  3. Skin uses a kind of UV light called UVB to make vitamin D. Vitamin D helps the body build strong bones. Melanin blocks some UVB. Why would lighter skin help people who live where UV light is weak for much of the year?

    Hint. Think about how much UVB gets into skin that has less melanin.

  4. Today, many people live far from the places where their ancestors lived for thousands of years. What health problem could a person with dark skin face in a place where winter UV light is weak?

    Hint. Think about which vitamin the skin makes with UVB light.

Exit ticket

In the video, Raven explains that skin color is a balance. Melanin blocks UV light, and blocking UV protects DNA from damage. Skin also needs some UV light to make vitamin D. Why did darker skin help people near the equator, while lighter skin helped people far from the equator?

Hint. Think about DNA damage and vitamin D.

Sources