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The Evolution of Skin Color, Middle school

A group of friends with a range of skin tones lying on the grass and laughing under a sunny sky

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?

The Evolution of Human Skin Color

This video explains why human skin comes in many shades. It shows how the sun’s UV light, melanin and vitamin D led to different skin colors over many generations. It also covers how people moving around the world changed where skin colors are found.

Video of sunbeams shining through the green leaves of a tree
An adapter helps a plug fit an outlet with a different shape.

Your word of the day is

ad-ap-TAY-shun

ad-to, towardfrom Latin ad-
apt-to fitfrom Latin aptāre
-ationmakes the word a nounfrom Latin -ātiō

A change, produced by natural selection, that makes a living thing better suited to survive and reproduce in its environment.

Microscope image of a stained slice of human skin, with the thin outer layer on top and a small mole made of melanocytes in the layer below

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?

A NASA TOMS satellite map of ultraviolet light reaching the ground, highest near the equator

Charles Darwin wrote down that skin was darker near the equator. NASA satellites later mapped the sun’s UV light all over Earth.

What did the NASA UV map show near the equator, where Darwin found the darkest skin?

Close-up of a person’s open palms lit by bright sunshine

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?

People walking along a snowy street in Berlin, Germany, decorated for the winter holidays

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?

College students with a range of skin tones laughing as they walk together on campus

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?

The whole Earth seen from space on December 7, 2022, with Africa, Asia and Antarctica in view

Lesson complete

Today’s word

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.

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Sources
  1. Nina Jablonski and George Chaplin, Department of Anthropology, Pennsylvania State University, PNAS, 2010
  2. Nina Jablonski and George Chaplin, Philosophical Transactions of the Royal Society B, 2012
  3. Nina Jablonski and George Chaplin, Philosophical Transactions of the Royal Society B, 2017
  4. Nina Jablonski and George Chaplin, Proceedings of the Royal Society B, 2014
  5. Nicholas Crawford, Sarah Tishkoff and colleagues, University of Pennsylvania, Science, 2017
  6. Ann Webb, Lesley Rhodes and colleagues, University of Manchester, Nutrients, 2018
  7. TEMIS, a satellite UV data service hosted by KNMI in the Netherlands, TEMIS UV station data
  8. The UV numbers average the daily cloud-free UV index at local solar noon for December, 2015 to 2024, from the TEMIS station files for Kuala Lumpur and Tromsø. TEMIS defines the clear-sky UV index for cloud-free conditions at local solar noon.
  9. Vision and Change core concepts and competencies, as summarized in Brownell and others, CBE Life Sciences Education, 2014
  10. Word origins from Dictionary.com: adaptation, adapt, ad-, apt, -ation, aptitude, adapter, adjacent, adrenal, ultraviolet, ultra-, photolysis, folate, cline
  11. Folate’s leaf root from Wiktionary, folic acid. Latin aptāre, Spanish and French words from Wiktionary, adaptō, adaptation, adaptación, apto