← The Evolution of Skin Color

Teacher guide

Middle school, high school and college

Charles Darwin saw that skin was darker near the equator, and NASA satellites later measured the strongest ultraviolet (UV) light in the same places. Melanin protects DNA from UV, and skin needs some UV to make vitamin D. As people moved away from equatorial Africa, natural selection balanced those two needs. Students follow Raven’s story from Darwin to the satellite maps, then use the evidence to work out why darker skin helped near the equator and lighter skin helped far from the equator. Like the video, the lesson closes on appreciating human differences. Pair this lesson with the melanin lesson.

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

At a glance

Middle school
Grades 6 to 8 · About 33 minutes
High school
Grades 9 to 12 · About 48 minutes
College
College · About 45 minutes
Materials
The worksheet for your level, a screen for the video.
Grouping
Students work alone. For partners, pair students for Questions.
Phenomenon
Charles Darwin saw that skin was darker near the equator and lighter toward the poles, and NASA’s satellite UV maps show the same pattern. Among people whose families lived in one region for many generations, skin is darker where UV stays strong all year and lighter where UV is weak and seasonal.
Topics
Skin color, UV light, DNA damage and skin cancer, vitamin D, satellite data, human migration, including forced migration. The high school Going further adds folate and healthy babies.

Preview the video before sharing it with your class.

Video and transcripts

  1. 1

    The Evolution of Human Skin Color

    Covers melanin, vitamin D, the environment and human migration.

    Watch on YouTube
    Transcript

    Transcribed from the posted video on YouTube. The thank-you to Patreon supporters near the end is left out.

    Hi everybody, welcome back to my channel. I’m glad to be back. If you have not seen my last video on the science of melanin, I’m going to link it here and you can click on it, watch it. But if you did watch it already, then you are already a melanin expert, and you are ready to move forward and understand about the evolution of human skin color over the past thousands of years.

    If that’s something that you’re interested in learning about today, then make sure you keep watching, take notes, buckle up, because you’re about to learn some science.

    If you recall, in the last video I talked about the role of melanin and what it does for skin color. There’s different types of melanin, yes. Melanin can play a role in protecting our bodies from the sun. That is going to be an important thing to remember for this video. So keep that in mind, or visit the last video for a refresher if you didn’t remember.

    Let’s talk about this as a story, right? Because science really, science really is a story. I’m going to preface this story with a story about Charles Darwin, but I don’t want you guys to assume that the science of skin color started with Charles Darwin. This was something that was always occurring in history. It’s a natural phenomenon.

    There just so happened to have been somebody with enough privilege to be able to travel around the world and make observations and write them down. He made a lot of contributions to our understandings of evolution today. He traveled around the world in a ship called the HMS Beagle, and he produced a few works that are very well known, one of which is called The Origin of Species.

    Charles Darwin, in his travels and in his observations of humans and other organisms on the planet, documented that human skin color was darker at the equator of the Earth and lighter as you went towards the poles of the Earth. And he kind of left that at that. He didn’t say too much, but what he did say was that he didn’t think that it was related to climate.

    But we know so much more now about humans, about our planet Earth, than we did in the 1800s. Thanks to technology, NASA has put out a multitude of satellites that orbit the Earth and take measurements of different things. NASA has put something out called TOMS satellites, and those are Total Ozone Mapping Spectrometer satellites.

    And they have the capability to measure ozone values of the planet, and they also have the capability to put out information about the planet’s UV radiation. So we have years and years of data that shows us what parts of the Earth are receiving what amounts of UV radiation.

    If you are a true science maven, okay, then you are reflecting back on the last video that I made about melanin and UV radiation. Pause the video. If you remember what I taught you in the last video, write it down in the comment section. Pause it and write it. I want to know if you remember what I taught you.

    From these TOMS satellites, we were able to create a graphic of UV radiation dispersal across the planet, and we also see a pattern. I’m going to put these graphics next to each other so you can look for yourself and see the patterns of human skin color in the world versus the patterns of what areas of the planet receive the highest amounts of UV radiation.

    The really hot pink and red areas of this map are those parts of the world that receive the highest amounts of UV during the year. Cooler colors, those blue, greens, yellows and grays, are areas that have much lower amounts of UV radiation.

    When you look at the human skin color map, you also see that very interesting gradient where you have very darkly pigmented skins concentrated around the equator, and then you have lighter skin pigments radiating out from the equator towards the poles. And this is not by coincidence. Remember what I taught you in the last video about melanin and how melanin protects from UV radiation.

    It’s very important to remember here that humans evolved in equatorial Africa, which means that the earliest humans lived there. So that environment, the climate there, the radiation that was happening in equatorial Africa impacted how humans evolved. The earliest humans had dark skin. They had lots of melanin because they lived at the equator.

    If you watched my previous video, you would know that that is a good thing. It’s a great thing if you live at the equator to have lots of melanin, because melanin protects you from UV radiation. Without UV radiation protection, you can have damage to your DNA and ultimately perhaps get something like skin cancer or various types of cancer. Melanin helps to absorb that sunlight and protect your skin, your cells, your body from UV radiation.

    But one thing that I did not tell you in that last video was that UV radiation actually helps you to produce vitamins in your body. Yes, the sunlight actually plays a role in vitamin production in human beings. And that vitamin that’s produced with the help of the sunlight is called vitamin D.

    And we need vitamin D, okay? We need vitamin D. Vitamin D helps us to produce strong bones, it helps us with our immune system, and it also plays a role in a lot of other functions in our bodies. So vitamin D production is very important, and it is made with the help of sunlight.

    Let’s talk about evolution on a grand scale, thousands of years. Humans did not stay in equatorial Africa. We moved, okay? We migrated all around the world. As that happened over thousands of years, our bodies began to make adaptations. As we moved away from the equator, the levels of melanin that our bodies had were no longer suiting what our bodies needs were.

    Remember, we need vitamin D, okay? We need vitamin D, but we also don’t want to have damage to our DNA from UV radiation. Our bodies have to consistently figure out how much melanin we need to be successful as a species.

    As humans moved away from the equator, we got lighter and lighter and lighter and lighter. Why? Because as you move away from the equator, UV radiation decreases and decreases and decreases and decreases.

    So over time, our skin color lightened because we needed to find the balance between existing in the right amount of UV radiation and also having a dark enough skin color to block out excess UV radiation, right? We need to make vitamin D, but we also didn’t want to have too much melanin to block out the sun rays, which help us make vitamin D, right? So if there’s less UV radiation, we don’t need as much melanin.

    Vitamin D deficiency can kind of creep up on you. We’re [unclear] trying to creep up on you and cause a lot of problems, like problems with your immune system, problems with your mental health, and probably some problems with your bones as well. So it’s very important that we maintain a proper amount of vitamin D in our systems.

    Now, let’s talk about why we see people of different skin colors all over the world today. We moved around quite a bit, okay? All of the things that I’ve talked about as far as humans migrating from equatorial Africa out into the rest of the parts of the world, that happened for thousands of years.

    I mean, tens of thousands of years it took humans to move out from equatorial Africa into different parts of the world. So all of the variations of skin color that you see today are a result of tens of thousands of years of evolution, right?

    But I’m a Black woman and I live in New York. You know what I’m saying? I live in New York. I’m very far from equatorial Africa. That has a lot of societal implications, okay? A lot of cultural implications that we can’t get into in this video because it’s too deep, and I’ll be talking forever.

    But we all know why people like me are in New York right now, okay? We moved way faster in the past 400 years than we’ve ever moved in the history of humanity, and that is why we see such a mixture of people all around the world.

    We’ve had our ups, we’ve had our downs, but I think one thing that we must appreciate are our similarities and our differences, because they’re all so beautiful. They are all so telling of our grand history that we have as a species.

    I mean, the fact that dark people like me, I mean, even darker people, there’s people that are as dark as my hair that exists on this planet, and people as light as this sheet of paper that exists on this planet. It’s so beautiful. And I think we need to really sit down and appreciate that, the processes that we’ve gone through over time to even display all of these differences in who we are.

    So if you see someone who looks different than you, maybe has a different skin color, maybe a different set of features, learn how to appreciate that. Take that in, and just remember that that is thousands and thousands of years of nature doing its thing, making us all unique and beautiful in our own special ways.

    Keep being your unapologetic selves, and I’ll see you next time. Bye, guys!

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

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

Word partComes fromMeaning
ad-Latin ad-to, toward
apt-Latin aptāreto fit
-ationLatin -ātiōnoun ending for an action, process or result
ultra- in ultraviolet (bonus word, middle and high school)Latin ultrābeyond, on the far side
fol- in folate (bonus word, college)Latin folium, by way of folic acidleaf
cline (bonus word, high school and college)Greek klī́neinto lean

Same roots, other subjects

  • BiologyThe adrenal glands sit on top of the kidneys. Adrenal joins ad- with Latin rēnēs, “kidneys.”
  • MathIn a right triangle, the adjacent side runs from a chosen angle to the right angle. Adjacent comes from Latin adjacēre, “to adjoin,” formed from ad-, “toward,” and jac-, “lie.”
  • ChemistryOxidation, evaporation and condensation end in the same -ation, the ending that names an action or process.
  • EngineeringAn adapter lets a plug fit an outlet with a different shape. Adapter joins adapt with -er.
  • EnglishApt means suited to the purpose, and aptitude means a natural ability. Both come from Latin aptus, “fastened, fitted.”
  • World languagesSpanish says adaptación and French says adaptation. Spanish apto means fit or suitable, from Latin aptus.

Word hunt. Ask students to find three more words that end in -ation, such as migration, and say what action or process each word names.

Dictionary.com traces adaptation to Latin adaptāre, “to fit, adjust,” from ad-, “to,” and aptāre, “to fit,” plus the noun ending -ation. In the video, Raven says “our bodies began to make adaptations” as people moved away from the equator over thousands of years. The change happened across many generations through natural selection, not inside one person’s body. Jablonski and Chaplin describe human skin color as an adaptation to UV. The middle and high school bonus word, ultraviolet, joins ultra-, “beyond,” with violet, for light beyond the violet end of the rainbow. Cline and folate come from the papers, not the video. Folate takes its name from folic acid, named from Latin folium, leaf, for the leafy vegetables that contain the vitamin. A cline is a gradual change in a trait across a geographic area, and Jablonski and Chaplin describe human skin color as two opposing clines. The authors call UV’s breakdown of folate photolysis, from Greek phôs, “light,” and lýsis, “a loosening.” The worksheets carry a short version. Use these for discussion or a word hunt.

Lesson flow

Lesson flow level
  1. 3 minPredictStudents answer the question and write one sentence.
  2. About 10 minVideo
  3. 4 minWord of the dayBreak the word into its parts together.
  4. 8 minQuestionsStudents answer on their own, then share out. With partners, pairs discuss first.
  5. 5 minExit ticket
  1. 3 minPredictStudents answer the question and write one sentence.
  2. About 10 minVideo
  3. 4 minWord of the dayBreak the word into its parts together.
  4. 8 minQuestionsStudents answer on their own, then share out. With partners, pairs discuss first.
  5. About 15 minClaim, evidence, reasoning and Going furtherStudents list evidence for the claim from the video and the UV numbers, then write the reasoning. The Going further question adds folate, research beyond the video.
  6. 5 minExit ticket
  1. About 10 minVideo
  2. 4 minWord of the dayBreak the word into its parts together.
  3. 3 minPredict
  4. About 20 minRead the paperStudents read Table 1 of the paper and answer the questions. The paper reading works as homework or a discussion section.
  5. 5 minExit ticket

Video simplifications

Skin cancer, vitamin D and folate
In the video, Raven gives two reasons tied to UV. Melanin protects against UV damage to DNA, which can lead to skin cancer. People need vitamin D, made with the help of sunlight, for strong bones and the immune system, and Raven adds that low vitamin D can cause problems with the immune system, mental health and bones. The middle and high school worksheets teach the balance between these two needs. The video doesn’t mention folate. Among the student questions, only the high school Going further brings in folate, labeled as research beyond the video, and the college bonus words define folate. Jablonski and Chaplin argue that UV also breaks down folate, which the body needs for healthy babies, and they weigh folate protection above skin cancer as a pressure behind dark skin near the equator. They argue that sunburn and skin cancer have little effect on reproductive success.
Darwin and climate
Raven says Darwin didn’t think skin color was related to climate. Jablonski and Chaplin write that Darwin “rejected a causal association of skin pigmentation with climate” and preferred sexual selection as the explanation. Satellite UV data came more than a century later.
“We moved way faster in the past 400 years”
Jablonski and Chaplin describe “over 500 years of voluntary and involuntary long-distance migrations.”
Culture
Natural selection under UV produced the range of skin colors. Culture changed how much skin color affected health. Clothing, shelter and vitamin D-rich diets let people live where skin alone could not supply enough vitamin D. Migration also mixed skin color gene versions. A light-skin gene version reached East Africa through gene flow from outside Africa.
Pronunciation
Ultraviolet is uhl-truh-VY-uh-lit. Folate is FOH-layt. Photolysis is foh-TOL-uh-sis.

Worksheet

Worksheet level
Print the middle school worksheet
The Evolution of Skin ColorMiddle school learnscience.org

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

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.

Print the high school worksheet
The Evolution of Skin ColorHigh school learnscience.org

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

Watch

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

Word of the day

Adaptation (ad-ap-TAY-shun). A heritable trait that evolved through natural selection and makes a living thing better suited to survive and reproduce in its environment.

Word partComes fromMeaning
ad-Latin ad-to, toward
apt-Latin aptāreto fit
-ationLatin -ātiōmakes the word a noun
  • An adapter lets a plug fit an outlet with a different shape.
  • Apt means suited to the purpose, and aptitude means a natural ability. Both come from Latin aptus, “fitted.”

Bonus words. Ultraviolet (uhl-truh-VY-uh-lit) names light beyond violet, the shortest-wavelength color people can see. The word joins Latin ultrā, “beyond,” with violet. Cline (KLINE) means a gradual change in a trait across a geographic area, from Greek klī́nein, “to lean.”

Questions

  1. Eumelanin is the brown-black form of melanin. Eumelanin absorbs UV light, and skin needs UVB light to make vitamin D. What trade-off does eumelanin create between UV protection and vitamin D? And how does the trade-off change with distance from the equator?

    Hint. Name one thing eumelanin protects and one thing eumelanin limits.

  2. Charles Darwin noticed that skin was darker near the equator and lighter toward the poles. Much later, NASA’s Total Ozone Mapping Spectrometer (TOMS) satellites measured UV across Earth for years. In the video, Raven sets the UV map beside a map of human skin color. What pattern do the UV map and the skin color map share? And why does a match between two maps need more evidence before it shows that UV caused the skin color pattern?

    Hint. A match shows that two things change together. Think about where the first humans lived and what happened to skin color as people moved.

  3. In the video, Raven explains that sunlight helps the body make vitamin D. Skin uses UVB light to make vitamin D, and melanin blocks some UVB. Far from the equator, UVB is weak for much of the year. What does vitamin D do for the body? And why did less melanin help people far from the equator make enough vitamin D?

    Hint. Name two jobs of vitamin D from the video. Then think about how much of the weak UVB gets into skin with less melanin.

  4. In the video, Raven says people moved faster in the past 400 years than ever before in human history. Voluntary and forced migrations took many people to places with UV far different from their ancestors’ homelands. What health risk could a person with dark skin face far from the equator? And what risk could a person with light skin face where UV is strong?

    Hint. One risk involves vitamin D. The other risk involves sunburn.

Claim, evidence, reasoning

Read this claim. Human skin color varies with distance from the equator because natural selection balanced two needs, protecting DNA from UV and making vitamin D. In December, the midday UV index is about 11.6 in Kuala Lumpur, Malaysia, near the equator, and 0.0 in Tromsø, Norway, far to the north. What evidence from the video and the UV numbers backs this claim? And what reasoning links the evidence to the claim? List at least three pieces of evidence, then write your reasoning.

Hint. Use Darwin’s observation, the UV map and the skin color map, where the first humans lived and the December UV numbers.

Going further: research beyond the video

  1. This question goes beyond the video. Scientists Nina Jablonski and George Chaplin study how human skin color evolved. They argue that strong UV also breaks down folate, a B vitamin the body needs to make new cells and to have healthy babies. Melanin blocks UV, which means darker skin protects folate as well as DNA. How does the folate idea from Jablonski and Chaplin add a second reason that dark skin helped people near the equator?

    Hint. The video gives one reason, protecting DNA. Think about what strong UV does to folate and why a growing baby needs folate.

Exit ticket

In the video, Raven describes skin color as a balance. Melanin blocks UV that can damage DNA, and skin needs some UV to make vitamin D. What two needs did natural selection balance to produce the range of human skin colors? And where was each need most important?

Hint. One need protects DNA from strong UV. The other need lets skin make vitamin D from weak UV.

Print the college worksheet
The Evolution of Skin ColorCollege learnscience.org

Watch

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

Word of the day

Adaptation (ad-ap-TAY-shun). A heritable change in an organism, resulting from natural selection, that makes the organism better suited to survive and reproduce in a particular environment.

Word partComes fromMeaning
ad-Latin ad-to, toward
apt-Latin aptāreto fit
-ationLatin -ātiōnoun ending for an action, process or result
  • Apt and aptitude come from Latin aptus, “fastened, fitted.”
  • Adjacent and adrenal share the prefix ad-, “toward.”

Bonus words. Folate (from Latin folium, “leaf”) names a B vitamin whose main blood form, 5-methyltetrahydrofolate, breaks down under UV. Cline (from Greek klī́nein, “to lean”) describes a gradual change in a trait across a geographic range.

Predict

  1. Jablonski and Chaplin mapped the world into zones by how well lightly pigmented skin can make vitamin D from casual sun exposure. In the equatorial zone, casual sun gives enough UVB all year. Before you read the paper, take a guess. What percent of the world’s people live in the equatorial zone? Give your reason in one sentence.

    Hint. The equatorial zone covers about 41% of the world’s land.

Read the paper

Jablonski and Chaplin, “Human skin pigmentation, migration and disease susceptibility,” Philosophical Transactions of the Royal Society B, 2012. The paper is free to read.

Jablonski and Chaplin sorted the world into vitamin D zones for lightly pigmented skin. In the equatorial zone, casual sun exposure gives enough UVB to make vitamin D all year. In the subtropical and warm temperate zone, at least one month has too little UVB, and people rely on stored vitamin D. In the cold temperate and polar zone, UVB averaged over the year falls short, and people need vitamin D-rich foods such as oily fish. Table 1 of the paper counts the people living in each zone, using population estimates from 2000.

ZonePeople (millions)Percent of world populationPercent of land area
Southern Hemisphere cold temperate and polar0.363.6
Southern Hemisphere subtropical and warm temperate9516.5
Equatorial3,19840.7
Northern Hemisphere subtropical and warm temperate2,39215.2
Northern Hemisphere cold temperate and polar38624.0

  1. Quantitative reasoning Start by adding the People column to get the world total. Then fill in the percent column. What percent of the world’s people live in zones where lightly pigmented skin has at least one month without enough UVB? And which hemisphere holds most of those people?

    Hint. All four zones outside the equatorial zone have at least one month with too little UVB.

  2. Process of science Table 1 uses zones drawn for lightly pigmented skin. The authors write that for darkly pigmented skin, the vitamin D safe zones are smaller and shifted toward the equator. How would the numbers in Table 1 change for darkly pigmented skin? And what data would you need to make that version of the table?

    Hint. Think about which rows would gain people and which rows would lose people.

  3. Evolution and systems People lived year-round in the cold temperate and polar zone long before vitamin supplements. The authors write that early people in Scotland lived mainly on the coast, gathering and hunting vitamin D-rich foods. How did skin color and diet work together to let people live in the zones with the least UVB?

    Hint. Think about the two ways a body gets vitamin D.

  4. Science and society The authors write that over 500 years of voluntary and forced migration moved many people into UV conditions unlike their ancestors’. Many people now living in the Northern Hemisphere’s low-UVB zones have moderately or darkly pigmented skin. What vitamin D and sun-safety advice would you give a public health department? Answer in one paragraph that uses at least two numbers from Table 1.

    Hint. Think about who faces low vitamin D and who faces too much UV in each zone.

Exit ticket

Table 1 counts the world’s people by vitamin D zone for lightly pigmented skin. What does Table 1 show? And what’s one question Table 1 can’t answer?

Hint. Think about skin color, time spent indoors and diet.

Standards

The lesson builds toward two Next Generation Science Standards (NGSS), the most widely used US science standards. Some states, like Texas and Virginia, write their own. NGSS covers kindergarten through grade 12. The college worksheet uses the AAAS Vision and Change framework for undergraduate biology. The HS-LS4-4 clarification statement includes light in its list of abiotic differences.

LevelStandardLesson partPracticeCrosscutting concept
Middle schoolMS-LS4-4. Explain with evidence how a trait can raise the odds of surviving and reproducing in a specific environment (core idea LS4.B)Middle school worksheet, Questions 3 and the exit ticketConstructing Explanations and Designing SolutionsCause and Effect
High schoolHS-LS4-4. Explain with evidence how natural selection leads to adaptation of populations (core idea LS4.C)High school worksheet, Questions and claim, evidence, reasoningConstructing Explanations and Designing SolutionsCause and Effect
CollegeEvolution and systems. AAAS Vision and Change core conceptsCollege worksheet. Question 1 covers quantitative reasoning, question 2 process of science, question 3 evolution and systems and question 4 science and society.Core competencies: quantitative reasoning; process of science; science and societyCore concept: evolution

Sources

Jablonski and Chaplin call skin pigmentation “probably one of the best examples of natural selection acting on a human trait.” The word probably shows students how careful scientists word a strong claim.

This lesson draws on several research teams. The lesson credits each team.

TopicWho found itWhere it was published
Skin color as an adaptation to UV, vitamin D, folate (the high school Going further), Darwin’s view of skin color and climateNina Jablonski and George Chaplin, Department of Anthropology, Pennsylvania State UniversityPNAS, 2010
Vitamin D zones, migration and health (the college paper)Nina Jablonski and George ChaplinPhilosophical Transactions of the Royal Society B, 2012
Skin color and autumn UV, clothing, shelter and diet in low-UV places (the Culture note)Nina Jablonski and George ChaplinPhilosophical Transactions of the Royal Society B, 2017
Skin cancer as a weak force of selectionNina Jablonski and George ChaplinProceedings of the Royal Society B, 2014
A light-skin gene version that reached East Africa through gene flow (the Culture note)Nicholas Crawford, Sarah Tishkoff and colleagues, University of PennsylvaniaScience, 2017
Brown skin needs more sunlight to make the same vitamin DAnn Webb, Lesley Rhodes and colleagues, University of ManchesterNutrients, 2018
UV index data for the high school claim, evidence, reasoningTEMIS, a satellite UV data service hosted by KNMI in the NetherlandsTEMIS UV station data

All of the papers are free to read. The 2012 college paper is a review article, and its Table 1 is the authors’ own analysis of world population by vitamin D zone.

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