Introduction to the Science of Skin Color (01:48)
Get a glimpse into the story of skin color and Dr. Nina Jablonski's work in the science behind skin pigmentation.
The gradation in human skin color is caused by melanin. Skin produces more melanin as a response to the sun's UV radiation, rendering melanin a remarkable product of evolution.
Emergence of Skin Tone Spectrum & Racial Discrimination (02:13)
As generations of humans migrated from Africa around the world, a spectrum of skin tones emerged. During the Age of Exploration, Europeans colonized and subjugated dark-skinned indigenous populations.
Science of Race (01:22)
Carl Linnaeus was the first scientist to sort and rank humans by skin color. For many years, the science of skin color was "frozen in time," since it was an unpopular science. Dr. Nina Jablonski explains how she took up the science of race.
Mapping Skin Variation (01:28)
In the early 20th century, Renato Biasutti studied the distribution of skin color across the globe by matching people to colored tiles and illustrating his findings on a map.
Link Between UV Radiation & Skin Color (02:43)
Anthropologist Nina Jablonski found that the relationship between location and UV radiation is more complex than latitude. She found a 90% match between UV levels and skin color.
Origins of Humanity in Africa (02:34)
Dr. Jablonski travels to the Great Rift Valley in Kenya to study the earliest humans. East Africa was not always hot and dry, and early humans were light-skinned and covered with hair.
Evolution of Dark Skin Pigmentation (02:28)
Turkana Boy, the earliest and most complete human skeleton, lived in hot, dry East Africa. Humans evolved to cope with heat, which included the loss of body hair and the development of permanent dark pigmentation.
Skin Cancer in Australia (02:20)
Australia has the highest rate of skin cancer in the world, due to the southern hemisphere's high exposure to UV radiation. Indigenous Australians are 10 times less likely to get skin cancer than fair-skinned Australians.
Questioning Theories of Skin Evolution (02:20)
Dr. Jablonski reasoned that, because skin cancer affects humans after their peak reproductive age, skin color must have evolved without regards to UV radiation. She learned that different wavelengths of UV light have different effects on human physiology.
Link Between UV Radiation & Fetus Health (03:17)
Folate is critical in DNA production and strongly correlates to birth defects. Because folate is reduced by UV radiation, it makes sense that dark human skin evolved to prevent UVA rays from entering the bloodstream.
Investigating Evolution of Light Skin (01:06)
Dr. Jablonski wondered: what was the evolutionary imperative for humans in low-UV areas to develop light skin?
Albinism is a condition caused by a single genetic mutation that results in a complete absence of melanin. Africans with albinism suffer cultural discrimination, as well as vulnerability to the sun.
Vitamin D Deficiency at High Latitudes (03:32)
During the industrial revolution in England, high numbers of children suffered from rickets due to a lack of exposure to UV radiation and subsequent vitamin D deficiency.
Evolutionary Reason for Depigmentation (01:15)
Dark-skinned people living at high latitudes are prone to vitamin D deficiency and the serious health risks that result from the deficiency. This provides key evidence in the study of evolutionary depigmentation.
Fair Skin in Scotland (00:59)
In Scotland, there's a high percentage of the population with red hair and fair skin. Their pale coloring makes them suited for a low-UV environment.
Dark Skin Among Inuits (01:32)
Inuits, the indigenous people of Canada's Arctic Circle, didn't develop the light skin associated with low-UV environments because their diet of arctic animals sufficiently provided them with vitamin D.
Pigment Evolution in a Human's Lifetime (01:57)
Skin color can vary due to different biological needs over a human's lifetime. Humans don't develop full pigmentation until they're fully competent reproductive adults. Skin pigmentation is vital to reproductive success.
Genetic Evidence in Depigmentation (01:53)
Professor Keith Cheng discovered a genetic mutation in zebrafish that reduced pigmentation. He then found the same mutation in humans, meaning that light-skinned humans were mutants of dark-skinned humans.
Light-Skinned Neanderthals (03:12)
Scientists worked to extract DNA from Neanderthal skeletons found in Spain and discovered a genetic mutation that restricted melanin production.
Mitigating Sun Exposure in a Modern World (03:23)
Evolution can't keep up with global migration, so humans must make adjustments when their skin tone doesn't match their environment. These include diet changes, vitamin supplements, and regulated sun exposure.
Skin Color & Culture (02:12)
Brazil is a melting pot of human pigmentation, where people have a vast vocabulary to describe skin color. Even in Brazil, however, incidents arise that expose the absurdity of classifying people by skin color.
Science's Triumph Over Race (01:18)
Only 50 of humans' 25,000 genes are involved in skin color, which makes a strong scientific argument for equality. Science has eroded outdated concepts of race.
Credits: Skin Deep: Nina Jablonski's Theory of Race (00:49)
Credits: Skin Deep: Nina Jablonski's Theory of Race
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