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Radio Shows | Origins of the Human Rainbow | mp3wmawav

Origins of the Human RainbowThe conflicts and divisiveness over skin color stretches across recorded history. Yet, the irony is the variations in skin colors is a recent evolutionary development.

Humans didnít develop different skin tones until fifty to one hundred thousand years ago — when modern man migrated northward out of Africa. Thatís when skin color began to lighten.

For years, scientists believed evolutionary pressures produced lighter skin because in these higher latitudes the sun is less intense. Given the same amount of sun exposure, lighter skin will produce more vitamin D compared to darker skin.

Thatís super important since Vitamin D is vital to bone growth and maintenance. Plus the nutrient also protects us against a number of other diseases. But itís possible some other evolutionary pressures were at work.

One idea is sexual selection, which argues that males preferred women with pale skin — a sign of youth and fertility. Lighter skin is also a feature of the early infant stage which may have induced less aggression and more protection.

Of course there are no ancient statistics or health records to verify either of these hypotheses.

Another idea has to do with the dangers of cold weather. Data from soldiers of the Korean War suggest dark skin is more susceptible to frostbite than pale skin, since it emits more heat. So the cold may have negatively selected against dark skin, but again, thereís little data to support this.

Though many ideas continue to be explored, the most likely explanation for the development of lighter skin tones is Vitamin D production. People with dark skin need sun exposure six times longer than light skinned people to make the same amount of vitamin D.

As for the rainbow of human skin colors we see today Ė itís likely many factors made that happen.

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For more information…

The Smithsonian National Museum of Natural History has an excellent webpage that includes information about the variation in human skin colors and its origins.
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For a discussion about the mystery of what controls human skin color dowload the pdf of an short artcile by Dr. Gregaory S. Barsh entitled "What Controls Varaiion in Human Skin Color?".
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Public Broadcasting System website includes an article about the work of anthropologist Nina Jablonski on the biology and origins of human skin color here.

For a detailed review by Anthropologist Nina Jablonski on the evolution of human skin and skin color go here.


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