20 January 2013

The nutritional biology of human skin color


The amount of melanin found within our skin has long been a source of division for humans culturally, but anthropologist Nina Jablonski of Penn State tells the story of how human skin color unites us all biologically.

It's become one of my favorite stories to share as it relates to nutritional biology: More pigment was naturally selected because it acted as a sunscreen needed to protect against DNA damage and destruction of folate, needed for reproduction. Depigmentation was selected for when humans dispersed from Africa and into the Northern Hemisphere where they needed skin light enough to absorb sufficient UVB rays to produce vitamin D.

I first heard Jablonski discuss the nature of human skin pigmentation almost two years ago at the AAAS conference in Washington DC. Later, I discovered her TED talk, which I've posted above. It's older, but worth watching over and over again. Jablonski has a simple message: instead of using skin color to discriminate, use skin color to teach people about evolution and health.

Now Jablonski has a new, richly illustrated book out called Living Color. It serves to complement to her previous book, Skin Color: A Natural History. You can read an excerpt from her book here, which includes this paragraph:

The properties of our skin — including color — affect our health. Most of us think that humans have used our collective intelligence to overcome biological limitations in a way that cultureless species cannot do. But at least with respect to our skin, this hubris is unwarranted. Many common health problems like skin cancer and vitamin D deficiency are caused by a mismatch between our habits and our heritage. The amount of pigment that our skin contains, which determines how our bodies deal with sunshine, evolved in our ancestors. Today, many of us live under very different conditions from those experienced by our predecessors and pursue dramatically different lifestyles. People living thousands of years ago did not have indoor jobs and go on vacation; they lived outside most of the time and generally didn’t travel much or very far. Because of these factors, many of us have an inherited skin tone that is not adapted to our current circumstances, and that mismatch places us at risk for specific health problems. Knowing our own particular risk factors can be a matter of life or death.

3 comments:

Teech said...

Have you read about the inclusion of cereal grains, which are low in vitamin d plus higher latitudes, possibly explaining some of the lightening of skin? Because there are some circumpolar cultures which are still dark skinned, despite the higher latitude. These darker skinned groups never adopted cereal grains as a staple, but relied heavily on vitamin d rich marine foods.

David Despain said...

Teech,

No, I hadn't read about the "cereal grains" element of the story. Although I knew of examples such as the Inuit, who have maintained the melanin in their skin because of their diet rich in marine foods.

Thanks for your comment,
David

sundas said...

The color in our skin and hair is because of melanin which is produced by the melanocytes. But it has been recently shown than the behavior of melanocytes can be modified by manipulating keratinocytes which do not have any pigment of their own.