A Natural History of Race

It seems that Americans have been talking a lot about race recently.  In this article, I would like to look at the natural history of race: where does it come from, does it even exist, how do we let it affect us.  In the fight against racism, colorblindness leaves our world a blur of grays.  But the human race creates a beautiful mosaic of skin tones and cultures.

Racism is nothing new the the US.  It has been around longer than we have been a country, but not much longer.  Human beings have always separated people into us-and-them.  It is what we do (it is why college rivalries have become increasingly heated).  The "us" probably began as family groups.  These are the people with similar genes to me.  So to protect my genes (the ultimate evolutionary imparative), I must protect my family.  As time passes the family group evolved into to tribal bands.  These bands included more genetic variation than the family, but many on my genes are still present.  And so, I must defend my tribe.

Over thousands of years, these tribal bands spread out over the world.  Some tribal bands stayed in Africa, but many migrated to Europe and Asia.  It is now that we will begin to see the differences in our skin color.  The tribes in Africa continued the thrive under the oppressive equatorial sun.  The UV radiation that plays havoc on DNA could only be blocked by the protein melanin.  Melanin not only acts as a sunscreen, but it also provides our skin color.  Therefore, the more of this protein that you have, the darker your skin.  Interestingly, populations in other parts of the world near the equator, also possess dark skin: southern India, Australia, Indonesia, etc. 

Could skin color be as simple as a sunscreen? Well, yes and no.  UV radiation determines our production of melanin (white individuals produce extra melanin when exposed to sunlight: it is called a tan).  But, the reasons are more complicated.  UV radiation has both bad and good qualities.  First the bad:  UV radiation breaks apart DNA which leads to skin cancers.  Across the board, individuals with darker skin have less skin cancer.  But, UV light also breaks down Folic Acid.  Folic Acid is necessary for the development of the fetus.  Studies have shown that decreased amount of folic acid leads to higher incidences of spina bifida (a frightnening, debilitating disorder when the nervous system fails to completely develop).  So more melanin blocks the destruction of folic acid, which is important when living in the tropics.  What about the good?  UV radiation also helps up produce Vitamin D.  When sunlight hits our skin, we make more of it.  Vitamin D is important in a lot of matters but especially the absorption of calcium into our bones (low vitamin D leads to rickets).

The skin color of our ancestry was a battle between the protection or folic acid and the production of vitamin D.  If we look at the world, sunlight is strongest in the tropics and weakest at the poles.  Those individuals of the tropics were getting plenty of vitamin D and needed to protect their folic acid and DNA.  So the individuals with darker skin were more successful in mating and that tribe evolved to have dark skin.

If we look at my tribe which had migrated to Europe there were different pressures.  The weaker UV light posed less of a problem for our folic acid levels.  But dark skin would mean not enough Vitamin D.  So our skin began to mutate, and tribal members with less melanin, produced more Vitamin D, were healthier and had more kids.  That tribe evolved lighter skin.

As long as our tribes were separated by continents, we began to produce other differences.  Hair types began to change (curly hair helps in hot climate, straight hair helps in cold climates) and more mutations took place (Sickle Cell Trait protects against malaria).  Only the occasional population migrated between the groups to keep our gene pools linked.  But also our cultures began to change. 

However, in the 1400's and 1500's Europeans began to travel.  Soon no tribal group was isolated and we began to run into our cousins once again.  The exploration age tore down the walls that separated our different populations.  The differences that accumulated through time, genes and culture, must have been a shock to both parties.  This leads to the idea that we must protect our own tribe, our own culture.  If we only think about humans in our recent past, the reintroduction to our family, then the racial divisions serve to protect our genes.  But in reality,  we all share the same genes. 

We are all 99.9% the same.  Also in any given society, 85% of the total variation in humans can be found.  And what I find the most telling: Africans, who we  tend to group as all the same, actually show the most variation of any population of humans.