Why are white people..white ?

Well now you finally know.....

ps. I'm just glad I have a sun-kissed complexion. :)

SM starts singing play that funky music white boy... :))

From The Times:

A GENE that partly explains why white people have pale skins has been identified for the first time.

Scientists in the United States have discovered that a tiny mutation in a gene plays a key role in determining skin colour, with Caucasians inheriting a different version from other racial groups.

While it is known that colour is genetically determined, this is the first research to pinpoint a particular stretch of DNA that underlies normal differences in human pigmentation.

The findings promise new insights into cancer and other diseases influenced by genes, and shed light on the evolution of different hues of skin.

The discovery of the gene, named slc245a5, has emerged from research into cancer that used zebrafish as an animal model. A team led by Keith Cheng, of Pennsylvania State University, noted that a variant of the fish, known as “golden”, had paler markings than usual, and that this lighter pigmentation was caused by a mutation in slc245a5.

As the gene is known to exist in people, Dr Cheng wondered whether it might be responsible for some of the variation in human skin colour. First he transplanted the human gene into fish and found that it had the same effect on pigmentation. He then teamed up with a colleague, Mark Shriver, to investigate how different versions of the gene were distributed across human populations, using the recently completed HapMap, which charts genetic variation.

The researchers have found that while people of African and Chinese origin carry one version of slc245a5, those of white European ancestry have a different one. The results, published today in the journal Science, indicate strongly a big influence over skin colour.

The work suggests that the dark version of the gene occurs as a default, and that the light variant is a mutation that probably evolved as humans moved out of Africa and migrated into northern latitudes. This supports a theory that lighter skin evolved as an adaptation to the weaker sunlight of northern climes. Sunlight is essential for the body to manufacture vitamin D, and pale skins make this easier when the Sun’s rays are not particularly strong.

The slc245a5 gene does not vary between Africans and much lighter-skinned Chinese, or between Europeans of Swedish and Greek ancestry. It is thought to be responsible for between 25 and 38 per cent of colour variation between Europeans and Africans, and other genes are certain to be involved.

While genes that are mutated in albino people have been identified, this is the first that has a significant influence on normal variations.

The results promise to assist research into malignant melanoma, the deadliest skin cancer, which is rarer among dark-skinned people. They should also help scientists seeking to tease out the genetic contribution to conditions such as heart disease and diabetes, which are often influenced, like skin colour, by multiple genes.

Dr Shriver said: “We cannot expect to use human genetics to understand complex diseases most effectively without first working out how fundamental characteristics, such as eye, hair and skin colour are determined.”

SKIN DEEP
- Scientists generally assume that the first anatomically modern humans, who evolved in Africa, had dark skins.

- The evolution of other skin types, particularly the fair complexions of Europeans, has long been one of the big mysteries of biology. It has been suggested that dark skin is an adaptation to strong sunlight in the tropics, and protects against skin cancer. While this might be possible if dark skins had evolved from light ones, the process happened the other way around

- A more plausible theory is that light skin evolved as an adaptation to the weaker sunlight of northern latitudes.

- Sunlight is necessary for the body to produce vitamin D, and dark-skinned people struggle to do this when the Sun is weak. Some ethnic minorities in northern Europe have higher rates of rickets, a disease caused by vitamin D deficiency

- Many scientists, however, think the adaptive advantages of light skin are too small for the effect to be the result of natural selection

http://www.timesonline.co.uk/article/0,,11069-1934310,00.html