"A genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a 'switch,' which literally 'turned off' the ability to produce brown eyes," Eiberg said.I find this fascinating.
The genetic switch is located in the gene adjacent to OCA2 and rather than completely turning off the gene, the switch limits its action, which reduces the production of melanin in the iris. In effect, the turned-down switch diluted brown eyes to blue.
If the OCA2 gene had been completely shut down, our hair, eyes and skin would be melanin-less, a condition known as albinism. [Snip]
Eiberg [from the Department of Cellular and Molecular Medicine at the University of Copenhagen.] and his team examined DNA from mitochondria, the cells' energy-making structures, of blue-eyed individuals in countries including Jordan, Denmark and Turkey. This genetic material comes from females, so it can trace maternal lineages. [Snip]
...we can conclude that all blue-eyed individuals are linked to the same ancestor," Eiberg said. "They have all inherited the same switch at exactly the same spot in their DNA." Eiberg and his colleagues detailed their study in the Jan. 3 online edition of the journal Human Genetics.
That genetic switch somehow spread throughout Europe and now other parts of the world.
"The question really is, 'Why did we go from having nobody on Earth with blue eyes 10,000 years ago to having 20 or 40 percent of Europeans having blue eyes now?" Hawks said. "This gene does something good for people. It makes them have more kids."
Now, just to satisfy my curiosity, when will the Chinese geneticists tell us about the history of the epicanthal fold that many people of East Asian and Southeast Asian descent have. But that is probably not something that can be pinned down to a single mutation so easily, and I'd guess that it's a little older than the blue-eye mutation. both are a direct result of the migration of human beings north out of Africa, as described in Nicholas Wade's outstanding book Before the Dawn: Recovering the Lost History of Our Ancestors.
Oh, wait. We don't need to find out those things, because the fundamentalist theological schools have already told us - those things are the results of decisions by the "Intelligent Designer." Such things are much to complicated for us mere human beings to understand, so we make a mistake trying. It is for us to do nothing more than worship the Intelligent Designer, obey the superior church leaders and tithe so that they can buy better cars and bigger mansions. Why would we mere sheep have to know about such things that are so far above our God-given station?
[Makes me want to contribute to some genetics research somewhere, just to spite the Discovery Institute and Mike Huckabee.]