This is pretty cool. Blue eyes are really new in our genetic history, just 6-10,000 years old. We can be traced back to a single genetic mutation that turned off the brown eyes that had heretofore been all humans had ever known. According to the article, all other eye colors, from brown to green, can be attributed to the amount of melanin in the iris, but only us lucky blue-eyes have an absolute lack of melanin there. I guess that's why albinos have blue eyes as well. Funny that one genetic switch was able to change our eyes but not our skin or hair levels.
(from Long Now)