Gene researchers at the University of Copenhagen have concluded that the mutation that created blue eyes in humans arose in Europe sometime between 10,000 and 6,000 years ago. Blue-eyed people all share exactly the same change to their genetic make-up.
"From this we can conclude that all blue-eyed individuals are linked to the same ancestor," [researcher Hans] 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.
See above for recent exemplars expressing this mutation.
Researcher John Hawks from the University of Wisconsin further speculates:
"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."
Link to Livescience article describing the research here.
Disclosure: I've said it before and I'm saying it again: Some of my best friends have blue eyes. In addition, my wife tells me that I have hazel eyes, although my driver's license says I have brown ones.