I, Mutant

It turns out that all of us blue eyed devils are descended from the same mutant ancestor from six to ten thousand years ago. Before the mutant came along, everybody had brown eyes. Imagine how exotic and sexy our mutant ancestor must have seemed to all his boring brown-eyed conspecifics. What a huge disappointment it must have been when his or her offspring turned out to have plain old brown eyes (what with the blueness being recessive), and he or she likely didn't live long enough to see the mutation expressed in subsequent generations.

What advantage did blue eyes confer to permit it to spread so rapidly (relatively speaking)? I'm going to go with its sexiness.