All blue-eyed people share a common ancestor, by Alice Scholl.
[A] genetic mutation … happened 6,000 to 10,000 years ago and determined the eye color of all blued-eyed people today. … Everyone had brown eyes, but a genetic mutation affecting a gene in our chromosomes “turned off” the ability to produce brown eyes.
This gene affects our levels of melanin … The reason scientists think it all goes back to one ancestor is that blue-eyed individuals only vary a little in the amount of melanin in their eyes – while brown-eyed people’s vary a lot more.
[A]ll blue-eyed individuals … have all inherited the same switch at exactly the same spot in their DNA.
The brown-eyed people with a recessive blue-eye gene also share that common ancestor.