Do All Blue-Eyed Humans Have a Single Common Ancestor? By Brian Simpson

This story goes that once upon a time in a land, far, far away, everybody had brown eyes, but a genetic mutation affecting the OCA2 gene resulted in the creation of a “switch” on a gene adjacent to the OCA2 gene, reducing the production of P protein, and the level of melanin in the iris, making brown eyes blue, so to speak: H. Eiberg (et al.), “Blue Eye Color in Humans May be Caused by a Perfectly Associated Founder Mutation in a Regulatory Element Located within the HERC2 Gene Inhibiting OCA2 Expression,” Human Genetics, vol. 123 (2), 2008: 177.

          The argument is that the variation in eye colour from brown to green is due to the quantity of melanin in the iris. Allegedly people with blue eyes have only a small variation in melanin levels. “From this we can conclude that all blue-eyed individuals are linked to the same ancestor. They have all inherited the same switch at exactly the same spot in their DNA,” according to Eiberg.

          As I see it, nothing as such flows about there being a single common ancestor as such, for all blue-eyed individuals. Who is to say that with the utter magic of mutations, the real engine of evolution (which natural selection selects), there could not have been a multi-regional origin of blue eyes? It is a fallacy of reason to infer from low variance to a single common ancestor.