Blue eyes emerging stands out as a striking example of a genetic mutation that spread across populations. Traced back to a single individual living between 6,000 and 8,000 BCE in the region near the Black Sea. The mutation involved is a specific change in the OCA2 gene, which alters the way melanin is produced in the iris. Originally, all humans had brown eyes, but this mutation led to the reduction of melanin in the iris, resulting in blue eyes.