While this switch explains most inherited blue eyes, other genetic pathways can produce pale eyes, indicating more factors beyond the single switch.

DNA evidence shows blue-eyed populations from diverse regions carry the same genetic signature around the switch, pointing to a common origin.

From this ancient mutation, hundreds of millions of blue-eyed individuals share a single origin encoded in their DNA.

Estimates are based on genetic inference rather than birth records, and ordinary blue eyes are the most common inherited form, not all light-eye conditions.

A tiny switch in the HERC2 gene controls the neighboring OCA2 gene, reducing iris pigment to produce blue eyes.

Eye color is controlled by multiple genes, but a specific mutation acts as the primary on-off switch for the common blue-eye trait, limiting pigment in the iris.

The mutation is believed to have emerged in Neolithic Europe or the Near East, though the exact origin and timing remain uncertain.

Blue-eyed people around the world are likely descendants of a single founder who lived roughly 6,000 to 10,000 years ago.