The exact cause remains to be determined ... born around 6,000 to 10,000 years ago. Blue eyes are caused by a gene mutation. For years, researchers had searched for it on the OCA2 gene.

Like most human traits, blue eyes are determined by genes, and no two people have exactly the same hue. It works a lot like individual fingerprints, making our eyes two of the most distinctive ...

The team, who experimented on themselves and others, hope their findings could one day help improve tools for studying color ...