Scientists studying the genetics of eye colour at the University of Copenhagen found that more than 99.5 per cent of blue-eyed people who volunteered to have their DNA analysed have the same tiny mutation in the gene that determines the colour of the iris.

Professor Hans Eiberg of the university said he has analysed the DNA of about 800 people with blue eyes, ranging from fair-skinned, blond-haired Scandinavians to dark-skinned, blue-eyed people living in Turkey and Jordan.

"All of them, apart from possibly one exception, had exactly the same DNA sequence in the region of the OCA2 gene. This to me indicates very strongly that there must have been a single, common ancestor of all these people," he said.

The study reported in the journal Human Genetics indicates that the mutation originated in just one person who became the ancestor of all subsequent people in the world with blue eyes.

"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," Professor Eiberg was quoted as saying by The Independent daily of Britain on Thursday.