Alistair Moffat, the lead researcher of the study, said the number of people with blue eyes is increasing because people find them more attractive. This means people with blue eyes are more successful at finding a partner and having children with blue eyes. He compares blue eyes to the tail of a peacock, saying a more colourful tail will get a peacock more mates. Dr Moffat says people are attracted to the sparkle in blue eyes. He said light reacts with blue eyes to give a glitter effect. Darker eyes absorb light so they generally have less sparkle. Another scientist, Hans Eiberg, offers an explanation why blue eyes are popular. He said: "There is something attractive about blue eyes, maybe because they used to be so rare."