Irish people developed their red hair because of a lack of sunlight, according to new research from a leading DNA lab.
Irelands DNA has revealed that one in 10 Irish people have red hair but it is thought that up to half the population could be carrying the redhead gene even though they are blonde or brunette.
The DNA laboratory carrying out research into the flame-haired gene believes it is so associated with Ireland and Scotland because it is connected to a lack of vitamin D, which is related to the lack of sunlight.
It is thought Ireland, Scotland and northern England have the highest concentration of Titian-haired people in the world because the Celtic colouring is genetically programmed to work better in our sun-starved countries.
"It's to do with the cloudy climate," said Helen Moffat, marketing manager at IrelandsDNA.
"Scandinavia has perhaps less hours of sunshine but Ireland and Britain are much cloudier so the Vitamin D we get is much lower in comparison to somewhere like Scandinavia where they seem to have more sunshine.
"The fairer you are, the more vitamin D you can absorb. Red hair is associated with fair skin due to the lower melanin concentration and this has advantages as more vitamin D can be absorbed."
Alastair Moffat, managing director of the genetic research laboratory, said two of the most common redhead gene variants came from just two Asian people 70,000 years ago.
IrelandsDNA, which focuses on probing people's heritage, has developed a new test that allows parents to see if they might have red-haired children.
They are hoping the test – which will show that many brunette and blondes unknowingly carry the redhead gene – will curb the prejudice and teasing some redheads face.
In Ireland 10 per cent of people are redheads while in Scotland up to 13 per cent have red hair and in England six per cent have red hair.
This is considerably higher than in the rest of the world. Outside Europe, only .06 per cent of people are redheaded.
For a child to have red hair, both parents must be carriers – but neither of them have to have red hair – and then there is still only a 25 per cent chance that their offspring will have it.