A project is being launched which aims to find out how many people in Scotland carry the red hair gene.
Researchers from the ScotlandsDNA project also hope to discover why Scotland appears to have the most red-headed people in the world.
ScotlandsDNA said about 1-2% of the world's population has red hair, but in Scotland the figure is much higher at around 13% or about 650,000 people.
The information will be used to make a "ginger" map of the British Isles.
Researchers at the ScotlandsDNA project believe the figure for Scottish red hair gene carriers may be much higher, and could be as many as 1.6m.
A person who doesn't have red hair can still produce red haired children if both they and their partner carry the gene.
Red hair appears in people with two copies of a recessive gene on chromosome 16 which causes a mutation in the MC1R protein and can often skip generations.
The ScotlandsDNA project is launching a new test which costs £25 and will tell participants whether or not they're a carrier of a red haired gene.
It will also inform them of which of three types of the gene they have, and possibly provide some insight into why Scotland is the most red-headed nation on earth.
Managing director of ScotlandsDNA Alastair Moffat is keen to map the number of possible carriers of the gene in Scotland and attempt to explain why there are so many Scots red-heads.
"It's not necessarily the people who have red hair that interest us at ScotlandsDNA, what we want to do is discover who carries the red hair gene variant," Mr Moffat told BBC Scotland.
"I think that's a much larger number. For example, in my own family, I have three kids and two of them have red hair - and while I haven't got much hair, it's certainly not red, and neither has my wife.
"In either side of our families, there was no red hair - and I thought, where has this come from? That was what got me interested.
"We're looking at people who have already had their DNA tested by Scotland's DNA, which is simple for us to do.
"But they have to be tested first, and then we can tell them if they're carriers of the red-head variant."
Red hair DNA
All physical colouring is a mixture of two pigments; black melanin and red/yellow melanin, but in red-heads a particular receptor in the pathway for pigmentation, MC1R, is disrupted and black melanin is suppressed while red/yellow melanin is allowed to be made.
The result is red hair, light skin colour, often freckles and a greater sensitivity to sunlight.
The three types of red-head gene are:
- Cysteine-red (or R151C) is carried by 10% of British people
- Tryptophan-red (or R160W) is carried by 9% of British people
- Histidine-red (or D294H) is carried by 2.5% of British people
There are also other, much rarer, variants.
Mr Moffat believes the origins of the gene are more an adaptation to Scotland's poor weather.
Mr Moffat added: "I think it's to do with sunshine - we all need vitamin D from sunshine - but Scotland is cloudy, we have an Atlantic climate and we need light skin to get as much vitamin D from the Sun as possible."