Human hair comes in a wide range of colours. Though your natural hair colour is largely determined by genetics, your hair colour doesn’t always match exactly what your genes suggest.

An AncestryDNA^® + Traits test can tell you if you’ve got some of the DNA for darker or lighter hair, based on six genetic markers—three markers associated with lighter or darker hair and three markers associated with red hair colour.

Melanin and Hair Colour

The same pigment that contributes to your eye colour and skin colour is involved in your hair colour. It’s called melanin. And your hair has two types of melanin in it: eumelanin and pheomelanin. Eumelanin comes in black and brown. And pheomelanin is a spectrum of pinkish-red to orange and yellow.

If you have dark hair—brunette or black hair—the eumelanin (the black and brown pigment) in your hair is high—and the pheomelanin in your hair is low. If you're blonde, you have low amounts of both pigments. And if you have red or auburn hair, you have low eumelanin levels and lots of pheomelanin (the pigment that ranges from pinkish-red to orange and yellow).

Hair Colour Genetics

While dark-haired parents tend to have dark-haired kids, hair colour genetics is quite complex. Your hair colour depends in part on how many genetic variants you inherit from both of your parents.

If you have brown hair, your shade of brown depends on how many light and dark markers you inherit from your mom and dad. If you have really blonde hair, you have lots of light markers—and you'll likely pass these on to your kids. But you could also end up with a different hair colour than both of your biological parents.

Environmental factors like sunlight and age can also influence your hair colour. For example, one theory of why hair colour changes with age—becoming grey hair—is that hair follicles eventually produce less melanin.

Science of Hair Colour

Scientists have identified many of the genetic markers involved in hair colour. But it's not always possible to tell how these genes will interact to produce your unique hue.

And they are almost certainly not the only DNA markers you’ve inherited that are involved in determining hair colour.

AncestryDNA looks at six well-studied genetic markers. Blonde or light hair is associated with three markers: one each in the KITLG, OCA2, and SLC24A4 genes.

Some people only have test results linked to either dark or light hair colour. Others have a combination. But if you have more markers for light hair than dark hair, it's more likely that you have lighter hair.

Hair Colour Fun Facts

Red hair colour is the most rare colour on any natural hair colours list. Scientists estimate that less than 2% of people across the world are redheads.

Blonde hair is another relatively rare hair colour. It was once largely associated only with European heritage. But scientists discovered a mutation in the dark-skinned indigenous people of the Solomon Islands that causes blonde hair in about 10% of the population.

And it turns out the genes involved in their blonde hair are different from the genes involved in Europeans’ blonde hair. So blonde hair evolved independently in both populations, thousands of miles apart.

 

References

Barnes, Hannah. "How many redheads are there in the world?" BBC News. October 2, 2013. https://www.bbc.co.uk/news/magazine-24331615.

Box, Neil F., Jason R. Wyeth, et al. "Characterization of Melanocyte Stimulating Hormone Receptor Variant Alleles in Twins with Red Hair." Human Molecular Genetics. October 1997. https://academic.oup.com/hmg/article/6/11/1891/686680.

Han, Jiali, Peter Kraft, et al. "A Genome-Wide Association Study Identifies Novel Alleles Associated with Hair Colour and Skin Pigmentation." PLoS Genetics. May 16, 2008. https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1000074.

Lallanilla, Marc. "Are You Carrying the Redhead Gene?" LiveScience. January 28, 2013. https://www.livescience.com/26633-redhead-dna-gene.html.

Porretto, Denise. "Genetics and Your Baby." Parents. October 3, 2001. http://www.parents.com/getting-pregnant/genetics/genetics-and-your-baby.

Starr, D. Barry. "Ask a Geneticist: Hair Colour." Stanford at The Tech Museum. December 19, 2007. http://genetics.thetech.org/ask/ask245.

Sulem, Patrick, Daniel F. Gudbjartsson, Simon N. Stacey, et al. "Genetic determinants of hair, eye and skin pigmentation in Europeans." Nature Genetics. October 21, 2007. https://www.nature.com/articles/ng.2007.13.

Valverde, Paloma, Eugene Healy, et al. "Variants of the Melanocyte-stimulating Hormone Receptor Gene Are Associated with Red Hair and Fair Skin in Humans." Nature Genetics. November 1, 1995. https://pubmed.ncbi.nlm.nih.gov/7581459/.