Stressheads, your hair colour is one less thing to worry about: a new study shows that going grey is at least partly caused by genes, and not totally by stress or environmental factors.
What's more, your eyebrows – or monobrow, if you have one – are also written in your DNA.
An international team delved into the genome of more than 6,000 people with varied ancestry across Latin America, and dug out genes dictating the curl, colour, greying and balding of head hair, along with beard thickness, monobrow and eyebrow thickness.
Lead author Kaustubh Adhikari, from University College London, says the findings published in Nature Communications could have forensic applications to build images of faces using DNA.
“It was only possible because we analysed a diverse melting pot of people, which hasn’t been done before on this scale," he says.
Out of the 18 genetic associations found by the study, 10 were new, including the gene identified for grey hair: IRF4. It regulates production and storage of melanin, the pigment that determines hair, skin and eye colour.
If you're endowed with a monobrow – technically called "synophrys" – the freshly uncovered gene PAX3 is behind it.
Another newly discovered gene, PRSS53, produces an enzyme in the follicle that dictates the shape, or curliness, of hair. A circular cross-section gives rise to straight hair, while an oval cross-section is curly or wavy hair.
"This new genetic variation, associated with straight hair in East Asians and Native Americans, supports the view that hair shape is a recent selection in the human family," says study co-author Desmond Tobin from the University of Bradford in the UK.
Other new genes included EDAR, which influences beard thickness and curliness, and FOXL2 for eyebrow thickness.
And even though a couple of genes affected more than one trait, there seemed to be little association between genes. For instance, balding genes occur equally regardless of your hair curliness.
Adhikari acknowledges that hair loss, colour change and growth aren't entirely steered by the few genes they found, but result from a complex set of interactions: “The genes we have identified are unlikely to work in isolation to cause greying or straight hair, or thick eyebrows, but have a role to play along with many other factors yet to be identified.”
So can this work help eradicate stubborn greys that seem to resist all but the strongest dyes, or a hairline that simply won't stop receding?
Well, those who are follicularly afflicated, rejoice: understanding how the relevent genes work "could also be relevant for developing ways to delay hair greying” and balding, says co-author Andres Ruiz-Linares.
Why do some people go bald?
Belinda Smith is a science and technology journalist in Melbourne, Australia.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.