Hair colour: Maybe we’re born with it. Maybe it’s a melanin gene
Roughly, for every redhead, there are three people with black hair, five with blonde, 15 with light brown and 20 with dark brown, according to a new Canadian study
A vast survey of nearly 13,000 Canadians of European background has uncovered new clues to the genetic causes of hair colour.
Using data from a massive genetic survey of Canadian volunteers, the study out of University of Toronto at Mississauga identified several possible previously unknown genetic causes for blonde, red and light or dark brown hair. It also offers a good estimate of how those colours are distributed among white Canadians.
Roughly, for every redhead, there are three people with black hair, five with blonde, 15 with light brown and 20 with dark brown, according to the study’s findings.
These colours are what geneticists refer to as phenotypes, the observable or measurable characteristics of an organism, such as a human being. Most phenotypes are determined by the interaction of an organism’s genotype, its set of genes, with the environment and experience.
But hair colour is curious. It is a genetically controlled expression of pigmentation, like eye colour and skin colour with which it correlates, and one of the few complex human traits that is largely unaffected by a person’s environment.
Hair colour arises from differences in the amount and ratio of melanins in the hair bulb, from which the strand grows. This is a process that is controlled by genetics and has been affected by many different evolutionary factors. The genes that are known to control it, however, do not seem to do so directly, more by regulating other genes.
“We know from recent studies that there are hundreds of variants in many genes involved in this, but sometimes just knowing the gene is not enough information because within one gene you can have mutation, what we call variants,” said lead author Frida Lona-Durazo, who recently completed doctoral research on the biology of hair, skin and eye pigmentation in the Department of Anthropology at the University of Toronto at Mississauga.
“Our objective was to pinpoint which variants are responsible, even if we know already some genes.”
The researchers did not discover any previously unknown genes, but they were able to “pinpoint other variants in or near genes that have not been described before,” Lona-Durazo said in an interview.
To do this, she and colleagues looked at many complex areas of the human genome that are known to change a person’s hair colour, seeking correlation with self-declared hair colour.
The research focused on people of European background because they show the greatest variation in hair colour. Asian and African populations show variation in hair colour, but the range is narrower, and it is harder to study as a self-reported variable. Ideally, Lona-Durazo said, research could be done on all populations by measuring melanin levels objectively in the lab, rather than asking subjects to report their own hair colour.