Sexual selection could also have allowed blond hair to spread.
"Lots of children have light hair - it's a color that's associated with youth," which may make blond hair more alluring, Kingsley said.
Or, given the relatively low prevalence of blond hair, the gene may have been subject to frequency dependent selection - meaning that golden tresses provided an edge in luring partners as long as they remained relatively uncommon.
"It may have been a celebrated trait because it was rare," Kingsley said.
Of course, blond hair could also have provided no evolutionary advantage, and simply persisted by random chance, he said.
The blond gene was detailed June 1 in the journal Nature Genetics.
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