Blondes may have a ditzy reputation, but their lighter locks are far more complex than scientists thought.
For true blonde hair requires some 200 genetic variants – compared with 60 for brown hair and even less for redheads.
In one of the biggest studies of its kind scientists at the Medical Research Council’s human genetics unit analysed DNA from 39,397 blonde women and men of European descent.
It was assumed that blonde hair had a basic genetic structure but the finding may explain why truly blonde people are rarer than other colours.
Only 12.7 per cent of women have pure blonde hair, and 9.9 per cent of men.
One theory is that blonde hair evolved at the end of the Ice Age, when females outnumbered males. Blondeness may have developed as a way to stand out.