Does this tell us anything? In most societies, blondes are much rarer than brunettes (more than 90 per cent of us have dark hair), so it may simply be that in a dark, noisy environment, blondes stand out. In fact, most evidence shows that men’s preference is swayed more by fashion than biology. In the Sixties, brunettes took over as the epitome of beauty when Jackie Kennedy supplanted Marilyn Monroe. In the Eighties, blondes reasserted themselves – the Diana effect.