In almost every study that I have seen, brunets are preferred over blonds. Why?
Although a peek on the Internet shows that people are intensely interested in what hair color mates prefer, there has yet to be much scientific study on this subject.
Recently, newspapers worldwide reported on a study that found that men preferred long brown hair. However, because this study was never published, it was not possible to assess its methods. It is known that the results reflected the preferences of a small number of male participants. Without knowing how representative of the population as a whole these participants were, it is difficult to know whether the study measured ethnic, regional, national, or global preferences.
One theory holds that people prefer mates similar to themselves. Most of the people in the world have dark hair, so if this theory is correct then brunets would definitely be preferred over blonds in any global survey.
Another theory asserts that rare hair color is an advantage. For example, in one study, male observers were shown photos of a single brunette pictured (1) in a group of brunettes, (2) as the only brunette in a small group of blondes, and (3) as the only brunette in a large group of blondes. As her hair color became steadily more rare, the woman was rated more attractive by male observers.
Similarly, it has been noted that hair color is unusually diverse in northern and eastern Europe. One researcher posits that the number of mutations involved and their independent origin over a short period of evolutionary time indicate that some kind of selection was at work in producing this unique array of hair color variation. According to this author's theory, the various mutations underlying hair color arose too fast to be attributable to either chance or the relaxation of natural selection. Male preference for women with unique hair colors may explain this interesting pattern. Northern and eastern Europe provided a novel environment in which females had little opportunity to gather food and were thus more dependent on males, who acquired food on long and risky hunts. Reliance on hunting as a means of survival may have had two consequences: a higher male mortality rate and a limitation on the number of female dependents that any one male could support. With male providers in high demand, men may have taken the opportunity to be a little more picky about the appearance of their mates than they would in other circumstances. If unique hair colors caused certain women to stand out as more desirable mates, this could explain the concentration of unique hair colors in this region of the world.
It certainly will be interesting to see how research on hair color preference progresses in the future!
For further reading:
Frost, P. 2006. European hair and eye color—a case of frequency-dependent sexual selection? Evolution and Human Behavior 27:85–103.
Thelen, T.H. 1983. Minority type human mate preference. Social Biology 30:162–180.