Golden Blonde Girl Wearing Black Stockings In The Bed

A typical explanation found in the scientific literature for the evolution of light hair is related to the requirement for vitamin D synthesis and northern Europe's seasonal deficiency of sunlight. Lighter skin is due to a low concentration in pigmentation, thus allowing more sunlight to trigger the production of vitamin D. In this way, high frequencies of light hair in northern latitudes are a result of the light skin adaptation to lower levels of sunlight, which reduces the prevalence of rickets caused by vitamin D deficiency. The darker pigmentation at higher latitudes in certain ethnic groups such as the Inuit is explained by a greater proportion of seafood in their diet. As seafood is high in vitamin D, vitamin D deficiency would not create a selective pressure for lighter pigmentation in that population.
An alternative hypothesis was presented by Canadian anthropologist Peter Frost, under the aegis of University of St Andrews, who published a study in March 2006 in the journal Evolution and Human Behavior. Frost said blond hair evolved very quickly in a specific area at the end of the last ice age by means of sexual selection. According to the study, the appearance of blond hair and blue eyes in some northern European women made them stand out from their rivals at a time of fierce competition for scarce males. The study argues that blond hair was produced higher in the Cro-Magnon descended population of the European region because of food shortages 10,000-11,000 years ago following the last glacial period when most of it was covered by steppe-tundra. Almost the only sustenance in northern Europe came from roaming herds of mammoths, reindeer, bison and horses and finding them required long, arduous hunting trips in which numerous males died, leading to a high ratio of surviving women to men. This hypothesis argues that women with blond hair posed an alternative that helped them mate and thus increased the number of blonds.
A theory propounded in The History and Geography of Human Genes (1994), says blond hair became predominant in Northern Europe beginning about 3,000 BC, in the area now known as Lithuania, among the recently arrived Proto-Indo-European settlers (according to the Kurgan hypothesis), and the trait spread quickly through sexual selection into Scandinavia. As above, the theory assumes that men found women with blond hair more attractive.
Social reasons why men may have preferred blonde women is that light hair color is a marker of youth. Since many Northern European children have blond hair, which darkens as they mature, blond hair could arguably be associated with youth and therefore, fertility. Blond as a color has also been associated with light and gold, things that people find attractive and desirable. Lighter color hair is usually more scarce or rare (exotic), arguably increasing its desirability.