Scand J Psychol. 2008 Apr 28 [Epub ahead of print]
The influence of skin tone, hair length, and hair colour on ratings of women's physical attractiveness, health and fertility.
Swami V, Furnham A, Joshi K.
The present study investigated the role of skin tone, hair colour and hair length in perceptions of women's physical attractiveness, health and fertility. One-hundred and thirty men and 112 women rated a series of 12 line drawings that varied in three levels of skin tone, two levels of hair colour and two levels of hair length. Results showed a number of interactions between the three variables, suggesting that these phenotypes are highly intercorrelated. However, there were also significant main effects of each of the variables, with hair colour generally explaining the greatest amount of variance. In general, light-toned figures were rated the most positively. Contrary to expectations, however, brunettes were rated more positively than blondes, and hair length had only a weak effect on ratings of attractiveness. Implications of these findings and the limitations of the use of line drawings are discussed in conclusion.
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This would tend to cast doubt on the theory of sexual selection for the spread of blondism in European populations. If males prefer brunettes, I'd say the theory is "dead in the water."
ReplyDeleteFrom the paper:
ReplyDelete"One
recent exception is Frost’s (2006) application of the “rare-colour
advantage” hypothesis to explain the evolution of blonde
hair. More generally, a number of studies have found evidence
for a rare-colour advantage in terms of hair colour. Thelen
(1983), for instance, showed that the preference for a
brunette increased in proportion to the rarity of her hair
colour. Corroborative evidence suggests that women tend to
change their hair colour and style to a type that is less
common in the general population (Schweder, 1994)."
The theory would seem to predict an oscillation between hair colours as rarity values changed. Also with red hair being even more rare in modern populations one would have to predict that red-heads would be especially sought after as mates. However, the levels of "anti-ginger" bias in countries such as Britain would seem to run counter to the hypothesis.
ReplyDeleteAlso the theory does not address the fact that the vast majority of "genetic blonds" are not "fast" and cease to be blond before they are of reproductive age. If the sexual selection theory were corredct then young adulthood should be most blond period of life. The infantile nature of blondism needs to be taken into account in any theory concerning its orgins and spread as a human trait.
Also with red hair being even more rare in modern populations one would have to predict that red-heads would be especially sought after as mates.
ReplyDeleteBut redheads have other problems that could explain aversion to them, e.g., frequent freckling. It has been observed that an even skin tone is usually preferred.
Dienekes mentioned, "a number of studies have found evidence
ReplyDeletefor a rare-colour advantage in terms of hair colour". But as Urselius said, "The theory would seem to predict an oscillation between hair colours as rarity values changed". Exactly. The 'rare-colour advantage' would dissappear long before blond hair occurred in anywhere near half the population. Other explanations are necessary. Unfortunately the most obvious one conflicts with the single recent out of Africa theory.
Dienekes mentioned, "a number of studies have found evidence
ReplyDeletefor a rare-colour advantage in terms of hair colour". But as Urselius said, "The theory would seem to predict an oscillation between hair colours as rarity values changed". Exactly. The 'rare-colour advantage' would dissappear long before blond hair occurred in anywhere near half the population. Other explanations are necessary. Unfortunately the most obvious one conflicts with the single recent out of Africa theory.
But as Urselius said, "The theory would seem to predict an oscillation between hair colours as rarity values changed".
ReplyDeleteI am not sure why you think there would be an oscillation. The initially rare color would be favored by selection but its competitive advantage would diminish as it became more frequent.
On the other hand, if a hair color had an intrinsic, frequency-independent, advantage, then the course of selection would finally lead to a monochromatic population composed entirely of the particular color.
"I am not sure why you think there would be an oscillation. The initially rare color would be favored by selection but its competitive advantage would diminish as it became more frequent."
ReplyDeleteForgive my literal mindedness but wouldn't a simple sexual advantage predict that all populations which had any blondism would, in the fullness of time, by your estimation end up with the same frequency of blondism?
Thus there are blond Italians and blond Swedes, if sexual selection were the only factor they should have the same frequency - but they demonstrably don't.
Blondism must have some connection to advantage in certain geographical, nutritional, behavioural etc. conditions. The connection to the advantageous traits may be merely coincidental, but it must be there.
Possibly, being an infantile condition in the majority of cases blondism, as super-size egg-substitutes in geese elicit increased parental care, then blond infants may have elicited greater parental care in humans than non-blonds.
Alternatively, some of the East Asian and Caucasian genes controlling lighter skin colour have been shown to be different. If the Caucasian 'light skin genes' were connected to genes controlling expression of pigment in hair and eyes, and the East Asian equivalents were not, this may give a window into how blondism spread within European populations' ie. it was connected to a trait - enhanced vitamin production though having lighter skin, which did confer advantage in high lattitudes.
Forgive my literal mindedness but wouldn't a simple sexual advantage predict that all populations which had any blondism would, in the fullness of time, by your estimation end up with the same frequency of blondism?
ReplyDeleteNot necessarily. The introduction of the relevant alleles may have started at different times, population sizes differed, different pigmentation types may have separate selection pressures, e.g., environmental selection against depigmentation in sunny areas, etc.
Equilibrium does not need to have been the same (i.e. 50-50 or 75-200, or reached at the same time in different populations. And, of course, equilibrium is always a temporary condition, which can be upset by changing environments, e.g., the invention of sun protection technology, or immigration, e.g., of depigmented individuals into Southern Europe in Late Antiquity or of pigmented individuals into Northern Europe in recent times.
Urselius may be onto something. The vitamin-enrichment theory could explain the higher incidence of European blondism in the childhood years, when bones grow fastest and the most Vitmain D is required. This model does not require sexual selection at all.
ReplyDeletevery nice article
ReplyDelete