Update: Women and red hair

The online magazine Evopsy has posted a summary, in French, of the paper on red hair that I wrote with Karel Kleisner and Jaroslav Flegr. It can be found here.

The online magazine Cultura VRN has posted a summary, in Russian, here.

Please let me know about any other magazines that might be interested in this topic.

References

Frost, P. (2018). Pыжая женщина – уникальна, Cultura VRN, January 15

http://culturavrn.ru/world/23304 

Frost, P. (2018). La rousse est particulière, Evopsy, January 7

http://www.evopsy.com/abstracts/rousse-frost.html 

Frost P, Kleisner K, Flegr J (2017) Health status by gender, hair color, and eye color: Red-haired women are the most divergent. PLoS ONE 12(12): e0190238. 

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0190238  

Red-haired women are special

The Damsel of the Sanct Grael – Dante Gabriel Rossetti (1828-1882)

It's known that red-haired women, but not red-haired men, are more sensitive to pain. Red hair is also associated with a higher risk of developing endometriosis, Parkinson's disease, and decreased platelet function.

A study in the latest issue of PLoS One has confirmed that red hair, especially in women, is linked to certain health issues. According to a survey of over seven thousand participants, red-haired women do worse than other women in ten health categories and better in only three, being especially prone to colorectal, cervical, uterine, and ovarian cancer. Red-haired men seem to be as healthy as other men, doing better in three categories and worse in three. Reproductive success, i.e., number of children, is the only category where redheads of both sexes do better than other participants.

This study has also confirmed that red hair is naturally more frequent in women than in men. To a lesser degree, the same is true for blond hair and green eyes. These bright colors seem to result from a selection pressure that mainly targeted women, i.e., sexual selection. In other words, among early Europeans there were too many women and not enough men; hence, competition between women for mates favored those who could better catch the attention of men, such as through a palette of bright hair and eye colors.

Because women are overrepresented among redheads, it may be that estrogen promotes synthesis of red pigments by hair follicles, particularly during fetal development. Thus, if a baby is born red-haired and female, estrogenization of its body tissues should be, on average, near the top end of the normal range. It will therefore be more at risk of developing certain health issues.

Another hypothesis can be put forward. If red hair was the last hair color to evolve, the underlying alleles may not have finished adapting to the rest of the genome, and vice versa. This reciprocal adaptation is all the more necessary because one of the five alleles for red hair seems to be of Neanderthal origin. The hypothesis of incomplete adaptation does not exclude the hypothesis of high estrogenization. In fact, there may be interaction between the two factors. Although it's likely that sexual selection did produce new hair and eye colors, we must still explain why, in this palette of colors, red hair seems to show the greatest difference between men and women both in population frequency and in associated health effects. 

Reference

Frost P, Kleisner K, Flegr J (2017) Health status by gender, hair color, and eye color: Red-haired women are the most divergent. PLoS ONE 12(12): e0190238. 

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0190238

----------------------------------------------------------------------------------

La rousse est particulière

On sait que les rousses, mais pas les roux, sont plus sensibles que les autres à la douleur. La rousseur est également associée à un plus grand risque de développer l'endométriose, la maladie de Parkinson, ainsi que des troubles de l'agrégation plaquettaire.

Une étude publiée dans le dernier numéro de la revue PLoS ONE confirme que la rousseur, surtout chez la femme, est reliée à certains problèmes de santé. Selon une enquête menée auprès de plus de sept mille participants, les rousses se classent pire que les autres femmes dans dix catégories de santé et mieux dans seulement trois, étant surtout susceptibles de développer des cancers du gros intestin, du col utérin, de l'utérus ou des ovaires. Quant aux roux, leur état de santé ressemble à celui des autres hommes : mieux dans trois catégories et pire dans trois. Le succès reproducteur, soit le nombre d'enfants, est la seule catégorie où les têtes rouges des deux sexes font mieux que les autres participants.

Cette étude confirme également que la rousseur est naturellement plus fréquente chez la femme que chez l'homme. Dans une moindre mesure,  c'est le même constat avec la blondeur et les yeux verts. Ces couleurs vives semblent être le résultat d'une pression de sélection visant surtout la femme, soit la sélection sexuelle. Autrement dit, il y aurait eu trop de femmes et pas assez d'hommes chez les premiers Européens, avec pour résultat une concurrence entre les femmes favorisant celles qui attiraient mieux les regards des hommes, comme par exemple par une palette de couleurs vives décorant les cheveux et les yeux.

Les femmes étant surreprésentées parmi les têtes rouges, on peut émettre l'hypothèse que l'œstrogène favorise la synthèse de pigments rouges dans les follicules pileux, particulièrement au cours du développement fœtal. Alors, si un enfant nait à la fois roux et de sexe féminin, l'œstrogénisation de ses tissus organiques doit être, en moyenne, vers la limite supérieure de la normale. La rousse sera donc plus à risque de connaitre certains problèmes de santé.

Une autre hypothèse est possible. Si la rousseur a été la dernière couleur de cheveux à paraître, il se peut que les allèles sous-jacents n’aient pas encore fini de s'adapter au reste du génome et vice versa. Cette adaptation réciproque est d'autant plus nécessaire parce que l'un des cinq allèles pour la rousseur semble être d'origine néandertalienne. Notons que l'hypothèse d'adaptation incomplète n'exclut pas celle de forte œstrogénisation. En fait, il pourrait y avoir une interaction entre les deux facteurs. S'il est vraisemblable que la sélection sexuelle ait produit de nouvelles couleurs des cheveux et des yeux, il faudra toujours expliquer pourquoi, dans cette palette de couleurs, la rousseur semble montrer la plus grande différence entre les hommes et les femmes, autant en termes de fréquence dans la population que sur le plan de la santé. 

What makes hair color "hot"?

The ‘hot’ hair color this year (source). While there seems to be a general trend to prefer average physical characteristics, this doesn’t seem to apply to hair color. People seek colors that are uncommon or even unnatural.

Europeans have departed from the species norm of black hair and brown eyes by evolving a wide range of bright hair and eye colors. What is the selective advantage of these new hues? Or are they merely a side effect of something else?

I’ve argued that these new colors were selected for … their newness and colorfulness. To be precise, their selective advantage lay in their novelty and brightness. These eye-catching qualities enabled women to improve their mating prospects at a time when the operational sex ratio was skewed toward a female surplus and a male shortage.

This is the logic of advertising. Visual merchandising matters most in saturated, highly competitive markets that offer too many interesting choices (Lea-Greenwood, 1998; Oakley, 1990). Such a context rewards products that stand out because of their bright or novel look, as seen in colors for home interiors. This market has grown more competitive over the past half-century, and the novelty factor has correspondingly grown more important: preference for one paint color rises until satiated, then falls and yields to preference for another (Stansfield & Whitfield, 2005).

In the natural world, and under conditions of intense sexual selection, this same logic leads to a color polymorphism. A new color appears through mutation and spreads through the population until it is as common as the established color. This equilibrium will then last until another color variant appears. The total number of colors thus grows over time.

This aspect of sexual selection can be demonstrated under controlled conditions. In an American study, male participants were shown pictures of attractive brunettes and blondes and asked to choose, for each series, the woman they would most like to marry. One series had equal numbers of brunettes and blondes, a second series 1 brunette for every 5 blondes, and a third series 1 brunette for every 11 blondes. Result: the scarcer the brunettes were in a series, the likelier any one of them would be chosen (Thelen, 1983).

The same trend appears in popular culture. On American TV programs, women are four and a half times more likely than men to have red or auburn hair and five times more likely than men to have blonde hair. Conversely, men are four times more likely than women to have gray hair and 40% more likely than women to have black hair (Davis, 1990). A similar trend has been observed on Turkish TV programs:

Women were more likely than men to have red (5.3%) or blonde (15.6%) hair. In fact, no primary male characters in this sample had red or blonde hair at all, but female characters did. (Ikizler, 2007, p. 39)

This sex difference undoubtedly reflects the use of artificial hair coloring, although female hair color is naturally more diverse than male hair color (a legacy of the female-directed nature of sexual selection in Europe). Interestingly, women are using hair dyes to give themselves less typical hues, rather than more typical ones. Such colors may be uncommon but naturally occurring, such as platinum blonde and red. Or they may not exist at all in nature, such as green, purple, and magenta.

This year, the leading hair colors are forecasted to be “red, burgundy, strawberry blonde, copper brown and auburn shades.” Among celebrities, the hottest colors will include “bright reds, vibrant blues and pastel pinks” (Fall Hair Color Trends 2012).

References

Davis, M. D. (1990). Portrayals of women in prime-time network television: Some demographic characteristics. Sex Roles, 23(5/6), 325-332.

Fall Hair Color Trends 2012
http://researchanalyst.hubpages.com/hub/Hair-Color-Trends

Ikizler, A.S. (2007). Gender role representations in Turkish television programs, Submitted as a St. Mary's Project in Partial Fulfillment of the Graduation Requirements, St. Mary's College of Maryland for the Degree of Bachelor of Arts in Psychology
http://www.smcm.edu/psyc/_assets/documents/SMP/Showcase/0607-AIkizler.pdf

Lea-Greenwood G. (1998). Visual merchandising: a neglected area in UK fashion marketing? International Journal of Retail & Distribution Management, 26, 324-329.

Oakley M. (ed.) (1990). Design management. A handbook of issues and methods. Oxford: Basil Blackwell.

Stansfield J., & T.W.A. Whitfield. (2005). Can future colour trends be predicted on the basis of past colour trends? An empirical investigation. Color Research and Application, 30(3), 235-242.

Thelen, T.H. (1983). Minority type human mate preference. Social Biology, 30, 162-180.

Why are redheads less common than blondes?

Gilbert Blythe tormenting Anne Shirley (Anne of Green Gables)

Male preference for female hair color seems to be frequency-dependent. The less common a hair color becomes, the more it is preferred. When male subjects are presented with a series of photos showing blondes and brunettes, preference for any one brunette is inversely proportional to the number of brunettes in the series (Thelen, 1983). This frequency dependence may explain why blonde hair is less strongly preferred in England than in France.

England is, however, somewhat fairer generally than most parts of Europe; so that, while it may be said that a very beautiful woman in France or Spain may belong to the blondest section of the community, a very beautiful woman in England, even though of the same degree of blondness as her Continental sister, will not belong to the extremely blonde section of the English community. (Ellis, 2007[1905], p. 160)

Hair color is normally a minor factor when men select mates. It becomes a major factor only when the level of sexual selection is intense, like the situation of a movie producer who has to choose one actress from a number of excellent candidates. Under such conditions, relatively unimportant factors can make a big difference, especially those that can attract and retain attention.

I’ve argued that such conditions once prevailed among ancestral Europeans, specifically European women (Frost, 1994, 2006, 2008). One result was an ever broader range of eye and hair colors. Whenever a new color appeared through mutation, it would be favored by sexual selection until it had become as frequent as the other colors. Although the pressure of sexual selection was on women, these changes in physical appearance spilled over on to men, thereby creating a new phenotype in both sexes.

But we still see some evidence that this selection pressure had targeted women. A twin study has shown that hair is, on average, lighter-colored in women than in men, with red hair being especially more frequent in females. Women also show greater variation in hair color (Shekar et al., 2008).

Do redheads have less fun?

Red is the least common of these new hair colors. It also seems to have a lower tipping point where preference gives way to non-preference—if not dislike. Indeed, in comparison to blondes, redheads become more easily the butt of ridicule and prejudice.

How come? Several reasons appear in the literature. One is that Judas, the betrayer of Christ, was red-haired. Yet this association of ideas may have originated in a much older one that the Church later recycled for its own purposes:

There can be little doubt that this tradition is simply the application of the old belief—much older than Judas Iscariot—that red-haired men are treacherous and dangerous, to the Arch-traitor, sometime during the early Middle Ages, when the popular imagination was busy making up biographies and biographical details for the saints and martyrs of the Church. (Baum, 1922)

This older folk belief had its basis in the idea that redheads are hotheaded and not to be trusted:

We must look further for an explanation of Judas color, and specially in the ill-omen of red hair. This itself took its beginning no doubt, like so much else of popular tradition, in the shrewd observation of natural phenomena. The common German proverb, "Roter Bart, untreue Art," represents a condensed popular judgment. Even to-day a red-haired man is assumed to be hot-headed and quick-tempered, and so not quite to be counted on. (Baum, 1922)

Is this true? Perhaps. Of all the different hair colors, red is the one that seems to have the most pleiotropic effects, e.g., skin type, freckling, beard color, etc. (Flanagan et al., 2000). There are also physiological consequences. Redheads seem to be more sensitive to painkillers, the effect being stronger in women than in men (Mogil et al., 2003). This increased sensitivity was noted over sixty years ago:

Dr. Paul M. Wood, Secretary-Treasurer of the American Board of Anaesthesiology, writes, " ... in twenty-two years of personal experience I have discovered that many difficulties have occurred with persons who have red hair. They do not seem to take anaesthetics in the same way that others do. Most of them are much more sensitive to the anaesthetic."

Dr. David M. Levy states that red headed persons in general go under anaesthetic more readily than do persons of other pigmentations.

Dr. Marco Nunez confirms these observations that red heads are affected more readily than are other persons. (Keeler, 1947)

We may have here one reason why red hair never became as common as other hair colors. There were too many side effects, and natural selection has probably not had enough time to iron them all out.

But culture has probably been just as important in determining the frequency of red hair. Whereas attitudes to red hair tend to be negative in Latin cultures, they are generally positive in Celtic cultures, as Curry (1916, pp. 18-19) notes in his study of medieval literature: “It is worthy of note, however, that in the Old Irish and Welsh red hair seems to be appreciated, tho to a less extent than the blonde.”

The last point is interesting because the frequency of red hair is much higher in the Celtic regions of Europe (Wikipedia). Has this prevalence been maintained at a higher level by a more “redhead-friendly” environment?

References

Baum, P.F. (1922). Judas's red hair, The Journal of English and Germanic Philology, 21, 520-529.

Curry, W.C. (1916). The Middle English Ideal of Personal Beauty, as found in the Metrical Romances, Chronicles, and Legends of the XIII, XIV, and XV Centuries. Baltimore: J.H. Furst Co.

Ellis, H. (2007 [1905]). Studies in the Psychology of Sex, Volume 4 (of 6), Teddington, Echo Library.

Flanagan, N., E. Healey, A. Ray, S. Philips, C. Todd, I.J. Jackson, M.A. Birch-Machin, & J.L. Rees. (2000). Pleiotropic effects of the melanocortin 1 receptor (MC1R) gene on human pigmentation, Human Molecular Genetics, 9, 2531-2537.

Frost, P. (2008). Sexual selection and human geographic variation, Special Issue: Proceedings of the 2nd Annual Meeting of the NorthEastern Evolutionary Psychology Society. Journal of Social, Evolutionary, and Cultural Psychology, 2(4),169-191.

http://137.140.1.71/jsec/articles/volume2/issue4/NEEPSfrost.pdf

Frost, P. (2006). European hair and eye color - A case of frequency-dependent sexual selection? Evolution and Human Behavior, 27, 85-103.

Frost, P. (1994). Geographic distribution of human skin colour: A selective compromise between natural selection and sexual selection? Human Evolution, 9, 141-153.

Keeler, C.E. (1947). Coat color, physique, and temperament. Materials for the Synthesis of Hereditary Behavior Trends in the Lower Mammals and Man, The Journal of Heredity, 38, 271-277.

Mogil, J.S., S.G. Wilson, E.J. Chesler, A.L. Rankin, K.V. S. Nemmani, W.R. Lariviere, M.K. Groce, M.R. Wallace, L. Kaplan, R. Staud, T.J. Ness, T.L. Glover, M. Stankova, A. Mayorov, V.J. Hruby, J.E. Grisel, & R.B. Fillingim. (2003). The melanocortin-1 receptor gene mediates female-specific mechanisms of analgesia in mice and humans, PNAS, 100, 4867–4872.

Shekar, S.N., D.L. Duffy, T. Frudakis, G.W. Montgomery, M.R. James, R.A. Sturm, & N.G. Martin. (2008). Spectrophotometric methods for quantifying pigmentation in human hair—Influence of MC1R genotype and environment. Photochemistry and Photobiology, 84, 719–726.

Thelen, T.H. (1983). Minority type human mate preference. Social Biology, 30, 162-180.

Wikipedia. Red hair
http://en.wikipedia.org/wiki/Red_hair