Assortative mating for height in the UK

PLoS ONE 8(1): e54186. doi:10.1371/journal.pone.0054186

Are Human Mating Preferences with Respect to Height Reflected in Actual Pairings?

Gert Stulp et al.

Pair formation, acquiring a mate to form a reproductive unit, is a complex process. Mating preferences are a step in this process. However, due to constraining factors such as availability of mates, rival competition, and mutual mate choice, preferred characteristics may not be realised in the actual partner. People value height in their partner and we investigated to what extent preferences for height are realised in actual couples. We used data from the Millennium Cohort Study (UK) and compared the distribution of height difference in actual couples to simulations of random mating to test how established mate preferences map on to actual mating patterns. In line with mate preferences, we found evidence for: (i) assortative mating (r = .18), (ii) the male-taller norm, and, for the first time, (iii) for the male-not-too-tall norm. Couples where the male partner was shorter, or over 25 cm taller than the female partner, occurred at lower frequency in actual couples than expected by chance, but the magnitude of these effects was modest. We also investigated another preference rule, namely that short women (and tall men) prefer large height differences with their partner, whereas tall women (and short men) prefer small height differences. These patterns were also observed in our population, although the strengths of these associations were weaker than previously reported strength of preferences. We conclude that while preferences for partner height generally translate into actual pairing, they do so only modestly.

Link

Quantifying an attractive body

An interesting study in which separate samples of young male and female students used software to "build" an attractive male and female body. It turns out that they both ended up creating quite similar physiques -with subtle differences- but while the ideal men's body had an "average" or even higher-than-average (accounting for mascularity) Body Mass Index, the ideal female's body had a lower BMI than almost all the women in the sample.

The figures on the left (A and B) were set by female participants, and on the right (C and D) by male ones. There is not much that is surprising in the paper, but here's an interesting finding:

An alternative explanation would be that the ideals are influenced by a common media environment which pushes them towards the same concept of the ideal body. However, there are subtle gender-specific differences in the media images seen in the magazines targeted at men and women. For the male body, magazines aimed at a male audience contain male models which are more muscular than those aimed at a female audience [31], [66]. For the female body, female models in women’s magazines are slimmer and have a smaller bust than female models in men’s magazines [53], [54]. This would suggest that there should be systematic differences between the ideals favoured by the two genders. 

This is partially what we find here. The male body selected by the male participants is indeed more muscular than the ideal male body chosen by the female participants. However, in the case of the ideal female body both men and women prefer a female body with the same low BMI, but the female participants prefer a larger bust size than the male participants. This directly contradicts what would be expected from the size and shape of the female models in their respective gender-specific media; the men should prefer a heavier female body than the women and a larger bust.

It might be interesting to repeat this experiment in a non-British sample as well as a sample that is not influenced by media. Anyone have an explanation to offer?

PLoS ONE 7(11): e50601. doi:10.1371/journal.pone.0050601

What Is an Attractive Body? Using an Interactive 3D Program to Create the Ideal Body for You and Your Partner

Kara L. Crossley

What is the ideal body size and shape that we want for ourselves and our partners? What are the important physical features in this ideal? And do both genders agree on what is an attractive body? To answer these questions we used a 3D interactive software system which allows our participants to produce a photorealistic, virtual male or female body. Forty female and forty male heterosexual Caucasian observers (females mean age 19.10 years, s.d. 1.01; 40 males mean age 19.84, s.d. 1.66) set their own ideal size and shape, and the size and shape of their ideal partner using the DAZ studio image manipulation programme. In this programme the shape and size of a 3D body can be altered along 94 independent dimensions, allowing each participant to create the exact size and shape of the body they want. The volume (and thus the weight assuming a standard density) and the circumference of the bust, waist and hips of these 3D models can then be measured. The ideal female body set by women (BMI = 18.9, WHR = 0.70, WCR = 0.67) was very similar to the ideal partner set by men, particularly in their BMI (BMI = 18.8, WHR = 0.73, WCR = 0.69). This was a lower BMI than the actual BMI of 39 of the 40 women. The ideal male body set by the men (BMI = 25.9, WHR = 0.87, WCR = 0.74) was very similar to the ideal partner set by the women (BMI = 24.5, WHR = 0.86, WCR = 0.77). This was a lower BMI than the actual BMI of roughly half of the men and a higher BMI than the other half. The results suggest a consistent preference for an ideal male and female body size and shape across both genders. The results also suggest that both BMI and torso shape are important components for the creation of the ideal body.

Link

Facial attractiveness and interracial marriage

The data:

From the paper:

The results of the experiment demonstrated that there are robust differences in the relative perceived attractiveness of different racial groups. Further, these differences are affected by the gender of the person being rated. Among males, Black faces were rated as the most attractive followed by White faces and then Asian faces. For the females, Asian faces were seen as the most attractive followed by White and then Black faces. The same pattern was found regardless of the ethnicity of the person doing the ratings.

Whatever the perceptions of attractiveness, it seems that people still tend to marry within their own races. For example, in the UK 0.24% of white females marry black males, and the corresponding percentage for the US is 0.56%. Since blacks make up roughly 1/10 of the population in the US, then if race was not an issue, we'd expect white females to marry black males about 10% of the time; the empirical figure is about ~20 times lower.

So, what this study shows is that while intra-racial marriage is still the norm, black males have an easier time overcoming the racial barrier compared to black females, and Asian females compared to Asian males.

The paper does not seem to present any facial attractiveness data, although it does present an analysis to discount an alternative hypothesis based on stature differences. According to that hypothesis, Asian females outmarry more easily than Asian males because Asians are shorter, and women tend to marry taller men than themselves.

PLoS ONE 7(2): e31703. doi:10.1371/journal.pone.0031703


A Facial Attractiveness Account of Gender Asymmetries in Interracial Marriage

Michael B. Lewis


Abstract 
Background
In the US and UK, more Black men are married to White women than vice versa and there are more White men married to Asian women than vice versa. Models of interracial marriage, based on the exchange of racial status for other capital, cannot explain these asymmetries. A new explanation is offered based on the relative perceived facial attractiveness of the different race-by-gender groups.

Method and Findings
This explanation was tested using a survey of perceived facial attractiveness. This found that Black males are perceived as more attractive than White or East Asian males whereas among females, it is the East Asians that are perceived as most attractive on average.

Conclusions
Incorporating these attractiveness patterns into the model of marriage decisions produces asymmetries in interracial marriage similar to those in the observed data in terms of direction and relative size. This model does not require differences in status between races nor different strategies based on gender. Predictions are also generated regarding the relative attractiveness of those engaging in interracial marriage.

Link

Voice pitch and semen quality

The effect was small, but, nonetheless quite interesting. If semen quality is linked to the probability of a pregnancy per copulation, and if voice attractiveness is linked to the expected number of copulations, then it's easy to see how a tradeoff between voice attractiveness and semen quality might work.

PLoS ONE 6(12): e29271. doi:10.1371/journal.pone.0029271

Low Pitched Voices Are Perceived as Masculine and Attractive but Do They Predict Semen Quality in Men?

Leigh W. Simmons et al.

Women find masculinity in men's faces, bodies, and voices attractive, and women's preferences for men's masculine features are thought to be biological adaptations for finding a high quality mate. Fertility is an important aspect of mate quality. Here we test the phenotype-linked fertility hypothesis, which proposes that male secondary sexual characters are positively related to semen quality, allowing females to obtain direct benefits from mate choice. Specifically, we examined women's preferences for men's voice pitch, and its relationship with men's semen quality. Consistent with previous voice research, women judged lower pitched voices as more masculine and more attractive. However men with lower pitched voices did not have better semen quality. On the contrary, men whose voices were rated as more attractive tended to have lower concentrations of sperm in their ejaculate. These data are more consistent with a trade off between sperm production and male investment in competing for and attracting females, than with the phenotype-linked fertility hypothesis.

Link

British men's hair color preferences

Scand J Psychol. 2011 Aug 29. doi: 10.1111/j.1467-9450.2011.00911.x. [Epub ahead of print]

British men's hair color preferences: An assessment of courtship solicitation and stimulus ratings.

Swami V, Barrett S.

Abstract

British men's hair color preferences: An assessment of courtship solicitation and stimulus ratings. Scandinavian Journal of Psychology. Two studies examined the influence of women's hair color on approach behavior by British men and on ratings of physical attractiveness and personality. In Study 1, a female confederate whose hair color was dyed blonde, brunette, or red was instructed to sit in several nightclubs. It was found that she was approached significantly more frequently by men in the blonde condition. In Study 2, images of the same confederate were rated by 126 men. Results showed that the brunette stimulus was rated as more physically attractive, intelligent, approachable, competent, and arrogant, whereas the blonde stimulus was rated as more needy. These results are discussed in relation to the literature on hair color and attractiveness, but also in terms of women's own perceptions of their hair color.

Link

Blue-eyed attractiveness: stereotype and reality

Aesthetic Plast Surg. 2011 Aug 20. [Epub ahead of print]

The Blue-Eyes Stereotype: Do Eye Color, Pupil Diameter, and Scleral Color Affect Attractiveness?

Abstract
BACKGROUND:
Blue eyes have been the embodiment of attractiveness not only for decades but even for centuries. The primary aim of this study was to determine whether iridal color, particularly color blue, can increase the attractiveness of a person's eye area. As a secondary aim, the study examined the impact of pupil diameter and scleral color on the attractiveness of the eye area.

METHODS:
The stimulus material comprised images of the eye areas of 60 women ages 15-65 years. A total of 80 participants rated the attractiveness of each eye area on a 7-point Likert scale and estimated the age of the person. The color values of the iris and sclera were measured. As an additional subsample, 50% of the participants were asked what features of each eye area they found particularly appealing.

RESULTS:
Most surprisingly, no correlation was found between iridal color and rated attractiveness. However, the participants mentioned the color blue more often as a positive aspect than other iridal colors. A high inverse correlation was observed between attractiveness of the eye area and age. The larger the pupil diameter and the whiter the scleral color, the lower was the real and perceived age and the higher was the attractiveness.

CONCLUSION:
The data showed that the "blue-eyes stereotype" does exist. People consider blue eyes attractive, but in reality, blue is rated as attractive as other iridal colors. Bright scleral color and large pupils positively affect attractiveness because both features are significantly correlated with youthfulness.

Link

Skin yellowness but not masculinity as indicators of male facial attractiveness

We should keep in mind that this sample was recruited from a fairly homogeneous population, and thus is not directly relevant if one is interested in attractiveness of people of different ancestry.

From the paper:

The regression retained only skin yellowness as a predictor of attractiveness, and the effect of skin yellowness was positive and highly significant (F(1,71) = 10.806, Beta = .366, t = 3.287, p less than .002). Skin lightness, redness and morphological masculinity did not significantly predict attractiveness (all p>.114, see Table 1).

On the left, faces that scored low/high in brightness (top), redness (middle), and yellowness (bottom). On the right, composites of low/high masculinity based on morphology (top row), ratings (middle row), and morphing of faces in a more feminine (bottom left) or more masculine direction (bottom right).

PLoS One. 2010 Oct 27;5(10):e13585.

Does masculinity matter? The contribution of masculine face shape to male attractiveness in humans.

Scott IM, Pound N, Stephen ID, Clark AP, Penton-Voak IS.

Abstract

BACKGROUND: In many animals, exaggerated sex-typical male traits are preferred by females, and may be a signal of both past and current disease resistance. The proposal that the same is true in humans - i.e., that masculine men are immunocompetent and attractive - underpins a large literature on facial masculinity preferences. Recently, theoretical models have suggested that current condition may be a better index of mate value than past immunocompetence. This is particularly likely in populations where pathogenic fluctuation is fast relative to host life history. As life history is slow in humans, there is reason to expect that, among humans, condition-dependent traits might contribute more to attractiveness than relatively stable traits such as masculinity. To date, however, there has been little rigorous assessment of whether, in the presence of variation in other cues, masculinity predicts attractiveness or not.

METHODOLOGY/PRINCIPAL FINDINGS: The relationship between masculinity and attractiveness was assessed in two samples of male faces. Most previous research has assessed masculinity either with subjective ratings or with simple anatomical measures. Here, we used geometric morphometric techniques to assess facial masculinity, generating a morphological masculinity measure based on a discriminant function that correctly classified >96% faces as male or female. When assessed using this measure, there was no relationship between morphological masculinity and rated attractiveness. In contrast, skin colour - a fluctuating, condition-dependent cue - was a significant predictor of attractiveness.

CONCLUSIONS/SIGNIFICANCE: These findings suggest that facial morphological masculinity may contribute less to men's attractiveness than previously assumed. Our results are consistent with the hypothesis that current condition is more relevant to male mate value than past disease resistance, and hence that temporally fluctuating traits (such as colour) contribute more to male attractiveness than stable cues of sexual dimorphism.

Link

Brown-eyed men perceived to be more dominant

(Last Update June 21)

The authors discovered that males with brown eyes were considered more dominant than males with blue eyes, but when they altered their pictures to turn brown eyes into blue, the effect persisted. Thus, it is not the color itself that creates the impression of dominance, but rather other factors correlated with the brown-eyed phenotype.

One of these "other factors" could be chin breadth, which is known to be perceived as dominant. From the paper:

The question arises: why are brown-eyed males rated as more dominant than blue-eyed? Some facial features such as square jaws, thick eyebrows and broad cheekbones are linked with higher perceived dominance; facial submissiveness, on the other hand, is characterized by a round face with large eyes, smallish nose, and high eyebrows (Berry, 1990; Berry & Mcarthur, 1986; Cunningham,Barbee, & Pike, 1990; Mazur, Halpern, & Udry, 1994; Mueller & Mazur,1997; Thornhill & Gangestad, 1994). The morphological differences between blue-eyed and brown-eyed males were visualized by deformation of thin-plate splines (Fig. 3). In contrast with blue-eyed males, brown-eyed males have statistically broader and rather massive chins, broader (laterally prolonged) mouths, larger noses, and eyes that are closer together with larger eyebrows. In contrast, blue-eyed males show smaller and sharper chins, mouths that are laterally narrower, noses smaller, and a greater span between the eyes. Especially the broader massive chin, bigger nose, and larger eyebrows of brown-eyed males may explain their higher perceived dominance.

The authors propose that true genetic linkage between eye color and these other facial features is unlikely, as eye color is determined by few loci, and these are unlikely to be the same ones that influence these other facial features. Thus, they propose a different explanation, namely that blue-eyed and brown-eyed children are treated differently by their parents as they grow up, and this "different treatment" manifests itself phenotypically. The argument in favor of different treatment stems from the fact that many people are born blue-eyed, but their eye color is set to a darker shade eventually. The authors write:

It is possible that subjects with blue eyes are treated as a small child for a longer period than brown-eyed children. Such early social experience may have been literally ‘‘inscribed” into their faces, preserved until adulthood, and finally bring on the perception of higher submissiveness. Rosenberg and Kagan (1987, 1989) investigated the association between eye color and behavioral inhibition, revealing that children with blue eyes are more inhibited. Coplan et al. (1998) found a significant interaction between eye color and social wariness within preschoolers. Blueeyed males were rated as more socially wary, i.e. being more temperamentally inhibited, displaying more reticent behavior and having more internalizing problems, than males with brown eyes, though there were no differences between blue- and brown-eyed females (Coplan et al., 1998).

There is an alternative explanation, that requires neither genetic linkage nor an environmental factor such as upbringing. That factor is latent population structure.

In a truly long-term random mating population, and assuming that eye color is not genetically linked with e.g. chin breadth, then all combinations of chin breadth and eye color would occur with a probability determined entirely by the frequency of their genetic determinants in the population.

However, consider the possibility that the population is an incomplete mixture of a blue-eyed "facially submissive" population element, and a brown-eyed "facially dominant" one. If that was the case, then brown-eyed folks would tend to have dominant facial features by reason of their ancestry rather than any genetic linkage between the two traits.

As an analogy, consider a hypothetical population made up of Europeans and East Asians. Initially, there would be a statistical association between straight hair and short stature in the total population that would be entirely due to population structure rather than either pleiotropic effects of genes affecting both characters or genetic linkage of hair/stature genes.

The Czech population is intermediate in its bigonial diameter between Germans and Slovaks (its immediate neighbors) [1], they are also genetically intermediate between Germans and Slavs. Procopius noted in early medieval times that Slavs had intermediate pigmentation. So, I wouldn't discount the possibility that population structure due to incomplete blending may account for eye color/facial structure associations in this population.

UPDATE:

Here are some values for German and Czech males from [1].

Bigonial (go-go): 97.6 / 109.5

Nasal height (n-sn): 52 / 54.0

Nasal breadth (al-al): 34.0 / 36.2

Mouth breadth (ch-ch): 50.9 / 53.8

Intercanthal distance (en-en): 31.2/30.9

Unfortunately there is no data for the eyebrows, but all of the above differences are in the expected direction under my theory: Germans have narrower jaws, smaller noses, narrower mouths, and eyes placed further apart than Czechs.

So, I think it is quite likely that the blue-eyed facially submissive type found in this sample may have a German origin.

PS: I did an average of the blue- and brown-eyed averages for reference:

[1] International anthropometric study of facial morphology in various ethnic groups/races, Leslie G Farkas, J Craniofac Surg 16:615-46

Personality and Individual Differences
Volume 49, Issue 1, July 2010, Pages 59-64

Eye color predicts but does not directly influence perceived dominance in men

Karel Kleisner et al.

This study focuses on the relationship between eye color, gender, and psychological characteristics perceived from the human face. Photographs of 40 male and 40 female students were rated for perceived dominance and attractiveness. Attractiveness showed no relation with eye color. In contrast, eye color had a significant effect on perceived dominance in males: brown-eyed men were rated as more dominant than men with blue eyes. To control for the effect of eye color, we studied perceived dominance on the same photographs of models after changing the iris color. The eye color had no effect on perceived dominance. This suggests that some other facial features associated with eye color affect the perception of dominance in males. Geometric morphometrics have been applied to reveal features responsible for the differences in facial morphospace of blue-eyed and brown-eyed males.

Link

Are mixed-race people more attractive?

This paper has received some attention in the media, so it is worthwhile to consider its thesis: that great attractiveness of mixed-race people is due to genetic heterosis.

From the paper:

Facial images were harvested from the social networking website facebook.com. These were collected according to social groups that the people submitting the images belonged to. People who were members of groups making reference to being of mixed race [eg ``mixed race and proud of it''](1) formed a mixed-race group (N . 483). People who were members of groups making reference to groups who were from geographical regions of the UK with minimal ethnic minorities (eg ``Cornish and proud of it'') formed a white group (N . 368). People who were members of groups that made reference to being Black and living in the UK (eg ``Black and brum'') or made reference to coming from parts of Africa (eg ``Gambian and proud'') formed a black group (N . 354).

...

Twenty white psychology students rated each face on its attractiveness on a 9-point scale (5 being of average attractiveness).

Before we consider the "Why" of the paper's title, it is worthwhile to consider whether the thesis itself "mixed-race people are perceived as more attractive" is supported by the evidence. I can think of several alternative explanations for the evidence:

• There is no reason to think that "mixed-race" people represent black-white mixes. In the British context, "mixed-race" may also include white-South Asian or white-East Asian people.
• There is no reason to think that white people from less cosmopolitan areas are equally attractive to white people from big cities. It's reasonable to assume that attractive people thrive in regions of high population density, since attractiveness is a social advantage: you will probably find more "hot" models, actors, PR people, waitresses, salesgirls, etc. in London than you will in Cornwall.
• There is no reason to think that people of average attractiveness (for their respective races) mate to produce mixed-race offspring. Interracial marriage is not the norm (it occurs at a far lower rating than random mating would predict), thus there appears to be a real psychological impediment to the practice. It is not unreasonable to postulate that people are willing to mate interracially for a higher-than-average member of a different race, with the greater attractiveness serving to overcome this obstacle. In any case, the assumption that random whites and blacks mate to produce interracial offspring is not obvious.
• There is no reason to think that people who join mixed-race groups on facebook are good representatives of mixed-race people in general. Non-normative individuals may have a positive, neutral, or negative attitude towards their ancestry, and it is reasonable that "happy" mixed-race people may be more likely to advertise the fact than "non-happy" ones, and that more attractive mixed-race people (representing more harmonious combinations) may be more likely to belong to the first category.
• Finally, there is no reason to think that people who are of mixed-race have the same age as non-mixed people. Race mixing is on the rise both due to immigration and to changing societal norms, so there is probably a negative correlation between racial admixture and age. Thus, the finding of this study may be simply an artifact of the higher average age of the unmixed vs. the mixed groups.

Thus, I don't really think there is any reason to seek the "why" of a non-evident fact. But, it is interesting to consider the explanation for the supposed greater attractiveness of mixed-race people: genetic heterosis. The paper really offers no new evidence that heterosis has an effect on attractiveness.

It would be worthwhile to do a comprehensive study of race and attractiveness. Thankfully, we now possess reasonable genetic estimators of racial admixture and heterozygosity; hopefully someone will have the funds and will to use them.

Nonetheless the paper is useful because it reveals a real effect: what the explanation for this effect is remains to be seen.

Perception 39(1) 136 – 138

Why are mixed-race people perceived as more attractive?

Michael B Lewis

Abstract

Previous, small scale, studies have suggested that people of mixed race are perceived as being more attractive than non-mixed-race people. Here, it is suggested that the reason for this is the genetic process of heterosis or hybrid vigour (ie cross-bred offspring have greater genetic fitness than pure-bred offspring). A random sample of 1205 black, white, and mixed-race faces was collected. These faces were then rated for their perceived attractiveness. There was a small but highly significant effect, with mixed-race faces, on average, being perceived as more attractive. This result is seen as a perceptual demonstration of heterosis in humans—a biological process that may have implications far beyond just attractiveness.

Link

Facial attractiveness ratios for Caucasoid women

Vision Research doi:10.1016/j.visres.2009.11.003

New “golden” ratios for facial beauty


Pamela M. Pallett et al.

Abstract

In four experiments, we tested the existence of an ideal facial feature arrangement that could optimize the attractiveness of any face given its facial features. Participants made paired comparisons of attractiveness between faces with identical facial features but different eye–mouth distances and different interocular distances. We found that although different faces have varying attractiveness, individual attractiveness is optimized when the face’s vertical distance between the eyes and the mouth is approximately 36% of its length, and the horizontal distance between the eyes is approximately 46% of the face’s width. These “new” golden ratios match those of an average face.

Link

Why Some Women Look Young for Their Age (Gunn et al. 2009)

On the left facial composites of younger/older (left/right) monozygotic/dizygotic twins (top/bottom).

PLoS ONE doi:10.1371/journal.pone.0008021

Why Some Women Look Young for Their Age

David A. Gunn et al.

Abstract

The desire of many to look young for their age has led to the establishment of a large cosmetics industry. However, the features of appearance that primarily determine how old women look for their age and whether genetic or environmental factors predominately influence such features are largely unknown. We studied the facial appearance of 102 pairs of female Danish twins aged 59 to 81 as well as 162 British females aged 45 to 75. Skin wrinkling, hair graying and lip height were significantly and independently associated with how old the women looked for their age. The appearance of facial sun-damage was also found to be significantly correlated to how old women look for their age and was primarily due to its commonality with the appearance of skin wrinkles. There was also considerable variation in the perceived age data that was unaccounted for. Composite facial images created from women who looked young or old for their age indicated that the structure of subcutaneous tissue was partly responsible. Heritability analyses of the appearance features revealed that perceived age, pigmented age spots, skin wrinkles and the appearance of sun-damage were influenced more or less equally by genetic and environmental factors. Hair graying, recession of hair from the forehead and lip height were influenced mainly by genetic factors whereas environmental factors influenced hair thinning. These findings indicate that women who look young for their age have large lips, avoid sun-exposure and possess genetic factors that protect against the development of gray hair and skin wrinkles. The findings also demonstrate that perceived age is a better biomarker of skin, hair and facial aging than chronological age.

Link

Ancestry-related assortative mating in latino populations (Risch et al. 2009)

When different races admix, then in the first few generations there is a spectrum of ancestry proportions, ranging from pure individuals of the constituent races to admixed individuals with varying proportions of ancestry.

If there is random mating, then over several generations all individuals tend to have similar ancestry proportions, determined by the number of founders from the two constituent races. Mix 30,000 Europeans with 70,000 Africans, randomly mate them for 10-20 generations, and pretty soon almost everyone will have 30:70 European/African ancestral proportions with a little variation.

However, if there is assortative mating, then this process takes much longer to complete, as matings of individuals with very different ancestry proportions are rare, and the spectrum of varying individual ancestry is maintained. In the above-mentioned example, if there is perfect assortative mating, then after 10-20 generations you will still have 30% of the population having 100% European genes, and 70% of them having 100% African ones.

Previously, I had argued that the fact that Latin Americans, unlike Central Asian Turkic populations (such as the Uyghurs), have such a wide spectrum of ancestry proportions is due to the more recent admixture in the Americas than in Central Asia (less time for homogenization to take place), and the continued importation of Europeans.

Assortative mating is a third factor that may be behind this phenomenon. A stronger parallel may be found in South Asia, where the two constituents have been co-existing for a much longer time, but under a rigid, formalized regime of assortative mating (the caste system), homogenization has not taken place.

Genome Biology doi:10.1186/gb-2009-10-11-r132

Ancestry-related assortative mating in latino populations

Neil Risch et al.

Abstract

Background

While spouse correlations have been documented for numerous traits, no prior studies have assessed assortative mating for genetic ancestry in admixed populations.

Results

Using 104 ancestry informative markers, we examined spouse correlations in genetic ancestry for Mexican spouse pairs recruited from Mexico City and the San Francisco Bay Area, and Puerto Rican spouse pairs recruited from Puerto Rico and New York City. In the Mexican pairs, we found strong spouse correlations for European and Native American ancestry, but no correlation in African ancestry. In the Puerto Rican pairs, we found significant spouse correlations for African ancestry and European ancestry but not Native American ancestry. Correlations were not attributable to variation in socioeconomic status or geographic heterogeneity. Past evidence of spouse correlation was also seen in the strong evidence of linkage disequilibrium between unlinked markers, which was accounted for in regression analysis by ancestral allele frequency difference at the pair of markers (European versus Native American for Mexicans, European versus African for Puerto Ricans). We also observed an excess of homozygosity at individual markers within the spouses, but this provided weaker evidence, as expected, of spouse correlation. Ancestry variance is predicted to decline in each generation, but less so under assortative mating. We used the current observed variances of ancestry to infer even stronger patterns of spouse ancestry correlation in previous generations.

Conclusions

Assortative mating related to genetic ancestry persists in Latino populations to the current day, and has impacted on the genomic structure in these populations.

Link

Facial contrast and attractiveness

This very interesting paper shows that there exists sexual dimorphism in facial contrast, with women having higher-contrast faces than males. By enhancing a face's contrast, it is made to appear more feminine, and thus (for women), more attractive. This empirical result demonstrates why women often enhance their appearance by applying makeup which increases the contrast of their eyes and mouth.

I only have one observation on the paper: it would be interesting to study the interplay between contrast and aspects of a face's geometry. Generally speaking there is sex dimorphism in lip geometry, with women having fuller lips. Lips that are too narrow or too full, however, are rated less attractive. By applying a dark shade on very narrow or very full lips, one may be emphasizing this unattractive trait and thus reducing the overall attractiveness of the face. It would be interesting to see whether increased contrast has positive effects across different facial geometries.

Another possible interplay might be between facial symmetry and contrast: enhanced contrast in an asymmetric face may bring into attention this asymmetry in a more pronounced way.

Finally it may be interesting to study the interplay of contrast with pigmentation traits: how does tracing the outline of the eyes affect attractiveness for light vs. dark eyes? How does pigmentation of the hair (which acts, as I have argued before, as a "frame" to the face, contrasting with lightness of skin), or conversely skin tanning combined with light hair, interplay with facial features?

Perception 2009 volume 38(8) pages 1211 – 1219doi:10.1068/p6331

A sex difference in facial contrast and its exaggeration by cosmetics

Richard Russell

Abstract. This study demonstrates the existence of a sex difference in facial contrast. By measuring carefully controlled photographic images, female faces were shown to have greater luminance contrast between the eyes, lips, and the surrounding skin than did male faces. This sex difference in facial contrast was found to influence the perception of facial gender. An androgynous face can be made to appear female by increasing the facial contrast, or to appear male by decreasing the facial contrast. Application of cosmetics was found to consistently increase facial contrast. Female faces wearing cosmetics had greater facial contrast than the same faces not wearing cosmetics. Female facial beauty is known to be closely linked to sex differences, with femininity considered attractive. These results suggest that cosmetics may function in part by exaggerating a sexually dimorphic attribute—facial contrast—to make the face appear more feminine and hence attractive.

Link

Facial shape preference in heterosexual and homosexual people

The finding that homosexual men prize masculine males faces and homosexual women prize masculine female ones seems consistent with the idea that there is a different etiology for homosexuality in men and women. As I have argued before, homosexual men are feminized, hence their preference for masculine male faces is easily explained. Homosexual behavior in women, however, is usually the outcome of either psychological trauma or plainness-of-appearance, and hence homosexual women do retain a preference for masculine appearance which they transfer to their own gender.

Arch Sex Behav. 2009 Oct 15. [Epub ahead of print]

Sex-Dimorphic Face Shape Preference in Heterosexual and Homosexual Men and Women.

Glassenberg AN, Feinberg DR, Jones BC, Little AC, Debruine LM.

Studies have used manipulated faces to test the preferences of heterosexual individuals for sexually dimorphic facial cues. In contrast to previous studies, which have generally excluded homosexual participants, we directly compared homosexual and heterosexual male and female preferences for manipulated sexual dimorphism in faces (homosexual males: n = 311; heterosexual males: n = 215; homosexual females: n = 159; heterosexual females: n = 218). Prior studies on sexual orientation and preferences for faces that were paired with masculine and feminine behavioral descriptors suggest that homosexual men prefer more masculine men and that homosexual women demonstrate no preference for either masculinity or femininity in women. In our study, we tested for similarities and differences among heterosexual and homosexual males and females with regard to their preferences for a more specific aspect of faces: sexual dimorphism of face shape. Homosexual men demonstrated stronger preferences for masculinity in male faces than did all of the other groups. Homosexual women demonstrated stronger preferences for masculinity in female faces than did heterosexual women. These results suggest attractiveness judgments of same-sex faces made by homosexual individuals are not a mirror image of those made by heterosexual individuals of the opposite sex. Our data suggest that face preferences of homosexual individuals reflect a system of biologically and socially guided preferences at least as complex as those found among heterosexual individuals.

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Hijab wearing and perception of intelligence/attractiveness

Body Image. 2009 Oct 6. [Epub ahead of print]

The influence of the hijab (Islamic head-cover) on perceptions of women's attractiveness and intelligence.

Mahmud Y, Swami V.

This study examined the effects of wearing the hijab, or Islamic headwear, on men's perceptions of women's attractiveness and intelligence. A total of 57 non-Muslim men and 41 Muslim men rated a series of images of women, half of whom were unveiled and half of whom wore the hijab. For attractiveness and intelligence ratings, a mixed analysis of variance showed a significant effect of hijab status, with women wearing the hijab being rated more negatively than unveiled women. For attractiveness ratings, there was no significant effect of participant religion, although non-Muslim men rated unveiled women significantly higher than veiled women. For intelligence ratings, non-Muslim men provided significantly higher ratings than Muslim men for both conditions. In addition, Muslim men's ratings of the attractiveness and intelligence of women wearing the hijab was positively correlated with self-reported religiosity. These results are discussed in relation to religious stereotyping within increasingly multi-cultural societies.

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Physical attractiveness and reproductive success

Evolution and Human Behavior
Volume 30, Issue 5, September 2009, Pages 342-350

Physical attractiveness and reproductive success in humans: evidence from the late 20th century United States

Markus Jokela

Abstract

Physical attractiveness has been associated with mating behavior, but its role in reproductive success of contemporary humans has received surprisingly little attention. In the Wisconsin Longitudinal Study (1244 women, 997 men born between 1937 and 1940), we examined whether attractiveness assessed from photographs taken at age 18 years predicted the number of biological children at age 53–56 years. In women, attractiveness predicted higher reproductive success in a nonlinear fashion, so that attractive (second highest quartile) women had 16% and very attractive (highest quartile) women 6% more children than their less attractive counterparts. In men, there was a threshold effect so that men in the lowest attractiveness quartile had 13% fewer children than others who did not differ from each other in the average number of children. These associations were partly but not completely accounted for by attractive participants' increased marriage probability. A linear regression analysis indicated relatively weak directional selection gradient for attractiveness (β=0.06 in women, β=0.07 in men). These findings indicate that physical attractiveness may be associated with reproductive success in humans living in industrialized settings.

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Eye-tracking of men's preferences for women's body shape

Arch Sex Behav. 2009 Aug 18. [Epub ahead of print]

Eye-Tracking of Men's Preferences for Waist-to-Hip Ratio and Breast Size of Women.

Dixson BJ, Grimshaw GM, Linklater WL, Dixson AF.

Studies of human physical traits and mate preferences often use questionnaires asking participants to rate the attractiveness of images. Female waist-to-hip ratio (WHR), breast size, and facial appearance have all been implicated in assessments by men of female attractiveness. However, very little is known about how men make fine-grained visual assessments of such images. We used eye-tracking techniques to measure the numbers of visual fixations, dwell times, and initial fixations made by men who viewed front-posed photographs of the same woman, computer-morphed so as to differ in her WHR (0.7 or 0.9) and breast size (small, medium, or large). Men also rated these images for attractiveness. Results showed that the initial visual fixation (occurring within 200 ms from the start of each 5 s test) involved either the breasts or the waist. Both these body areas received more first fixations than the face or the lower body (pubic area and legs). Men looked more often and for longer at the breasts, irrespective of the WHR of the images. However, men rated images with an hourglass shape and a slim waist (0.7 WHR) as most attractive, irrespective of breast size. These results provide quantitative data on eye movements that occur during male judgments of the attractiveness of female images, and indicate that assessments of the female hourglass figure probably occur very rapidly.

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Major Histocompatibility Complex (MHC) diversity and human facial attractiveness

Previous research has shown that faces of MHC heterozygous males are judged more attractive. The new study confirms the findings of the earlier one, by finding a preference of females to MHC heterozygous males, with MHC heterozygosity being predictive of facial averageness in both sexes.

Evolution Volume 62 Issue 10, Pages 2473 - 2486

GENETIC DIVERSITY REVEALED IN HUMAN FACES

Hanne C. Lie et al.

Abstract

From an evolutionary perspective, human facial attractiveness is proposed to signal mate quality. Using a novel approach to the study of the genetic basis of human preferences for facial features, we investigated whether attractiveness signals mate quality in terms of genetic diversity. Genetic diversity in general has been linked to fitness and reproductive success, and genetic diversity within the major histocompatibility complex (MHC) has been linked to immunocompetence and mate preferences. We asked whether any preference for genetic diversity is specific to MHC diversity or reflects a more general preference for overall genetic diversity. We photographed and genotyped 160 participants using microsatellite markers situated within and outside the MHC, and calculated two measures of genetic diversity: mean heterozygosity and standardized mean d2. Our results suggest a special role for the MHC in female preferences for male faces. MHC heterozygosity positively predicted male attractiveness, and specifically facial averageness, with averageness mediating the MHC-attractiveness relationship. For females, standardized mean d2 at non-MHC loci predicted facial symmetry. Thus, attractive facial characteristics appear to provide visual cues to genetic quality in both males and females, supporting the view that face preferences have been shaped by selection pressures to identify high-quality mates.

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Female mice prefer outbred males

BMC Evol Biol. 2009 May 16;9(1):104. [Epub ahead of print]

Females prefer the scent of outbred males: good-genes-as-heterozygosity?

Ilmonen P, Stundner G, Thosz M, Penn DJ.

ABSTRACT: BACKGROUND: There is increasing interest to determine the relative importance of non-additive genetic benefits as opposed to additive ones for the evolution of mating preferences and maintenance of genetic variation in sexual ornaments. The 'good-genes-as-heterozygosity' hypothesis predicts that females should prefer to mate with more heterozygous males to gain more heterozygous (and less inbred) offspring. Heterozygosity increases males' sexual ornamentation, mating success and reproduction success, yet few experiments have tested whether females are preferentially attracted to heterozygous males, and none have tested whether females' own heterozygosity influences their preferences. Outbred females might have the luxury of being more choosey, but on the other hand, inbred females might have more to gain by mating with heterozygous males. We manipulated heterozygosity in wild-derived house mice (Mus musculus musculus) through inbreeding and tested whether the females are more attracted to the scent of outbred versus inbred males, and whether females' own inbreeding status affects their preferences. We also tested whether infecting both inbred and outbred males with Salmonella would magnify females' preferences for outbred males. RESULTS: Females showed a significant preference for outbred males, and this preference was slightly more pronounced among inbred females. We found no evidence that Salmonella infection increased the relative attractiveness of outbred versus inbred males; however, we found no evidence that inbreeding affected males' disease resistance in this study. CONCLUSIONS: Our findings support the idea that females are more attracted to outbred males, and they suggest that such preferences may be stronger among inbred than outbred females, which is consistent with the 'good-genes-as-heterozygosity' hypothesis. It is unclear whether this odour preference reflects females' actual mating preferences, though it suggests that future studies should consider females' as well as males' heterozygosity. Our study has implications for efforts to understand how mate choice can provide genetic benefits without eroding genetic diversity (lek paradox), and also conservation efforts to determine the fitness consequences of inbreeding and the maintenance of genetic diversity in small, inbred populations.

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Waist-to-Hip Ratio across cultures

CURRENT ANTHROPOLOGY Volume 49, Number 6, December 2008
DOI: 10.1086/593036

Waist-to-Hip Ratio across Cultures: Trade-Offs between Androgen- and Estrogen-Dependent Traits


Elizabeth Cashdan

Abstract

A gynoid pattern of fat distribution, with small waist and large hips (low waist-to-hip ratio, or WHR) holds significant fitness benefits for women: women with a low WHR of about 0.7 are more fecund, are less prone to chronic disease, and (in most cultures) are considered more attractive. Why, then, do nearly all women have a WHR higher than this putative optimum? Is the marked variation in this trait adaptive? This paper first documents the conundrum by showing that female WHR, especially in non-Western populations, is higher than the putative optimum even among samples that are young, lean, and dependent on traditional diets. The paper then proposes compensating benefits to a high WHR that can explain both its prevalence and variation in the trait. The evidence indicates that the hormonal profile associated with high WHR (high androgen and cortisol levels, low estrogens) favors success in resource competition, particularly under stressful and difficult circumstances, even though this carries fitness costs in fecundity and health. Adrenal androgens, in particular, may play an important role in enabling women to respond to stressful challenges.

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