Is there a link between paternity concern and female genital cutting in West Africa?

Here we explore the relationship between female genital cutting (FGC), sexual behaviour, and marriage opportunities in five West African countries. Using large demographic datasets (n 72,438 women, 12,704 men, 10,695 couples) we explore key (but untested) assumptions of an evolutionary proposal that FGC persists because it provides evolutionary fitness benefits for men by reducing non-paternity rates. We identify and test three assumptions implicit in this proposal. We test whether cut women have reduced extra-pair sex before or within marriage; whether FGC is associated with a younger age at marriage as an indication of partner preference; and whether individual and group-level indicators of paternity concern are associated with a stronger preference for marriage to women with FGC.Our results show that FGC status does not affect the odds of women engaging in several indicators of premarital sex, however women with FGC have significantly lower odds of having more than one lifetime sexual partner. We also show that women with FGC get married at a younger age which supports the argument that FGC status influences women's marriage opportunities, even when it does not restrict sexual activity. Finally, we find that in population groups where reported sexual activity and perceived risk of women's extra-pair sex is high, men have higher odds of marrying a first wife with FGC. Together, these results indicate that paternity certainty may be one of several factors contributing to the persistence of FGC in this sample, and that group-level sexual norms are key to maintaining the practice of FGC through the marriage market.     

Socioeconomic status during childhood and health status in adulthood: the Wrocław growth study

It has been widely observed that socioeconomic status (SES) is associated with frequency of cardiovascular disease. Both men and women of low socioeconomic position have increased risk of cardiovascular disease morbidity and premature death. In this study the relationship between SES in childhood, and health status at the age of 50 years was examined. Socioeconomic status in childhood was measured using objective (father's educational level and number of children in the family) and subjective (self-assessed SES in childhood declared in early adulthood) indicators. Data from the Wroclaw Growth Study were completed when subjects were 50 years old, and information concerning health status was added. The results indicated that the objective, universally used measures of SES in childhood such as father's educational level and size of family did not show any essential relationships with health outcomes in adulthood, both for men and women. By contrast, retrospective, self-assessed SES (as better, average or worse as compared with peers) in childhood was significantly associated with the appearance of cardiovascular disease among women aged 50 years. Women who at the beginning of their adult life declared better socioeconomic condition in childhood were significantly healthier at the age of 50 years (OR=3.43; p=0.02). Moreover, this appeared to be independent of BMI, SES and life-style in adulthood. For men, retrospective self-assessed SES showed no relation to health status at the age of 50 years. The gender differences in the relationships between self-assessed SES in childhood and health status in adulthood are explained by possible selective premature mortality among men from lower childhood SES and/or sex differences in cognitive abilities.     

Teenage childbearing: structural determinants in developing countries

Data for a sample of 50 developing countries are analysed to investigate the social correlates of the teenage birth rate. Of five major factors considered as predictors of national birth rates (socioeconomic development, family planning programmes, women's status, the sex ratio, and marriage patterns), regression analyses reveal that only the average age at marriage for women has a significant effect on the teenage birth rate. In contrast, all variables except the sex ratio and the average age at marriage for women have a significant effect on the total fertility rate.     

Mobility and Navigation among the Yucatec Maya

Sex differences in range size and navigation are widely reported, with males traveling farther than females, being less spatially anxious, and in many studies navigating more effectively. One explanation holds that these differences are the result of sexual selection, with larger ranges conferring mating benefits on males, while another explanation focuses on greater parenting costs that large ranges impose on reproductive-aged females. We evaluated these arguments with data from a community of highly monogamous Maya farmers. Maya men and women do not differ in distance traveled over the region during the mate-seeking years, suggesting that mating competition does not affect range size in this monogamous population. However, men’s regional and daily travel increases after marriage, apparently in pursuit of resources that benefit families, whereas women reduce their daily travel after marriage. This suggests that parental effort is more important than mating effort in this population. Despite the relatively modest overall sex difference in mobility, Maya men were less spatially anxious than women, thought themselves to be better navigators, and pointed more accurately to distant locations. A structural equation model showed that the sex by marital status interaction had a direct effect on mobility, with a weaker indirect effect of sex on mobility mediated by navigational ability.     

How does marriage affect length of life? Analysis of a French historical dataset from an evolutionary perspective

There are broadly two explanations for why human longevity appears to be extended by marriage. First, there is the social explanation, whereby the companionship, division of labour and the economic support that marriage offers is thought to extend life. Second, there is a selective explanation, whereby those individuals with high potential longevity are more attractive to the opposite sex and therefore more likely to get married. Here we analyse the “TRA” dataset from 19th century France, using an evolutionary approach to address the question of why marriage is linked to longevity, focussing particularly on sex differences. The dataset is based on death and marriage records from all of France between 1798 and 1901 and includes information on age at death, marriage and wealth for individuals whose surnames began with the letters TRA. We find that marriage is positively associated with longevity, particularly for men. In part, this is related to the higher rate of deaths for single males during marriageable age, as compared to a higher rate of deaths for females during marriage. There is a positive association between wealth (at death) and longevity for individuals who were single or married at death, with a stronger effect for singles. Analysis of the effect of spousal age gap on duration of survival after first marriage indicates that men who were married to younger women lived longer, whereas the longevity of women was not associated with the spousal age gap. We put forward an evolutionary perspective on marriage and longevity, hypothesizing that there is an important role for sexual selection in the association between marriage and longevity, with women selecting on characteristics associated with longevity, whilst men select on characteristics associated with reproductive potential.     

Male-biased operational sex ratios and the Viking phenomenon: an evolutionary anthropological perspective on Late Iron Age Scandinavian raiding

In this paper, we use a combination of evolutionary theory, ethnographic data, written sources, and archaeological evidence to develop a new explanation for the origins of Viking raiding. Our argument focuses on the operational sex ratio, which is the ratio of males to females in a society who are ready to mate at a given time. We propose that a combination of two practices – polygyny and concubinage – and the increase in social inequality that occurred in Scandinavia during the Late Iron Age resulted in a male-biased operational sex ratio. This would have created a pool of unmarried men motivated to engage in risky behaviours that had the potential to increase their wealth and status, and therefore their probability of entering the marriage market. With high-status men looking to instigate expeditions to acquire plunder and develop their reputations as war leaders, raiding represented a mutually beneficial means of achieving social advancement and success.     

Socio-economic Predictors of Life Style. A pilot study

In epidemiological studies there exists the evidence of relationship between socio-economic status (SES) and health. The suspicious cause of these differences is life-style. The aim of the presented study was to identify the relationship between SES, demographic characteristics and the life-style in an industrial region. A structured questionnaire was distributed to a random sample of some 3,000 aged 25-70 and collected by postal delivery. The SES and demographic factors being analysed were sex, age, education, marital status and economic situation of the family in the relationship with a wide range of information on life style. The data was analysed using the chi-square test and logistic regression. The total number of analysed questionnaires was 634. The lowest response-rate was in the group with the basic education. Significant differences were found by sex in education (less women with university degree) and household income (more women in the lowest income category, men in the highest one). A detail analysis of the aggregated variables (adjusted for all SES variables) found: passivity and contentment were in adverse correlation with the level of education and economic situation; psychical well-being was correlated with family status and economic situation, risk behaviour was correlated with all SES factors except sex and education. Among the analysed factors economical situation of respondents, family and education were the most significant determinants of the differences in life-style.     

Voice pitch alters mate-choice-relevant perception in hunter–gatherers

In humans, voice pitch is thought to be a cue of underlying quality and an important criterion for mate choice, but data from non-Western cultures have not been provided. Here we test attributions to and preferences for voices with raised and lowered pitch in hunter–gatherers. Using a forced-choice playback experiment, we found that both men and women viewed lower pitched voices in the opposite sex as being better at acquiring resources (e.g. hunting and gathering). While men preferred higher pitched women''s voices as marriage partners, women showed no overall preference for voice pitch in men. However, women who were currently breastfeeding had stronger preferences for higher pitched male voices whereas women not currently breastfeeding preferred lower pitched voices. As testosterone is considered a costly signal associated with dominance, heritable immunity to infection and low paternal investment, women''s preferences potentially reflect a trade-off between securing good genes and paternal investment. Men''s preferences for higher pitched female voices are probably due to an evolved preference for markers of fecundity, reflected in voice pitch.     

Possible evolutionary origins of human female sexual fluidity

I propose an evolutionary theory of human female sexual fluidity and argue that women may have been evolutionarily designed to be sexually fluid in order to allow them to have sex with their cowives in polygynous marriage and thus reduce conflict and tension inherent in such marriage. In addition to providing an extensive definition and operationalization of the concept of sexual fluidity and specifying its ultimate function for women, the proposed theory can potentially solve several theoretical and empirical puzzles in evolutionary psychology and sex research. Analyses of the National Longitudinal Study of Adolescent Health (Add Health) confirm the theory's predictions that: (i) women (but not men) who experience increased levels of sexual fluidity have a larger number of children (suggesting that female sexual fluidity, if heritable, may be evolutionarily selected); (ii) women (but not men) who experience marriage or parenthood early in adult life subsequently experience increased levels of sexual fluidity; and (iii) sexual fluidity is significantly positively correlated with known markers of unrestricted sexual orientation among women whereas it is significantly negatively correlated with such markers among men.     

HIV status and age at first marriage among women in Cameroon

Recent research has highlighted the risk of HIV infection for married teenage women compared with their unmarried counterparts (Clark, 2004). This study assesses whether a relationship exists, for women who have completed their adolescence (age 20-29 years), between HIV status with age at first marriage and the length of time between first sex and first marriage. Multivariate analysis utilizing the nationally representative 2004 Cameroon Demographic and Health Survey shows that late-marrying women and those with a longer period of pre-marital sex have the highest risk of HIV. Although women in urban areas overall marry later than their rural counterparts, the positive relationship between age at marriage and HIV risk is stronger in rural areas. The higher wealth status and greater number of lifetime sexual partners of late-marrying women contribute to their higher HIV risk. Given that the age at first marriage and the gap between first marriage and first sex have increased in recent years, focusing preventive efforts on late-marrying women will be of much importance in reducing HIV prevalence among females.     

Low Socioeconomic Status and Female-Biased Parental Investment: The Mukogodo Example

Hierarchies of wealth and ethnic prestige among East African herders present an opportunity to test the Trivers-Willard hypothesis that low socioeconomic status should correlate with female biases in parental investment. The Mukogodo are at the bottom of such a regional hierarchy due to their poverty and low status as former hunters. As a result of these factors, Mukogodo men have lower polygyny rates than their neighbors, and Mukogodo women have higher mean reproductive success than Mukogodo men. The data fulfill the prediction that there should be a bias in parental investment in favor of daughters. The sex ratio of the 0–4 age group and the reported sex ratio at birth are both female-biased. Although there is no evidence of infanticide, sons may be neglected in favor of daughters. Evidence from a dispensary and from a clinic run by a Catholic mission both show that the Mukogodo take daughters for treatment more often than they take sons. Also, daughters may be nursed longer than sons.     

Body mass index, socio-economic status and socio-behavioral practices among Tz’utujil Maya women

This study investigates the associations between body mass index (BMI), socio-economic status (SES) and related socio-behavioral practices including marriage and market visits in a population of adult Tz’utujil Maya women in Santiago Atitlán, Guatemala, aged 18-82. Mixed qualitative and quantitative methods include cross-sectional anthropometric measurements and semi-structured interviews gathered in 2007, as well as participant observation and purposive interviews conducted in 2007-2008. The regional quota sample of 53 semi-structured interviews was designed to be representative of the cantones (municipal divisions) of Santiago Atitlán. BMI was positively associated with years of schooling, income and literacy, all measures of SES. A statistical analysis of our data indicates that increased income, increased market visits and being married are significantly positively associated with BMI. Qualitative analysis based on the grounded theory method reveals relevant themes including a preoccupation with hunger and undernutrition rather than obesity, a preference for food quantity over dietary diversity, the economic and social influence of a husband, the effects of market distance and the increasing consumption of food from tiendas. These themes help to explain how SES, socio-behavioral practices and BMI are positively associated and can inform future public health interventions related to obesity and undernutrition.     

Unequal chances for reaching 'a good old age'. Socio-economic health differences among older adults from a life course perspective

This article provides an overview of the socioeconomic inequality in physical and psychological health of older adults between 55 and 85 years of age, with a focus on the older adults whose socioeconomic status (SES) remains at a low level all their life. Data are derived from 1471 men and 1568 women, participating in the Longitudinal Aging Study Amsterdam (LASA) in 1992/1993. Based on the parental and own level of education, respondents are divided in four categories: those with a life time low level of SES, those with downward or upward mobility in SES, and those with a life time high level of SES. Logistic regression analyses showed that older adults with upward SES mobility and life time high SES, had a lower risk for functional limitations, chronic diseases (men only), 6-year mortality, depression and loneliness, compared with the older adults with life time low SES. The disadvantaged position of the low SES persons with regard to age, health and psychosocial conditions explained the SES differences in depression, but SES differences in mortality (for men) and in functional disability (for men and women) are not explained by the risk factors under study. SES differences in loneliness were attributed to differences in psychosocial conditions. Lifestyle did not add to the explanation of any of the SES differences. There were only small differences between those with a life time low SES and those with downward mobility in SES. It is concluded that a low level of education (regardless of the parental level) contributes to restricted psychosocial conditions, health problems and low well-being in old age, thereby decreasing the chances for a 'good old age' considerably.     

BMI may overestimate the prevalence of obesity among women of lower socioeconomic status

Objective: Our objective was to examine gender differences in height and weight associated with socioeconomic status (SES) and the consequent effect on body mass index in a multiethnic society. Research Methods and Procedures: A cross‐sectional study, the First Israeli National Health and Nutrition Survey, was performed on a representative population sample of 3246 adults 25 to 64 years of age, between the years 1999 to 2001. Height and weight were measured, and BMI and other weight‐height indices were calculated. SES was assessed by income and education. Results: Age‐adjusted height was significantly lower at lower levels of SES among both women and men (p < 0.001). As opposed to men, women of lower SES were heavier than those of higher SES, and the mean age‐adjusted weight was 4.6 kg higher among those of lower SES (p < 0.001). Thus, using the standard index of BMI, the prevalence of obesity was significantly higher among shorter women. Discussion: In this group of Israeli adults, the unfavorable effect of low SES on BMI was evident among women, partly due to their decreased height combined with increased weight common in this socioeconomic sector. Since BMI is only partly independent of height, it may overestimate the prevalence of obesity among women of lower SES. Alternative measures for classifying obesity in the lower SES groups that put less emphasis on height may be considered and studied.     

Ritual fights and male reproductive success in a human population

Ritual fights are widespread across human populations. However, the evolutionary advantage associated with this behaviour is unclear because these fights rarely provide direct benefits such as territory, resources or mates. Here, the reproductive success of men competing in a traditional ritual fight, Sereer wrestling, was investigated for the first time. Involvement in wrestling had a significant positive effect on men’s number of offspring and a marginally significant effect on polygyny, controlling for age, body condition and socio‐economic status. These positive effects suggest that being involved in wrestling competition provides prestige, facilitating access to mates and thereby increasing fecundity. However, when women were interviewed on their preference concerning qualities of potential mates, the quality ‘being involved in wrestling competition’ was poorly ranked. This discrepancy may arise either from deceptive reports or from discordance between parents and daughters in the choice of a husband.     

Sex,status, and reproductive success in the contemporary United States

This paper reexamines the relationship between status and reproductive success (at the ultimate and proximate levels) using data on sex frequency and number of biological children from representative samples of the U.S. population. An ordered probit analysis of data from the 1989–2000 General Social Survey (GSS) shows that high-income men report greater frequency of sex than all others do. An OLS regression of data from the 1994 GSS shows that high-income men have more biological children than do low-income men and high-income women. Furthermore, more educated men have more biological children than do more educated women. Results also show that intelligence decreases the number of offspring and frequency of sex for both men and women.     

The effect of socio-economic status and food availability on first birth interval in a pre-industrial human population

Individual variation in nutritional status has direct implications for fitness and thus is crucial in shaping patterns of life-history variation. Nevertheless, it is difficult to measure in natural populations, especially in humans. Here, we used longitudinal data on individual life-histories and annual crop yield variation collected from pre-industrial Finnish populations experiencing natural mortality and fertility to test the validity of first birth interval (FBI; time between marriage and first birth) as a surrogate measure of nutritional status. We evaluated whether women with different socio-economic groups differ in length of FBI, whether women of poorer socio-economic status and experiencing lower crop yields conceive slower following marriage, and whether shorter FBI is associated with higher lifetime breeding success. We found that poorer women had longer FBI and reduced probability of giving birth in months with low food availability, while the FBI of richer women was not affected by variation in food availability. Women with shorter FBI achieved higher lifetime breeding success and a faster reproductive rate. This is, to our knowledge, the first study to show a direct relationship between environmental conditions and speed of childbirth following marriage, highlighting the value of FBI as an indicator of nutritional status when direct data are lacking.     

Preferences for sex of children: a multivariate analysis

Data from the 1973-74 Growth of Alberta Family Study were used to determine whether women who express a preference for sons versus daughters differ from each other in terms of selected characteristics. 67% of the 599 women surveyed indicated a preference for at least 1 child of each sex. However, the majority of those who wanted 3 children desired 2 sons and 1 daughter, indicating a slight son preference. Discriminant function analysis indicated the pull toward son preference was greater the higher the woman's education, the more sisters the wife has, and the higher the current family size and number of additional children expected. While the number of wife's sisters makes the greatest contribution to daughter preference among adolescent mothers, birth place (Canada) was most important among older women. Finally, it was shown that acceptance of traditional female roles was a significant discriminator among women with a strong sex preference and those with no sex preference at all. These findings suggest that sex preference may become an important factor in fertility decisions as family size continues to decrease. If sex predetermination were to become possible, an imbalance in the sex ratio is a likely result.     

Social status and the secondary sex ratio: new evidence on a lingering controversy

Because women are more likely than men to use social status as a criterion in mate selection, evolutionary theory has led to the hypothesis that higher proportions of males will be born to parents of high social status than to parents of low status. To date, the research that has tested this deduction has not provided consistent support. This could be partly due to the small sample size in several of the studies. The present study tested the hypothesis using 6 different social status measures provided by more than 11,000 United States and Canadian college students. The offspring sex ratio was measured by asking the students their own sex plus that of each of their siblings. No evidence was found to support the hypothesis that parental social status has any significant effect on the sex ratio of offspring.     

Musical improvisation skill in a prospective partner is associated with mate value and preferences,consistent with sexual selection and parental investment theory: Implications for the origin of music

Music is a human universal, which suggests a biological adaptation. Several evolutionary explanations have been proposed, covering the entire spectrum of natural, sexual, and group selection. Here we consider the hypothesis that musical behaviour constitutes a reliable or even costly signal of fitness, and thus may have evolved as a human trait through sexual selection. We experimentally tested how musical performance quality (MPQ), in improvisations on the drums, saxophone, and violin, affects mate values and mate preferences perceived by a prospective partner. Swedish student participants (27 of each sex) saw a face of a person of the opposite sex and heard a piece of improvised music being played. The music occurred in three levels of MPQ and the faces in three levels of facial attractiveness (FA). For each parametric combination of MPG and FA, the participants rated four mate value scales (intelligence, health, social status, and parenting skill) and four mate preference scales (date, intercourse, and short- and long term relationship). Consistent with sexual selection theory, mate value ratings were generally increased by MPQ for raters of both sexes. Consistent with more specific hypotheses that follow from combining sexual selection and parental investment theory, women’s but not men’s preference for a long-term, but not short-term, relationship was significantly increased by MPQ, MPQ generally affected women’s ratings more than men’s, FA generally affected men’s ratings more than women’s, and women’s ratings of intelligence were even more influenced by MPQ than by FA.