Gender disparities in material and educational resources differ by kinship system

Contemporary inequality exists at an unprecedented scale. Social scientists have emphasized the role played by material wealth in driving its escalation. Evolutionary anthropologists understand the drive to accumulate material wealth as one that is coupled ultimately to increasing reproductive success. Owing to biological caps on reproduction for women, the efficiency of this conversion can differ by gender, with implications for understanding the evolution of gender disparities in resource accumulation. Efficiency also differs according to the type of resources used to support reproductive success. In this paper, we review evolutionary explanations of gender disparities in resources and investigate empirical evidence to support or refute those explanations among matrilineal and patrilineal subpopulations of ethnic Chinese Mosuo, who share an ethnolinguistic identity, but differ strikingly in terms of institutions and norms surrounding kinship and gender. We find that gender differentially predicts income and educational attainment. Men were more likely to report income than women; amounts earned were higher for men overall, but the difference between men and women was minimal under matriliny. Men reported higher levels of educational attainment than women, unexpectedly more so in matrilineal contexts. The results reveal nuances in how biology and cultural institutions affect gender disparities in wealth. This article is part of the theme issue 'Evolutionary ecology of inequality'.

Communal breeding by women is associated with lower investment from husbands

According to Hamilton's rule, matrilineal-biased investment restrains men in matrilineal societies from maximising their inclusive fitness (the 'matrilineal puzzle'). A recent hypothesis argues that when women breed communally and share household resources, a man should help his sisters' household, rather than his wife's household, as investment to the later but not the former would be diluted by other unrelated members (Wu et al., 2013). According to this hypothesis, a man is less likely to help on his wife's farm when there are more women reproducing in the wife's household, because on average he would be less related to his wife's household. We used a farm-work observational dataset, that we collected in the matrilineal Mosuo in southwest China, to test this hypothesis. As predicted, high levels of communal breeding by women in his wife's households do predict less effort spent by men on their wife's farm, and communal breeding in men's natal households do not affect whether men help on their natal farms. Thus, communal breeding by women dilutes the inclusive fitness benefits men receive from investment to their wife and children, and may drive the evolution of matrilineal-biased investment by men. These results can help solve the 'matrilineal puzzle'.

A Cross-Cultural Comparison of Climacteric Symptoms, Health-Seeking Behavior, and Attitudes towards Menopause Among Mosuo Women and Han Chinese Women in Yunnan, China

Cultural *YZ and XZ contributed equally. background has been shown to influence climacteric symptoms of women. This study compares various characteristics of climacteric symptoms, illness conception, health-seeking behavior, and attitude towards menopause of Mosuo women, a Chinese ethnic minority with a matriarchal structure, and Han Chinese women, the majority ethnic group of China with a patriarchal structure. Through convenience sampling, 51 Mosuo and 47 Han women ages 40 to 60 completed a sociodemographic questionnaire, the modified Kupperman Menopause Index (KMI), the Self-Rating Scale of Illness Conception and Health Seeking Behavior (SSICHSB) and the Menopause Attitude Questionnaire (MAQ). The Mosuo and Han Chinese women are comparable with regard to their age, educational levels and menstrual status. During climacteric, Mosuo women showed less severe melancholia ( p = .009), reported less health-seeking behavior ( p = .009), and displayed more positive attitudes towards menopause than their Han Chinese counterparts ( p < .001). One predictive variable of the melancholia severity in Mosuo was "menarche age", while that in the Han group was "social view on the menopause". Future research with a larger sample is needed to deepen our understanding about the interaction between culture and climacteric symptoms.

Not leaving home: grandmothers and male dispersal in a duolocal human society

Some models predict that when husband and wife live separately in their own natal household, grandmothers maximize their inclusive fitness by favoring their sons over daughters, as daughters are in reproductive competition with each other. Analyses on the Mosuo living in Southwest China show some support for this argument, with grandmothers helping both sons and daughters but in different ways. Helping sons to stay at home may reduce their workload and help them gain mates.

Models suggest that dispersal patterns will influence age- and sex-dependent helping behavior in social species. Duolocal social systems (where neither sex disperses and mating is outside the group) are predicted to be associated with mothers favoring sons over daughters (because the latter are in reproductive competition with each other). Other models predict daughter-biased investment when benefits of wealth to sons are less than daughters. Here, we test whether sex-biased investment is occurring in the duolocal Mosuo of southwestern China. Using demographic and observational data from Mosuo, we show support for both hypotheses, in that 1) males are more likely to disperse from their natal household if their mother dies, but females are not; 2) a large number of brothers increases the likelihood that both females and males disperse, whereas a large number of sisters only increases female dispersal; 3) mothers help daughters reproduce earlier and reduce death risk of daughter’s children, but not sons or sons’ children; 4) data on multiple paternity show that female reproductive success does not suffer from multiple partners, and in males multiple mates are associated with higher reproductive success, indicating that mothers can benefit from investing in their sons’ mating effort; and 5) gift decisions reveal similar kin effects to those shown in the demographic data, with mothers helping adult daughters and adult sons equally, but helping only her daughter’s children, not her son’s children. Mosuo mothers may invest resources for parental investment in their daughters and their offspring, while investing in their sons mating effort.