Discriminative Grandparental Investment in China : Evidence from an Undergraduate Questionnaire Study

Many studies in Western societies show a pattern of discriminative grandparental investment as follows: maternal grandmothers (MGMs) > maternal grandfathers (MGFs) > paternal grandmothers (PGMs) > paternal grandfathers (PGFs). This pattern is in line with the expectation from evolutionary reasoning. Yet whether or not this pattern applies in China is in question. The present study was based on a questionnaire survey at a university in Central China (N = 1,195). Results show that (1) when grandparent-grandchild residential distance during grandchildren's childhood is controlled, in the case of grandsons and granddaughters as a whole and granddaughters only, both grandparental caregiving and grandchildren's emotional closeness to grandparents display a rank order of MGM > MGF > PGM > PGF, but in the case of grandsons only, this order is not statistically significant. (2) There are stable relationships between grandparental caregiving/grandchildren's emotional closeness and residential distance/similarity in appearance. (3) The effects of residential distance on either PGFs' or PGMs' caregiving exceed those on either MGFs' or MGMs'. (4) The PGF and PGM prefer grandsons to granddaughters in their caregiving, whereas the MGF and MGM do not have a sex preference, and (5) the fact that the PGF and PGM invest more in grandsons than in granddaughters does not depend on grandsons' duration of living in a rural area. Our results suggest that (1) in general, the Chinese display a pattern of differential grandparental investment predicted by an evolutionary perspective, (2) the evolutionary perspective that combines the two factors of paternal uncertainty and sex-specific reproductive strategies is applicable to grandparental investment in China, and (3) the traditional son-preference culture also plays some role in affecting grandparental investment in China, though the roles of culture and urban-rural cultural difference should not be exaggerated.

Men's Psychopathy and Mating Effort in Intimate Relationships: Links with Jealousy and Sexual Coercion

Psychopathic men sometimes direct sexual aggression toward prospective female partners (e.g., using sexually aggressive behavior on a first date) and such behavior may be indicative of a high mating effort strategy. Less research has investigated the role of psychopathy in men's use of sexually coercive behaviors in their intimate relationships (e.g., sexual aggression directed toward one's long-term romantic partner) or the relationship processes that might facilitate such behavior. The present study surveyed 143 heterosexual dyads to assess men's psychopathic traits and their relation to self-reports and partner-reports of men's jealousy and partner sexual coercion. Results across informant models showed that men's psychopathy was associated with higher suspicious jealousy and partner sexual coercion. Suspicious jealousy also indirectly linked men's psychopathic traits with engaging in partner sexual coercion. The findings provide novel insights using dyadic data and suggest that both psychopathy and jealousy are important for men's engagement in partner sexual coercion.

Paternity Uncertainty and Parent-Offspring Conflict Explain Restrictions on Female Premarital Sex across Societies

Although norms of premarital sex vary cross-culturally, the sexuality of adolescent girls has been consistently more restricted than that of adolescent boys. Three major theories that attempt to explain restrictions on female premarital sex (FPS) concern male, female, and parental control. These competing theories have not been tested against each other cross-culturally. In this study, we do this using a sample of 128 nonindustrial societies and socioecological predictors capturing extramarital sex, paternal care, female status, sex ratio, parental control over a daughter's mate choice, residence, and marriage transactions, while also controlling for phylogenetic non-independence across societies. We found that multiple parties benefit from restrictions on FPS. Specifically, FPS is more restricted in societies intolerant of extramarital sex and where men transfer property to their children (male control), as well as where marriages are arranged by parents (parental control). Both paternity uncertainty (partitioned among marital fidelity and paternal investment) and parent-offspring conflict (prompting parents to control their daughter's sexuality) were identified as possible mechanisms of FPS restrictions. The evidence for female control is ambiguous, mainly because it can be equally well interpreted as both male control and parental control, and because fathers, rather than mothers, are often the primary decision makers about a daughter's mate choice. Our results also emphasize the importance of social roles, rather than stereotyped sex roles, as a more useful approach to understanding the evolution of FPS restrictions.

Reevaluating the grandmother hypothesis

Menopause is an evolutionary mystery: how could living longer with no capacity to reproduce possibly be advantageous? Several explanations have been offered for why female humans, unlike our closest primate relatives, have such an extensive post-reproductive lifespan. Proponents of the so-called "grandmother hypothesis" suggest that older women are able to increase their fitness by helping to care for their grandchildren as allomothers. This paper first distinguishes the grandmother hypothesis from several other hypotheses that attempt to explain menopause, and then develops a formal model by which these hypotheses can be compared and tested by empirical researchers. The model is then modified and used to respond to a common objection to the grandmother hypothesis: that human fathers, rather than grandmothers, are better suited to be allomothers due to their physical strength and a high incentive to invest in their own children. However, fathers-unlike maternal grandmothers-can never be sure that the children they are caring for are their own. Incorporating paternity uncertainty into the model demonstrates the conditions under which the grandmother hypothesis is more plausible than a hypothesis that focuses on the contributions of men.

Parental Investment Is Biased toward Children Named for Their Fathers

Namesaking (naming a child after a parent or other relative) can be viewed as a mechanism to increase perceived parent-child similarity and, consequently, parental investment. Male and, to a lesser extent, firstborn children are more frequently namesakes than female and later-born children, respectively. However, a direct link between namesaking and parental investment has not been examined. In the present study, 632 participants (98 men and 534 women) from Central Europe indicated their first name, sex, birth order, number of siblings, sexual orientation, socioeconomic status, paternal and maternal first names, as well as relationship quality with, and time and financial investment they received from, both parents during childhood. Mixed-effects models revealed associations between namesaking and parental investment. However, the effect of namesaking often appeared significant only in interaction with specific predictors, such as sex and primogeniture. It suggests instead that namesaking has an additive effect-it enhances the effect of biological factors on parental investment. In general, we found evidence for the bias in parental investment linked to name similarity among both parents, and support for the hypothesis that namesaking serves as a mechanism to increase paternity confidence and, thus, paternal investment. The effect of namesaking influences only certain types of parental investment-namely, those at the level of relationship quality. In addition, nonheterosexual orientation was the strongest negative predictor of paternal investment. Our study extends the research on parental investment by showing that cultural mechanisms, such as namesaking, can also exert some influence on parental rearing behavior.

Mother-male bond, but not paternity, influences male-infant affiliation in wild crested macaques

Abstract

In promiscuous primates, interactions between adult males and infants have rarely been investigated. However, recent evidence suggests that male affiliation towards infants has an influence on several aspects of the infants’ life. Furthermore, affiliations may be associated with male reproductive strategy. In this study, we examined which social factors influenced male-infant affiliation initiated by either male or infant, in wild crested macaques (Macaca nigra). We combined behavioral data and genetic paternity analysis from 30 infants living in three wild groups in Tangkoko Reserve, Indonesia. Our results indicate that adult males and infants do not interact at random, but rather form preferential associations. The social factors with the highest influence on infant-initiated interactions were male rank and male association with the infant’s mother. While infants initiated affiliations with males more often in the absence of their mothers, adult males initiated more affiliations with infants when their mothers were present. Furthermore, males initiated affiliations more often when they were in the same group at the time the infant was conceived, when they held a high dominance rank, or when they had a close relationship with the mother. Interestingly, paternity did not affect male-infant affiliation despite being highly skewed in this species. Overall, our results suggest that adult males potentially associate with an infant to secure future mating with the mother. Infants are more likely to associate with a male to receive better support, suggesting a strategy to increase the chance of infant survival in a primate society with high infant mortality.

Significance statement

We explore social relationships between males and infants in a promiscuous primate, the wild crested macaque. Our novel approach addresses the nature of affiliations both from males’ and infants’ perspectives. The results show that males and infants form preferential associations. Male-female affiliation, but not paternity, was a significant predictor of interactions initiated both by males and infants. Males initiated more interactions towards infants when the mother was in proximity, while infants initiated more interactions in her absence. Finally, high-ranking males were more likely to initiate interactions towards infants. We demonstrated that paternity is not a good predictor of male-infant affiliations, even in a species with a high reproductive skew and a relatively high confidence of paternity. Our paper is one of the first to show that infants are active agents in establishing and maintaining preferential relationships with males.

Electronic supplementary material

The online version of this article (doi:10.1007/s00265-016-2116-0) contains supplementary material, which is available to authorized users.