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Ecological and socio-cultural impacts on mating and marriage systems
Abstract
This article explores how human mating and marriage systems are affected by conditions of ecology, by cultural practices, and by the interactions of these two forces. Given the great diversity in marriage rules and rules about association and sexual conduct across societies, it would be easy to throw up one's hands and regard these patterns as somehow 'purely cultural'. There are, however, often (sometimes non-obvious) influences of the distribution, abundance, and predictability of resources that shift the likelihood of success and persistence for different cultural systems. Thus, cultural and genetic changes over time seem to be inevitably linked, and marriage rules lie at the heart of this phenomenon. However, defining 'culture' in a way useful to hypothesis testing is difficult, and culture and genetics change in different ways.
... In nonhuman species mate provisioning tends to be associated with copulation (e.g., courtship feeding), and transfers of resources in this context typically flow from males to females rather than reciprocally ( Stevens and Gilby, 2004). A further peculiar aspect of marital unions, compared to nonhuman mating partnerships, is the potential direct involvement of third parties ( Low, 2003Low, , 2007). For example, parents may be actively involved in selecting a spouse for their offspring; together with other kin, they may exert control over the timing of the union. ...
... In the evolutionary literature these peculiarities have often been portrayed as cultural 'frills' attached to the human mating system. In one view, the marriage system is simply a set of rules and norms grafted onto the mating system (e.g., Low, 2003Low, , 2007). Another view draws on the distinction, developed for nonhuman species, between the social mating system and the sexual/genetic one. ...
... The central idea derived from the classical paradigm of behavioral biology is that in humans, as in other mammals, polygyny is the 'default' mating system (see recent reviews in Low, 2003Low, , 2007). Men, like males in other species, seek to increase the number of matings, often through intrasexual competition. ...
A marriage system is the set of rules and norms that regulate reproduction in a given human society. This article provides an overview of key concepts and general themes in the study of their evolution. The focus is on the number of spouses allowed (i.e., whether marriage is monogamous or polygamous), and the social and ecological factors associated with this aspect of the marriage system.
... Extension of this paradigm to human social systems is used to explain the cross-cultural prevalence of polygynous marriage (e.g. Low, 2003Low, , 2007Marlowe, 2003). In some societies that allow polygynous marriage the majority of men may be each married to a single wife, because few command sufficient skill or resources to marry polygynously (White, 1988). ...
... 'monogamy ' (e.g. Marlowe, 2003), is common among foragers and likely evolved because of the benefits of biparental care to offspring survival (Low, 2003(Low, , 2007. This is distinct from the system of social monogamy found in the remaining 17% of societies, in which polygynous marriage is forbidden or disapproved (Murdock & White, 1969;Murdock & Wilson, 1972). ...
... These findings suggest that monogamous marriage can be understood within the framework of inclusive fitness theory. In turn, this challenges previous evolutionary explanations for the emergence of monogamous marriage, and for variation in marriage strategies across societies more generally: the former assume the implication of group-level processes, while both assume that male reproductive success is always maximized by polygynous marriage or, equivalently, that variance in male reproductive success is always greater under polygynous than under monogamous marriage (Low, 2003(Low, , 2007. The framework we develop makes both assumptions unnecessary. ...
The majority of human societies allow polygynous marriage, and the prevalence of this practice is readily understood in evolutionary terms. Why some societies prescribe monogamous marriage is however not clear: current evolutionary explanations--that social monogamy increases within-group co-operation, giving societies an advantage in competition with other groups--conflict with the historical and ethnographic evidence. We show that, within the framework of inclusive fitness theory, monogamous marriage can be viewed as the outcome of the strategic behaviour of males and females in the allocation of resources to the next generation. Where resources are transferred across generations, social monogamy can be advantageous if partitioning of resources among the offspring of multiple wives causes a depletion of their fitness value, and/or if females grant husbands higher fidelity in exchange for exclusive investment of resources in their offspring. This may explain why monogamous marriage prevailed among the historical societies of Eurasia: here, intensive agriculture led to scarcity of land, with depletion in the value of estates through partitioning among multiple heirs. Norms promoting high paternity were common among ancient societies in the region, and may have further facilitated the establishment of social monogamy. In line with the historical and ethnographic evidence, this suggests that monogamous marriage emerged in Eurasia following the adoption of intensive agriculture, as ownership of land became critical to productive and reproductive success.
... This may constrain variation in these 'ecological' traits, as inappropriate variants would be less desirable and purifying selection would quickly act to remove them should they be adopted. The success of different 'social' traits may be more indirect and harder to evaluate, with the 'best' system potentially being very different for different individuals within a society [26,28], resulting in greater change between alternate forms of such traits. Alternatively, if the environment changes relatively rapidly, as may occur during a population expansion into new habitats, then environmental traits may be more liable to change than 'social' traits. ...
... Our 'environmental' traits are of course mediated and perpetuated by social structures, norms and interactions. Equally, the traits we classified as 'social' can be plausibly linked to underlying ecological conditions [28,42], albeit at least a step removed from the kinds of environmental traits we have discussed. In other words, while the fitness consequences of employing a sub-optimal subsistence strategy are likely to be severe and immediate, the consequences for a society of having an inefficient inheritance system may be less obvious and may take longer to act on the fitness of individuals. ...
A fundamental issue in understanding human diversity is whether or not there are regular patterns and processes involved in cultural change. Theoretical and mathematical models of cultural evolution have been developed and are increasingly being used and assessed in empirical analyses. Here, we test the hypothesis that the rates of change of features of human socio-cultural organization are governed by general rules. One prediction of this hypothesis is that different cultural traits will tend to evolve at similar relative rates in different world regions, despite the unique historical backgrounds of groups inhabiting these regions. We used phylogenetic comparative methods and systematic cross-cultural data to assess how different socio-cultural traits changed in (i) island southeast Asia and the Pacific, and (ii) sub-Saharan Africa. The relative rates of change in these two regions are significantly correlated. Furthermore, cultural traits that are more directly related to external environmental conditions evolve more slowly than traits related to social structures. This is consistent with the idea that a form of purifying selection is acting with greater strength on these more environmentally linked traits. These results suggest that despite contingent historical events and the role of humans as active agents in the historical process, culture does indeed evolve in ways that can be predicted from general principles.
... Humans show all types of mating systems such as polyandrous relationships, polygynous, promiscuity, and monogamous. As human is a social animal, thus 83% of human societies are polygynous, and 0.05% are polyandrous (Low 2007). Hippies and some taboo culture peoples are often show promiscuity mating relationships where they believe in extrapair copulations. ...
Mating is the purpose of sexual reproduction by pairing of either two opposite sexually reproducing animals or hermaphrodite organisms in terms of copulation for insemination and subsequent internal fertilization to uphold the gene pool from generation to generation for existing species.
... Infanticide has been practiced in every culture (Williamson, 1978) and is more often performed by women than men (e.g., Kaye et al., 1990). Polygynous mating, which characterizes many current and past societies (Low, 2007), means that a husband is more likely to have a son than any one of his wives (because he has multiple mates), and this coupled with patrilineal inheritance may motivate a mother to commit infanticide of her daughter or a rival wife's son (e.g., Strassmann, 1997). Lying about sexual infidelity may be another such context, given that women are more likely than men to be killed for sexual infidelity by romantic partners (e.g., Chimbos, 1978;Gartner et al., 1998). ...
Beliefs about which sex lies more or is better at lying can have subtle but widespread effects on human interactions, yet little is known about such beliefs. In Study 1, an American sample of participants ( N = 407, ages 18–64) completed a 12-item survey on perceptions of sex differences in deception. In Study 2, a Korean sample ( N = 197, ages 19–58) completed the same survey. Men from both cultures and Korean women perceived no difference regarding which sex tells more white (i.e., relatively harmless or low-stakes) lies. American women perceived that women tell more white lies. Women from both cultures and American men perceived that men tell a greater number of serious (i.e., nonwhite or high-stakes) lies. Korean men perceived no difference regarding which sex tells a greater number of serious lies. Both sexes from both countries reported a perception that (1) men are more likely to lie about height, income, and sexual infidelity, (2) women are more likely to lie about weight and age, and (3) women are better at lying. The findings were mixed regarding perceptions about emotional infidelity. Results are interpreted in light of sex-different challenges to mating and parenting.
... The predominant form of family relationship in humans is biparental care [1][2][3], which occurs in less than 10% of all mammalian species [4]. In biparental family structures, the father supports the mother in caring for the young. ...
When fathers leave the family, mothers are at increased risk of developing depression and anxiety disorders. In biparental, socially monogamous prairie voles (Microtus ochrogaster), sudden bond disruption increases passive stress-coping, indicative of depressive-like behavior, and acts as chronic stressor in both males and females. However, the consequences of separation in lactating prairie vole mothers are unknown. In the present study, following 18 days of cohousing, half of the prairie vole pairs were separated by removing the male. In early lactation, maternal care was unaffected by separation, whereas anxiety-related behavior and passive stress-coping were significantly elevated in separated mothers. Separation significantly increased corticotropin-releasing factor (CRF) mRNA expression in the paraventricular nucleus of the hypothalamus under basal conditions, similar to levels of paired females after acute exposure to forced swim stress. A second cohort of lactating prairie voles was infused intracerebroventricularly with either vehicle or the CRF receptor antagonist D-Phe just prior to behavioral testing. The brief restraining during acute infusion significantly decreased arched back nursing in vehicle-treated paired and separated groups, whereas in the D-Phe-treated separated group the behavior was not impaired. Furthermore, in the latter, anxiety-related behavior and passive stress-coping were normalized to levels similar to vehicle-treated paired mothers. In conclusion, maternal investment is robust enough to withstand loss of the partner, whereas the mother's emotionality is affected, which may be - at least partly - mediated by a CRF-dependent mechanism. This animal model has potential for mechanistic studies of behavioral and physiological consequences of partner loss in single mothers.
... Sororal polygyny is very common across the globe; 72 in fact, it is almost as common as non-sororal polygyny. 73 Evolutionary theorists suggest that "competition among co-wives for scarce resources may be one of the reasons why sororal polygyny is very common," 74 as kin selection encourages them to cooperate rather than compete. In these marriages, there is "less conflict among the wives because each is an aunt to the other's children," 75 and thus mothers are less resentful about material resources being diverted to the other wives' children. ...
Cases concerning polygamous households can present difficult challenges for family courts. Though a growing number of Americans practice polygamy, the lifestyle still remains shrouded in mystery. Many polygamists are religious (and sometimes racial) minorities that have suffered from discrimination. The most influential judicial precedents concerning polygamy come from the nineteenth century and are tinged with religious and racial stereotypes, which can make judges uncomfortable with citing those decisions. There is a need for reliable, unprejudiced, and up-to-date information about polygamy that judges can cite while maintaining an image of objectivity and impartiality. This working paper seeks to provide that resource. It provides information about the evolutionary influences that shape polygamy, how polygamy is practiced in the modern world, and common problems affecting polygamous households that judges should be aware of.
... Polygyny is the most common mammalian mating system, probably because of the prevalence of female specialization in infant nutritional provisioning and care and male specialization in mating effort (Low, 2003(Low, , 2007Reichard and Boesch, 2003). In highly polygynous species, a few males will have many offspring while many others will have none. ...
Sex differences in human mortality rates emerge from a complex interaction of genetic heritage and developmental environment, incorporating genetic, physiological, psychological, social, and environmental factors whose influences and interconnections are best understood in an integrative evolutionary life history framework. Across mammals, males allocate greater investment to reproductive effort at the expense of investment in somatic effort and more investment in mating effort at the expense of investment in parenting effort compared to female life history. Thus, the generally higher male mortality rates result from the trade-off between reproductive competitiveness and longevity. Men on average have riskier behavioral patterns and greater physiological susceptibility than women, dying at higher rates from behavioral and most nonbehavioral causes across the life span. The magnitude of the sex difference in mortality in developed nations peaks when males sexually mature and enter into mating competition. Sex differences in investment towards parenting and mating competition are ultimately responsible for sex differences in mortality rates, and the intensity of male mating competition predicts the extent to which male mortality rates exceed those for females. In humans, male competition for mates includes competition for resources and social status utilized to attract and retain mates. Social and environmental conditions intensifying such male competition lead to increased male mortality.
... journals/1568539x. (Low, 2003(Low, , 2009, presumably because some males can attract and defend more mates when the need to provide for them is reduced, or conversely, because the absence of male productivity as a factor in female mate choice reveals other male qualities with greater variance (Scelza, 2013). Similarly, polygyny is more common in high pathogen environments were fewer men make viable partners (Low, 1990). ...
Our closest living relatives, bonobos and chimpanzees, along with small-scale human societies figure prominently in debates about human nature. Here we emphasize and explain behavioural variation within and among these three species. In the logic of behavioural ecology, individuals have been selected to adjust their behaviour along evolved reaction norms that maximize fitness given current socio-ecological conditions. We discuss variation in three behavioural contexts: relationships between the sexes, hierarchy and inequality, and intergroup interactions. In each context, behavioural variation can be related to two broad socio-ecological conditions: (i) the defensibility of contested resources, and (ii) differences in bargaining power. When defensibility of resources and differences in bargaining power are great, interactions are rife with conflict; when they are minimal, interactions are more harmonious. These socio-ecological conditions therefore constitute key catalysts and obstacles of cooperation. We conclude that human nature should be seen as consisting of evolved reaction norms.
... Most mammal species are polygynous, probably because of the relative male specialization in mating eff ort and female specialization in infant nutritional provisioning and care (Low, 2003(Low, , 2007Reichard & Boesch, 2003). In highly polygynous species, a few males will have many off spring while many others will have none, thus creating powerful selection for traits that lead to success in mating competition-even if these traits are detrimental to many individuals (Kirkwood & Rose, 1991;Stearns, 1992;Williams, 1957). ...
Aggression and violence are common elements of male mating competition across animal species. The level of violence across species, across human populations, and across individuals within societies corresponds with the intensity of male mating competition. In humans, peak rates of violence and homicide occur as males reach reproductive maturity and contest directly for mates, as well as for the social status and resources that facilitate attraction of prospective partners. In modern societies, levels of mortality from violence decrease considerably as males marry, start families, and undergo a life history shift from mating effort to paternal investment. In other societies, especially those with extended male fertility from additional sequential and/or simultaneous mating partners, risky behaviors including violence persist at higher levels throughout adulthood. Across species, those with higher degrees of male reproductive inequality (polygyny) have higher rates of violence and male mortality. There is a parallel pattern for the degree of polygyny across human populations, as well as for the degree of inequality in social status and resource holdings that are historically tied to male reproductive success. Temporal fluctuations in social stressors such as higher extrinsic mortality and higher socioeconomic inequality also elevate rates of violent behavior and mortality from homicide within societies. Androgen production mirrors the pattern of risky and violent male behavior across the life span, indicating a physiological basis in the mechanisms underlying male sexuality.
... <h3>Polygyny increases the effective population sex ratio Most mammal species are polygynyous, where one male has several female mates and male reproductive success is more highly skewed. This is likely due to the high degree of female parental investment, including breastfeeding, and male specialization in mating effort (Low, 2003(Low, , 2007Reichard and Boesch, 2003). In highly polygynous species, a few males will have many offspring while many others will have none, creating powerful selection pressure for traits that lead to success in mating competition at the expense of longevity (Plavcan, 2000). ...
The degree and form of sexual conflict is strongly influenced by the relative proportions of potentially reproductive males and females in a population. Patterns following from the operational sex ratio of groups in other species are reflected in human populations. Because the reproductive strategies of men and women are somewhat divergent, market influences on the intensity of mating competition and selectivity for partners produce different outcomes in female-biased and male-biased populations. Male mating opportunities are enhanced by scarcity, and incentives for long-term commitment are diminished, encouraging serial and simultaneous polygyny. Scarce females may be able to more effectively secure commitment from partners as well as demand higher levels of resource investment. However, male social power often constrains women's ability to leverage their market scarcity for serial or simultaneous polyandry. Imbalanced sex ratios are associated with largely consistent social and cultural trends in specific historical periods and populations.
... Thus, B m , the benefit of pregnancy under exclusive marital sex is greater than B c and, importantly for the proof in the online Appendix that girls will typically not choose to mix even if we allow it in the model, the benefit of pregnancy is B c for any level of casual sex. 23 This utility structure follows the literature in anthropology and evolutionary biology concerning monogamy in humans and other primates (see, for example, Fortunato and Archetti 2010;Low 2007;Reichard and Boesch 2003;and Marlowe 2000): the idea is that if a father finds out that the mother has been engaged in any level of sex with anyone 22 At the extreme, if we imposed the risk of pregnancy to be zero in a casual relationship, the second factor in the model can be interpreted as the choice between vaginal and anal sex, instead of committed versus casual. 23 What matters is that there is a discrete drop in the benefit for pregnancy for any amount of casual sex. ...
A seven-year randomized evaluation suggests education subsidies reduce adolescent girls' dropout, pregnancy, and marriage but not sexually transmitted infection (STI). The government's HIV curriculum, which stresses abstinence until marriage, does not reduce pregnancy or STI. Both programs combined reduce STI more, but cut dropout and pregnancy less, than education subsidies alone. These results are inconsistent with a model of schooling and sexual behavior in which both pregnancy and STI are determined by one factor (unprotected sex), but consistent with a two-factor model in which choices between committed and casual relationships also affect these outcomes.
... Therefore, among women with a high social status, there is potentially a stronger competition over mates than among women with a low social status. An extreme example of this is found in societies with strongly patrilineal and patrifocal marriage and inheritance systems, where the marriage prospects of women of the highest socio-economic levels are relatively poor because it is considered unacceptable for women to marry into a lower socio-economic class, whereas men can marry women of lower socio-economic levels (Low, 2007). ...
A study among 1,881 adolescents (52.3% girls) with a mean age of 19.1 years examined the effects of parental social status upon intrasexual competitiveness. Whereas females were consistently more intrasexually competitive the higher the socio-economic status of their parents, males with parents of the lowest socio-economic status tended to be more intrasexually competitive than those with parents of medium socio-economic status, and nearly as intrasexually competitive as those with parents of high socio-economic status. Only among adolescents with parents of low socio-economic status were males more intrasexually competitive than females. Among males and females, higher levels of intrasexual competitiveness were related to a higher family income, to a higher occupational status of the father as well as of the mother, and to a higher educational level of the mother. Only among females were higher levels of intrasexual competitiveness associated with a higher educational level of the father. Males whose fathers had only elementary education had a relatively high level of intrasexual competitiveness. The results are discussed in the context of the multifaceted nature of human status, and the potential relevance of intrasexual competitiveness for individuals of high versus low social status.
... Sex differences in physiology and behavior follow from the degree of polygyny, which could be thought of as the extent of male reproductive inequality. Polygyny is common amongst mammalian species, likely due to the relative male specialization in mating effort and female specialization in infant care and nutritional provisioning (Low, 2003(Low, , 2007Reichard & Boesch, 2003). In highly polygynous species, a few males virtually monopolize reproductive success, creating powerful selection for traits that lead to success in mating competition, even if these traits are also detrimental to the health and longevity of high proportions of individuals (Williams, 1957;Kirkwood & Rose, 1991;Stearns, 1992). ...
Researchers have known about sex differences in longevity for at least 250 years. There are multiple levels of mechanisms which contribute to this disparity, an ultimate explanation follows from reproductive patterns. Women provide greater investment in offspring and have greater constraints on reproductive potential, so men compete for reproductive access to women. In humans, male competition includes competition for social status and resource control, which are related to male reproductive success. Sex differences in human mortality rates are greatest in young adulthood, when males are reaching sexual maturity. This mortality is mainly from behavioral causes, such as accidents, homicides, and suicides. Rates of behaviorally mediated internal causes of death, as well as sex differences in mortality rates, are greater in mid to late adulthood. We predicted that there will be higher degrees of excess male mortality (above that for females) where there is a greater degree of male competition. In areas where there is high potential or actual variability and skew in male resource holding or status, comparatively more risky male behavioral strategies will lead to greater male mortality rates and more excess male mortality. We demonstrate that the population sex ratio, the degree of economic inequality, and the degree of polygyny are all related to sex differences in mortality rates. Changes in socioeconomic conditions within countries, such as the rapid transition to market economies in Eastern Europe in the 1990s, have also affected sex differences in mortality rates.
... As noted in previous sections, extrinsic risk due to endemic violence and famine stress can be ameliorated through increases in intra-household labor specialization and the size of kin networks facilitated by polygynous marriages. However, in environments with high levels of pathogen stress male genetic quality is an especially important consideration (Low 1988(Low , 1990(Low , 2003(Low , 2007. Polygynous marriages not only make it possible for females to share high genetic quality husbands, but also facilitate female extramarital matings with males of the highest genetic quality, since males find it harder to guard multiple wives. 2 Monogamy should therefore be more prevalent in environments with low pathogen stress; we test this hypothesis using a new scale of pathogen stress. ...
Multiple proposed determinants of the long-term historical shift in marriage preference from polygynous to monogamous unions are tested simultaneously using data on a worldwide sample of 186 pre-industrial societies. Since the diffusion of monogamy though conquest and population migration is well documented, we employ network autocorrelation regression models that include the cultural transmission of monogamy as an endogenous predictor variable. Linguistic and spatial transmission processes are found to be significant factors that jointly affect the world-wide variance of monogamy, while religious transmission processes are not significant, suggesting genomic variation may play a role in shaping the incidence of monogamy. Other significant factors are reduction of extrinsic risks due to pathogen stress and endemic violence, a highly articulated extra-household division of labor, and a beneficent environment, results which are consistent with female choice as a binding constraint in marriage decisions. (PsycINFO Database Record (c) 2014 APA, all rights reserved)
... Such observations have led to studies of whether human mate preferences are also influenced by environmental factors (e.g., Gangestad & Simpson 2000;McGraw 2002;Hill & Reeve 2004;Low 2007;Moore et al. 2006;Moore & Cassidy 2007;Sear & Marlowe 2009;DeBruine et al. 2010). In their review of the evolution of human mating practices, Gangestad & Simpson (2000) argued that geographic variation in human mate choice is a consequence of the trade-off faced by men and women between short-term and long-term mating strategies [also see Buss & Schmitt (1993) on 'Sexual Strategies Theory'] and that environmental variation can affect the costs and benefits associated with these strategies. ...
AbstractA growing body of evidence shows that human mating preferences, like those of other animal species, can vary geographically. For example, women living in areas with a high cost of living have been shown to seek potential mates that can provide resources (e.g., large salaries). In this study, we present data from a large (N = 2944) nationally representative (United States) sample of Internet dating profiles. The profiles allowed daters’ to report their own income and the minimum income they desired in a dating partner, and we analyzed these data at the level of zip code. Our analysis shows that women engage in more resource seeking than men. We also find a positive relationship between cost of living in the dater's zip code and resource seeking among both men and women. Importantly, however, this relationship disappears if one's own income is accounted for in the analysis; that is, individuals of both sexes seek mates with an income similar to their own, regardless of local resource pressures. Our data highlight the importance of considering individual characteristics when measuring the effects of environmental factors on behavior.
... Polygyny is the most common mammalian mating system, probably because of the prevalence of female specialization in infant nutritional provisioning and care and male specialization in mating effort (Low, 2003(Low, , 2007Reichard and Boesch, 2003). In highly polygynous species, a few males will have many offspring while many others will have none. ...
Sex differences in mortality rates stem from a complex set of genetic, physiological, psychological, and social causes whose influences and interconnections are best understood in an integrative evolutionary life history framework. Although there are multiple levels of mechanisms contributing to sex based disparities in mortality rates, the intensity of male mating competition in a population may have a crucial role in shaping the level of excess male mortality. The degree of variation and skew in male reproductive success may shape the intensity of male mating competition, leading to riskier behavioral and physiological strategies. This study examines three socio-demographic factors related to variation in human male reproductive success; polygyny, economic inequality, and the population ratio of reproductively viable men to women across nations with available data. The degrees of economic inequality and polygyny explained unique portions in the sex difference in mortality rates, these predictors accounted for 53% of the variance. The population ratio of reproductively viable men to women did not explain any additional variance. These results demonstrate the association between social conditions and health outcomes in modern nations, as well as the power of an evolutionary life history framework for understanding important social issues.
... This social system continued in early human societies which were characterized by polygynous marriage arrangements (Low 2003(Low , 2007. Darwin (1871, Chapter XX, pag. ...
Intriguingly, across the world the main social groups which practice polygyny do not consume alcohol. We investigate whether there is a correlation between alcohol consumption and polygynous/monogamous arrangements, both over time and across cultures. Historically, we find a correlation between the shift from polygyny to monogamy and the growth of alcohol consumption. Cross-culturally we also find that monogamous societies consume more alcohol than polygynous societies in the preindustrial world. We provide a series of possible explanations to explain the positive correlation between monogamy and alcohol consumption over time and across societies.
... Polygyny is the most common mammalian mating system, probably because of the prevalence of female specialization in infant nutritional provisioning and care and male specialization in mating effort (Low, 2003(Low, , 2007Reichard and Boesch, 2003). In highly polygynous species, a few males will have many offspring while many others will have none. ...
Sex differences in mortality rates stem from a complex set of genetic, physiological, psychological, and social causes whose influences and interconnections are best understood in an integrative evolutionary life history framework. Although there are multiple levels of mechanisms contributing to sex based disparities in mortality rates, the intensity of male mating competition in a population may have a crucial role in shaping the level of excess male mortality. The degree of variation and skew in male reproductive success may shape the intensity of male mating competition, leading to riskier behavioral and physiological strategies. This study examines three socio-demographic factors related to variation in human male reproductive success; polygyny, economic inequality, and the population ratio of reproductively viable men to women across nations with available data. The degrees of economic inequality and polygyny explained unique portions in the sex difference in mortality rates, these predictors accounted for 53% of the variance. The population ratio of reproductively viable men to women did not explain any additional variance. These results demonstrate the association between social conditions and health outcomes in modern nations, as well as the power of an evolutionary life history framework for understanding important social issues.
... This social system continued in early human societies which were characterized by polygynous marriage arrangements (Low 2003(Low , 2007. Darwin (1871, Chapter XX, pag. ...
Intriguingly, across the world the main social groups which practice polygyny do not consume alcohol. We investigate whether there is a correlation between alcohol consumption and polygynous/monogamous arrangements, both over time and across cultures. Historically, we find a correlation between the shift from polygyny to monogamy and the growth of alcohol consumption. Cross-culturally we also find that monogamous societies consume more alcohol than polygynous societies in the pre-industrial world. We provide a series of possible explanations to explain the positive correlation between monogamy and alcohol consumption over time and across societies.
... Human marriage system is more complex than other species with bi-parental care in that marriage is not only a game of cooperative partnership but it is a social institution . Although societal rules differ regarding the allowed number of spouses at a time [22], long term investment and faithful commitment by both genders in childcare is central to the system. Further, faithful monogamy is highly valued in most cultures. ...
The human mating system is characterized by bi-parental care and faithful monogamy is highly valued in most cultures. Marriage has evolved as a social institution and punishment for extra pair mating (EPM) or adultery is common. However, similar to other species with bi-parental care, both males and females frequently indulge in EPM in secrecy since it confers certain gender specific genetic benefits. Stability of faithful monogamy is therefore a conundrum. We model human mating system using game theory framework to study the effects of factors that can stabilize or destabilize faithful committed monogamy.
Although mate guarding can partly protect the genetic interests, we show that it does not ensure monogamy. Social policing enabled by gossiping is another line of defense against adultery unique to humans. However, social policing has a small but positive cost to an individual and therefore is prone to free riding. We suggest that since exposure of adultery can invite severe punishment, the policing individuals can blackmail opportunistically whenever the circumstances permit. If the maximum probabilistic benefit of blackmailing is greater than the cost of policing, policing becomes a non-altruistic act and stabilizes in the society. We show that this dynamics leads to the coexistence of different strategies in oscillations, with obligate monogamy maintained at a high level. Deletion of blackmailing benefit from the model leads to the complete disappearance of obligate monogamy.
Obligate monogamy can be maintained in the population in spite of the advantages of EPM. Blackmailing, which makes policing a non-altruistic act, is crucial for the maintenance of faithful monogamy. Although biparental care, EPM, mate guarding and punishment are shared by many species, gossiping and blackmailing make the human mating system unique.
... Humans often exhibit selective social bonds between adult partners and biparental care of offspring (Fortunato & Archetti, 2010;Low, 2007;Murdoch, 1981;Sbarra & Hazan, 2008;Schor, 2003). Human studies have revealed an important link between these family relationships and corollaries such as adult pair-bond stability, maternal and paternal investment, parental coordination, and family structure and long-term behavioral, and mental health outcomes, including cognitive performance, emotional regulation, behavioral control, and sociality, in adults and children (Amato, 2000;Boyum & Parke, 1995;Feinberg, 2002;Maccoby, 2000;Matheson et al., 2005;McEwen & Flouri, 2009;McLanahan & Sandefur, 1994;Meaney, 2001;Schor, 2003;Shear & Shair, 2005;Wen, 2008). ...
Family relationships help shape species-typical social and emotional development, but our understanding of how this shaping occurs is still relatively limited. Prairie voles are a socially monogamous and biparental species that is well situated to complement traditional animal models, such as rats and mice, in investigating the effects of family experience. In this series of studies, we aimed to test hypotheses relating to how prairie vole families function under undisturbed, standard laboratory conditions. In the first study, we compared the parental behavior of primiparous biparental (BP) and single-mother (SM) prairie vole family units for 12 postnatal days and then tested for sex differences, behavioral coordination, and family structure effects. Under BP conditions, nest attendance was coordinated and shared equally by both sexes, while pup-directed and partner-directed licking and grooming (LG) were coordinated in a sex and social-context-dependent manner. Contrary to our expectations, SMs showed no evidence of strong parental compensation in response to the lack of the father, indicating a minimal effect of family structure on maternal behavior but a large effect on pup care. In the second study, we examined the effects of these BP and SM rearing conditions on family dynamics in the next generation and found that SM-reared adult parents exhibited lower rates of pup-directed LG in comparison to BP-reared counterparts. Situated in the context of human family dynamics and psychology, these results suggest that the study in prairie voles may help improve our understanding of family systems and how perturbations to these systems can affect adults and offspring.
... Cultural values (like chastity or freedom of self-expression), traditions (like religious commandments), and institutions (like marriage systems) tend to reflect the reproductive demands of the environment, and can thereby reinforce the adaptive degree of sociosexuality in populations (Gangestad, Haselton & Buss, 2006;Low, 2007). ...
Evolutionäre Herangehensweisen hatten in der Persönlichkeitspsychologie nicht den gleichen Erfolg wie in anderen Bereichen der Psychologie. In dieser Dissertation werden zwei alternative evolutionäre Herangehensweisen an die Persönlichkeitspsychologie diskutiert und angewendet. Die evolutionsgenetische Herangehensweise fragt, warum genetische Varianz in Persönlichkeitsunterschieden existiert. Im ersten Teil dieser Dissertation werden verschiedene evolutionsgenetische Mechanismen, die genetische Varianz erklären können, verglichen. Auf Grundlage evolutionsgenetischer Theorie und empirischen Befunden aus der Verhaltensgenetik und Persönlichkeitspsychologie wird geschlussfolgert, dass ein Mutations-Selektions-Gleichgewicht genetische Varianz in Intelligenz gut erklären kann, während ausgleichende Selektion durch Umweltheterogenität die plausibelste Erklärung für genetische Unterschiede in Persönlichkeitseigenschaften ist. Komplementär zur evolutionsgenetischen Herangehensweise beginnt die „Life History“-Herangehensweise damit, wie Menschen ihre Ressourcen in evolutionär relevante Lebensbereiche investieren. Im zweiten Teil der Dissertationsschrift wird diese Herangehensweise am Beispiel von Investitionsunterschieden in Langzeit- versus Kurzzeit-Paarungstaktiken (wie im Konstrukt der Soziosexualität abgebildet) erläutert. Zwei neue Maße zur Erfassung von Soziosexualitätskomponenten werden vorgestellt. Während das revidierte Soziosexuelle Orientierungsinventar (SOI-R) ein Fragebogen zur Erfassung der Facetten „Verhalten“, „Einstellung“ und „Begehren“ ist, wurde mit dem Single-Attribute Impliziten Assoziationstest (SA-IAT) eine neue Methode zur indirekten Erfassung impliziter Soziosexualität entwickelt. Beide Maße zeigten konkurrente Validität in Onlinestudien, aber nur der SOI-R erwies sich als prädiktiv für Paarungstaktiken, einschließlich beobachtetem Flirtverhalten sowie der Zahl der Sexualpartner und Veränderungen im Beziehungsstatus innerhalb der nächsten 12 Monate.
The Oxford Handbook of Human Mating covers the contributions and up-to-date theories and empirical evidence from scientists regarding human mating strategies. The scientific studies of human mating have only recently risen, revealing fresh discoveries about mate attraction, mate choice, marital satisfaction, and other topics. Darwin’s sexual selection theory primarily guides most of the research in the scientific study of mating strategies. Indeed, research on the complexities of human mate competition and mate choice has centred around Darwin’s classic book. This book discusses theories of human mating; mate selection and mate attraction; mate competition; sexual conflict in mating; human pair bonding; the endocrinology of mating; and mating in the modern world.
We explore abortion access, abortion experiences, and abortion stigma. We emphasize global perspectives on abortion diversity and the relationship between pregnancy norms and expectations, abortion stigma, and practical constraints on reproductive freedom. Evolutionary psychological, clinical psychological, and social-psychological perspectives illuminate how abortion decisions are shaped by strategies to optimize survival and success, support services that emphasize the costs and risks of pregnancy termination, and pronatalist norms and punishment of departures from those expectations. We call for future abortion research that integrates multiple subfields in psychology and is rooted in an intention to effect public policy and social change that promotes reproductive autonomy.
Anthropologists comprehensively study marriage practices because of the cross‐cultural consistency of marital institutions and their consequential influence on many aspects of human societies, including social, political, economic, and biological realms. The evolutionary ecology approach attempts to understand the wide‐ranging variation in marriage practices in terms of adaptive cultural strategies in local ecologies. Observed variation across and within societies in marriage systems, conflict between men and women, arrangement of marriages, marital property exchange, and postmarital residence reflects differences in fitness‐enhancing behaviors and strategies under different environmental conditions.
Language is a social construct that subsumes a high degree of cooperative action on the part of the interactants. Shared cooperative motifs are deeply embedded in linguistic practice as symbol use requires two speakers to focus their attention on a shared referent in order to reach an understanding. Evolutionary precursors to this cooperative endeavour can be found in triadic interactions of nonhuman animals, involving a signaller, a recipient and a third entity or object. Here, we introduce two of the most compelling examples of triadic communicative
interactions in nonhuman animals —referential gesturing of chimpanzees (Pan troglodytes) and ravens (Corvus corax) living in natural environments. These examples of homologue and convergent evolution enable a better understanding of the communicative complexity and the
cognitive mechanism underlying triadic referential abilities and may hold promising clues to unravel the factors influencing the evolution of human cooperative communication.
In this chapter, we consider what evolutionary anthropology contributes to the study of population health, focusing specifically on family structure and its relationship to child and adult physical health. Evolutionary anthropologists have now built a substantial body of literature on relationships between family structure and various dimensions of human wellbeing, particularly in the context of small-scale ‘traditional’ societies and developing rural communities most at risk of poor health outcomes. Crucially, they have also constructed theoretical models to account for variation in key dimensions of family structure in relation to individual, ecological, and cultural factors. Thus, evolutionary anthropologists have much to say, not only about the extent to which specific family structures may influence health but also why certain family forms may persist or change across time and space. Here, focusing on studies primarily conducted in sub-Saharan Africa, we review the literature on three interrelated dimensions of family structure and their relationship to health: (1) family size, (2) polygynous versus monogamous marriage, and (3) the role of extended kin. Using these examples, we highlight the theoretical and empirical contributions of evolutionary anthropology and draw out implications for population policy and related initiatives seeking to improve family health in the developing world.
We hypothesize that distinct mating strategies are identifiable in the female characters created by popular British author Jane Austen. Although Austen wrote her novels in the early 19th Century, and consequently the novels reflect social constraints not applicable to similarly aged women in modern Western societies, we contend that research participants can accurately identify the mating strategies of characters and express relationship preferences consistent with their own fitness interests. Austen's characterizations of women's mating strategies are remarkably similar to depictions in the modern literature of evolutionary psychology. We use personality descriptions of four primary characters assembled from passages in Austen’s novels, Pride and Prejudice and Mansfield Park. When selecting characters with whom to form a hypothetical long-term romantic relationship, participants preferentially chose those who successfully established long-term relationships in the novels. Participants generally favored characters who exemplified short-term mating strategies, such as those who generally valued partners more so for the direct benefits they provided rather than emotional connection, for noncommitted sexual relationships. These results provide stronger empirical support of our hypotheses than earlier efforts. (PsycINFO Database Record (c) 2014 APA, all rights reserved)
This article analyzes the configuration of biology, anthropology, and history over the last generation by taking the sub-field of the “history of sexuality” as a case study. The history of sexuality developed at a particularly important site of engagement with neighboring disciplines. I argue that the concepts of nature and culture that came to prevail among historians of sexuality were deeply influenced by the debate between a particular strand of evolutionary biology, namely sociobiology, and its critics, who were committed to cultural hermeneutics. This debate encouraged a formulation of nature and culture which is effectively dualist and which remains present within the sub-field. By focusing the analysis on the study of ancient (classical Mediterranean) sexuality, I seek detailed insights into the reception of this debate within a specific domain of historical investigation, one whose stakes have been particularly high because of the intervention of Michel Foucault. The article closes by arguing that biologists and anthropologists in the last two decades have advanced the study of culture as a part of nature, and that historians have much to gain by engaging with more recent models. The institution of monogamy is highlighted as an emerging theme of investigation that can only be approached with the unified insights of history, anthropology, and biology.
This paper examines social network size in contemporary Western society based on the exchange of Christmas cards. Maximum
network size averaged 153.5 individuals, with a mean network size of 124.9 for those individuals explicitly contacted; these
values are remarkably close to the group size of 150 predicted for humans on the basis of the size of their neocortex. Age,
household type, and the relationship to the individual influence network structure, although the proportion of kin remained
relatively constant at around 21%. Frequency of contact between network members was primarily determined by two classes of
variable: passive factors (distance, work colleague, overseas) and active factors (emotional closeness, genetic relatedness).
Controlling for the influence of passive factors on contact rates allowed the hierarchical structure of human social groups
to be delimited. These findings suggest that there may be cognitive constraints on network size.
Attempts to explain not only the rarity of dowry, but also why it occurs in the societies it does. The model builds on theory derived from behavioural ecology and views dowry as a form of competition among women for husbands. Before developing this model, reviews an alternative explanation of dowry that views the practice as an outcome of the sexual division of agricultural labour. -from Authors
The People's Republic of China, during the second half of the twentieth century, has been repeatedly affected by social and political upheavals associated with government policies. These have produced strong but unexpected impacts on Chinese demographic patterns. Many of these policies are of the sorts that alter reproductive costs and benefits. This study examines patterns in Hebei, Shaanxi, and Shanghai, three provinces with differing ecological, geographic, and economic characteristics. Government policies affected the three populations differentially; this was evident at both aggregate and individual levels. The Great Leap Forward and subsequent famine created higher birth deficits and mortality among the largely rural populations of Hebei and Shaanxi than the more urban Shanghai. In contrast, the Cultural Revolution and family planning resulted in lower fertility levels for women in Shanghai. The population history of China during the second half of last century thus reflects strong state interventions in the lives of its citizens. Government policies, along with regional variations in geographic, social, and economic conditions, strongly influence individual access to resources in China. Variations in timing and intensity of women's reproductive patterns reflect differential access to resources and subsequent trade‐offs.
Life history theory postulates tradeoffs of current versus future reproduction; in both developed and developing nations today, women face evolutionarily novel versions of these tradeoffs. Here we use a nonlinear dynamic model to explore: [1] the general issues of tradeoffs of education, work, and current fertility; [2] some specific examples (e.g., what increase in fertility will compensate for particular delays of age at first birth under given conditions). Finally, we model a largely unrecognized issue. Demographic transitions of the past have been characterized by decreases in fertility accompanied by (sometimes quite large) increases in per capita investment in offspring. The Rio Conference and its followup highlighted the conflicts between low-fertility, high-consumption, versus highfertility, lower consumption strategies — yet we have few ways to make testable predictions about future conflicts. We explore outcomes when impending resource constraints differentially affect short-generation-time-strategists, versus delayed-reproduction-resource-acquirers. The conditions favoring delayed fertility with resource accumulation are highly constrained; under almost all conditions reproduction in the early 20s leads to the greatest lineage success for women in the models.
Reproductive effort, defined as the cost in energy spent and risks taken in reproduction, has two components: parental effort and mating effort. Environmental uncertainties influencing juvenile survivorship affect the temporal pattern of parental effort: when the parent cannot decrease offspring mortality by increased investment, it must minimize the effort invested in offspring which die. Environmental uncertainty responsible for juvenile mortalities before the termination of parental care causes juveniles to have low reproductive values and is responsible for the apparently widespread tendency toward low early parental effort. Several predictions about the pattern of expenditure of parental effort result, although at present the empirical bases for testing these predictions fully are inadequate, and comparisons are largely inferential. A comparison of marsupial and placental parental strategies as a test of these predictions suggests that marsupials have long been under selection imposed by frequent los...
The term ‘monogamy’ can mean a number of things. Genetic monogamy is unlikely unless it raises (male) reproductive success enough to compensate for the loss of reproductive success (RS) that would have come from additional mating efforts. We expect to see male parental polygyny under these conditions: (i) whenever a female can raise offspring successfully alone, and (ii) when male care that sufficiently enhances offspring survivorship and competitive success can be ‘generalizable’ – no more expensive for several offspring than for one (e.g., a nest or den that can serve several clutches or litters). Consider red-winged blackbirds, in which males watch and warn at the approach of potential predators; a male can do this effectively for several nests, at the same cost as for one. For a system to be genetically monogamous, then, it is important that the male care be a non-generalizable, true parental investment such as feeding (Trivers, 1974), rather than a more general parental effort (such as a nesting den, which can function for numerous offspring: Low, 1978). Other routes to monogamy also exist: in some species, both mate guarding (that eliminates other mating chances), and the ecology of female dispersion may make males unable to monopolize more than one female, and therefore lead to monogamy (Jarman, 1974; Emlen&Oring, 1977). But when females are controllable and/or must be guarded constantly, or when male effort can be generalized, we see either open polygyny or social monogamy without true genetic monogamy.
This paper describes the results of a series of cross-cultural tests of several different explanations of matrilocal versus patrilocal residence. The first explanation tested was the traditional assumption that division of labor determines residence. The results did not support that assumption. The results of other tests suggest rather that patrilocal residence is favored by internal warfare, whether or not such warfare interferes with a normally patridominant division of labor; and matrilocal residence appears to be favored by purely external warfare if such warfare compels the women to do at least as much subsistence work as the men.
Boserup (1970) views dowry as a payment made by women to guarantee future support for them and their children under circumstances where their own contributions to subsistence are relatively small. We call this the labor-value model. Here, building on the polygyny threshold theory from behavioral ecology (Orians 1969), we view dowry as a reproductive tactic used by prospective brides and their kin to attract the wealthiest bridegrooms. Our model predicts dowry in stratified, nonpolygynous societies where the desirability of wealthy males is not reduced by diversion of resources to additional wives and their children. We call this the female-competition model. We use discriminant analysis to test both these models on the 1,267 societies of the Ethnographic Atlas. While both models perform better than chance, the female-competition model is clearly superior. It accurately predicts the occurrence of dowry in nearly 95% of societies and identifies coding errors in the Standard Cross-Cultural Sample with extreme efficiency.
Significant changes have occurred in the practice of dowry in south India. From being an upper caste/class practice, dowry has become an all caste/class phenomenon, replacing the symbolic exchange of gifts between families of the groom and the bride. It has become a euphemism for strategies to acquire higher standards of material life, status, and security, with negative consequences to women’s status, including their survival. The antifemale bias of the practice cannot be tackled from within the dowry trap. Raising the critical consciousness of women about their identity and self-esteem remains a critical component of effective strategies.
No good formal arguments exist for a central question in biology: Why, in species that have sexual reproduction, are there usually only "males" and "females"? We present a nonlinear optimization model that supports the conclusion that having only two sexes maximizes long-run viability.
Primate social groups frequently contain multiple males. Male group size has been hypothesized to result from male mating competition, but the selective factors responsible for the evolution of multimale groups are unclear. Short breeding seasons create situations that are not conducive for single males to monopolize mating access to females, and may therefore favor the formation of large male groups. Alternatively, since the costs of mate defense increase with the spatial clumping of females, female group size may be a primary determinant of the number of males in a primate group. We used comparative methods designed to control for the potentially confounding effects of hidden third variables associated with phylogeny to test the breeding season and female group size hypotheses for the evolution of multimale groups. Our results revealed no association between breeding season duration and the number of males in groups. In contrast, we provide support for the female group size hypothesis by demonstrating a strong pattern of correlated evolution between female and male group size. © 1996 Wiley-Liss, Inc.
Society uses law to encourage people to behave differently than they would behave in the absence of law. This fundamental purpose makes law highly dependent on sound understandings of the multiple causes of human behavior. The better those understandings, the better law can achieve social goals with legal tools. In this Article, Professors Jones and Goldsmith argue that many long-held understandings about where behavior comes from are rapidly obsolescing as a consequence of developments in the various fields constituting behavioral biology. By helping to refine law's understandings of behavior's causes, they argue, behavioral biology can help to improve law's effectiveness and efficiency. Part I examines how and why law and behavioral biology are connected. Part II provides an introduction to key concepts in behavioral biology. Part III identifies, explores, and illustrates a wide variety of contexts in which behavioral biology can be useful to law. Part I-V addresses concerns that sometimes arise when considering biological influences on human behavior.
In order to explain the variation in primate social systems, socio-ecology has focussed on the role of ecological factors to explain female associations and relationships and on the spatio-temporal distribution of mating opportunities to explain male associations and relationships. While this approach has been quite successful, it ignores male-female associations and relationships and ignores the possibility that male behaviour modifies other aspects of the social system. In this paper, the ecological approach is complemented by consideration of a social factor found to limit fitness, namely infanticide by males. Infanticide risk is proposed to have selected for male-female associations and relationships, and to have modified female-female relationships in some cases. It is also hypothesized to have selected for the unusual male bonding by species such as chimpanzees. Finally, its possible impact on between-group relations is examined. The findings suggest that infanticide is of equal importance to ecological factors, with which it may interact in sometimes complex ways, in shaping primate social systems.
Ultra-selfish genes increase in frequency in a population despite the harm they inflict on their host. The spread of both ultra-selfish genes and their suppressors is evidence of conflicts between genes within an individual for transmission into the next generation. Here I synthesize a body of past work, and argue that intragenomic conflict might be an important evolutionary force. I discuss the evolutionary history of cytoplasmic genes as an illustration. I first consider the evolution of sex. Recent evidence suggests that the initial evolution of sex might have been driven by an ultra-selfish gene. The existence of sex in turn creates a series of new conflicts which may explain the existence of sexes and uniparental inheritance of cytoplasmic genes. Uniparental inheritance of cytoplasmic genes sets up a new set of conflicts over the sex ratio, which in turn may influence the evolution of sex determining systems, sex allocation systems and post-zygotic isolating mechanisms.
Binary mating types are proposed to arise in a three-stage process through selection of nuclear genes to minimize cytoplasmic gene conflict at the time of gamete fusion. In support of this view we argue that: (i) in systems with fusion of gametes, the mating type genes are typically binary and regulate cytoplasmic inheritance; (ii) binary sexes have evolved several times independently associated with fusion, although at least twice binary types have been lost, associated with a loss of fusion; further, in accordance with the theory are findings for isogamous species that (iii) close inbreeding may correlate with less than two sexes and biparental inheritance of cytoplasmic genes; and (iv) species with more than two sexes may have uniparental inheritance of cytoplasmic genes, be rare and be afflicted by deleterious cytoplasmic genes which attempt to pervert normal cytoplasmic genetics. Such facts and their rationale support a new and unified definition of sexes based on the control of the inheritance of cytoplasmic genes. For the common cases, the male sex is that which resigns attempts to contribute cytoplasmic genes to the next generation. We differentiate between sexes and the incompatibility types of ciliates, basidiomycetes, some angiosperms and a few other organisms which are independent of organelle contribution.
This chapter discusses the morphological development and evolutionary history of red sexual skin, and of sexual swellings, among female catarrhines. It examines the various facets of anatomy, endocrinology, behavior, and ecology in extant primates and considers some fossil evidence of catarrhine evolution. This comparative approach offers some clues to the mystery of why sexual skin has such a peculiar, discontinuous distribution among the extant Old World monkeys and apes. The chapter explains that sexual skin may have arisen by elaboration of the same type of vulval swelling and pinkness that occurs during estrus in many female prosimians. This hypothesis derives from the observations of sexual skin ontogeny and from comparative studies of its morphology in adult females. Sexual skin acts primarily as a sexually attractive distance cue in many species. It might therefore be adaptive in any environment where a monkey group spreads out over a wide area or fragments into subgroups. It is suggested that a complementary degree of penile elongation occurs in order to facilitate mating behavior in those species, where females have prominent swellings. The prominent penis of the chimpanzee is best explained on this basis, since the sexual swelling is enormous and adds considerably to the depth of the female's reproductive tract.
A model suggests that female-bonded (FB) groups have evolved as a result of competition for high-quality food patches containing a limited number of feeding sites. These relationships are beneficial based on cooperative relationships among females. These relationships are beneficial because cooperators act together to supplant others from preferred food patches. Ecological data support the model for most FB species, but not for Theropithecus gelada or Colobus guereza, whose foods are not found in high-quality patches with limited feeding sites. Non-FB species conform to expectation, either because they do not use high-quality patches, or because feeding competition has disruptive effects during periods of food scarcity. Multi-male groups tend to be found in non-territorial FB species. The presence of several males per group is suggested to benefit females by raising the competitive ability of the group in inter-group interactions. Competitive relationships among females are more strongly marked in FB groups.-from AuthorTheropithecus gelada Colobus guereza
The social brain (or Machiavellian Intelligence) hypothesis was proposed to explain primates' unusually large brains: It argues that the cognitive demands of living in complexly bonded social groups selected for increases in executive brain (principally neocortex). The evidence for this and alternative hypotheses is reviewed. Although there remain difficulties of interpretation, the bulk of the evidence comes down in favor of the social brain hypothesis. The extent to which the cognitive demands of bonding large intensely social groups involve aspects of social cognition, such as theory of mind, is explored. These findings are then related to the evolution of social group size, language, and culture within the hominid lineage.
Qualitative data on Thai views of male and female sexuality and sexual behavior are examined in light of hypotheses that have emerged from an evolutionary perspective. The data were derived through focus group discussions and individual in‐depth interviews. In particular, we examined how Thai married adults consider men's and women's sexual natures to differ, what men and women seek in a long‐term mate, and views of spouse's extramarital sexual activities. In a number of key respects Thai views conform to standard evolutionary predictions. The analysis also illustrates how qualitative research techniques can generate useful data for assessing these predictions.
Ridley (1986) emet une hypothese selon laquelle il existe une relation entre la saisonnalite de la reproduction et le nombre de mâles contenus dans un groupe de primates. Cet article discute cette hypothese
Cross-cultural data are used to test the hypotheses that (1) polygyny in humans is resource polygyny and (2) parents transfer wealth to male heirs when wealth increases the heirs' chance of obtaining multiple mates. A reinterpretation of Freud's Oedipus complex follows as an adjunct.
Dowries in most regions of South Asia have steadily become larger over the last 40 years, causing widespread destitution among families with daughters to be married. This paper attempts to investigate the reasons behind dowry ‘inflation’ with data on marriage transactions and other individual and household information from six villages in south-central India, and from the Indian census. It is found that a ‘marriage squeeze’ caused by population growth which resulted in a surplus of younger women in the marriage market, has played an important role in the increase in dowries. Other factors that increase the size of dowries include differences in the landholdings of the parental households, and residence in regions in the more northerly parts of India.
Pressure of parasites that are short-lived and rapid-evolving compared to the hosts they attack could be an evolutionary factor sufficiently general to account for sex wherever it exists. To be such a factor, parasites must show virulences specific to differing genotypes. Models are set up on this basis (one-locus diploid-selection and two-locus haploid-selection) in which the rapid demographic reactivity of parasite strains to abundance of susceptible hosts becomes represented in a single frequency-dependent fitness function which applies to every host genotype. It is shown that with frequency dependence sufficiently intense such models generate cycles, and that in certain states of cycling sexual species easily obtain higher long-term geometric mean fitness than any competing monotypic asexual species or mixture of such. In the successful cycle of the two-locus model, it is seen that both population size and gene frequencies may be steady while only oscillating linkage disequilibrium reflects the intense selection by parasites. High levels of recombination work best. Fecundity in the models can be low and no incidence of competition of siblings or other relatives is required. /// Пресс паразитов с коротким циклом и быстро распространяющихся в сравне-нии с их хозяевами, может оказаться эволюционным фактором, достаточно важным для определения соотношения полов в случае разнополых животных. Будучи таким фактором, паразиты могут проявлять видулентную специфич-ность в отношении разных генотипов хозяина. На этой основе созданы мо-дели (1-локусная диплоидная селекция и 2-локусная гаплоидная селекция), в которых быстрая демографическая реактивность популяций паразита на обилие доступных особей хозяина описывается единственной функцией, час-тоты встречаемости, что имеет значение для любого генотида хозяина. По-казано, что если частотная зависимость достаточно интенсивна, такие мо-дели дают законченные циклы, и на определенной стадии цикла у разноло-лых видов легко получаются более высокие долговременные геометрические средние, чем у конкурирующих монотипических асексуальных видов или у комплексов таких видов. На законченном тсикле в 2-локусной модели видно, что размеры популяции и частота генов могут быть стабильны, и лишь колебания отдельных связей при нарушенном равновесии отражают интенсивную селекцию паразита. Лучше всего работают высокие уровни рекомбинации. Плодовитость в моделяи мо-жеь быть низкой, и случай конкуренции между особями одного помета или другими родственными особями необязателны.
We have introduced recently a model for the spread of sexually transmitted diseases, in which the social behavior is incorporated as a key factor for the further propagation of the infection. The system may be regarded as a society of agents where in principle anyone can sexually interact with any other one in the population. The social behavior is taking into account by means of two parameters: the fraction of singles rho(s) and the promiscuity p. The promiscuity parameter defines the per individual daily probability of going out to look for a sexual partner, abandoning its eventual mate. In this contribution we show that the interaction between this two parameters give rise to a non-trivial epidemic threshold condition, when going from the homogeneous case (rho(s) = 1) to heterogeneous cases (rho(s) < 1). These results can have profound implication in the interpretation of real epidemic data. (C) 2004 Elsevier B.V. All rights reserved.
Monogamy among the large primates is not accompanied by high levels of male care for infants. This paper evaluates 4 hypotheses. Monogamy in these species did not evolve because males are unable to defend access to more than one female. Hence, it must be related to behavioural services provided by the male which substantially increase the female's reproductive output. Data argue against the suggestion that these services involve protection against predators or defence of an exclusive feeding area. The male's service may consist primarily in protecting the female against infanticide by other males. To the extent that the predictions can be tested with the data currently available, evidence supports the infanticide hypothesis. Infanticide avoidance is possibly also responsible for the near-universal occurrence among primates of male-female bonds. -from Authors
Predictions from a theory assuming mate selection on the part of females, which maximizes reproductive success of individuals, are found to accord closely, though not completely, with known mating patterns. These predictions are that (1) polyandry should be rare, (2) polygyny should be more common among mammals than among birds, (3) polygyny should be more prevalent among precocial than among altricial birds, (4) conditions for polygyny should be met in marshes more regularly than among terrestrial environments, (5) polygyny should be more prevalent among species of early successional habitats, (6) polygyny should be more prevalent among species in which feeding areas are widespread but nesting sites are restricted, and (7) polygyny should evolve more readily among species in which clutch size is strongly influenced by factors other than the ability of the adults to provide food for the young. Most cases of polygyny in birds, a group in which monogamy is the most common mating pattern, can be explained on...
In this article we present a biosocial model of human male parental care that allows re-lationship (mating) effort to influence male parental allocations. The model recognizes four classes of relationships between men and the children they parent: genetic off-spring of current mates (combined relationship and parental effort), genetic offspring of previous mates (parental effort solely), step offspring of current mates (relationship ef-fort solely), and stepchildren of previous mates (essentially no expected investment). We test the model using data on parental investment collected from 340 Xhosa high school students in Cape Town, South Africa. Six measures of paternal investment are exam-ined: the amount of money men spent on students for school, clothing, and miscella-neous expenditures, respectively, and how often men spent time with children, helped them with their homework, or spoke English with them. The tests provide support for the roles of both parental and relationship effort in influencing parental care: men in-vest significantly more in their genetic offspring and in the children of their current mates. We also examine several proximate influences on parental care, specifically the age and sex of the child, and the percentage of the child's life the father figure coresided with him or her. © 1999 Elsevier Science Inc.
We present a biosocial model of human male parental care that allows male parental al-locations to be influenced not only by changes in the fitness (welfare) of the recipient off-spring, but also by their effects on the man's relationship with the child's mother. The model recognizes four classes of relationships between males and the children they par-ent: genetic offspring of current mates (combined relationship and parental effort), ge-netic offspring of previous mates (parental effort solely), step offspring of current mates (relationship effort solely), and stepchildren of previous mates (essentially no expected investment). We test the model using data on parental investments collected from adult males living in Albuquerque, New Mexico, U.S.A. Four measures of paternal investment are examined: the probability that a child attends college (2,191 offspring), the probabil-ity that a child who attends college receives money for it (N 1,212), current financial expenditures on children (N 635), and the amount of time per week that men spend with children ages 5 to 12 years (N 2,589). The tests are consistent with a role for rela-tionship effort in parental care: men invest more in the children of their current mates, even when coresidence with offspring is not a confounder. © 1999 Elsevier Science Inc. KEY WORDS: Paternal investment; Mating effort; Stepfathers. en's involvement with and investment in their offspring figures prom-inently in many models of human evolution (e.g., Alexander and Noonan 1979; Belsky et al.
Nonhuman primates occupy a special niche in anthropology because of the comparative insights into humans they provide. Initial anthropological interest in primates targeted the apes for their close phylogenetic relationships with humans, and the semiterrestrial Old World monkeys for their ecological similarities with hominids adapting to life on the ground. From the earliest anecdotal reports of tool use and hunting to more contemporary quantitative analyses of local "cultural" traditions, nonhuman primates have challenged deep-rooted concepts of human uniqueness and redefined the boundaries between us and other animals. Yet, despite the long-standing influence of primate studies in anthropology, approaches to studying primates began diverging from those of earlier ethnographers. Advances in primatology, particularly during the 1990s, have included a much deeper understanding of how ecology, phylogeny, and demography affect behavior. Insights into intraspecific, population-level variation represent an important area of convergence between primatology, other areas of anthropology, and conservation biology. [Keywords: primate behavioral ecology, anthropocentrism, evolutionary theory, systematic methods, biology]
The stepfather relationship provides a source of potential conflict in remarriage families, because the mother and partner may have different interests in the well-being of children from a prior union. Using three different theoretical perspectives—biology, sociology, and selection—this paper examines the engagement, availability, participation, and warmth of residential fathers in married biological parent, unmarried biological parent, married stepparent, and cohabiting father families. The data come from 2,531 children and their parents who were interviewed during the 1997 wave of the Child Development Supplement to the Panel Study of Income Dynamics. Biology explains less of father involvement than anticipated once differences between fathers are controlled. Marriage continues to differentiate paternal investment levels, as do age of child and financial responsibility to nonresidential children.
Responses of mated individuals to playbacks of the songs of solitary females and males permit evaluating the behavioral mechanisms maintaining monogamy in gibbons. When female songs are played back from the centers of their ranges, mated female gibbons typically initiate duets and group approaches toward playback sites. Female songs played back from range boundary locations elicit duetting responses. Responses to solitary female songs do not differ from responses to song duets used by established mated pairs to mediate patterns of intergroup spacing. Mated males lead silent group approaches toward the sites of male song playbacks. These results suggest that range defense by female gibbons forces males into accepting monogamous mating relationships and that monogamy in gibbons is regulated by intersexually-supported, intrasexual aggression.
Predictions of the model of van Schaik (1989) of female-bonding in primates are tested by systematically comparing the ecology,
level of within-group contest competition for food (WGC), and patterns of social behaviour found in two contrasting baboon
populations. Significant differences were found in food distribution (percentage of the diet from clumped sources), feeding
supplant rates and grooming patterns. In accord with the model, the tendencies of females to affiliate and form coalitions
with one another, and to be philopatric, were strongest where ecological conditions promoted WGC. Group fission in the population
with strong WGC was “horizontal” with respect to female dominance rank, and associated with female-female aggression during
a period of elevated feeding competition. In contrast, where WGC was low, females’ grooming was focused on adult males rather
than other females. Recent evidence suggests that group fission here is initiated by males, tends to result in the formation
of one-male groups, and is not related to feeding competition but to male-male competition for mates. An ecological model
of baboon social structure is presented which incorporates the effects of female-female competition, male-male competition,
and predation pressure. The model potentially accounts for wide variability in group size, group structure and social relationships
within the genus Papio. Socio-ecological convergence between common baboons and hamadryas baboons, however, may be limited in some respects by phylogenetic
inertia.
Saddle-back tamarins Saguinus fuscicollis in Peru live in small groups with 1 reproductive female and 1-2 breeding males. Most animals do not first breed for at least 1yr past the age of potential sexual maturity. Data on survival of adults and lengths of tenure of breeders suggest that breeding vacancies are not frequent. Emigration and survival patterns are not significantly different for the sexes. Delayed first breeding may occur in this species for any or all of the following reasons: a shortage of breeding positions, territories, or helpers; the risks of solitary dispersal; and the inclusive fitness benefits gained from helping. -from Authors
There is a strong correlation between marriage system and wealth inheritance pattern across societies (Hartung 1982); as the degree of polygyny increases, so too does the degree of male bias in inheritance. In this paper, we reevaluate this pattern using a new technique in cross-cultural analyses that effectively controls for the nonindependence of cultures (Galton's problem) through the identification of independent instances of cultural change (Mace and Pagel 1994). First, we produce cultural phylogenetic trees for the societies under study, from phylogenies previously constructed on the basis of linguistic similarity (Ruhlen 1987). Then, following standard methods for the analysis of discrete characters on phylogenetic trees, we use parsimony to determine the ancestral condition of both marriage and inheritance, and subsequently tally the number of independent instances of cultural change in each trait. The results show that transitions to polygyny are much more commonly associated with male-biased inheritance than are transitions to monogamy across human societies in our sample. They illustrate how the degree of change in the evolution of these traits differs considerably between divergent cultural groups. The advantages of this technique are discussed.
The radical shift in human reproduction in the late 19th century, known as the demographic transition, constitutes a major challenge to evolutionary approaches to human behaviour. Why would people ever choose to limit their reproduction voluntarily when, at the peak of the Industrial Revolution, resources were apparently so plentiful? Can the transition be attributed to standard life history tradeoffs, is it a consequence of cultural evolutionary processes, or is it simply a maladaptive outcome of novel and environmental social conditions? Empirical analyses and new models suggest that reproductive decision making might be driven by a human psychology designed by natural selection to maximize material wealth. If this is the case, the mechanisms governing fertility and parental investment are likely to respond to modern conditions with a fertility level much lower than that that would maximize fitness.
Primate species in which the breeding group contains more than one adult female may typically live in ‘harems’, with one male, or multi-male troops. This paper shows, in a review of the published evidence for 33 species, that that variable is associated with the duration of the breeding season: harems are commoner when the breeding season is long, multi-male troops when it is short. The sex ratio of adults in a troop is likewise correlated with the length of the breeding season.
We examined the claim that sperm competition is an important selection pressure operating in human populations. We recruited 222 men and 194 women to complete a survey of their sexual behaviour. Of these, 28% of men and 22% of women reported engaging in extrapair copulations (EPCs). A review of the literature suggests that rates of extrapair paternity are in the region of 2%. These values suggest that the risk of sperm competition in humans is relatively low, in line with comparative studies of relative testis sizes of humans and other primates. Testis volume was positively correlated with the number of sperm ejaculated. However, we found no support for a recent controversial claim that the within-population frequency distribution of testis size reflects a balanced polymorphism between men who specialize in sperm competition through EPCs and men who are monogamous.
This study was undertaken to quantify various risks to children as a function of the identity of the person(s) in loco parentis. The household circumtances of children in Hamilton (a midsized Canadian city) were surveyed by telephone, and combined with information on child abuse victims, runaways, and juvenile offenders, to arrive at victimization rates according to age and household type.Both abuse and police apprehension were least likely for children living with two natural parents. Preschoolers living with one natural and one stepparent were 40 times more likely to become child abuse cases than were like-aged children living with two natural parents. Whereas abuse risk was significantly higher for children living with a stepparent than for those with a single parent, the reverse was true of the risk of apprehension for criminal offenses.Several variables were examined as possible confounds of household composition. Socioeconomic status, family size, and maternal age at the child's birth were all predictors of abuse risk, but these factors differed little or not at all between natural-parent and stepparent families and could not account for the stepparent-abuse association. As predicted from Darwinian considerations, stepparents themselves evidently constitute a risk factor for child abuse.
Sex is likely to be an adaptation that enables large multicellular long-lived organisms to resist exploitation by specialized smaller shorter-lived organisms — that is, by parasites/pathogens. Antagonistic coadaptation of genotypes between such species tends to entrain limit cycles or else repeating and largely nonprogressive situations of counter-transience of new defense and attack alleles. Models on these lines can account for (a) correlation of stable sexual reproduction with size and longevity and with biotic complexity of habitat, (b) abundance of protein polymorphism, (c) diversity of adaptive linkage values, (d) common linkage disequilibria in multi-locus genotypes, and (e) “good genes” mate choice and the excesses of sexual selection. Through parasites, frequency-dependent selection may account for much more variation than has been credited while immediate heterozygote advantage may account for much less. Through frequency-dependent selection, polymorphism based even on generally concave fitness profiles may be common.