Male care and mating effort among Hadza foragers

1999

Paternal care plays an important role in many scenarios of human evolution. Lately, however, this "Man the Provisioner" view has been challenged. The showoff hypothesis, for example, proposes that men hunt not to provision children but to gain extra mating opportunities, and some have suggested that male care among mammals is always a form of mating, rather than parenting, effort. This study, based on observation in a hunting and gathering society, the Hadza of Tanzania, tests whether men provide care as parenting effort. If male care were mating effort only, stepchildren should receive no less care than biological children. My data, however, reveal that stepchildren do receive less care. This suggests that care is provided, at least in part, as parenting effort. Although lower direct care implies stepfathers are less motivated to care for stepchildren, resource acquisition data raise the question of whether stepfathers are less motivated, or simply less skilled.

Proceedings of The Royal Society B: Biological Sciences, 2009

The 'challenge hypothesis' posits that testosterone facilitates reproductive effort (investment in male-male competition and mate-seeking) at the expense of parenting effort (investment in offspring and mates). Multiple studies, primarily in North America, have shown that men in committed relationships, fathers, or both maintain lower levels of testosterone than unpaired men. Data from non-western populations, however, show inconsistent results. We hypothesized that much of this cross-cultural variation can be attributed to differential investment in mating versus parenting effort, even among married fathers. Here, we directly test this idea by comparing two neighbouring Tanzanian groups that exhibit divergent styles of paternal involvement: Hadza foragers and Datoga pastoralists. We predicted that high levels of paternal care by Hadza fathers would be associated with decreased testosterone in comparison with non-fathers, and that no such difference between fathers and non-fathers would be evident in Datoga men, who provide minimal direct paternal care. Twenty-seven Hadza men and 80 Datoga men between the ages of 17 and 60 provided morning and afternoon saliva samples from which testosterone was assayed. Measurements in both populations confirmed these predictions, adding further support to the hypothesis that paternal care is associated with decreased testosterone production in men.

2000

Paternal investment has long been considered responsible for the evolution of predominantly monogamous marriage in humans. However, male-male competition resulting in mate-guarding and male coercion could be equally important. In this review, I use a comparative approach to examine the effect of variation in human paternal investment on our mating system. I conclude paternal investment is important but so too is mate-guarding. I propose a model of our mating system incorporating both factors. Variation in the mating system is explained by variation in male resource control and contribution, resulting in ecologically imposed monogamy or polygyny, as predicted by the polygyny threshold model, as well as variation in male -male competition for status, resulting in socially imposed monogamy or polygyny.

1998

Males play a variable parental role in reproduction, ranging from no male parental care to extensive male care. Females may acquire either direct or indirect fitness benefits from their mate choice, and direct fitness benefits include male parental care. Theoreticians have traditionally emphasized direct fitness benefits to females in species with extensive male parental care. We review the literature and show extensive variation in the patterns of male care, related to the attractiveness of males to females. At one extreme of this continuum, females invest differentially in parental care, investing more when paired with attractive males. The costs of female parental care and other aspects of parental investment may be balanced by benefits in terms of more attractive sons and/or more viable offspring. At the other extreme, in species with extensive direct fitness benefits, males with preferred sexual phenotypes provide the largest relative share of parental care. A comparative study of birds revealed that the extent of the differential female parental investment was directly related to the frequency of extra-pair paternity. Since extra-pair paternity may arise mainly as a consequence of female choice for indirect fitness benefits, this result supports our prediction that differential parental investment is prevalent in species where females benefit indirectly from their mate choice. The consequences for sexual selection theory of these patterns of male care in relation to male attractiveness are emphasized.

Scientific Reports

Humans are rare among mammals in exhibiting paternal care and the capacity for broad hyper-cooperation, which were likely critical to the evolutionary emergence of human life history. In humans and other species, testosterone is often a mediator of life history trade-offs between mating/competition and parenting. There is also evidence that lower testosterone men may often engage in greater prosocial behavior compared to higher testosterone men. Given the evolutionary importance of paternal care and heightened cooperation to human life history, human fathers’ testosterone may be linked to these two behavioral domains, but they have not been studied together. We conducted research among highly egalitarian Congolese BaYaka foragers and compared them with their more hierarchical Bondongo fisher-farmer neighbors. Testing whether BaYaka men’s testosterone was linked to locally-valued fathering roles, we found that fathers who were seen as better community sharers had lower testosterone t...

Journal of Social and Personal Relationships, 2011

Wealth is often controlled by a society's male members and as such passes to future generations through the male line. Sons have a strong interest in the wealth they receive from their fathers, which enables the latter to employ inheritance rights so as to manipulate the former's mating decisions. On this basis, two hypotheses are tested. First, in societies where male offspring enjoy inheritance rights, men are more influential over marriage arrangements. Second, as more male-controlled wealth is produced in agropastoral than in hunting and gathering societies, male offspring are more likely to benefit from inheritance rights in the former that in the latter societies. Evidence from the Standard Cross-cultural Sample provides support for both hypotheses. These findings explain partially why sexual selection under male parental choice is stronger in agropastoral than in foraging societies.

Proceedings of the National Academy of Sciences, 2020

Paternal provisioning among humans is puzzling because it is rare among primates and absent in nonhuman apes and because emergent provisioning would have been subject to paternity theft. A provisioning “dad” loses fitness at the hands of nonprovisioning, mate-seeking “cads.” Recent models require exacting interplay between male provisioning and female choice to overcome this social dilemma. We instead posit that ecological change favored widespread improvements in male provisioning incentives, and we show theoretically how social obstacles to male provisioning can be overcome. Greater availability of energetically rich, difficult-to-acquire foods enhances female–male and male–male complementarities, thus altering the fitness of dads versus cads. We identify a tipping point where gains from provisioning overcome costs from paternity uncertainty and the dad strategy becomes viable. Stable polymorphic states are possible, meaning that dads need not necessarily eliminate cads. Our simul...

American Naturalist, 2002

Males and females are often defined by differences in their energetic investment in gametes. In most sexual species, females produce few large ova, whereas males produce many tiny sperm. This difference in initial parental investment is presumed to exert a fundamental influence on sex differences in mating and parental behavior, resulting in a taxonomic bias toward parental care in females and away from parental care in males. In this article, we reexamine the logic of this argument as well as the evolutionarily stable strategy (ESS) theory often used to substantiate it. We show that the classic ESS model, which contrasts parental care with offspring desertion, violates the necessary relationship between mean male and female fitness. When the constraint of equal male and female mean fitness is correctly incorporated into the ESS model, its results are congruent with those of evolutionary genetic theory for the evolution of genes with direct and indirect effects. Male parental care evolves whenever half the magnitude of the indirect effect of paternal care on offspring viability exceeds the direct effect of additional mating success gained by desertion. When the converse is true, desertion invades and spreads. In the absence of a genetic correlation between the sexes, the evolution of paternal care is independent of maternal care. Theories based on sex differences in gametic investment make no such specific predictions. We discuss whether inferences about the evolution of sex differences in parental care can hold if the ESS theory on which they are based contains internal contradictions.

Human Nature, 2019

Identifying the determinants of reproductive success in small-scale societies is critical for understanding how natural selection has shaped human evolution and behavior. The available evidence suggests that status-accruing behaviors such as hunting and prosociality are pathways to reproductive success, but social egalitarianism may diminish this pathway. Here we introduce a mixed longitudinal/cross-sectional dataset based on 45 years of research with the Batek, a population of egalitarian rain forest hunter-gatherers in Peninsular Malaysia, and use it to test the effects of four predictors of lifetime reproductive success: (i) foraging return rate, (ii) sharing proclivity, (iii) cooperative foraging tendency, and (iv) kin presence. We found that none of these factors can explain variation in lifetime reproduction among males or females. We suggest that social egalitarianism, combined with strikingly low infant and juvenile mortality rates, can mediate the pathway between foraging, status-accruing behavior, and reproductive success. Our approach advocates for greater theoretical and empirical attention to quantitative social network measures, female foraging, and fitness outcomes.

The role of men in hunter-gatherer societies has been subject to vigorous debate over the past fifteen years. The proposal that men hunt wild game as a form of status signaling or "showing off" to provide reproductive benefits to the hunter challenges the traditional view that men hunt to provision their families. Two broad assumptions underlie the signaling view: 1) hunting is an inefficient means of obtaining reliable calories; 2) hunted game is a public good and shared widely to others when there is an audience, and without expectation of future reciprocation. If hunters lack the ability to direct food shares, then the ubiquitous observations of male hunting and universal pair bonding cannot be explained from a perspective that emphasizes provisioning and a division of labor. Here we show, however, that there is little direct empirical support for the assumptions of the signaling hypothesis. The ethnographic record depicts a more complex relationship between food sharing patterns, subsistence strategies and the sexual division of labor than has been suggested by recent treatments. We then describe a framework that incorporates trade-offs between mating and subsistence strategies in an economic bargaining context that can help improve our understanding of men's and women's roles in hunter-gatherer societies. 4 "show-off" hypothesis of Hawkes , Hawkes 1993 initially proposed that men hunt because of the social attention and mating benefits that come from providing game resources that are widely shared. This hypothesis was reformulated using costly signaling theory Zahavi 1997, Bliege Bird, Smith, and, and hereafter referred to as the signaling model, to suggest that men's subsistence behavior is designed to provide an honest signal of underlying genotypic or phenotypic quality by targeting large game that are difficult to acquire. This signaling is particularly effective because the transfer of shares of large prey is believed to be outside the control of the hunter and all consumers pay careful attention to men's hunting results in order to obtain shares for themselves (see Bird 1999, Hawkes and. Because hunting is viewed as a form of mating effort or status competition, rather than familial provisioning, pair bonds and marriage have been reinterpreted as publicly recognized property rights designed to reduce mating competition among men, rather than as cooperative unions designed to reap gains from the joint production of offspring O'Connell 1999, Hawkes 2004). The proponents of the signaling model suggest that if men were primarily concerned with familial provisioning their subsistence patterns would mirror those of women, and also that the sexual division of labor will be most pronounced wherever mating yields highest payoffs for men (Bird 1999:72). As Bird (1999:72) states in a recent review, "the sexual division of labor seems to make more sense as an outcome of conflicts rather than similarities in reproductive goals". Primatologists have considered similar proposals emphasizing male coercion and mate-guarding, rather than provisioning, in considerations of the evolution of pair bonds and monogamous mating systems (