Humans are obligate cooperative breeders, relying heavily on support from kin to raise children. To date, most studies of cooperative breeding have focused on help that supplements rather than replaces parental care. Here we propose that fosterage can act as a form of dispersed cooperative breeding, one that enhances women’s fitness by allowing them to disinvest in some children and reallocate effort to others. We test this hypothesis through a series of predictions about the costs and benefits of fosterage for (...) mothers, foster parents, and foster children using data from the Himba, a group of Namibian agro-pastoralists. We show that fostering out children enhances mothers’ fitness, and we provide evidence for a causal link from fosterage to enhanced fitness by showing that fosterage of early-born children is associated with greater maternal reproductive success. Foster parents minimize the costs of fosterage by skewing their care toward their postreproductive years, and by mainly fostering close kin. However, the system is associated with some detrimental effects on foster children, who are more likely to be stunted and underweight than their non-fostered counterparts. (shrink)

Maternal grandmothers play a key role in allomaternal care, directly caring for and provisioning their grandchildren as well as helping their daughters with household chores and productive labor. Previous studies have investigated these contributions across a broad time period, from infancy through toddlerhood. Here, we extend and refine the grandmothering literature to investigate the perinatal period as a critical window for grandmaternal contributions. We propose that mother-daughter co-residence during this period affords targeted grandmaternal effort during a period of heightened vulnerability (...) and appreciable impact. We conducted two focus groups and 37 semi-structured interviews with Himba women. Interviews focused on experiences from their first and, if applicable, their most recent birth and included information on social support, domains of teaching and learning, and infant feeding practices. Our qualitative findings reveal three domains in which grandmothers contribute: learning to mother, breastfeeding support, and postnatal health and well-being. We show that informational, emotional, and instrumental support provided to new mothers and their neonates during the perinatal period can aid in the establishment of the mother-infant bond, buffer maternal energy balance, and improve nutritional outcomes for infants. These findings demonstrate that the role of grandmother can be crucial, even when alloparenting is common and breastfeeding is frequent and highly visible. Situated within the broader anthropological and clinical literature, these findings substantiate the claim that humans have evolved in an adaptive sociocultural perinatal complex in which grandmothers provide significant contributions to the health and well-being of their reproductive-age daughters and grandchildren. (shrink)

Humans have been called “cooperative breeders” because mothers rely heavily on alloparental assistance, and the grandmother life stage has been interpreted as an adaptation for alloparenting. Many studies indicate that women invest preferentially in their daughters’ children, but little research has been conducted where patrilocal residence is normative. Bangladesh is such a place, but women nevertheless receive substantial alloparental investment from the matrilateral family, and child outcomes improve when maternal grandmothers are alloparents. To garner this support, women must maintain contact (...) with their natal families. Here, the visiting behavior of 151 interviewed mothers was analyzed. Despite the challenges of patrilocality and purdah, almost all respondents visited their own mothers, and mothers-in-law were visited far less. This contrast persists in analyses controlling for proximity, respondent age, postmarital residence, family income, and marital status. These results affirm the importance women place on matrilateral ties, even under a countervailing ideology. (shrink)

The suppression of sexuality is culturally widespread, and women’s sexual promiscuity, activity, and enjoyment are almost always judged and punished more harshly than men’s. It remains disputed, however, to what end people suppress sexuality, and who benefits from the suppression of female sexuality. Different theories predict that women in general, men in general, women’s intimate partners, or parents benefit most. Here we use the lies women and men tell—or imagine telling—about their sexual histories as an indirect measure of who is (...) most involved in the suppression of sexuality. We asked men and women what they would reply if asked questions by their mother, father, current partner, attractive confederate, and various same- or opposite-sex friends and colleagues about their number of previous sex partners, age at first romantic kiss, age at first consensual sex, and cheating on a previous partner or spouse. By comparing the size and direction of the lies that subjects told, we tested competing predictions of several cultural and evolutionary theories concerning why female sexuality is suppressed and who is driving its suppression. We found that men and women told larger and more frequent lies to their parents, with women telling the largest and most frequent lies of all to their fathers. Additionally, the majority of lies by both men and women were in sexually conservative directions. Our findings suggest that mothers, and especially fathers, restrict female sexuality. (shrink)