Why aren’t we all hutterites?

In this paper I explore the psychology of ritual performance and present a simple graphical model that clarifies several issues in William Irons’s theory of religion as a “hard-to-fake” sign of commitment. Irons posits that religious behaviors or rituals serve as costly signals of an individual’s commitment to a religious group. Increased commitment among members of a religious group may facilitate intra-group cooperation, which is argued to be the primary adaptive benefit of religion. Here I propose a proximate explanation for how individuals are able to pay the short-term costs of ritual performance to achieve the long-term fitness benefits offered by religious groups. The model addresses three significant problems raised by Irons’s theory. First, the model explains why potential free-riders do not join religious groups even when there are significant net benefits that members of religious groups can achieve. Second, the model clarifies how costly a ritual must be to achieve stability and prevent potential free-riders from joining the religious group. Third, the model suggests why religious groups may require adherents to perform private rituals that are not observed by others. Several hypotheses generated from the model are also discussed. Richard Sosis is an assistant professor of anthropology at the University of Connecticut. His research interests include the evolution of cooperation, utopian societies, and the behavioral ecology of religion. In collaboration with Bradley Ruffle (Ben Gurion University) he is currently investigating the impact of privatization and religiosity on intra-group trust within Israeli Kibbutzim.     

Birth order, sibling investment, and fertility among Ju/’Hoansi (!Kung)

Birth order has been examined over a wide variety of dimensions in the context of modern populations. A consistent message has been that it is better to be born first. The analysis of birth order in this paper is different in several ways from other investigations into birth order effects. First, we examine the effect of birth order in an egalitarian, small-scale, kin-based society, which has not been done before. Second, we use a different outcome measure, fertility, rather than outcome measures of social, psychological, or economic success. We find, third, that being born late in an egalitarian, technologically simple society rather than being born early has a positive outcome on fertility, and fourth, that number of older siblings and sibling set size are even stronger predictors of fertility, especially for males. Patricia Draper is a professor in the Department of Anthropology at the University of Nebraska. Her research interests are in cross-cultural human development, evolutionary theory, hunter-gatherer society, and comparative family organization. Raymond Hames is also a professor in the Department of Anthropology at the University of Nebraska. His research interests are in behavioral and evolutionary ecology, exchange systems, and tropical forest peoples.     

Male-female differences in effects of parental absence on glucocorticoid stress response

This study examines the family environments and hormone profiles of 316 individuals aged 2 months-58 years residing in a rural village on the east coast of Dominica, a former British colony in the West Indies. Fieldwork was conducted over an eight-year period (1988–1995). Research methods and techniques include radioimmunoassay of cortisol and testosterone from saliva samples (N=22,340), residence histories, behavioral observations of family interactions, extensive ethnographic interview and participant observation, psychological questionnaires, and medical examinations. Analyses of data indicate complex, sex-specific effects of family environment on endocrine function. Male endocrine profiles exhibit greater sensitivity to presence of father than do female endocrine profiles. Father-absent males tend to have (a) low cortisol levels during infancy, (b) high or abnormal cortisol profiles during childhood and adolescence, and (c) high cortisol and low testosterone levels during adulthood compared with those of males raised with a resident father. These results indicate that early family environment has significant effects on endocrine response throughout male life histories. Mark V. Flinn is an Associate Professor of Anthropology at the University of Missouri, Columbia. He studies family relationships, endocrine stress response, and child health from a mix of evolutionary and developmental psychology perspectives. Robert J. Quinlan is a graduate student in the Department of Anthropology at the University of Missouri, Columbia. His interests include time allocation, family relationships, and medical anthropology. He is planning a long-term ethnographic study of cross-cousin marriage among the E’nyepa of Venezuela. Mark T. Turner is a graduate student in the Department of Anthropology at Northwestern University. He studies covariance of mother and infant hormone and immune function in naturalistic settings using assays from saliva and breast milk samples and ethnographic observations. Seamus A. Decker is a graduate student in the Department of Anthropology at Emory University. He has studied social factors associated with daily variations of salivary cortisol and testosterone levels among males in a Caribbean village. He is currently investigating levels of stress in rural and urban populations in Botswana. Barry G. England is an Associate Professor of Pathology and director of the ligand assay laboratories of the University of Michigan Hospitals. His primary interests concern reproductive endocrinology.     

The evolutionary ecology of attachment organization

Life history theory’s principle of allocation suggests that because immature organisms cannot expend reproductive effort, the major trade-off facing juveniles will be the one between survival, on one hand, and growth and development, on the other. As a consequence, infants and children might be expected to possess psychobiological mechanisms for optimizing this trade-off. The main argument of this paper is that the attachment process serves this function and that individual differences in attachment organization (secure, insecure, and possibly others) may represent facultative adaptations to conditions of risk and uncertainty that were probably recurrent in the environment of human evolutionary adaptedness. An early version of this paper was presented in the symposium “Childhood in Life-history Perspective: Developing Views” organized by Gilda Morelli and Paula Ivey for the Annual Meeting of the Society for Cross-Cultural Research in Santa Fe, New Mexico, February 16–20, 1994. James S. Chisholm recently joined the Department of Anatomy and Human Biology at the University of Western Australia. Previously he taught in the Department of Anthropology at the University of New Mexico and in the Division of Human Development at the University of California, Davis. He is a biosocial anthropologist whose research interests lie in the fields of human behavioral biology, evolutionary ecology, and life history theory, where he focuses on infant social-emotional development and the development of reproductive strategies in adolescence and young adulthood. In addition to numerous articles he is the author ofNavajo Infancy: An Ethological Study of Child Development (Aldine de Gruyter, 1983).     

The evolution of magnanimity

Conspicuous consumption associated with status reinforcement behavior can be explained in terms of costly signaling, or strategic handicap theory, first articulated by Zahavi and later formalized by Grafen. A theory is introduced which suggests that the evolutionary raison d’être of status reinforcement behavior lies not only in its effects on lifetime reproductive success, but in its positive effects on the probability of survival through infrequent, unpredictable demographic bottlenecks. Under some circumstances, such “wasteful” displays may take the form of displays of altruistic behavior and generosity on the part of high status individuals, in that is signals the ability to bear the short-term costs of being generous or “cooperative,” while at the same time reinforcing the long-term benefits of higher status. James L. Boone is an associate professor in the Department of Anthropology at the University of New Mexico, where he carries out research in behavioral ecology and the archaeology of complex societies. His current interests are in the evolution of social status reinforcement behavior and variation in patterns of conspicuous consumption in human history.     

Evolutionary and ecological aspects of early brain malnutrition in humans

This article reviews the effects of malnutrition on early brain development using data generated from animal experiments and human clinical studies. Three related processes, each with their own functional consequences, are implicated in the alteration of brain development. (1) Maternal undernutrition at the start of pregnancy results in reduced transfer of nutrients across the placenta, allowing the conservation of effort for future reproductive episodes. (2) Differential allocation to growing organs by the fetus in response to nutritional stress spares the brain to a large though still limited degree, reflecting the organ’s relative contribution to survival and reproductive success. (3) Prenatal malnutrition disrupts developing neurotransmitter systems, which results in the expression of specific cognitive and affective traits. It is argued that the increasing size and therefore cost of the brain, in conjunction with increasing ecological instability and marginality, reinforced selection for maternally controlled growth suppression of offspring, reallocation of organ growth rates by offspring, and behavioral changes related to development of neurotransmitter systems. William D. Lukas is a graduate student in the Department of Anthropology at Boston University. He is currently studying the relationship of hormones to immune function and body composition in different populations of African men. Benjamin C. Campbell is Assistant Professor of Anthropology at Boston University. He studies human reproductive ecology, the endocrinology of male fertility and health over the life span, and biocultural interactions in African populations.     

Trade-offs in skillacquisition and time allocation among juvenile chacma baboons

We hypothesize that juvenile baboons are less efficient foragers than adult baboons owing to their small size, lower level of knowledge and skill, and/or lesser ability to maintain access to resources. We predict that as resources are more difficult to extract, juvenile baboons will demonstrate lower efficiency than adults will because of their lower levels of experience. In addition, we hypothesize that juvenile baboons will be more likely to allocate foraging time to easier-to-extract resources owing to their greater efficiency in acquiring those resources. We use feeding efficiency and time allocation data collected on a wild, free-ranging, non-provisioned population of chacma baboons (Papio hamadryas ursinus) in the Moremi Wildlife Reserve, Okavango Delta, Botswana to test these hypotheses. The major findings of this study are: 1. Juvenile baboons are significantly less efficient foragers than adult baboons primarily for difficult-to-extract resources. We propose that this age-dependent variation in efficiency is due to differences in memory and other cognitive functions related to locating food resources, as is indicated by the greater amount of time juvenile baboons spend searching for food. There is no evidence that smaller body size or competitive disruption influences the differences in return rates found between adult and juvenile baboons in this study. 2. An individual baboon’s feeding efficiency for a given resource can be used to predict the duration of its foraging bouts for that resource. These results contribute both to our understanding of the ontogeny of behavioral development in nonhuman primates, especially regarding foraging ability, and to current debate within the field of human behavioral ecology regarding the evolution of the juvenile period in primates and humans. Sara E. Johnson is Assistant Professor of Anthropology at California State University, Fullerton. She received her Ph.D. in Anthropology (Human Evolutionary Ecology) from the University of New Mexico in 2001. She uses behavioral ecology and life history theory to address her research interests in the evolution of primate and human growth; ecological variation and phenotypic plasticity in growth and development; ecological variation in life course trajectories, including fertility, health, morbidity, and mortality differentials; food acquisition and production related to nutrition; societal transofmration and roles of the elderly among indigenous peoples; and women’s reproductive and productive roles in both traditional and nontraditional societies. For the past decade she has conducted research on these issues in several different populations, including chacma baboons in the Okavango Delta of Botswana, two multiethnic communities of forager/agropastoralists in the Okavango Delta of Botswana, and among New Mexican men. John Bock is Associate Professor of Anthropology at California State University at Fullerton and is Associate Editor of Human Nature. He received a Ph.D. in Anthropology (Human Evolutionary EcologY) from the University of New Mexico in 1995, and from 1995 to 1998 was an Andrew W. Mellon Foundation postdoctoral fellow in demography and epidemiology at the National Centre for Epidemiology and Population Health at Australian National University. His recent research has focused on applying life history theory to understanding the evolution of the primate and human juvenile period. Bock has been conducting research among the Okavango Delta peoples of Botswana since 1992, and his current research there is an examination of child development and family demography in relation to socioecology and the HIV/AIDS epidemic. Other research is focused on health disparties among minorities and indigenous peoples in Botswana and the United States related to differential access to health care.     

Girl helpers and time allocation of nursing women among the Toba of Argentina

In this paper we outline the activities of young girls in a Toba community of northern Argentina and examine the effect of girl helpers on time allocation of nursing women. Activity budgets were obtained for 41 girls aged 3 to 15 using spot observations. Girls spent substantial portions of observations engaged in helping behaviors. Individual values varied with age, anthropometric characteristics, and birth order. Activity budgets of 21 nursing women were obtained through focal observation sessions. Women living in households with girls aged 7 to 15 allocated 17% less time to domestic work and 9% more time to socializing during afternoon observation sessions. For nursing women in this community, direct childcare (provided by the infant’s own mother) seemed to be a priority. Living with a girl helper did not have any measurable effect on the frequency or duration of nursing, or on the time that women spent caring for their infants. Based on these findings, hypotheses are outlined for future work on the effect of girl helpers on women’s fertility. Research for this project was funded by the Nestlé Foundation, the Harvard Anthropology Goelet Fund, and the Harvard College Research Program. Eduardo Fernandez-Duque commented on an early draft of this paper. Riley Bove (A.B., Harvard, 1998) is a research associate in the Department of Anthropology at Harvard University with research interests in intergenerational female networks and polygyny as a social mediator of women’s health (esp. urban, African). Claudia Valeggia (Ph.D., U.C. Davis, 1996) is a postdoctoral fellow in the Department of Anthropology at Harvard University with research interests in reproductive ecology and ethnopediatry. Peter Ellison (Ph.D., Harvard, 1983) is a professor of anthropology and director of the Reproductive Ecology Laboratory at Harvard University. He is the author of On Fertile Ground: Ecology, Evolution and Human Reproduction (Harvard University Press, 2001).     

The public health implications of maternal care trade-offs

The socioeconomic and ethnic characteristics of parents are some of the most important correlates of adverse health outcomes in childhood. However, the relationships between ethnic, economic, and behavioral factors and the health outcomes responsible for this pervasive finding have not been specified in child health epidemiology. The general objective of this paper is to propose a theoretical approach to the study of maternal behaviors and child health in diverse ethnic and socioeconomic environments. The specific aims are: (a) to describe a causal pathway between the utility that women obtain through work outside the home and through child care and disease hazard rates in childhood using an optimization model; (b) to specify the influence of ethnic and socioeconomic factors on model constraints; (c) to use the model as a tool to learn about how different combinations of maternal wage labor and child care time might influence child health outcomes in diverse social contexts; (d) to identify parameters that will require measurement in future research; (e) to discuss research strategies that will enable us to obtain these measurements; and (f) to discuss the implications of the model for biostatistical modeling and public health intervention. Optimization models are powerful heuristic tools for understanding how ethnic, environmental, family, and personal characteristics can place important constraints on both the quality and quantity of care that women can provide to their children. They provide a quantitative appreciation for the difficult trade-offs that most women face between working in order to purchase basic goods that children cannot do without (e.g., food, clothing, shelter, health insurance), and increasing offspring well-being through child care (e.g., training in social skills, affection, protection from environmental hazards, help with homework). The research was funded by a Faculty Scholars Award from the William T. Grant Foundation to A. Magdalena Hurtado. A. Magdalena Hurtado, Ph.D., is an associate professor in the Department of Anthropology, University of New Mexico. Her research interests include the origins of the sexual division of labor, epidemiology of indigenous peoples, disease susceptibility, the development and intergenerational transmission of antigens and immune defense, immune function and allergic sensitization, and trauma. She also works on public health interventions, biological capital and poverty, and land tenure and human rights in native communities of South America. Carol Lambourne, M.Sc., is a doctoral candidate in the Department of Anthropology, University of New Mexico. Her research interests are evolutionary models of child and adolescent development, life history theory, family composition and investment patterns, pubertal timing and psychosexual maturation, juvenile stress, and infanticide. Kim Hill, Ph.D., is a professor in the Department of Anthropology, University of New Mexico. His research interests are modern hunter-gatherers, including extensive fieldwork in lowland South America. Current topics of interest include human evolution, economic strategies, life history theory, the evolution of cooperation, and the emergence of social norms enforced by punishment. He is also involved in economic development, health and education projects with lowland South American native populations. Karen Kessler received her M.S. in Anthropology from the University of New Mexico in 1996. Her research interests are the application of mathematical modeling to the prevention of diabetes and other causes of morbidity and mortality in historical populations.     

Mate preferences among Hadza hunter-gatherers

The literature on human mate preferences is vast but most data come from studies on college students in complex societies, who represent a thin slice of cultural variation in an evolutionarily novel environment. Here, I present data on the mate preferences of men and women in a society of hunter-gatherers, the Hadza of Tanzania. Hadza men value fertility in a mate more than women do, and women value intelligence more than men do. Women place great importance on men’s foraging, and both sexes rate character as important. Unlike college students, Hadza men place considerable importance on women being hard-working, and Hadza women cite looks about as often as men do. This research was made possible by a grant from the National Science Foundation and the Leakey Foundation. Frank Marlowe (B.A., M.A., M.F.A., Ph.D.) is associate professor in the Department of Anthropology, Harvard University. His research interests include the behavioral ecology of hunter-gatherers, mating systems, parental care, mate choice, and cooperation.     

Consequences of wooded shrine rituals on vegetation conservation in West Africa: a case study from the Bwaba cultural area (West Burkina Faso)

Anthropological contributions that challenge several common perceptions on sacred sites are still poorly taken into account in conservation and ecological studies. This paper aims at filling this gap and providing a better framework for biological studies. Local concepts of natural sacred sites and their ritual administration were studied and the ritual practices relating to the vegetation of these sites were analyzed in the Bwaba cultural area in West Burkina Faso. Our research shows that these ritual practices are much more diverse and fluid than might have been supposed. Protection ‘by tradition’ is thus rather different from what we call conservation. While vegetation does matter, its presence on sacred sites is not essential. In addition, under certain circumstances, sacred sites may be transferred or reproduced elsewhere. Attention is drawn to the inadequacy of ‘sacred woods’ as a category, in an ecological as well as an anthropological sense. Even if wooded shrines may contribute to biodiversity conservation as a side-effect of their religious purpose, the idea that they fundamentally are ‘endogenous’ nature conservatories must be disproved.     

Relationship between subsistence and age at weaning in “preindustrial” societies

Cross-cultural studies have revealed broad quantitative associations between subsistence practice and demographic parameters for preindustrial populations. One explanation is that variationin the availability of suitable weaning foods influenced the frequency and duration of breastfeeding and thus the length of interbirth intervals and the probability of child survival (the “weaning food availability” hypothesis). We examine the available data on weaning age variation in preindustrial populations and report results of a cross-cultural test of the predictions that weaning occurred earlier in agricultural and pastoral populations because dairy and cereal production increased the availability of easily digestible, nutrientrich foods appropriate for weaning. We found that, contrary to predictions, supplementation with liquid foods other than breast milk was delayed in agricultural populations relative to less agriculturally dependent ones and complementary feeding with solid foods was delayed in pastoral populations relative to those less dependent on herding. Although the duration of breastfeeding was longer in populations dependent on hunting, there was no qualitative evidence that such populations lacked foods appropriate for weaning. The patterns observed suggest that the relationships between demography and subsistence observed among preindustrial societies cannot be explained by the “weaning food availability” hypothesis. We discuss the implications for understanding the mechanisms underlying prehistoric human demography, subsistence shifts, allocation to parenting and mating effort, and the evolutionary implications of tradeoffs between diet and disease. Earlier versions of this paper were presented at the 11th Annual Meeting of the Human Behavior and Evolution Society, Salt Lake City, 5 June 1999 and the 4th International Anthropological Congress of Ales Hrdlička, Prague, Czech Republic, 4 September 1999. Daniel Sellen is an assistant professor in the Department of Anthropology at Emory University; adjunct professor in the Department of International Health, Rollins School of Public Health; and an Honorary Lecturer in the Public Health Nutrition Unit at the london School of Hygiene and Tropical Medicine. His research interests are in nutritional ecology; the relations between subsistence and demography; and the evolution and current diversity of young child feeding and caregiving practices. In addition to work on demography among traditional populations, he has published “Age, Sex and Anthropometric Status of Children in an African Pastoral Community” (Annals of Human Biology 27:1–21, 2000), “Polygyny and Child Growth in a Traditional Pastoral Society: The Case of the Datoga of Tanzania” (Human Nature 10:327–371, 1999), and “Growth Patterns among Seminomadic Pastoralists (Datoga) of Tanzania” (American Journal of Physical Anthropology 109:187–209, 1999). Diana Smay is a graduate student in the Department of Anthropology, Emory University. Her research interests include bioarchaeology, paleoepidemiology, the evolution of disease, and the behavioral determinants of paleodemography. Her dissertation work concerns aspects of selective inclusion bias and short-term stress events in skeletal samples.     

Primates got personality,too: Toward an integrative primatology of consistent individual differences in behavior

In recent years, research on animal personality has exploded within the field of behavioral ecology. Consistent individual differences in behavior exist in a wide range of species, and these differences can have fitness consequences and influence several aspects of a species' ecology. In comparison to studies of other animals, however, there has been relatively little research on the behavioral ecology of primate personality. This is surprising given the large body of research within psychology and biomedicine showing that primate personality traits are heritable and linked to health and life history outcomes. In this article, I bring together theoretical perspectives on the ecology and evolution of animal personality with an integrative review of what we know about primate personality from studies conducted on captive, free‐ranging, and wild primates. Incorporating frameworks that emphasize consistency in behavior into primate behavioral ecology research holds promise for improving our understanding of primate behavioral evolution.     

Signaling,solidarity, and the sacred: The evolution of religious behavior

Anthropologists have repeatedly noted that there has been little theoretical progress in the anthropology of religion over the past fifty years.^1–7 By the 1960s, Geertz² had pronounced the field dead. Recently, however, evolutionary researchers have turned their attention toward understanding the selective pressures that have shaped the human capacity for religious thoughts and behaviors, and appear to be resurrecting this long‐dormant but important area of research.^8–19 This work, which focuses on ultimate evolutionary explanations, is being complemented by advances in neuropsychology and a growing interest among neuroscientists in how ritual, trance, meditation, and other altered states affect brain functioning and development.^20–26 This latter research is providing critical insights into the evolution of the proximate mechanisms responsible for religious behavior. Here we review these literatures and examine both the proximate mechanisms and ultimate evolutionary processes essential for developing a comprehensive evolutionary explanation of religion.     

Song evolution,speciation, and vocal learning in passerine birds

Phenotypic divergence can promote reproductive isolation and speciation, suggesting a possible link between rates of phenotypic evolution and the tempo of speciation at multiple evolutionary scales. To date, most macroevolutionary studies of diversification have focused on morphological traits, whereas behavioral traits─including vocal signals─are rarely considered. Thus, although behavioral traits often mediate mate choice and gene flow, we have a limited understanding of how behavioral evolution contributes to diversification. Furthermore, the developmental mode by which behavioral traits are acquired may affect rates of behavioral evolution, although this hypothesis is seldom tested in a phylogenetic framework. Here, we examine evidence for rate shifts in vocal evolution and speciation across two major radiations of codistributed passerines: one oscine clade with learned songs (Thraupidae) and one suboscine clade with innate songs (Furnariidae). We find that evolutionary bursts in rates of speciation and song evolution are coincident in both thraupids and furnariids. Further, overall rates of vocal evolution are higher among taxa with learned rather than innate songs. Taken together, these findings suggest an association between macroevolutionary bursts in speciation and vocal evolution, and that the tempo of behavioral evolution can be influenced by variation in developmental modes among lineages.     

Early stress predicts age at menarche and first birth,adult attachment,and expected lifespan

Life history theory suggests that in risky and uncertain environments the optimal reproductive strategy is to reproduce early in order to maximize the probability of leaving any descendants at all. The fact that early menarche facilitates early reproduction provides an adaptationist rationale for our first two hypotheses: that women who experience more risky and uncertain environments early in life would have (1) earlier menarche and (2) earlier first births than women who experience less stress at an early age. Attachment theory and research provide the rationale for our second two hypotheses: that the subjective early experience of risky and uncertain environments (insecurity) is (3) part of an evolved mechanism for entraining alternative reproductive strategies contingent on environmental risk and uncertainty and (4) reflected in expected lifespan. Evidence from our pilot study of 100 women attending antenatal clinics at a large metropolitan hospital is consistent with all four hypotheses: Women reporting more troubled family relations early in life had earlier menarche, earlier first birth, were more likely to identify with insecure adult attachment styles, and expected shorter lifespans. Multivariate analyses show that early stress directly affected age at menarche and first birth, affected adult attachment in interaction with expected lifespan, but had no effect on expected lifespan, where its original effect was taken over by interactions between age at menarche and adult attachment as well as age at first birth and adult attachment. We discuss our results in terms of the need to combine evolutionary and developmental perspectives and the relation between early stress in general and father absence in particular. This work was supported by The University of Melbourne Department of Obstetrics and Gynaecology. James S. Chisholm is Professor in the School of Anatomy and Human Biology at the University of Western Australia. He is an anthropologist whose interests lie in the fields of human behavioral biology, evolutionary ecology, life history theory, and parental investment theory, where he focuses on infant social-emotional development, the development of reproductive strategies, and the integration of evolutionary, developmental, and cultural psychology and public health. Julie A. Quinlivan is Associate Professor in Obstetrics and Gynaecology at the University of Melbourne and Head of the Maternity Care Program at the Royal Women’s Hospital, Melbourne. Her interests are teenage pregnancy, domestic violence, child abuse prevention, and high-risk pregnancy. Rodney W. Petersen is Senior Lecturer in Obstetrics and Gynaecology at the University of Melbourne and Senior Consultant in Obstetrics and Gynaecology at the Royal Women’s Hospital and Sunshine Hospital in Melbourne. His interests are in psychosocial aspects of women’s health and cancer. David A. Coall is a Ph.D. student in the School of Anatomy and Human Biology at the University of Western Australia. His main interest lies in the application of evolutionary theory within an epidemiological framework. He is currently working on the synthesis of life history theory, parental investment theory, and parent-offspring conflict theory in exploring factors that influence variation in human birth weight and placental weight.     

Preferential parental investment in daughters over sons

Female-biased parental investment is unusual but not unknown in human societies. Relevant explanatory models include Fisher’s principle, the Trivers-Willard model, local mate and resource competition and enhancement, and economic rational actor models. Possible evidence of female-biased parental investment includes sex ratios, mortality rates, parents’ stated preferences for offspring of one sex, and direct and indirect measurements of actual parental behavior. Possible examples of female-biased parental investment include the Mukogodo of Kenya, the Ifalukese of Micronesia, the Cheyenne of North America, the Herero of southern Africa, the Kanjar of south Asia, the Mundugumor of New Guinea, contemporary North America, and historical Germany, Portugal, and the United States. Lee Cronk is Assistant Professor of Anthropology at Texas A&M University, College Station, Texas. His main research interests are in human behavioral ecology, reproductive strategies, and East African hunter-gatherers and pastoralists.     

The patriarch hypothesis

Menopause is puzzling because life-history theory predicts there should be no selection for outliving one’s reproductive capacity. Adaptive explanations of menopause offered thus far turn on women’s long-term investment in offspring and grandoffspring, all variations on the grandmother hypothesis. Here, I offer a very different explanation. The patriarch hypothesis proposes that once males became capable of maintaining high status and reproductive access beyond their peak physical condition, selection favored the extension of maximum life span in males. Because the relevant genes were not on the Y chromosome, life span increased in females as well. However, the female reproductive span was constrained by the depletion of viable oocytes, which resulted in menopause. Frank Marlowe, Ph.D., is Assistant Professor of Anthropology at Harvard University. He conducts research with the Hadza and his interests include the behavioral ecology of mating systems, life-history theory, and cooperation.     

Hunter-Gatherers and the Origins of Religion

Recent studies of the evolution of religion have revealed the cognitive underpinnings of belief in supernatural agents, the role of ritual in promoting cooperation, and the contribution of morally punishing high gods to the growth and stabilization of human society. The universality of religion across human society points to a deep evolutionary past. However, specific traits of nascent religiosity, and the sequence in which they emerged, have remained unknown. Here we reconstruct the evolution of religious beliefs and behaviors in early modern humans using a global sample of hunter-gatherers and seven traits describing hunter-gatherer religiosity: animism, belief in an afterlife, shamanism, ancestor worship, high gods, and worship of ancestors or high gods who are active in human affairs. We reconstruct ancestral character states using a time-calibrated supertree based on published phylogenetic trees and linguistic classification and then test for correlated evolution between the characters and for the direction of cultural change. Results indicate that the oldest trait of religion, present in the most recent common ancestor of present-day hunter-gatherers, was animism, in agreement with long-standing beliefs about the fundamental role of this trait. Belief in an afterlife emerged, followed by shamanism and ancestor worship. Ancestor spirits or high gods who are active in human affairs were absent in early humans, suggesting a deep history for the egalitarian nature of hunter-gatherer societies. There is a significant positive relationship between most characters investigated, but the trait “high gods” stands apart, suggesting that belief in a single creator deity can emerge in a society regardless of other aspects of its religion.