Altruistic cooperation during foraging by the Ache, and the evolved human predisposition to cooperate

This paper presents quantitative data on altruistic cooperation during food acquisition by Ache foragers. Cooperative activities are defined as those that entail a cost of time and energy to the donor but primarily lead to an increase in the foraging success of the recipient. Data show that Ache men and women spend about 10% of all foraging time engaged in altruistic cooperation on average, and that on some days they may spend more than 50% of their foraging time in such activities. The most time-consuming cooperative activity for both sexes is helping during the pursuit of game animals, a pattern that is probably linked to the widespread sharing of game by Ache foragers. Cooperative food acquisition and subsequent food redistribution in hunter-gatherer societies are critical behaviors that probably helped shape universal, evolved, cooperative tendencies that are well illustrated in modern experimental economics. This paper was originally presented at a Max Planck symposium on cooperation in Leipzig in June 1999. This work was partially funded by a grant from the L.S.B. Leakey Foundation and NSF grant BNS 9727656. Kim Hill is a professor of anthropology in the Human Evolutionary Ecology (HEE) program at the University of New Mexico. His primary research interests include hunter-gatherer behavioral ecology, life history theory, food acquisition strategies, food sharing, cooperation, and biodiversity conservation in lowland South America. He has done fieldwork with Nahautl, Ache, Guarani, Hiwi, Mashco Piro, Matsiguenga, and Yora indigenous peoples of Central and South America.     

Determinants of time allocation across the lifespan

This paper lays the groundwork for a theory of time allocation across the life course, based on the idea that strength and skill vary as a function of age, and that return rates for different activities vary as a function of the combination of strength and skills involved in performing those tasks. We apply the model to traditional human subsistence patterns. The model predicts that young children engage most heavily in low-strength/low-skill activities, middle-aged adults in high-strength/high-skill activities, and older adults in low-strength/high-skill activities. Tests among Machiguenga and Piro forager-horticulturalists of southeastern Peru show that males and females focus on low-strength/low-skill tasks early in life (domestic tasks and several forms of fishing), switch to higher-strength/higher-skill activities in their twenties and thirties (hunting, fishing, and gardening for males; fishing and gardening for females), and shift focus to high-skill activities late in life (manufacture/repair, food processing). Michael Gurven is an assistant professor of anthropology at the University of California-Santa Barbara. He received his Ph.D. from the University of New Mexico in 2000. He has conducted fieldwork in Paraguay and Bolivia with Ache and Tsimane forager-horticulturalists. His research interests include intragroup cooperation and problems of collective action, and the application of life history theory to explaining human longevity, cognitive development, delayed maturation, and sociality. Since 2002, Gurven and Kaplan have co-directed the Tsimane Health and Life History Initiative, a five-year project to develop theory and test implications of different models of human life history evolution. Hillard Kaplan is a professor of anthropology at University of New Mexico. He received his Ph.D. from the University of Utah in 1983. He has conducted fieldwork in Paraguay, Brazil, Botswana, and Bolivia. His research interests include evolutionary perspectives on life course development and senescence, and brain evolution. He has launched theoretical and empirical investigations into each of these areas, uniting evolutionary and economic approaches. He has applied human capital theory toward explaining human life history evolution, and the proximate physiological and psychological mechanisms governing fertility and parental investment in both traditional, high-fertility, subsistence economies and modern, low-fertility, industrial societies.     

Why do good hunters have higher reproductive success?

Anecdotal evidence from many hunter-gatherer societies suggests that successful hunters experience higher prestige and greater reproductive success. Detailed quantitative data on these patterns are now available for five widely dispersed cases (Ache, Hadza, !Kung, Lamalera, and Meriam) and indicate that better hunters exhibit higher age-corrected reproductive success than other men in their social group. Leading explanations to account for this pattern are: (1) direct provisioning of hunters’ wives and offspring, (2) dyadic reciprocity, (3) indirect reciprocity, (4) costly signaling, and (5) phenotypic correlation. I examine the qualitative and quantitative evidence bearing on these explanations and conclude that although none can be definitively rejected, extensive and apparently unconditional sharing of large game somewhat weakens the first three explanations. The costly signaling explanation has support in some cases, although the exact nature of the benefits gained from mating or allying with or deferring to better hunters needs further study. For comments on earlier drafts, I thank Monique Borgerhoff Mulder, Mike Gurven, Ray Hames, Kristen Hawkes, Kim Hill, Robert Kelly, Frank Marlowe, John Patton, and Polly Wiessner. Rebecca Bliege Bird and Douglas W. Bird invited me to collaborate in the Meriam research and (along with Del Passi of Mer) collected the data on Meriam demography. Geoff Kushnick and Matt Wimmer ably assisted with coding and statistical analysis of these data. Eric Alden Smith (PhD 1980, Cornell University) is a professor of anthropology at the University of Washington, Seattle. His research interests include the links between production and reproduction, the ecology and evolution of collective action, and politics in small-scale societies. He has conducted fieldwork among Inuit on Hudson Bay, Meriam in Torres Strait, and Mardu Aborigines in the Australian Western Desert.     

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.     

Trade-Offs between female food acquisition and child care among hiwi and ache foragers

Even though female food acquisition is an area of considerable interest in hunter-gatherer research, the ecological determinants of women’s economic decisions in these populations are still poorly understood. The literature on female foraging behavior indicates that there is considerable variation within and across foraging societies in the amount of time that women spend foraging and in the amount and types of food that they acquire. It is possible that this heterogeneity reflects variation in the trade-offs between time spent in food acquisition and child care activities that women face in different groups of hunter-gatherers. In this paper we discuss the fitness trade-offs between food acquisition and child care that Hiwi and Ache women foragers might face. Multiple regression analyses show that in both populations the daily food acquisition of a woman’s spouse is negatively related to female foraging effort. In addition, nursing mothers spend less time foraging and acquire less food than do nonnursing women. As the number of dependents that a woman has increases, however, women also increase foraging time and the amount of food they acquire. Some interesting exceptions to these general trends are as follows: (a) differences in foraging effort between nursing and nonnursing women are less pronounced when fruits and roots are in season than in other seasons of the year; (b) foraging return rates decrease for Ache women as their numbers of dependents increase; and (c) among Ache women, the positive effect of number of dependents on foraging behavior is less pronounced when fruits are in season than at other times of the year. Lastly, in the Hiwi sample we found that postreproductive women work considerably harder than women of reproductive age in the root season but not in other seasons of the year. We discuss how ecological variation in constraints, the number of health insults to children that Hiwi and Ache mothers can avoid, and the fitness benefits they can gain from spending time in food acquisition and child care might account for differences and similarities in the foraging behaviors of subgroups of Hiwi and Ache mothers across different seasons of the year. Valid tests of the explanations we propose will require considerable effort to measure the relationship between maternal food acquisition, child care, and adverse health outcomes in offspring. This paper is dedicated to Nutsiya, the hardest-working grandmother we ever observed Kristen Hawkes contributed useful information on female foraging among the Hadza. The research was funded by the National Science Foundation (BNS-8613215, BNS-538228, BNS-8309834, BNS-8121209) and the L. S. B. Leakey Foundation. The senior author was supported by fellowships from the Fundacion Gran Mariscal de Ayacucho of Venezuela and the National Institute of Health (Grant No. 1 RO1 HD16221-01A2). A. Magdalena Hurtado, Kim Hill, and Hillard Kaplan collaborate in research on the evolutionary ecology of the division of labor by sex. Ines Hurtado is Senior Research Scientist at the Instituto Venezolano de Investigaciones Científicas, Venezuela. She studies the immunology of parasite load and atopic illness in Hiwi foragers.     

Showing off: Tests of an hypothesis about men's foraging goals

It is widely assumed that among hunter-gatherers, men work to provision their families. However, men may have more to gain by giving food to a wide range of companions who treat them favorably in return. If so, and if some resources better serve this end, men's foraging behavior should vary accordingly. Aspects of this hypothesis are tested on observations of food acquisition and sharing among Ache foragers of Eastern Paraguay. Previous analysis showed that different Ache food types were differently shared. Resources shared most widely were game animals. Further analysis and additional data presented here suggest a causal association between the wide sharing of game and the fact that men hunt and women do not. Data show that men preferentially target resources in both hunting and gathering which are more widely shared, resources more likely to be consumed outside their own nuclear families. These results have implications for 1) the identification of male reproductive trade-offs in human societies, 2) the view that families are units of common interest integrated by the sexual division of labor, 3) current reconstructions of the evolution of foraging and food sharing among early hominids, and 4) assessments of the role of risk and reciprocity in hunter-gatherer foraging strategies.     

The evolutionary history of childbirth

Consideration of the evolutionary and cross-cultural history of childbirth reveals many differences between the ways in which most human females have experienced childbirth and the ways in which most women in contemporary industrialized obstetric settings experience the event. In this paper I review two of these differences: the pain and anxiety of labor and delivery and the discontinuity of care provided for the mother and infant. I argue that much of the dissatisfaction with birth practices in the United States results from the failure of modern obstetric practice to meet the evolved needs of mothers and infants. Wenda Trevathan is an associate professor of anthropology at New Mexico State University. Her research interests focus on evolutionary and biosocial aspects of human female reproductive behavior, including childbirth, sexuality, and menopause. She is the recipient of the 1990 Margaret Mead Award and has received midwifery training.     

Testosterone levels among Aché hunter-gatherer men

Salivary testosterone levels were measured in a population of New World indigenous adult hunter-gatherer males in order to compare circulating levels of free unbound bioactive steroid with those previously reported among Boston and nonwestern males. The study population consisted of adult Aché hunter-gatherer males (n=45) living in eastern Paraguay. Morning and evening salivary testosterone levels (TsalA.M.; TsalP.M.) among the Aché were considerably lower than western values (Boston) and even lower than other previously reported nonwestern populations (Efe, Lese, Nepalese). No association was observed between height, weight, or age and salivary testosterone levels within the Aché group, although older men (ages>40) were poorly represented in the study sample. Nevertheless, a mild correlation was observed between Aché TsalA.M. levels and BMI (r=0.133,p=0.0725). Comparison of Aché values with those for other populations confirms the prevalence of significant interpopulational variation in testosterone levels among adult males. Interpopulational variation in male testosterone is not as great, however, as has been documented for ovarian steroids among females, nor is it likely that such variation reflects differences in male fecundity. Nevertheless, such interpopulational variation in salivary testosterone levels may have a functional significance in the regulation of protein anabolism in skeletal muscle, thereby affecting the overall energy budget of the organism. It is suggested that relative suppression of average testosterone may be adaptive under conditions of chronic energy shortage. This research was funded by the National Science Foundation, the Mellon Foundation, Sigma Xi, and Harvard University. The author is a doctoral candidate in biological anthropology at Harvard University. He received his B.A. in anthropology and psychology from UCLA in 1988 and his M.A. in anthropology from Harvard in 1994. His research interests include male reproductive ecology, male hormone function, foraging societies, evolutionary biology, and behavioral evolution.     

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.     

Norm enforcement among the Ju/’hoansi Bushmen

The concept of cooperative communities that enforce norm conformity through reward, as well as shaming, ridicule, and ostracism, has been central to anthropology since the work of Durkheim. Prevailing approaches from evolutionary theory explain the willingness to exert sanctions to enforce norms as self-interested behavior, while recent experimental studies suggest that altruistic rewarding and punishing—“strong reciprocity”—play an important role in promoting cooperation. This paper will use data from 308 conversations among the Ju/’hoansi (!Kung) Bushmen (a) to examine the dynamics of norm enforcement, (b) to evaluate the costs of punishment in a forager society and understand how they are reduced, and (c) to determine whether hypotheses that center on individual self-interest provide sufficient explanations for bearing the costs of norm enforcement, or whether there is evidence for strong reciprocity. Polly Wiessner is a professor of anthropology at the University of Utah. She has carried out fieldwork with the Ju/’hoansi of the Kalahari for the past 30 years on social networks, style in artifacts, economy, population, nutrition, and social change. She has also worked among the Enga of Papua New Guinea since 1985 on the oral history of exchange, ritual, and warfare.     

Parent-offspring conflict and the cultural ecology of breast-feeding

Lactation constitutes a major focus for research in international health because of its dramatic impact on child survival; evolutionary biology has investigated lactation as an important aspect of parenting strategy, with implications for understanding parent-offspring conflict. These perspectives are brought together in an attempt to develop integrated models for an issue of key international health concern: the duration of exclusive breast-feeding and the timing of weaning. This analysis highlights the relevance of evolutionary theory for practical problems in public health, and it suggests the utility of public health outcomes for addressing evolutionary questions. Thomas McDade received his Ph.D. degree in anthropology from Emory University in 1999 and is currently an assistant professor in the anthropology department at Northwestern University. His research interests include biocultural perspectives on issues related to health and human development, with current attention focused on the cultural and evolutionary ecology of human immune function.     

Are kubo hunters ‘show offs’?

The ‘show off’ hypothesis proposed by K. Hawkes, and tested using data on Ache foragers, makes important connections between food resource choice, reproductive strategies, and food sharing by human foragers. We test predictions derived from that hypothesis concerning contexts of meat acquisition, association between individuals, mobility, and reproductive success among Kubo hunter-horticulturalists of the interior lowlands of Papua New Guinea. Application of the hypothesis to both the Kubo and Ache cases is questioned. Differences between Kubo males in means and variances of returns from hunting arise as a consequence of differential target specialization; they do not map onto variation in reproductive success.     

Subsistence ecology and play among the okavango delta peoples of botswana

Children’s play is widely believed by educators and social scientists to have a training function that contributes to psychosocial development as well as the acquisition of skills related to adult competency in task performance. In this paper we examine these assumptions from the perspective of life-history theory using behavioral observation and household economic data collected among children in a community in the Okavango Delta of Botswana where people engage in mixed subsistence regimes of dry farming, foraging, and herding. We hypothesize that if play contributes to adult competency then time allocation to play will decrease as children approach adult levels of competence. This hypothesis generates the following predictions: (1) time allocated to play activities that develop specific productive skills should decline in relation to the proportion of adult competency achieved; (2) children will spend more time in forms of play that are related to skill development in tasks specific to the subsistence ecology in which that child participates or expects to participate; and (3) children will spend more time in forms of play that are related to skill development in tasks clearly related to the gender-specific productive role in the subsistence ecology in which that child participates or expects to participate. We contrast these expectations with the alternative hypothesis that if play is not preparatory for adult competence then time allocated to each play activity should diminish at the same rate. This latter hypothesis generates the following two predictions: (1) time allocation to play should be unaffected by subsistence regime and (2) patterns of time allocation to play should track patterns of growth and energy balance. Results from multiple regression analysis support earlier research in this community showing that trade-offs between immediate productivity and future returns were a primary determinant of children’s activity patterns. Children whose labor was in greater demand spent significantly less time playing. In addition, controlling for age and gender, children spent significantly more time in play activities related to tasks specific to their household subsistence economy. These results are consistent with the assertion that play is an important factor in the development of adult competency and highlight the important contributions of an evolutionary ecological perspective in understanding children’s developmental trajectories. John Bock is an associate professor of anthropology at Cal State Fullerton and 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 the application of 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 disparities among minorities and indigenous peoples in Botswana and the United States related to differential access to health care. Sara E. Johnson is an 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 transformation and roles of the elderly among indigenous peoples; and women’s reproductive and productive roles in both traditional and nontraditional societies. Over the past 10 years 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.     

Conservation by native peoples

Native peoples have often been portrayed as natural conservationists, living a “balanced” existence with nature. It is argued that this perspective is a result of an imprecise operational definition of conservation. Conservation is defined here in contrast to the predictions of foraging theory, which assumes that foragers will behave to maximize their short-term harvesting rate. A behavior is deemed conservation when a short-term cost is paid by the resource harvester in exchange for long-term benefits in the form of sustainable harvests. An example of the usefulness of such an operational definition is presented using data on patch and prey choice decisions of a group of subsistence hunters, the Piro of Amazonian Peru. Results indicate that the area around the Piro village is depleted of prey, and that hunters allocate more time to patches where return rates are highest. This response is consistent with both a conservation strategy and foraging theory. Contrary to the expectation of the conservation strategy, however, hunters do not restrain from pursing opportunistically encountered prey in the depleted areas. The implications for conservation policy are briefly discussed. Michael Alvard received his Ph.D. at the University of New Mexico in 1993 and is currently an assistant professor of anthropology at Dickinson College. His interests include the impact of traditional hunting on prey species and the evolution of conservation. He is currently pursuing research opportunities with the Wana, a group of subsistence hunters living in the rain forests of Sulawesi, Indonesia.     

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.     

The human breast and the ancestral reproductive cycle

This paper, using modern Darwinian theory, proposes an explanation for the increasingly high incidence of breast cancer found among pre-and post-menopausal women living today in westernized countries. A number of factors have been said to be responsible: genetic inheritance (BRCA-1), diet (specifically the increased consumption of dietary fat), exposure to carcinogenic agents, lifetime menstrual activity, and reproductive factors. The primary aim of this paper is to demonstrate the value of a perspective based on Darwinian theory. In this paper, Darwinian theory is used to explore the possibility that the increased incidence of breast cancer is due primarily to the failure to complete in a timely manner the reproductive developmental cycle, beginning at menarche and continuing through a series of pregnancies and lactation. On the basis of comparative data, we assume that most women in ancestral populations began having children before age 20 or so and tended to remain either pregnant or nursing for most of their adult lives. If a woman did not have a child by age 25 or so, she probably would never have one. Therefore, selection would probably not have acted against deleterious traits, such as cancer, that appeared after that age, just as it does not act against such traits in old age. This article is based upon a paper presented at the Sixth Annual Scientific Meeting of the Human Behavior and Evolution Society, June 18th, 1994, University of Michigan, Ann Arbor. Kathryn Coe is a Ph.D. candidate in anthropology at Arizona State University and project director of an NCI grant focusing on cervical and breast cancer in Hispanic women. Field research for her doctoral dissertation focused on the health, fertility, and culture of the Chachi Indians of the coastal rain forest of Ecuador. Lyle Steadman is an assistant professor of anthropology at Arizona State University. He has conducted research for more than two years among the isolated Hewa of Papua New Guinea. His research interests include evolutionary theory and culture, particularly religion and kinship.     

Ritual,emotion, and sacred symbols

This paper considers religion in relation to four recurrent traits: belief systems incorporating supernatural agents and counterintuitive concepts, communal ritual, separation of the sacred and the profane, and adolescence as a preferred developmental period for religious transmission. These co-occurring traits are viewed as an adaptive complex that offers clues to the evolution of religion from its nonhuman ritual roots. We consider the critical element differentiating religious from non-human ritual to be the conditioned association of emotion and abstract symbols. We propose neurophysiological mechanisms underlying such associations and argue that the brain plasticity of human adolescence constitutes an “experience expectant” developmental period for ritual conditioning of sacred symbols. We suggest that such symbols evolved to solve an ecological problem by extending communication and coordination of social relations across time and space. Candace Alcorta is currently a doctoral student in the Department of Anthropology at the University of Connecticut. Her research interests include the behavioral ecology and evolution of religion, and the interrelationship between cultural and neurophysiological systems. She is currently conducting research on adolescent religious participation, stress, and health. Richard Sosis is an associate professor in the Department of Anthropology at the University of Connecticut and a senior lecturer in the Department of Sociology and Anthropology at The Hebrew University of Jerusalem. His current research interests include the evolution of cooperation, utopian societies, and the behavioral ecology of religion. He has conducted fieldwork on Ifaluk Atoll in the Federated States of Micronesia and is currently pursuing various projects in Israel aimed at understanding the benefits and costs associated with religious behavior.     

Does observed fertility maximize fitness among New Mexican men?

Our objective is to test an optimality model of human fertility that specifies the behavioral requirements for fitness maximization in order (a) to determine whether current behavior does maximize fitness and, if not, (b) to use the specific nature of the behavioral deviations from fitness maximization towards the development of models of evolved proximate mechanisms that may have maximized fitness in the past but lead to deviations under present conditions. To test the model we use data from a representative sample of 7,107 men living in Albuquerque, New Mexico, between 1990 and 1993. The model we test proposes that low fertility in modern settings maximizes number of grandchildren as a result of a trade-off between parental fertility and next generation fertility. Results do not show the optimization, although the data do reveal a trade-off between parental fertility and offspring education and income. We propose that two characteristics of modern economies have led to a period of sustained fertility reduction and to a corresponding lack of association between income and fertility. The first is the direct link between costs of investment and wage rates due to the forces of supply and demand for labor in competitive economies. The second is the increasing emphasis on cumulative knowledge, skills, and technologies in the production of resources. Together they produce historically novel conditions. These two features of modern economies may interact with evolved psychological and physiological mechanisms governing fertility and parental investment to produce behavior that maximizes the economic productivity of lineages at the expense of fitness. If cognitive processes evolved to track diminishing returns to parental investment and if physiological processes evolved to regulate fertility in response to nutritional state and patterns of breast feeding, we might expect non-adaptive responses when returns from parental investment do not diminish until extremely high levels are reached. With high economic payoffs from parental investment, people have begun to exercise cognitive regulation of fertility through contraception and family planning practices. Those cognitive processes maynot have evolved to handle fitness trade-offs between fertility and parental investment. A preliminary presentation of this data was published in R. I. M. Dunbar, ed.,Human Reproduction Decisions: Biological and Social Perspectives. New York: St. Martin’s Press, 1995. Support for the research project, “Male Fertility and Parenting in New Mexico,” began with two seed grants from the University of New Mexico’s Biomedical Research Grants Program, 1988 and 1989, and one from the University of New Mexico Research Allocations Committee, 1988. Further seed money as well as interim funding came from the William T. Grant Foundation (#89130589 and #91130501). The major support for the project came from the National Science Foundation from 1990 to 1993 (#BNS-9011723 and #DBS-911552). Both National Science Foundation grants included Research Experience for Undergraduates supplements. Hillard S. Kaplan is an Associate Professor of Anthropology at the University of New Mexico. His earlier research and publications focused on food sharing, time allocation, parental investment, and reproductive strategies among Ache hunter-gatherers in Paraguay, Machiguenga and Piro forager-horticulturalists in Peru, and villagers of several ethnicities in Botswana. New research and theory concern fertility, parental investment, and mating strategies in developed and developing nations. This research formulates a new theory of reproductive decision-making and the demographic transition, integrating human capital and parental investment theory in a synthesis of economic and evolutionary approaches. Jane B. Lancaster is a Professor of Anthropology at the University of New Mexico. Her research and publications are on human reproductive biology and behavior, especially human parental investment; women’s reproductive biology of pregnancy, lactation, and child-spacing; and male fertility and investment in children. Current research with Hillard S. Kaplan is on male life history strategies among a large sample of men in New Mexico. She has coedited three books on human parental investment:School-Age Pregnancy and Parenthood (with B. Hamburg),Parenting across the Life Span (with J. Altmann, A. Rossi, and L. Sherrod), andOffspring Abuse and Neglect (with R. Gelles). She is scientific editor of a quarterly journal,Human Nature: An Interdisciplinary, Biosocial Perspective published by Aldine de Gruyter. She is also a council member of the newly formed Human Behavior and Evolution Society. John A. Bock is Andrew W. Mellon Post-Doctoral Fellow in Epidemiology and Population Health at the National Centre for Epidemiology and Population Health, The Australian National University. His research focuses on the allocation of parental investment and the determinants of children’s activities, integrating aspects of economic and evolutionary theory. He has ongoing field research with Bantu and Bushmen agro-pastoralists and forager-horticulturalists in the Okavango Delta, Botswana. He is also collaborating with Lancaster and Kaplan on the determinants of progeny distribution and homosexuality among New Mexican men. Sara E. Johnson is a Ph.D. candidate at the University of New Mexico. Her major research trajectory focuses on trade-offs in life history characters. Her research experience includes participation in a study of variation in growth and development among children in a multi-ethnic community in the Okavango Delta, Botswana, in addition to her dissertation work on individual variation in growth and mortality among juvenile baboons. She is collaborating with Lancaster and Kaplan on the association between survival and fertility among Albuquerque men.     

Low birth weight,intrauterine growth-retarded,and pre-term infants

Low birth weight, intrauterine growth retardation, and prematurity are overwhelming risk factors associated with infant mortality and morbidity. The lack of efficacious prenatal screening tests for these three outcomes illuminates the problems inherent in bivariate estimates of association. A biocultural strategy for research is presented, integrating societal and familial levels of analysis with the metabolic, immune, vascular, and neuroendocrine systems of the body. Policy decisions, it is argued, need to be based on this type of biocultural information in order to impact the difficult-to-change problems of low birth weight, intrauterine growth retardation, and prematurity. The analysis and writing of this study was funded, in part, by a grant from the National Institute of Child Health and Human Development (NICHD RO1 HD 20511). Troy D. Abell is associate professor of anthropology and adjunct associate professor of family medicine at the University of Oklahoma. His major interests are in the biocultural determinants of fetal growth and the epistemologic issues inherent in statistical reasoning in scientific inference and decision analysis.     

Exploiting redundancy to boost performance in a RAID-10 style cluster-based file system

While aggregating the throughput of existing disks on cluster nodes is a cost-effective approach to alleviate the I/O bottleneck in cluster computing, this approach suffers from potential performance degradations due to contentions for shared resources on the same node between storage data processing and user task computation. This paper proposes to judiciously utilize the storage redundancy in the form of mirroring existed in a RAID-10 style file system to alleviate this performance degradation. More specifically, a heuristic scheduling algorithm is developed, motivated from the observations of a simple cluster configuration, to spatially schedule write operations on the nodes with less load among each mirroring pair. The duplication of modified data to the mirroring nodes is performed asynchronously in the background. The read performance is improved by two techniques: doubling the degree of parallelism and hot-spot skipping. A synthetic benchmark is used to evaluate these algorithms in a real cluster environment and the proposed algorithms are shown to be very effective in performance enhancement. Yifeng Zhu received his B.Sc. degree in Electrical Engineering in 1998 from Huazhong University of Science and Technology, Wuhan, China; the M.S. and Ph.D. degree in Computer Science from University of Nebraska – Lincoln in 2002 and 2005 respectively. He is an assistant professor in the Electrical and Computer Engineering department at University of Maine. His main research interests are cluster computing, grid computing, computer architecture and systems, and parallel I/O storage systems. Dr. Zhu is a Member of ACM, IEEE, the IEEE Computer Society, and the Francis Crowe Society. Hong Jiang received the B.Sc. degree in Computer Engineering in 1982 from Huazhong University of Science and Technology, Wuhan, China; the M.A.Sc. degree in Computer Engineering in 1987 from the University of Toronto, Toronto, Canada; and the PhD degree in Computer Science in 1991 from the Texas A&M University, College Station, Texas, USA. Since August 1991 he has been at the University of Nebraska-Lincoln, Lincoln, Nebraska, USA, where he is Professor and Vice Chair in the Department of Computer Science and Engineering. His present research interests are computer architecture, parallel/distributed computing, cluster and Grid computing, computer storage systems and parallel I/O, performance evaluation, real-time systems, middleware, and distributed systems for distance education. He has over 100 publications in major journals and international Conferences in these areas and his research has been supported by NSF, DOD and the State of Nebraska. Dr. Jiang is a Member of ACM, the IEEE Computer Society, and the ACM SIGARCH. Xiao Qin received the BS and MS degrees in computer science from Huazhong University of Science and Technology in 1992 and 1999, respectively. He received the PhD degree in computer science from the University of Nebraska-Lincoln in 2004. Currently, he is an assistant professor in the department of computer science at the New Mexico Institute of Mining and Technology. He had served as a subject area editor of IEEE Distributed System Online (2000–2001). His research interests are in parallel and distributed systems, storage systems, real-time computing, performance evaluation, and fault-tolerance. He is a member of the IEEE. Dan Feng received the Ph.D degree from Huazhong University of Science and Technology, Wuhan, China, in 1997. She is currently a professor of School of Computer, Huazhong University of Science and Technology, Wuhan, China. She is the principal scientist of the the National Grand Fundamental Research 973 Program of China “Research on the organization and key technologies of the Storage System on the next generation Internet.” Her research interests include computer architecture, storage system, parallel I/O, massive storage and performance evaluation. David Swanson received a Ph.D. in physical (computational) chemistry at the University of Nebraska-Lincoln (UNL) in 1995, after which he worked as an NSF-NATO postdoctoral fellow at the Technical University of Wroclaw, Poland, in 1996, and subsequently as a National Research Council Research Associate at the Naval Research Laboratory in Washington, DC, from 1997–1998. In 1999 he returned to UNL where he directs the Research Computing Facility and currently serves as an Assistant Research Professor in the Department of Computer Science and Engineering. The Office of Naval Research, the National Science Foundation, and the State of Nebraska have supported his research in areas such as large-scale scientific simulation and distributed systems.