John Bock

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.

Learning, life history, and productivity

AbstractThis article introduces a new model of the relationship between growth and learning and tests a set of hypotheses related to the development of adult competency using time allocation, anthropometric, and experimental task performance data collected between 1992 and 1997 in a multiethnic community in the Okavango Delta, Botswana. Building on seminal work in life history theory by Hawkes, Blurton Jones and associates, and Kaplan and associates, the punctuated development model presented here incorporates the effects of both growth and learning constraints on age-specific task performance. In addition, the payoff to investment in two forms of embodied capital, growth-based and learning-based, are examined in relation to features of the socioecology, including subsistence economy and family composition.The three main findings are:1.The development of adult competency in specific tasks entails a steplike relationship between growth- and experience-based forms of embodied capital in the ontogeny of ability acquisition.2.There is a trade-off between the acquisition of experience-based embodied capital in the form of skills and knowledge and immediate productivity among children. Time allocation to these alternatives is primarily determined by the short- and long-term costs and benefits to parents of investment in children’s embodied capital.3.The availability of laborers and the overall labor requirements of the household are major determinants of investment in alternate forms of embodied capital and resulting variation in children’s time allocation. The value of children’s labor to their parents is dependent upon the opportunity costs to engaging in other activities not only for the child in question but also for potential substitute laborers. These results have important implications for our understanding of the role of growth and learning in the evolution of the human juvenile period, as well as for our understanding of cross-cultural variation in child growth and development and patterns of work and play.

Safety-Net Institutions Buffer the Impact of Medicaid Managed Care: A Multi-Method Assessment in a Rural State

OBJECTIVES This project used a long-term, multi-method approach to study the impact of Medicaid managed care. METHODS Survey techniques measured impacts on individuals, and ethnographic methods assessed effects on safety-net providers in New Mexico. RESULTS After the first year of Medicaid managed care, uninsured adults reported less access and use (odds ratio [OR] = 0.46; 95% confidence interval [CI] = 0.34, 0.64) and worse barriers to care (OR = 6.60; 95% CI = 3.95, 11.54) than adults in other insurance categories. Medicaid children experienced greater access and use (OR = 2.11; 95% CI = 1.21, 3.72) and greater communication and satisfaction (OR = 3.64; 95% CI = 1.13, 12.54) than children in other insurance categories; uninsured children encountered greater barriers to care (OR = 6.29; 95% CI = 1.58, 42.21). There were no consistent changes in the major outcome variables over the period of transition to Medicaid managed care. Safety-net institutions experienced marked increases in workload and financial stress, especially in rural areas. Availability of mental health services declined sharply. Providers worked to buffer the impact of Medicaid managed care for patients. CONCLUSIONS In its first year, Medicaid managed care exerted major effects on safety-net providers but relatively few measurable effects on individuals. This reform did not address the problems of the uninsured.

Fertility and Fitness Among Albuquerque Men: A Competitive Labour Market Theory

The reduction in fertility accompanying modernisation poses a scientific puzzle that has yet to be solved. Despite the fact the problem has received a great deal of attention from economists, sociologists, demographers, anthropologists and biologists, no discipline in the social or biological sciences has offered a fully developed and coherent theory of fertility reduction that explains the timing and pattern of fertility reduction in the developed or developing world. The inability to offer an adequate theory raises fundamental questions about the theoretical foundations of those disciplines. For example, although economics has made great strides in explaining consumer behaviour, time allocation and labour force participation through the recognition that the household is a fundamental organisational unit of human action, there is no adequate explanation of why households are mostly composed of men and women who marry and have children. There is no economic theory of why reproductive partnerships form such a fundamental organisational principle in human societies nor of why people have and want children in the first place. The very modest progress of economists in explaining long-, medium- and short-term trends in fertility highlights this weakness.

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.

Grandmothers’ Productivity and the HIV/AIDS Pandemic in sub-Saharan Africa

The human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) pandemic has left large numbers of orphans in sub-Saharan Africa. Botswana has an HIV prevalence rate of approximately 40% in adults. Morbidity and mortality are high, and in a population of a 1.3 million there are nearly 50,000 children who have lost one or both parents to HIV/AIDS. The extended family, particularly grandparents, absorbs much of the childrearing responsibilities. This creates large amounts of additional work for grandmothers especially. The embodied capital model and the grandmother hypothesis are both derived from life history theory within evolutionary ecology, and both predict that one important factor in the evolution of the human extended family structure is that postreproductive individuals such as grandmothers provide substantial support to their grandchildrens survival. Data collected in the pre-pandemic context in a traditional multi-ethnic community in the Okavango Delta of Botswana are analyzed to calculate the amount of work effort provided to a household by women of different ages. Results show that the contributions of older and younger women to the household in term of both productivity and childrearing are qualitatively and quantitatively different. These results indicate that it is unrealistic to expect older women to be able to compensate for the loss of younger womens contributions to the household, and that interventions be specifically designed to support older women based on the type of activities in which they engage that affect child survival, growth, and development.

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.

Childhood and the evolution of the human life course

Childhood has been the focus of research and debate among anthropologists, developmental psychologists, demographers, economists, and other social scientists for fifty years (Konner 1991; Panter-Brick 1998). As a result, there are diverse research traditions and trajectories that have arisen with varying levels of intercommunication. Recent theoretical developments in human evolutionary ecology have shifted away from description of the normative characteristics of childhood across societies towards exploration of the evolutionary history of primate ontogeny and the fitness consequences of a life history that has childhood as a component (Blurton Jones 1993; Blurton Jones et al. 1989, 1997, 1999; Bogin and Smith 1996; Charnov 1993; Charnov and Berrigan 1993; Hawkes et al. 1997, 1998; Janson and van Schaik 1993; Kaplan et al. 2000). Leigh (2001) has identified four models based in life history theory that have recently been used to explain the slow growth and extended juvenility of primates in general and humans in particular. The brain growth model asserts that slow growth is a consequence of the amount of learning-based knowledge necessarily acquired by adulthood. Essentially, slow growth provides the time needed to fully program the brain with the information needed for adult competence (Bogin 1999). The pleiotropic model developed by Charnov and colleagues (Charnov and Berrigan 1993) argues that among primates the benefits of continued growth to the

Fertility Theory: Caldwell's Theory of Intergenerational Wealth Flows

John Caldwells wealth flows theory proposes a direct link between family structure and fertility. In ‘primitive’ and ‘traditional’ societies with net upward wealth flows, the economically rational decision is to have as many surviving children as possible (within the constraints imposed by biology), because each additional child adds positively to a parents wealth, security in old age, and social and political well- being. In ‘modern’ industrial societies with net downward wealth flows, the economically rational decision is to have no children or the minimum number allowed by a psychological disposition that derives pleasure from children and parenting. The transition from ‘traditional’ to ‘modern’ fertility and family structure occurs when a critical mass of individuals adopt the new values, and respond with low fertility. The attainment of mass education in a country should therefore precipitate and predict the fertility transition. The most serious challenge to this theory has come from evolutionary biologists. The argument that prior to modernization, upward wealth flows characterized human family structures is inherently antithetical to theory in evolutionary biology. There is no direct quantitative evidence of net-upward wealth flows in any traditional high-fertility society. The wealth flows theory of fertility transition is a major contribution to demography. The theory helped to lay the groundwork for theories of the family to become a major perspective within the field of demography, and broadened the scope of demography by directing attention to culture.

Evolutionary approaches to population: implications for research and policy.

Evolutionary theory is becoming an increasingly important perspective in many social science disciplines. Ironically, the impact of evolutionary theory has been minimal in the study of human population although among the social sciences it is in demography and related fields that evolutionary approaches would be most appropriate. In this paper I review varying perspectives within evolutionary theory, proceeding to a brief review of theoretical paradigms within the field of demography. I then examine how evolutionary perspectives can interface with these theories, showing how evolutionary approaches elaborate, strengthen, and unify these outlooks. Lastly, I explore the implications of evolutionary approaches for research and policy.