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. (shrink)

Reproduction places severe demands on the energy metabolism in human females. When physical work entails higher energy expenditure, not enough energy will be left for the support of the reproductive processes and temporal suppression of the reproductive function is expected. While energy needed for reproduction may be obtained by increases in energy intake, utilization of fat reserves, or reallocation of energy from basal metabolism, several environmental or physiological constraints render such solutions unlikely. For human ancestors increases in energy intake were (...) limited by availability of food, by labor of food preparation and by metabolic ceilings to energy assimilation. Energy stored as fat may support only a fraction of the requirements for reproduction (especially lactation). Effects of intense physical activity on basal metabolism may also interfere with fat accumulation during pregnancy. Finally, the female physiology may experience demands on increasing the basal metabolism as a consequence of physical activity and, at the same time, on decreasing the basal metabolism, when energy to support the ongoing pregnancy or lactation is inadequate. The resulting metabolic dilemmas could constitute a plausible cause for the occurrence of reproductive suppression in response to physical activity. It is, therefore, likely that allocating enough energy to the reproductive processes during periods when energy expenditure rises may be difficult due to physiological and bioenergetic constraints. Females attempting pregnancy in such conditions may compromise their lifetime reproductive output. A reproductive suppression occurring in low energy availability situations may thus represent an adaptive rather then a pathological response. (shrink)

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. (shrink)

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. (shrink)

Given an equal sex ratio at conception, the excess of human males at birth can only be explained by greater loss of females during pregnancy. It is proposed that the bias against females during human development is the result of a greater degree of genetic and metabolic “differentness” between female embryos and maternal tissues than for similarly aged males, and that successful implantation and placentation represents a threshold dichotomy, where the acceptance threshold shifts depending on maternal condition, especially stress. Right (...) and left ovaries are not equal, and neither are the eggs and follicular fluid that they produce, and it is further hypothesized that during times of stress, the implantation threshold is shifted sufficiently to favor survival of females, most likely those originating from the right ovary, and that this, rather than simply a greater loss of males, explains at least some of the variability in the human sex ratio at birth. (shrink)