Evolutionary Insights into Human Fertility: A Biological Anthropological Perspective
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Few fields of inquiry draw from as diverse an array of disciplines as the study of human fertility. Contributions come from sociology, public health, medicine, demography, political science, economics, and anthropology, each discipline bringing to bear its own particular perspectives and theoretical agenda. The perspective of the biological anthropologist among these others is unique in two respects: the central position of evolutionary theory and evolutionary history in anthropological thinking, and the commitment to understanding human fertility, its determinants and consequences, as part of an integrated species biology.
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These two elements give rise to the two primary motivations of biological anthropologists for studying human fertility. The first motivation is to understand as fully as possible our evolutionary past, both the history of change that we and our phyletic relatives have undergone and the forces and constraints that have shaped its course. Understanding the reproductive biology of our species is fundamental to that effort, since in its essentials, evolution or natural selection can be broken down into variability in the processes of birth and death. If we can fully comprehend the way in which our fertility is regulated by physiological, ecological and social mechanisms, we will be in a better position to elucidate critical junctures of human evolution, such as the transition to subsistence horticulture, the transition to cooperative hunting and gathering societies, or even the original diversion from other hominoid lines.
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The second motivation is in some ways the converse of the first: to understand our species in the present as the product of our formative evolutionary past. That is, as distinct from the often eidetic perspective of medicine or the mechanical perspective of physiology, the biological anthropologist views the apparatus and process of human fertility as shaped by the action of natural selection and searches for the logic of ultimate functionality that can provide a theoretical framework unifying this and other aspects of human biology. As a result of these two motivations and the basic tenets of the discipline underlying them, the most important contribution of biological anthropology to the study of human fertility is theoretical cohesion, providing a connection to the overarching framework of evolutionary biology.
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A quiet revolution has occurred in the last 30 years in our understanding of human fertility which has brought the perspective of biological anthropology to the forefront of the field. The previous view, directly descended from Thomas Malthus, postulated a constant and prolific biology manipulated and constrained by culture, with all the important determinants of variance in human fertility deriving from cultural conventions, societal pressures or individual choice. We now appreciate more fully the degree to which human reproductive physiology is naturally variable and human fertility biologically determined, and the extent to which that determination can be accounted for by evolutionary theory. Rather than the empirical quagmire that characterized the state of the field in the 1950s, we are now well on the way to a theory of natural human fertility. Such an organized theoretical perspective is necessary to support practical applications of knowledge in this area, as, for instance, in anticipating important policy issues in developing societies, or informing clinical perspectives on fertility and infertility. However, scientific knowledge can only support and inform practical decisions concerning policy and intervention. It can never dictate a particular course of action or validate a given policy…