Social Context, Life History, and the Biology of Human Development

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

The processes of growth and development are critical to understanding human biological diversity, and as ongoing research is documenting, this must be investigated in a biocultural framework that incorporates variation in social context. This study will contribute to the understanding of human biology by elucidating the developmental mechanisms that underlie variation in the life-history parameters of three components of what is termed "age at maturity:" age at puberty, menarche, and first birth. These mechanisms will be examined in the context of the social environment for the children in the study, filling critical gaps in our understanding of how different social contexts might accelerate or delay important developmental milestones. The understanding of the biological mechanisms involved in development has direct implications for public health; early development is a risk factor for teenage pregnancy, breast cancer, and obesity. In the United States, it is increasingly common for girls to reach menarche at eight years of age, and these early maturers may be at risk for a variety of adverse health outcomes that are costly--not only to individuals, but also to society at large. Prior research has explored the role of adverse social environments, such as families with absent fathers, on age at maturity, or the effects of early childhood obesity and body mass index on development. This study innovates by simultaneously testing for an effect of social context on development while controlling for body size and growth, and testing for an effect of body size and growth while controlling for social context. The research design has the advantage of being prospective and longitudinal, with measurement of the growth and development of over 1200 boys and girls from infancy to adulthood. These subjects are part of an ongoing, prospective cohort study of the Dogon people of Mali. By focusing on this study population, not only does a wealth of critical data become available, but the potential for understanding basic biological mechanisms at the level of the human species is greatly enhanced. Investigating developmental processes in a population not impacted by confounding factors, such as ready access to high-quality health care, facilitates detection of evolved biological mechanisms and key aspects of the balancing of biological investments (i.e., what are termed life-history trade-offs). A better understanding of these life history trade-offs is vital to understanding age at maturity; thus, the study will increase scientific knowledge of human biology, not just for the Dogon specifically, but for Homo sapiens in general. In so doing, the project will offer critical insights into adolescence, the important life stage in which an individual transitions from childhood to adulthood. A U.S. graduate student and a Malian university student will be mentored by the primary investigator, collaborating on data analysis and manuscript preparation so as to promote the education of the next generation of scientists. U.S. undergraduate students also will contribute to the positive societal impact of the study through the collaborative design of local infrastructure development at the research site, while advancing their knowledge and training in civil engineering. To foster collaboration with other researchers and to promote public education in the U.S. and Mali, a bilingual website will be created. The results should advance the science of human development in a wide array of academic disciplines, including anthropology, psychology, biology, demography, and public health.