This study uses evolutionary life history theory to gain insight into the developmental origins of some global health problems, especially high blood pressure and low birth weight. The research takes place in the Dogon people of Mali, West Africa, who face many of the environmental conditions that prevailed when the metabolic and developmental mechanisms that underlie human disease were shaped by natural selection. The research addresses the questions: (1) Are children who were stunted and underweight as infants at elevated risk for high blood pressure if they catch up to their peers as they mature? (2) Do children who were better nourished in childhood mature more quickly and reproduce sooner than their peers? (3) What is the influence of family size (number of siblings) on growth rates, maturation (puberty and menarche), age at first birth, and birth weight in the next generation? This research stands out as a rare example of a study that follows children in an African community longitudinally from infancy to adulthood. The study has reached a critical stage wherein the cohort (N = 1700) is experiencing major life transitions (puberty, menarche, and first birth) whose timing is documented. To the extensive data already in hand, new data are added including measurements of blood pressure, nutritional status, body size and composition, birth weights, and salivary testosterone.
High blood pressure and low birth weight are problems of global significance that disproportionately affect individuals of African descent. The research is carried out by an international francophone team thereby promoting the cross-fertilization of ideas and knowledge. The graduate research assistants gain valuable field work experience and the involvement of Malian governmental agencies and local personnel helps to develop human resources in the host country. To foster collaboration and to educate the broad public, a bilingual web site is also being created.
Intellectual Merit. The increase in high blood pressure starting in childhood has raised serious concerns about the developmental origins of hypertension. Another concern is the rise in health disparities that has caused some groups, such as African Americans, to be affected more than others. According to the developmental origins of disease paradigm, environmental factors operating during development—both in utero and in childhood—can permanently program the adult phenotype. This field was initiated by Barker who, together with his colleagues, found that low birth weight increased the risk for diabetes, obesity, coronary heart disease, and systolic hypertension. More recent research has extended Barker’s hypothesis to the postnatal environment. The present study monitored the health and development of children from infancy and early childhood to mid/late adolescence and adulthood. It demonstrates that children who are very small (stunted and underweight) as infants (under age 2 years), are at elevated risk for high blood pressure if they catch up to their peers as they mature. Although it was previously known that adiposity leads to hypertension, the finding that catch-up growth leads to high blood pressure even under conditions of under-nutrition is novel. The implication is that when screening for high blood pressure, the focus should be as much on developmental changes in body size as on current body mass index (BMI). Early puberty in girls can have adverse health consequences such as increased risk for teenage pregnancy and breast cancer. Therefore it is important to understand the causes of the variation in age at puberty as a first step toward appropriate interventions. This research showed that, in both girls and boys, age at puberty is strongly influenced by body size (height, waist circumference, and body fat). Furthermore, this study demonstrated that early childhood stunting (pathologically short stature) and under-weight delayed puberty in boys and girls. The decrease in age at puberty across generations in the United States is most likely due to improvement in nutrition. Similarly, late ages at puberty in low income countries in Africa (for example, Mali) are due to under-nutrition. Rapid catch-up growth in early childhood decreases age at puberty more so than does rapid growth in later childhood. Taken together, these results show that excessive weight gain and catch-up growth in early childhood is a risk factor for early puberty and its adverse consequences. It was previously believed that psychosocial adversity (for example, having an absent father) could decrease age at menarche; however, the current study casts doubt on this viewpoint. Instead the critical variables are body size and catch-up growth which are often confounded with family dynamics. Broader impacts These results not only have useful public health implications; they also shed light on the respective contributions of constraint and adaptation in human biology. Several young scientists were mentored and trained in research methods, statistical analysis, and computer programming. Moreover, they learned how to draft articles for publication. One undergraduate student gained field work experience in West Africa and two Malian students were able to pursue higher education. The members of the Malian field team became highly professionally trained so that they can collect data on their own with minimal supervision. The Malian field workers learned how to use computers and to access the internet so as to participate in the international community of scientists. Help in the form of surgical gloves and other supplies was given to the local hospital and an American professor visited the study site to identify a suitable site for a pedestrian footbridge that will span a gorge. Using funding from private philanthropy, 400 metric tonnes of grain (millet) were purchased in Mali and distributed to 19 villages in dire need due to food shortages caused by climate change. The distribution scheme relied on a head count of families that was obtained in the course of this research. The international research community will benefit through data sharing and the results have the potential to interest a wide array of academic disciplines from anthropology to psychology, epidemiology, and medicine.
