Developmental Integration and the Ecology of Life Histories in Phylogenetic Perspective

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Of central importance in the science of human biology, as well as that of other species, is full understanding of the complex processes that underlie development, including both the integration of these processes and their evolutionary bases. While experiences during the critical period of childhood are known to have important and lasting effects on future growth, reproduction, health and behavior, the fundamental biology of this system remains poorly understood. This is especially salient for the human species, which has the longest juvenile phase of any animal. By incorporating a phylogenetic approach that examines physical, hormonal, and behavioral development in our closest living relative, the chimpanzee, we can advance understanding of this critical period of development, and determine how different developmental trajectories interact with each other and with the environment to produce adult traits. Comparison of chimpanzees and humans will provide a model for the ways in which biological influences combine with the ecological and social environments to generate adult characteristics, and contribute to understanding when and how unique features of human life history arose in our lineage (such as early weaning, prolonged reliance on parental support, and the adolescent growth spurt). By using a series of novel, non-invasive techniques, this study will achieve the first detailed documentation of the development of wild chimpanzees, and provide the basis for a comparative, phylogenetic approach to the science of primate, including human, development. Trajectories to be analyzed include physical growth (linear growth, body weight, muscle mass, and tooth eruption), nutrition (behavioral measures of nursing intensity, hormonal measures of maternal and infant energy balance, and isotopic measures of maternal and infant diet), hormones (testosterone, cortisol, estradiol, progesterone, DHEAS and C-peptide), and multiple dimensions of behavior. Hypotheses to be tested will assess how maternal condition, early life nutrition, stress, and related factors influence the timing and rates of development, and the role of hormones in these interactions. The results will be important for understanding sex differences in physiology and behavior. Ultimately, understanding these relationships will allow us to better infer life history shifts associated with changing habitats, ecologies, and morphologies in the hominin evolutionary lineage. Numerous domestic and international broader impacts are tied to the project. Data generated by the research will be utilized to promote K-12 education in the U.S., working with teachers in both New York and New Mexico to enhance curricula and foster science literacy and appreciation. Education and training of both U.S. and Ugandan undergraduate and graduate students will be fostered through incorporation of these students into the project, and through utilization of the generated data for future research. International collaboration and capacity building, as well as conservation of endangered species, will be promoted by providing economic incentives for protection in Kibale National Park (job creation, training, research fees), supporting anti-poaching and ecotourism programs, and educating Ugandan primary school children about wildlife and habitat conservation.