The Evolutionary Ecology of Human Infancy

Infancy is a time of profound energetic trade-offs, and in many South American native groups, infant growth is stunted and mortality by infectious disease is high. The goal of this dissertation was to explore the nature of human infancy from a life history theoretical perspective. Specifically, I investigated infant growth, feeding patterns, and thymic development in two South American native populations, the Tsimane of Bolivia and the Pumé of Venezuela. This broad goal is addressed through four specific goals: 1) to model the weaning transition using behavioral data collected in Tsimane communities where infants experience varying mortality rates, 2) to consider the relationship between infant feeding and growth patterns; 3) to compare infant body and thymus size in two South American native societies, and 4) to theorize how the thymus may be shaped by natural selection. Results suggest that infant feeding is a complex and varied process that is influenced more by infant growth than by perceptible mortality risk, and that trade-offs between investment in growth and cellular immune function vary between native communities inhabiting diverse ecologic settings. These findings illuminate the role of early postnatal conditions in shaping maternal behaviors and infant health outcomes; and underscore the pressing need to identify the mechanisms leading to the establishment of immunophenotypes in South American native populations.National Science FoundationAnthropologyDoctoralUniversity of New Mexico. Dept. of AnthropologyKaplan, HillardGurven, MichaelKramer, KarenWinking, JeffLancaster, Jan