Tradeoffs between immune function and childhood growth among Amazonian forager-horticulturalists

The energetic impact of immune function on human growth remains unclear. Using data from Amazonian forager-horticulturalists, we show that diverse, low-level immune activity predicts reduced childhood growth over periods of competing energy use ranging from 1 wk to 20 mo. We also demonstrate that modest body fat stores (i.e., energy reserves) protect children from the particularly detrimental impact of acute inflammation on growth. These findings provide evidence for considerable energetic tradeoffs between immune function and growth among humans, highlighting the energy constraint of childhood and the characteristic ability of our species to respond sensitively to dynamic environmental conditions. We outline the possible role of immune-related tradeoffs in driving patterns of human growth faltering, developmental metabolic plasticity, and life history evolution.