Determinants of infant carrying behavior in rural Papua New Guinea

The determinants of variability in infant carrying within and across societies is an understudied area within parental investment research. Carrying has positive and negative consequences as it may protect the infant from predators and pathogens but is energetically costly for caregivers. Moreover, carrying may delay independent locomotor development and exposure to antigens necessary for immunological competence. The purpose of this study is to compare infants' ages and developmental milestone attainment as predictors of carrying behavior and to identify other determinants of carrying behavior among traditional forager-horticulturalists in Papua New Guinea.

We analyze quantitative data collected among 107 infant-caregiver dyads during 354 hours of focal follows on infant carrying. Random effects logistic regression was used to model carrying behavior in these dyads.

Infants' chronological age and milestone achievement are equally reliable predictors of abatement of carrying and increased time on the ground. Further, the presence or absence of the mother and the location of the infant-caregiver pair are significantly associated with carrying behavior. Indices of mother's and infants' condition such as anthropometric measures were not predictive of carrying behaviors.

Mothers vary the amount of carrying based on assessment of infant and local environmental conditions. Age and milestone attainment are equally predictive of time on the ground and therefore increased exposure to antigens, pathogens and other dangers. High levels of infant carrying function as offspring protection by increasing exposure to ground level pathogens gradually, thus allowing for the naïve immune system to develop immunocompetence incrementally.