Tradeoffs Between Indirect Parental Investment and Direct Childcare:
Long-Term Effects of Household Production and Breastfeeding Duration on Children’s Cortisol Levels, Fluctuating Asymmetry and Growth.
A Paper presented at the Human Behavior & Evolution Society annual meeting
June 2003, Lincoln, Nebraska
Robert J. Quinlan, Ball State University
David V. Leone, U. of Missouri
Marsha B. Quinlan, Ball State U.
Steven W. Gangestad, U. of New Mexico
Randy Thornhill, U. of New Mexico
Barry G. England, U. of Michigan
Mark V. Flinn, U. of Missouri
Parental investment (PI) among humans is a complex behavior involving types of resources that may differentially affect child development. Recent evolutionary models of PI suggest a tradeoff between indirect investment (wealth, education etc.) and direct childcare. Child development may be relatively insensitive to indirect PI, because in the course of human evolution there were few avenues for indirect investment. If human parenting behavior evolved to foster offspring social competency, then children may be particularly attuned to qualities of direct parental care. Here we examine direct care (breastfeeding duration), indicators of indirect PI (household wealth) and their association with children’s long-term well-being in a rural Caribbean village. The aim is to isolate independent effects of breastfeeding and household production on children’s growth, developmental stability, and psychosocial stress. Longitudinal data are for 106 children between 6 and 18 years of age in the Commonwealth of Dominica. Multivariate analyses indicate that duration of breastfeeding is negatively associated with children’s fluctuating asymmetry and psychosocial stress (salivary cortisol level). Wealth, mother’s pair-bond status and coresidence with adult female kin were not associated with developmental stability or stress levels independent of the duration of breastfeeding. Long-term growth was not significantly associated with breastfeeding, wealth or household composition; however, wealth and breastfeeding duration were positively associated with children’s bodyfat. These results and other studies in this community suggest that parental attention focused on economic production in lieu of direct childcare may entail fitness costs.
Keywords: parental investment, child development, psychosocial stress, breastfeeding