Darryl Holman's Research
For the past several years, my collaborators Michael Grimes, Kathleen O'Connor, Eleanor Brindle and I have been investigating the ecology of breastfeeding in Bangladeshi women. This project began as an investigation of the determinants of early breastfeeding behavior in Bangladeshi women (Holman and Grimes 2001). From there, we became interested in differences among mammalian species in distributions of the onset of breastfeeding, and how they change for different life history traits, like the degree of physical and neurological maturity at birth. Although this question cannot yet be answered (there are no data for any species except humans), we collected data from the primary literature on times to initiation of breastfeeding in humans. We hypothesized that if there were preprogrammed early maternal behaviors in humans (as suggested in the psychobiology literature), we would detect it as a statistical mixture of two distributions: one reflecting preprogrammed behaviors and another reflecting culturally-mediated behavior. From that investigation we concluded that there is evidence for a weak effect of preprogrammed early maternal behavior in humans (Holman and Grimes 2003).
In a related project, we used endocrine and questionnaire data collected in the Bangladesh study to investigate the effects of pregnancy hormones on the time to initiation of breastfeeding. We found that a urinary form of estrogen was weakly associated with time to initiation of breastfeeding--estrogen concentrations "explained" only 4% of the variation in initiation of breastfeeding (Holman et al. 2004). The relatively weak association, combined with our other results, suggest that human mothers are largely emancipated from preprogrammed behaviors directed to the newborn; and, we believe this makes sense in light of other life history characteristics of humans.
Most recently, we are investigating the determinants of postpartum amenorrhea and endocrine changes through the resumption of ovulation in Bangladeshi women (Holman et al. in press).