Evolutionary and empirical perspectives on 'demand' breastfeeding: The baby in the driver's seat or the back seat?

Background/Objectives: The concept of 'demand' breastfeeding is central in public health. A key feature of the concept is that the infant is the locus of control in the breastfeeding process; when the breast is demanded by the infant, it is given the opportunity to feed. This study questions this notion of the infant as the locus of control in demand breastfeeding for empirical and theoretical reasons. From an evolutionary perspective, infants are expected to seek maximal investment and, against this backdrop of maximal investment-seeking, parents decide how much investment to put into offspring. Methodology: Focal follows were conducted among 113 mother-infant dyads in Papua New Guinea. During these follows, response times and types of responses, including breastfeeding to offspring fussing and crying, were recorded. Results: Infants were breastfed an average of 3.6 times/hour for just over 2 min/feed. Fussing and crying were responded to quickly, with most response times under 1 min. When the mother responded, she breastfed the child approximately 52% of the time. The other 48% of the time, mothers responded to infants with other forms of pacification. Mothers were significantly less likely to respond to infants by breastfeeding if the child had been breastfed within the past 59-76 min. Conclusion/Implications: As predicted by evolutionary parental investment theory, infants make frequent demands on their parents for investment, but mothers are ultimately the locus of control in the investment process. The mother decides whether and how frequently to breastfeed her offspring against this backdrop of near-continuous investment demands.