But we’re going to take a different route. Let’s talk about the mother, and more specifically, the changes in her body as it readies itself to nourish a hungry newborn. With her breasts enlarged and hormones flowing, what happens if no newborn appears to suckle? How will her body—and brain—react?
First, a little background. The obvious physical changes in the pregnant human body (including swelling breasts) occur in response to escalating levels of the hormones prolactin, lactogen, estrogen, progesterone, adrenocorticotropic hormone (ACTH) and growth hormone. Placental birth serves as a sort of trigger event signaling to the mother’s body that it’s time to begin releasing milk. The baby’s physical suckling behavior—that is to say, lips tugging on teats—stimulates the first ejections, but eventually milk flow can start up by simply thinking about the baby, smelling it, or hearing it cry. “Involution,” the physiological process by which women’s breasts revert back to those dormant objects that give so much pleasure to adult human males, coincides with slowly weaning the growing infant away from breast milk and onto regular foods.
So what happens when, for whatever reason, mothers do not breastfeed their healthy infants? According to a new theory being proposed by University of Albany evolutionary psychologist Gordon Gallup and his colleagues, the decision to bottle-feed is tantamount, in the mother’s psyche, to mourning the loss of the child. At least, that’s how a woman’s body seems to respond to the absence of a suckling infant at its breasts in the wake of a successful childbirth. In a soon-to-be-published article in Medical Hypotheses, the authors argue that bottle-feeding simulates the unsettling ancestral condition of an infant’s death:
Opting not to breastfeed precludes and/or brings all of the processes involved in lactation to a halt. For most of human evolution the absence or early cessation of breastfeeding would have been occasioned by miscarriage, loss, or death of a child. We contend, therefore, that at the level of her basic biology a mother’s decision to bottle feed unknowingly simulates child loss.
There is at least correlational evidence to support this evolutionary claim, too. For example, in a paper presented earlier this year at the annual meeting of the Northeastern Evolutionary Psychology Society, Gallup and his colleagues reported their findings that, among a sample of 50 mothers recruited from local pediatric clinics and who had given birth in the previous 4-6 months, those who bottle fed scored significantly higher on the Edinburgh Postnatal Depression Scale than breastfeeders did. This effect panned out even after controlling for the mother’s age, education, income and relationship status with her current partner.
Another telling finding to emerge was that the bottle-feeding mothers reported wanting to hold their babies significantly more than the breastfeeders did, which the authors believe:
...parallels findings among nonhuman primates where in response to the death of an infant, mothers of some species have been known to tenaciously hold, cling to, and carry their infants for prolonged periods after they die.
It’s an interesting (if morbid) idea that bottle-feeders are implicitly conceptualizing their babies as corpses, but there are plenty of alternative interpretations. For example, these women may simply want to make up for lost bonding time that would otherwise occur during breastfeeding. In any event, if Gallup’s theory about the “unnaturalness” of bottle-feeding simulating child loss holds up in future studies, it would have obvious, and important, clinical applications. This would also be an excellent example of how evolutionary psychological explanations of human behavior can improve the quality of human life. Of course the reasons for bottle-feeding are complex and many, and not all women have the luxury of a choice in this regard. But for those who do, the present logic may give new meaning to the expression “breast is best”—if not for infants, then at least for their mothers.
In this column presented by Scientific American Mind magazine, research psychologist Jesse Bering of Queen's University Belfast ponders some of the more obscure aspects of everyday human behavior. Ever wonder why yawning is contagious, why we point with our index fingers instead of our thumbs or whether being breastfed as an infant influences your sexual preferences as an adult? Get a closer look at the latest data as “Bering in Mind” tackles these and other quirky questions about human nature. Sign up for the RSS feed or friend Dr. Bering on Facebook and never miss an installment again.