Last week I was helping a student who had questions on human physiology. Jenn was very comfortable with the details of physiology—the chemicals, cell types, processes—but she was having trouble seeing the forest for the trees. As we talked, it became apparent that she had been unable thus far to fit these easily memorized facts into a thing that is greater than its parts, parts that merely contribute to the broader function. The system was escaping her.
We had a breakthrough, though. “My professor mentioned something about vasopressin…and breast feeding…that the baby makes the mother produce vasopressin, and that affects the baby… Do I have that right?” More or less, she was completely on point. It appeared, though, that her teacher had presented this as a fact without any context. What is vasopressin and how does it modulate mother-child interactions? How is it involved in other interactions? How can knowing the evolved function of the vasopressin system help us to understand and remember all these things?
So, yes, mothers’ bodies release vasopressin during the act of nursing. The same happens in the baby’s body, in fact. Actually, males holding babies, specifically their own, experience bursts of vasopressin. Vasopressin and its teammate oxytocin are key players in just about any interaction that creates a strong biological bond, from childbirth, to nursing, to cuddling, to orgasm (how’s that for full circle?). When one has experienced a surge of vasopressin while interacting with someone, they perceive a greater bond with that person. (This is exactly why casual sex is so rarely casual and tends to get people in way more trouble than they bargained for.)
Taking all of this information together, Jenn was for the first time seeing the evolved system as a whole. Vasopressin and related chemicals have an important social role that has been shaped over millions of years. This in hand, it was much easier for her to understand the physiology that underlies the complexity of the mother-child interaction, and to pose her next question, the kind of question that drives applied evolutionary research: “What does that mean for mothers who can’t breastfeed?” Well, if a mother does not breastfeed, she experiences less of a bond with the child, because a chemical that propels that bond is released by this behavior that, until recently, wasn’t just natural but absolutely imperative for the baby’s survival. Some cool survey research done by Nate Pipitone and Gordon Gallup, Jr. at SUNY Albany showed that new mothers who are not breastfeeding experience more symptoms of postpartum depression (PPD). In some senses, the body is uncertain whether the baby—its baby—is even alive!
She was horrified (can you blame her?). However, her next question was, can we use this information to alleviate such issues for women who cannot breastfeed? We then discussed how a mother could make extra efforts to bond with the child, forcing vasopressin bursts in both of them. The mother should also be aware that not being able to breastfeed might put her at risk for developing PPD. Being that neither of us are experts in this realm, it’s certain that other more sophisticated solutions are out there.
This example illustrates the blog’s main perspective: how is an everyday event a manifestation of some more complex system, and how can understanding this system’s evolved function inform the way we view the commonplace behavior?