You may have heard the bit of doggerel that goes:
Man is polygamous
Well, there’s an element of truth to the contrast it makes between the genders, but only an element. The drive for monogamy is weaker in men than it is in women, but despite this human beings are still a monogamous species. I’ll look at male monogamy in the next post, but here I’d like to note a bit of recent scientific evidence that can be added to the case for female monogamy.
You may not have been aware of it, but recent evidence has shown that the exchange of biological material between husband and wife is more complex than is commonly thought. It isn’t just that the husband’s nucleic DNA is used to contribute to the genetic code of a baby. More is going on than that. It turns out that as a result of the marital act, genetic material from the husband is permanently absorbed by the wife’s body and becomes part of her–a dimension of the “one flesh” union between husband and wife that previous generations have been unaware of.
This material plays an important role in subsequent maternal health. Though all of the ways it contributes to the wife’s health are not known, it is known to serve as a preventative against several serious problems during pregnancy, including high blood pressure, and pre-eclampsia, and miscarriage. When a woman has not received sufficient amounts of this genetic material from the father of her child, the chance of the previous problems are increased, but if she has absorbed this material through regular marital congress with her husband, the chance of these problems is reduced.
One of the ways these problems are reduced is that having absorbed sufficient quantities of the husband’s genetic material better enables the mother to perform the immune modulation needed to allow her child–with its foreign genetic code–to exist in her body without her immune system trying to eliminate it.
Here is a fairly accessible article dealing with the topic. I want to take issue with something it says, though:
Gustaaf Dekker, one of the Adelaide researchers, said: “If there’s repeated exposure to that signal [from transforming growth factor beta] then eventually when the woman conceives, her [immune] cells will say, ‘we know that guy, he’s been around a long time, we’ll allow the pregnancy to continue.'”
I think this is the wrong way to look at the matter and would propose this way instead: It is hard enough for the mother’s body to undergo immune modulation and accept the child’s presence within her. Having the genetic material of her regular sexual partner–her husband–on hand makes it easier to recognize the child as a non-threat and thus increases the chances of carrying it to term. It is not that the mother’s body tries to kill the child of another man because his father wasn’t her regular partner. It is that having a regular partner makes it easier for her body to do its job of protecting a child, and her body goes to extra efforts to protect the child if it is recognized as a non-threat because it shares genetic elements of her husband.
In any event–since the above effect only takes place when the mother has a single partner whose genetic material her body has absorbed over time–it serves to reinforce female monogamy. We already knew that female monogamy is rooted in human nature on the psychological level. We now know it is also rooted in human nature on the level of immunology and direct reproductive success.
Next up, male monogamy . . .