Psychiatrists Christopher Ryan and Cacilda Jethá have a new book out entitled Sex at Dawn: The Prehistoric Origins of Modern Sexuality. Ryan blogs about its thesis over at Psychology Today:
Biologists distinguish sexual monogamy from social monogamy. As DNA testing has grown cheaper in recent years, we’ve learned that most species formerly classified as “monogamous” (primarily birds) are socially monogamous, but not sexually so. In other words, they form pairs that cooperatively care for that season’s brood of young, but the male may well not be the biological father.
Most of this is not new. My first encounter with these arguments was in 2001’s The Myth of Monogamy, which is a popularization of much of the science involved. Basically, female animals frequently have more control over mate choice than was previously believed, and will frequently exercise that control before going on to choose a mate to raise offspring with.
But Ryan and Jethá take it a step farther:
I’m always worried when we start trying to tie evolution to modern morality. Perhaps, as the authors point out, we’re as sexually rambunctious as the bonobos. But we’ve surrounded ourselves with a very complex culture, and we’re just as much social and cultural beings as we are sexual ones.
Applied to humans, we argue that a more flexible approach to sexual fidelity can increase marital stability and thus lead to greater social and family stability.
I’ll admit, I’m defensive. I’ve just celebrated ten years of monogamy. Of course, the authors don’t do much to help. Consider this analogy for accepting the costs of going against our polygamous nature:
For example, you might happily choose to work the night shift, but the resulting disruption of your circadian clock will increase your risk of cancer, cardio-vascular disease, gastric disorders, and so on no matter how committed you are to your decision. Similarly, we can choose to wear tight corsets, or ill-fitting shoes, or to live on chili-dogs and ice cream, but because all these behaviors run counter to our evolved nature they will cost us over time.
I believe that the authors are correct that our evolution has given us instincts that leave us more suited for serial monogamy. But I think it would be wrong to conclude that we’re all that beholden to those instincts.
Humans are varied and flexible creatures, and each of us will deal with our instincts in our own way. Some will ignore them, some will go with them, and some will subvert them. While I agree its best to be aware of them, I suspect that we shouldn’t be drawing too many conclusions from our evolutionary past about our current behavior.