Sex at Dawn

Exploring the evolutionary origins of modern sexuality

First Winner of Free Copy of Sex at Dawn

Stephen B. wins a free copy of Sex at Dawn.

I recently invited readers to send me questions concerning the material we cover in our book (which I also address here on the blog and on our web site devoted to the book). We've received many great questions so far, and they keep coming in every day. We'll be running five of these questions and sending a free book to the winners. In cases where we get nearly the same question (and it's a winner), the first received wins.

First winner is Stephen B., who writes:

First of all, I completely agree with many of the premises of your book, at least the ones I have read about so far, but other people I have discussed the topic of monogamy with always bring up the idea about monogamy being more advantageous in modern society. So my question is, could there be a natural selective pressure in post-agricultural societies to favor monogamy, such as if offspring raised by monogamous parents would be more likely to "succeed" (have higher fitness, or reproductive success) than those raised by single parents? This higher fitness may perhaps be brought about due to the advantage of potentially having access to more resources or increased parental care?

As recently as a few years ago, the standard response to this would have been to assert that the time since people have been living in agricultural societies is just too short for significant evolutionary changes to have occured. If you're familiar with the evolutionary psychology (EP) literature, you know this is a central assumption underlying the field. You've read it a million times: "Humans have stone-aged minds in modern skulls."

But recent research has shown this to be not quite true. For example, genetic testing shows that some societies in northern Europe and East Africa developed the generalized ability to digest lactose in just a few thousand years. Furthermore, as we discuss in Sex at Dawn, there is good reason to believe that human male genitalia may have undergone significant changes in the same very brief period. (For more on this, see The 10,000 Year Explosion.) So theoretically, at least, Stephen, the scenario you describe seems possible.

But here's where I see a problem. What's the genetic correlate to "monogamy?" In other words, assuming there are no genes specifically devoted to making one more or less prone to long-term sexual monogamy, how would the very significant selective pressures you describe affect the genome?

I have to say up front that neither I nor my co-author are experts in genetics, so I may well be missing something, but while I see how monogamy could have been promoted by very strong familial, cultural, and economic pressures (see centuries of arranged marriage among the wealthy and powerful of Europe, for example), I don't see how that would be replicated at a genetic level. (Royalty and the filthy rich certainly don't seem to be more into fidelity than the rest of us!) There may be some association with genes that affect novelty-seeking behavior perhaps, or overall libido, but I can't imagine it getting more specific than that.

Readers with deeper knowledge of the genetic science involved, please let us know what you think.

Your book is on the way, Stephen. Thanks for your question.

Christopher Ryan, Ph.D., is co-author of Sex at Dawn: The Prehistoric Origins of Modern Sexuality (HarperCollins 2010).

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