There are two articles of note in The New York Times up about about human sexuality, one by Nick Wade, and another by Natalie Angier. I found the Angier article too verbose, and Wade's was a bit simplistic, but reading them both emphasizes some insights from sex research. First, men and women are different, and in particular males seem to be more exclusively hetero or homosexual. No surprise to anyone. Additionally, there is within population variation in sexual response and attitudes. Some of this, I suspect, is due to the prevalence of mixed-strategies within the human population. In other words, negative frequency dependent selection maintains some behavioral tendencies within the population at low proportions. But I was especially interested in this:

Romantic love, which in its intense early stage "can last 12-18 months," is a universal human phenomenon, Dr. Fisher wrote last year in The Proceedings of the Royal Society, and is likely to be a built-in feature of the brain. Brain imaging studies show that a particular area of the brain, one associated with the reward system, is activated when subjects contemplate a photo of their lover.

I read a fair amount of history, and historians often say things like "love was invented by the troubadours in the 14th century in the Provence." But what does "love" mean? Clearly not all cultures lionize romantic love to the same extent, but, the idea of the love ballad or stories of tragic love seem universal. Some of you may know that I've been interested in the levels of selection debate: to me the universality of the psychological propensity toward love is a strong argument for the power of within group selection as opposed to between group selection. As the story of Romeo and Juliet illustrates romantic love across group boundaries can cause serious problems. The most extreme form of arranged marriages are normative in many "advanced traditional" societies (e.g., parts of Eurasia with a long history of complex civilization), and especially prevalent amongst elites for whom marriage ties serve as bounds which cement between family alliances. And the norms of society can make many individuals comfortable with the idea of arranged marriage, but it seems that it is rather easy to change these attitudes in the offspring of immigrants who come from cultures where arranged marriage is the norm. Parents may attempt to inculcate the importance of arranged marriage in their children, but unlike say nominal religious affiliation, this is one case where parent-child transmission exhibits a great deal of erosion.

Labels: Evolution