Awhile back Jesse Bering wrote in favor of monogamy - gay or straight - by arguing that "heartbreak is every bit as much a psychological adaptation as is the compulsion to have sex with those other than our partners, and it throws a monster of a monkey wrench into the evolutionists' otherwise practical polyamory." Christopher Ryan responds:

Where's the proof that sexual jealousy (experienced as heartbreak) is an unavoidable response to a partner's extra-pair sexual activity? If it were a genetically encoded behavioral response, there would be very few, if any exceptions to this pattern. Yet every major city (and plenty of small towns) have sex clubs where couples have sex with extra-pair partners with no discernible emotional consequences at allat least not negative ones. These clubs exist all over the worldabsent only in countries where they are illegal. Most surveys of these so-called "swingers" indicate that they are more satisfied with their marriages than couples in more conventional arrangments. Add to this the large number of men who actually find the notion of being cuckholded very appealing (described by fellow PT blogger, David Ley in his fascinating book, Insatiable Wives). Then add the societies we describe in Sex at Dawn in which a party without extra-pair sex is like breakfast without coffee, and the genetic argument starts looking very wobbly indeed.

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