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December 01, 2004

"Opposites Attract"

Regular readers know that I often blurb the late William D. Hamilton's Narrow Roads of Gene Land: Volume 2 (many copies of which are selling for $20-25 on AMAZON!), which tends to revolve around his fixation on the evolution of sex in response to parasites. Well, here is an article titled Good vs complementary genes for parasite resistance and the evolution of mate choice, this in the context of "Opposites Attract" (OA) vs. "Condition Dependent" (CD) vs. "Random Mating" strategies (RM). OA is the type of behavior alluded to in posts like Rare male advantage, while CD is selection for "fitness" (resistance to disease in this case) and RM is buckwild sluttiness. The authors ran a few models, and their general conclusion is that the OA populations manifested an ESS that was able to resist invasion from both CD & RM strategies, while it was able to "invade" both. The full article (PDF) is sinfull in its brevity so I recommend you check it out.

Addendum: There is conflicting evidence about whether humans engage in OA, for example, some research suggests women are attracted to shirts worn by men with different MHC profiles while other researchers find that women prefer those worn by men with MHC profiles similar to their fathers (smell is the proximate here).1 It is clear though on a social level that humans tend to engage in like-to-like mating, that is, they generally match for religion, ethnicity and socioeconomic status. Various forms of exogamy and endogamy also play into the mix.

Addendum II: New readers might be interested in this older post: Of pathogens & polygyny. The upshot is that an environment more rife with pathogens tends to favor polygyny (greater reproductive skew for males, CD preference) and exogamy (OA).

Addendum III: In response to a comment from Frank M. I linked to this post which suggests people are "attracted to faces like their own" because of some sort of influence from their parents. This is basically like imprinting, there is a genetic tendency that you are "primed" for that must be triggered by environmental inputs.

1 - Some have suggested that though randomizing the immune profile of your offspring might increase their fitness after birth, mating with someone with a similar immune profile boosts viability during gestation because of a lower likelihood of fetus-mother conflicts.

Posted by razib at 08:04 PM