It's not worth getting all hot and bothered every time evolutionary theologists -- I mean psychologists -- come up with a study that explains how a given gender stereotype is just a natural reflection of Darwinian impulses: why men like blondes, why women like pink. But a recent study snagged my attention. It found that women who marry older men have more children.

I've always cast a jaundiced eye on our cultural assumptions that men should be older (not to mention taller) than their wives. It seemed just another manifestation of the gender imbalances that coursed through our workplaces, government and educational system. Of course, when in love, all bets are off: My anti-age-gap theories didn't stop me from marrying a guy 11 years older. I'd always thought I was making this choice myself, but was there some deep biological impulse driving me to ignore my political analysis to find an optimal breeding partner?

One study analyzed data from that scientific treasure trove, the Swedish census, and found that men who marry women four to six years their junior end up with the highest breeding productivity. The scientists assume the age-gap preference has evolved because men choose on the basis of fertility potential and women choose on the basis of financial stability. Exactly how financial stability translates to our cave-dwelling ancestors they don't explain, but maybe this evolutionary development is actually (horror of horrors) cultural. A study of the Sami people of northern Finland between the 17th and 19th centuries, which found that the optimal age gap was 15 years, would suggest that age-gap proclivities are in fact a result of messy and changeable cultural practices, not pure evolutionary impulses.