Spit, Swallows, And The Science Of Cuckolding

An over-the-counter paternity test inspires Intelligent Life to ask: What percentage of kids are “not the child of the man assumed to be their father?” And does human cuckolding actually have an evolutionary purpose?

Catherine Nixey writes that the test, now available in Britain, determines paternity via cheek swabs, which must be sent out to a lab. Its arrival raises the obvious question, how often is a dad not really a (biological) dad? What’s surprising about the answer is how widely it varies: from 1-2% in studies in Sweden and Iceland, to 20-30% in a study from Liverpool, England. Nixey writes that “clearly large-scale, randomised testing is needed to find reliable average levels of non-paternity” — and until that happens, we just don’t know what percentage of kids are really the milkman’s.

Or the banker’s. Nixey also advances a rather odd evolutionary argument for cuckolding. She echoes the frequently offered explanation that female animals want the most genetically fit males to father their kids, but the most reliable ones to help bring them up. Nixey writes,

Research on swallows is illuminating. In their eyes, attractiveness correlates with tail length. Scientists have found that females mated with lesser, shorter-tailed males are much more likely to be unfaithful than females mated with more attractive specimens. And their bit on the side is likely to be a male with longer tail feathers than her mate. It seems that, when faced with a choice between a bird in the hand and a bird in the bush, the female swallow opts for both.

And she says research shows “that women, like swallows, tend to be unfaithful up the social scale, seeking the human equivalent of long tails—fat wallets.” Now maybe fat wallets are indicative of some genetic superiority (I’m skeptical), but if women are really this calculating, shouldn’t they seek out rich men as providers? And get knocked up by guys with long, um, tails?