Baby’s Blues Call Cheatin’ Moms

When a mother holds her newborn child for the first time, she’s had nine months of weight gain, mood swings and sleep deprivation to reassure her that the baby she’s cradling is truly hers. But for the father, who has only his partner’s assurance that she’s been faithful, there is no such guarantee. At least, no guarantee short of a paternity test, a private investigator or a guest appearance on Jerry Springer. But a recent study on mate selection in people suggests that for blue-eyed couples, the eyes are more than a window to the soul – they’re the hotel receipts of a woman that cheats.

Bruno Laeng, at the University of Tromsø, Norway, and his colleagues published the results of several studies investigating attraction between men and women of various eye colors. Eye color is a hereditary characteristic passed from parents to their children mostly through the interplay of dominant (X) and recessive (x) genes. Brown eyes (BB) are dominant, blue (bb) are recessive; a brown-eyed individual can also carry the recessive gene for blue eyes (Bb). Thus, based on the Mendelian genetics of inheritance (remember Gregor Mendel and his peas?), brown-eyed parents can still have blue-eyed babes. But a blue-eyed couple, carrying only the recessive blue gene, is guaranteed a blue-eyed child.

It follows that the father in a blue-eyed couple would check his offspring’s eye color for any signs of dubious genetic heritage. Curiously, infants’ irises are typically blue at birth (especially in Caucasians) and only reach their adult color by age three. It’s a trait that some researchers have speculated is an evolved strategy in infants to hide their true eye color and hence parentage; during those fragile early years two parents are a boon to survival. But a brown-eyed baby born to a blue-eyed couple? Well, that’s a sure sign that “daddy” isn’t.

To investigate whether blue-eyed males show a preference toward blue-eyed females, Laeng’s team showed 88 participants photographs of blue- and brown-eyed models. For some of the photos, the scientists substituted “mutant clones” – photos of a model whose eye color had been swapped using Photoshop. Subjects were then asked to rate the “attractiveness” of a group of photos. To prevent them from detecting the color-swap, they were never shown both the undoctored and mutant photos of any one model. As Laeng reported in this month’s issue of Behavioral Ecology and Sociobiology, only blue-eyed men showed a significant bias toward a particular eye color in the opposite sex – blue of course. 

The investigators next asked 443 young, white Scandinavian men and women of all eye colors (blue, brown and green) for their romantic partner’s eye color. Assuming that everyone remembered correctly (those who didn’t had to check their wallets first), Laeng found evidence of assortative mating – pairing of like with like. Not only were the study’s participants more likely to have chosen a partner with similar eye color (and, to a lesser degree, hair color), but blue-eyed males represented the highest percentage of individuals with same-eye-colored partners. Sixty-eight percent of the study’s blue-eyed males were with blue-eyed females, while only 43 percent of the brown-eyed males and 44 percent of green-eyed males were paired off with similar-eyed partners. 

According to Laeng and his colleagues, the results of their studies suggest that a blue-eyed male’s attraction to blue-eyed females is an adaptation against cuckoldry, providing men with a means to confirm they are the biological father and to detect when their partners have cheated on them.

Of course there are some competing explanations for eye- and even hair-color attractions. Previous studies have shown that people are attracted to mates who resemble their parents – possibly because exposure to traits in childhood leads to preferences for them in adulthood. In the case of eye color, if you yourself had blue eyes, so would your parents, and any preference for blue-eyed dates could have developed in infancy. The findings may also be biased by cultural attitudes and racial prejudices against darker-skinned, -haired and -eyed immigrants in the largely blond and blue-eyed Norwegian population (55% of the study population had blue eyes).

Of course with so many blue-eyed men running around it would be far easier for a blue-eyed woman from a blue-eyed couple to cuckold her husband with out leaving a trace, at least not in the eyes of her babe. This would mean that infant eye color is a poor indicator of fidelity and not a terribly adaptive preference. According to the authors, it is “remarkable that the present study, conducted within one of the world’s populations with the highest prevalence of blue-eyed individuals, was able to reveal clear-cut biases for eye color in mate choices.” Which just begs the question of what would happen if you repeated these trials in say, Italy, where only one-quarter of the population has blue eyes. Theory predicts blue-eyed male preference for like-eyed ladies should be even stronger. We’ll just have to wait it out.

At the time of this writing, the author’s son Noah was running around the living room snorting like a pig, interrupted only by bouts of licking the sliding glass door in the hopes of being let “out.. out…” For better or worse, the author, his wife, and son are all blue-eyed.