Evolution and Those Baby Blues (Published 2006) (2024)

It is virtually impossible for two blue-eyed people to have a brown-eyed baby, a fact that led some Norwegian researchers to wonder if such romantic pairings might have an evolutionary advantage.

Blue-eyed men and women carry genes for only blue eyes, meaning that two blue-eyed partners can only have blue-eyed children. But brown-eyed men and women can carry genes for both eye colors and can have either blue-eyed or brown-eyed children.

The researchers, whose study was published online earlier this month in the journal Behavioral Ecology and Sociobiology, theorized that for a blue-eyed man, finding a blue-eyed mate might have a Darwinian payoff: as a father, he could be more certain that a blue-eyed child was his own.

To test this idea, the researchers showed a group of 88 college students head shots of male and female models, their eye colors digitally manipulated to appear either blue or brown. The students were asked to rank the photos by attractiveness on a scale of one to five.

Blue-eyed men — or at least the male Norwegian students — preferred blue-eyed women, rating them an average 3.29, compared with 2.79 for the brown-eyed women.

Female students and brown-eyed men registered no preference by eye color.

Dr. Bruno Laeng, the study’s lead author and a professor of psychology at the University of Tromso, said evolutionary theory very nicely explained the findings. “There is strong evolutionary pressure for a man not to invest his paternal resources in another man’s child,” he said.

Since most Norwegians — 55 percent — have blue eyes, it is possible that the results would differ in other populations, the researchers acknowledged.

“A cultural explanation is not impossible,” Dr. Laeng said, “but it requires a lot of assumptions.”

What about men with green eyes?

Dr. Laeng’s answer is guarded. “For practical reasons we focused at the beginning on the most straightforward comparison of brown versus blue,” he said in an e-mail message.