Gay uncles command a vital role in evolution, a surprising new Canadian study reveals.

Dr. Paul Vasey, an evolutionary psychologist at the University of Lethbridge, based his findings on repeated study of the “third gender” fa’afafine in Samoa – men who live as women and are universally accepted in the island’s culture.

Fa’afafine are far more likely to care for and help their nieces and nephews than heterosexual men and women, the study found. But the same nurturing, altruistic behaviour wasn’t there for children who weren’t relatives.

“No one was more surprised than I was. I was so skeptical, the next year I went back and did the exact study over again with different participants. I got exactly the same results,” said Vasey in an interview Monday. “You’re gobsmacked.”

The “highly statistically significant” results, based on interviews with nearly 300 people each time, uncovered not only a strong will to help nieces and nephews but a far lower interest than other people in helping Samoan children they weren’t related to.

Vasey described it as their tendency to be more avuncular – uncle-like.

To connect this behaviour to evolution, they would have to be “super uncles,” allowing their female relatives to produce lots of children. Vasey intends to test for that next, but has found clear evidence of the “female fecundity” theory: that the female relatives of gay men produce more children.

That theory, verified in Italian research, says that the androphilia gene – the gene for attraction to men – appears in men and women in one family. In men, it produces homosexuality. In women, it produces greater fertility, balancing out evolution.

Do the two theories fit together and do they hold outside of the collectivist Samoan culture? In Samoa, fa’afafine are “very tolerated and very respected,” said Vasey.

“In order for an androphilic male to be avuncular, he has to be in a culture that doesn’t discriminate against him,” said Vasey. “The right cultural factors have to be in place. But it might not all be just cultural.

“There may be a pre-disposition for androphilic males to be more altruistic to their families. Fa’afafine have significantly higher childhood separation anxiety. The same research in Canada shows gay men have significantly higher separation anxiety.

“So the childhood attachment is the same but the adult attachment, in Canada, is different. In order to develop that adult expression, you need the appropriate environment.”

Which, in lay terms, means: “If society is really freaking out around them, gay men aren’t going to make those same contributions to their family,” said Vasey.

Vasey’s research, with graduate student Doug VanderLaan, is reported in the journal Psychological Science.