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How does evolution affect human behaviour? The University of Toronto's Doug VanderLaan has chased the answer to that question from Japan to Samoa and across Canada, searching for clues about why humans behave as we do.

As a specialist in evolutionary psychology, VanderLaan investigates how biological adaptations may contribute to specific human behaviours that occur across cultures, such as the ability to infer emotions or discern kin from non-kin.

The assistant professor at the University of Toronto Mississauga applies that evolutionary perspective to his research on gender identity and sexual orientation.

“I’m interested in understanding the development and evolution of same-sex sexual orientation and atypical gender expression,” he says. “The existence of same-sex sexual orientation is an unresolved evolutionary puzzle.

“How do genes underlying this sexual preference persist if it lowers reproduction?”

VanderLaan’s early field research took him to mountains of Japan’s Arashiyama district, near Tokyo, to observe the same-sex habits of macaque monkeys. He next found himself in the South Pacific, studying a part of the Samoan population known as the fa’afafine.

“Fa’afafine do not identify as men or women, but as a third group,” VanderLaan says. “They are identified when they’re children, based on exhibiting marked ‘female’ behaviour such as playing with girls, avoiding rough-and-tumble play and preferring to do ‘female’ chores.”

VanderLaan interviewed hundreds of fa’afafine about their experiences and social roles, revealing that the fa’afafine play an important role in raising the next generation of Samoan children.

“Androphilic males, like the fa’afafine, don’t have their own kids, but they do share genes with siblings. They can help the success and survival of related genes,” VanderLaan says. “It’s about allocating investment of resources to nieces and nephews who need it most.”

For the fa’afafine, that investment comes in the form of babysitting, helping with homework, teaching songs, providing advice and culturally relevant material, as well as monetary support for school or medical visits. 

“My research shows that it’s important for male androphiles to be involved in family life," he says. "This behaviour brings some benefit to oneself and is important to motivating or facilitating a valued role in the family. It suggests that there’s something developmentally important going on. 

"Male femininity is often regarded as not a good thing, but this research casts it in a positive pro-social light and provides information about the factors that might underlie the development of male same-sex sexual orientation.”

In November, VanderLaan was awarded the 2015 Ira and Harriet Reiss Theory Award from the Society for the Scientific Study of Sexuality, which recognized empirical and theoretical advances that resulted from his cross-cultural research on sexual orientation and gender identity.

VanderLaan is in the final year of a four-year CIHR-funded research project with Toronto’s Centre for Addiction and Mental Health, focusing on the mental health challenges facing sexual and gender minority groups.

“Studies have found that members of these groups are at an elevated risk for mental health issues,” he says. “I’m particularly interested in developmental issues, such as separation anxiety.”

The study is investigating how gender confusion, peer relations and family environment may contribute to mental health issues in children, such as anxiety and depression.

“This information will be useful for informing mental health issues in gender minority groups and contribute toward a more equitable and inclusive Canadian health system.”