Filmmaker Bryce Sage has a heavy question that eats away at his curiosity: are gay men actually “born this way?” In other words, do biological factors (e.g., genes) play a role in sexual orientation?

Sage travels across the country looking for answers. Along the way, he encounters internationally acclaimed sexuality expert Anthony Bogaert.

A professor in Brock University’s Community Health Sciences and Psychology departments, Bogaert is doing the kind of breakthrough research which, when all the results are in, will lend science to the homosexuality question.

So Sage, who himself is gay, asks his mom to take a blood test. He accompanies the blood sample to Bogaert’s lab at Brock University, where they have a long chat.

Bogaert’s research will be featured in an upcoming episode of CBC’s long-running science series The Nature of Things with David Suzuki. Survival of the Fabulous, written and directed by Bryce Sage and produced by Connie Edwards for Souleado Entertainment, airs Nov. 28, 8 p.m. on CBC-TV.

“I’m pleased that there’s promotion for some of the research that I do,” Bogaert says of the upcoming documentary. “It promotes Brock – that’s great.

“It also gets the message across, in a positive way, that there’s opportunities for increased research participation,” he says. “Often times, people are interested in contributing to research. After seeing the show they may give me a call or answer a research recruitment advertisement.”

Bogaert’s research on the “older brother effect” stretches back to 1996, when he and colleague Ray Blanchard discovered that, on average, gay men have more older brothers than do heterosexual men. Studies have replicated this finding many times over the following 20 years.

Bogaert and colleagues have conducted similar studies on women and found no sibling characteristic reliably predicts their sexual orientation.

In 2006, Bogaert published a paper suggesting that the older brother effect “is probably a biological phenomenon. It’s probably not psycho-social, nothing to do with your learning environment,” he says.

His current research is exploring the “maternal immune response” theory, which states that some women produce antibodies affecting prenatal male development after one or more male pregnancies. According to the theory, these antibodies have some impact on the sexual differentiation of the fetus’s brain.

The CBC documentary looks at this and other research in more detail.

Watch a preview