Paul Vasey, of the University of Lethbridge in Alberta, Canada, is the fourth speaker in MSU’s semester-long series “Whom You Love: the biology of sexual orientation,” which aims to demonstrate that homosexuality is a natural occurrence in humans. Vasey is a professor in U of L´s Department of Psychology. His lecture includes content from his studies on Japanese macaques and Samoan society.

What general themes will your lecture cover? 

The broad themes pertain to evolution, same-sex sexuality, cross-cultural research and non-reproductive sex. I´ll specifically be talking about the evolution of same-sex sexual attraction in males, and how such a sexual attraction can persist over evolutionary time, despite the fact that males who exhibit it do not reproduce. 

What have you learned from your studies with Japanese macaques? 

My research on Japanese macaques focuses on female homosexual behavior. There is no evidence that this behavior is an adaptation.  Instead, we think that female homosexual behavior in Japanese macaques is a byproduct of a female-to-male mounting adaptation, which happens routinely in this species. We suspect that females use mounting to control male movement. Once female-to-male mounting evolved as an adaptation in females, it then spilled over into a female-female context.

This research raises the possibility that same-sex sexual attraction in humans is not an adaptation, but rather a byproduct of some adaptation. Indeed, I would say my human research in Samoa, Japan and Canada furnishes more support for the byproduct hypothesis than the adaptation hypothesis.

What did you study in Samoa? 

In Samoa, there is a segment of the population consisting of feminine biological males who are recognized as a sort of "third" gender called fa´afafine. These fa´afafine enjoy a high degree of acceptance in Samoan culture, which is very striking from a Western cultural perspective where feminine and transgendered men are marginalized. Our research shows that fa´afafine are more willing to help out with nieces and nephews than regular men and women. It´s likely that having a supportive fa´afafine in the family influence, those family members’ attitudes about fa´afafine in general.  

So why don´t gay men go extinct? 

We are working on testing two hypotheses that attempt to account for why genes associated with same-sex sexual attraction in males do not go extinct. One is called the Kin Selection Hypothesis, and it basically holds that by helping close kin survive and reproduce, individuals can pass on genes indirectly. The second hypothesis is called the Sexually Antagonistic Gene Hypothesis, which holds that genes associated with sexual attraction to males have a reproductive cost when they occur in males, but a reproductive benefit when they occur in females. The reproductive benefit is that the females produce more offspring. Our research has furnished support for both of these hypotheses and we think that, in Samoa, they may work in concert to preserve genes associated with male same-sex sexual attraction over evolutionary time.

What inspired you to follow this line of research? 

The fact that I´m gay had something to do with sparking my initial interest, but I´ve been doing this research for about 20 years, and I doubt my sustained interest in the topic can be attributed to my sexual orientation.  The existence of same-sex sexuality and, more broadly, non-reproductive sex, is a fascinating topic when viewed from an evolutionary perspective. If reproduction is the engine that drives evolution, why do various forms of non-conceptive sex exist? This is one of the outstanding questions in evolutionary biology and can provide a more nuanced insight in to how evolution works.  

What do you think this speaker series could do for the social perception of homosexuality? 

Audience members will get an opportunity to see that there are other cultures that have different approaches to how they deal with same-sex sexuality and male femininity. It’s good to remind ourselves that our way of doing things is just one of many options, and not necessarily the best way. Hopefully audience members will see that questions pertaining to sexuality can be studied in a rigorous, hypothesis-driven, evidence- based manner.  I think this evidence-based approach to sexuality is important because I´m interested in understanding the world of sexuality on its own terms rather than through some lens of personal values.  

Sexuality is a pervasive aspect of everyone´s life, even if you´re not having any sex. Overall, I think the series is a good thing because it might get people thinking — and hopefully talking — about sexuality in general, not just same-sex sexuality.  This, in turn, might reduce shame associated with reflection about one´s own sexual needs.

For more information on this series, go to

Paul Vasey
“No Dodos: What Cross-Cultural Research Tells us About Why Homosexual Men Do Not Become Extinct”
4 p.m. Monday
Wells Hall room 115B
MSU Campus