When Dr. Jean-Baptiste Leca was studying for his undergraduate degree in his hometown of Bordeaux, France, it's likely he never expected that one day he'd be doing post-doctoral work at the University of Lethbridge, and that the Japanese macaques would be the conduits for that link.
And yet here he is, with his wife Dr. Noëlle Gunst, studying these monkeys alongside Dr. Paul Vasey of the University's Department of Psychology.
"We met for the first time 10 years ago because we happened to be studying the same monkeys at the same place, Arashiyama, near Kyoto city, central Japan," says Leca, who recently co-edited a book with Vasey and Dr. Michael Huffman from Kyoto University, specifically dedicated to these monkeys. "The Japanese macaques of Arashiyama are probably one of the best known and longest studied primate groups in the world and yet we continue to find new and interesting aspects to their behaviour."
Leca and Gunst have worked with Vasey for the past two years, continuing his research focus on female homosexual behaviour of Japanese macaques at Arashiyama. Last year, they explored a new field site – Minoo, near Osaka city – where free-ranging Japanese macaques also occur. By chance, the trio came across a little studied demographic setting in primates and were fortunate enough to observe male homosexual behaviour. After analyzing these new data, Leca co-authored a manuscript with Gunst and Vasey for publication in the journal Archives of Sexual Behavior.
"Japanese macaques live in societies that are typically multi-male, multi-female. Males, when they reach sexual maturity, leave their natal group, with some transferring directly into a new multi-male, multi-female group, while others wander around solitarily for a period of time, and even others join what we call an all-male group. Being elusive, these all-male groups are difficult to track and observe, which is why we know little about them," says Leca. "As far as we know, young males stick together, travel independently, have social interactions and form a sub-group by themselves. When the mating season comes (October through January) some of these males will walk around a multi-male, multi-female group, hopefully to mate with females. What we observed in this particular all-male group however was male homosexual behaviour. While it's not the first time that this behaviour has been reported in Japanese macaques, it is the first time it has been reported in an all-male group."
The significance of this discovery is that it may speak to the evolution of male homosexuality in humans.
"We observe sexual behaviour – not sexual orientation – in monkeys. So the link will never be direct," cautions Leca. "But our findings may provide insights into the possible origins of human homosexuality."
He describes a possible evolutionary scenario proposed by Dr. Bernard Chapais from the Université de Montréal, where ancestral humans may have transitioned from multi-male, multi-female groups to polygynous groups, or harems. After reducing the number of females associated with each male of these harem societies, early humans then may have transitioned to monogamous units, which are widespread today.
"What we suspect, is that among polygynous ancestral humans, not all the males had access to females to form their harem, so maybe some of these males ended up in all-male groups, like Japanese macaques," says Leca. "One possibility is that the earliest forms of male homosexual behaviour occurred in these all-male groups. That's why we can make a kind of parallel between monkeys and humans."
Leca and his wife have been studying monkeys for 15 years and have travelled to Japan to study the macaques each of the past 10 years, calling the area their second home. This fall, when mating season arrives, Leca says the group may not venture to Japan and instead invest their time writing papers before returning in 2014. The lure of what is possible with this new line of study is invigorating.
"This time we got very lucky and our observations are really preliminary on this male homosexual behavior," he says. "So we want to return and continue our study on these all-male groups because they are not typically researched. We'd like to know more about the social interactions between these males and by understanding some of their social bonds, see how these particular relationships may impact their sexual behaviour."
It is groundbreaking work uniting three researchers from two very distant countries in a foreign land – with science the link that brought them together.
This story first appeared in the April 2013 edition of the Legend. For a look at the full issue in a flipbook format, follow this link.