Mental illness exists for a reason (part 2)

In part 1 we discussed the differences in behaviour between Bonobo chimp’s and their closest relatives, the Chimpanzee. Bonobo’s and Chimpanzee’s each have distinct temperaments between their two species and minimal variation in the these temperaments within their own species. What does this mean? Most Chimpanzee’s are territorial, aggressive, and violent, and most Bonobo’s are chill, horny, and non-violent.

And now, to the promised star of part 2, the Vole.


Voles are a group of small rodents that reside in North America. Unlike the Chimpanzee and Bonobo, Vole’s occupy an extremely wide variety of habitats. If you recall, Bonobo’s live in one small part of Africa, in a very specific habitat, while Chimpanzee’s have a large range of similar habitats (to their own, not Bonobo’s) all across Africa. You can find Vole’s in prairies, meadows, mountains, and your basement. So what is it that make voles extremely adaptable?

Behaviour, for one.Voles, unlike Chimpanzee’s and Bonobo’s, have a wide variety of behaviours within their species. Some voles are monogamous, and some are not. Some are territorial, and some are not. By having a wide range of available behaviours within their population, the Vole species always ensures that there’s somebody (somevole?) around who are able to handle the demands of the environment. Prairie Vole’s, for example, are monogamous, while Meadow Vole’s are not. Maybe this means that a gentle, monogamous Vole may not survive in the meadow, but it ensures, on a population level, the survival of the species across a wide range of environments.

What’s responsible for the variations in behaviour seen across the Vole’s? If you recall, in part 1 we discussed the role of a gene, vasopression 1a receptor, in the different behaviours observed in Chimpanzee’s and Bonobo’s. Well, as it turns out, the vasopression 1a receptor gene is also responsible for the different behaviours among the Vole’s.

Credit: Science Magazine

As you can read in this study, genetic testing has shown a variety of vasopression 1a receptor mutations within the Vole genome. We would call this a polymorphic gene, meaning that many different forms of the gene exist within the same species. Humans have polymorphic genes for hair, eye, and skin colour, for example. Monogamous Vole’s appear to have a higher density of vasopressin 1a receptor and, similar to Bonobo’s, a “longer” version of the gene.

The take away? It’s not that vasopressin 1a receptor is the God-gene controlling our every instinct. The reality is there are thousands of genes that play a role in behaviour, and each one is more nuanced than the next. This should however stand as an example of how variation of a gene within the same species produces a variety of behaviours!

In part 3, we examine the role of vasopressin 1a receptor in human behaviour in an effort to extrapolate why mental illness exists!

Editor’s note: I do not want to diminish the role of, “nurture,” in the nature vs nurture argument. By no means in personality 100% genetic (most studies show it’s around 50%)! This blog simply looks at the genetic side of things.

I would like to credit Dr. Albert Wong at the Centre for Addiction and Mental Health for inspiring most of the content of this blog post.

Dr. Travis Barron is a resident physician in Toronto, Canada.

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