Don’t blame it on the testicles!

I got an e-mail from a student studying scientific journalism today. She sent me an article and asked my opinion about it as the authors had referred to my work. At first I thought it was some kind of a joke, but then I clicked the link she sent and realised it was actually a real article, published in a scientific journal. The title is “Testicular volume is inversely correlated with nurturing-related brain activity in human fathers”. I wrote her a pretty elaborate response and did not think so much more of it. But then, what do I see scrolling down DN, my favourite Swedish newspaper’s website? The paper being quoted there! The journalist had done a good job seeking out an expert’s opinion so it’s not like all Swedish men are going to run home to measure their testicles and wonder if they might shrink if they put the kids to bed while she goes to the gym.

But. I have an urge to share with you some of the thoughts I jotted down for this ambitious journalist-to-be, now that the article is out there for all to view. I don’t have a problem with us being biological organisms with specific hormonal profiles and reproductive biological realities based on gender. But I do have a problem when that fact is a priori decided to affect our behaviours.

So the article presents a hypothesis that males are by nature necessitated to choose between mating and caregiving and that the size of the testicles as well as testosterone levels will be related to this choice. To begin with, I cannot see any proof of testicular volume or testosterone levels being related to mating behaviour, unless of course you are prepared to draw direct conclusions based on Lapland Longspurs (a bird) or “mammalian fathers”. The closest “proof” comes from a polygynous subculture of men. Because the authors’ main hypothesis is a proposed trade-off effect between caregiving and mating this would be a pretty important point to have some proof for.

Then they go on to say that brain responses of caregivers and maters will differ. Well, maters defined as those with bigger testicles, but oops wasn’t there a problem there? But sure, a photo of the child activated these father’s brains in specific ways and the more they took part in the child’s care, the more their child’s picture activated their brains. But oops, there was also a correlation between unknown child/adult contrasting pictures and brain activity in that region. So any kid will get these softies going? Or are we as humans wired to react intensely to infant photographs expressing different emotions? Remember that the first social skill we learn is smiling back at a face when we are six weeks of age?

Recent research has been clearly able to show that as humans we are the products of BOTH our genes and our environments. The way our brain is wired in situations that elicit caregiving behaviour is affected by early childhood care experiences and attachment representations. So although neuro-imaging is a fantastically exciting new field, in which I am not an expert, caution is warranted in viewing the brain as a simple switchboard where when certain lights come on, a specific causal pathway of events can be assumed. While even thinking of moving your right ring finger will light up a specific area in your motor cortex, the same cannot be said about the more complicated mesolimbic system.

In this paper, the correlation between reported caregiving and testosterone/testicle volume is very low (0.2) with results scattered all over the place. So really, this mating/caregiving thing is not something to build on. Yet, the authors push the hypothesis and test if testicle volumes correlate with the reactions elicited in the brain by the image contrasts. And they do, a bit. With both contrasts. But so what? I still don’t get the mating-caregiving bit. Why does it not even cross the authors’ minds that an alternative explanation would be that strong social skills (as in reacting strongly to child images) will predict prosocial behaviours and not antisocial, which are indeed correlated with higher levels of testosterone?

And this thing with the birds… The corvid was described as not being aggressive or protective at the time of mating in a serious scientific study from 1992 (Marzluff, cited in Ah-King). Well, not the males… Because of their gender-biased preconceptions, the researchers only studied aggressive behaviour of the males during mating season. But guess what? In the corvid society it is the females who do the fighting about who gets the prettiest guy! This anecdote is cited in an excellent booklet on the gendered nature of biology as a science by Ah-King, and it really serves as a reminder that science is socially constructed. Even if you measure your results in hormone levels or images of the brain.

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