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PMS: Pretty Mediocre Science

Gillings gets its wrong, writes Leigh Nicholson.

A recent paper published by Professor Michael Gillings, a molecular evolutionist at Macquarie University, has put forward a possible explanation for PMS in those who go through the delightful hormonal changes once a month; it evolved to break up infertile partners. The paper has received a lot of scathing attention since its publication two weeks ago, for rational and irrational reasons.

The paper, titled ‘Were there evolutionary advantages to premenstrual syndrome?’, is a review of knowledge in the area of PMS, which affects around 80 per cent of people menstruating. The paper springboards from two main points – because PMS is heritable and because there are no hormone level differences between those who experience PMS more severely than others, that it could be seen to have evolved as a highly advantageous behaviour to break up infertile couples (TL;DR: the woman isn’t pregnant, break up the partnership and find a new one).

Gillings explained that his hypothesis was framed through an anthropological perspective. In a context where pregnancy was a desirable and constant outcome, “if 80 per cent of women have PMS, and some women are paired up with a sterile man, and some have a relationship which is susceptible enough to be dissolved, the PMS behaviour would be advantageous”. However, because people can have the same hormone levels but experience PMS in different severity, it’s more likely that the syndrome itself is a difference in sensitivity to these hormones. So, what determines this sensitivity difference? Evolutionary advantages, which is the crux of the paper.

There are a lot of assumptions in this paper, however, and Gillings appears to also be completely aware of that. He writes “while it is not possible to know what conditions prevailed across 200,000 years of modern human evolution …it is still productive to think about the modern human condition as having recently emerged from our evolutionary past”. When pressed on this, Gillings reminded me that “the title is phrased as a question … it provides a different way of looking at it”, and that also it he is making assumptions about human culture, talking about “small family groups with male and female bonding”.

There are a lot of questions raised, though. Heritable traits do not immediately mean advantageous evolution. Differing sensitivities to hormones can be the result of numerous interacting factors. Also, to talk about a cross cultural phenomenon over such a long period of time is tricky. Saying that PMS would be advantageous in breaking up infertile couples is making sweeping generalisations about cultural and traditional values of relationships and monogamy. In some instances it might not have been viable to just swap partnerships when pregnancy did not occur. In others, there might not even be the requirement for some hidden evolutionary tactic to excuse dissolving a pair.

The paper frames PMS not as a disorder, or a medical condition, but just an inevitable part of menstruating folks’ lives. Like pretty much everything written on it ever, there is an assumed conflation between PMS and horrible, mean, irrational behaviour. In doing so, it stigmatises it and gives others a platform to say your emotional state is not real. For example, all the stuff that’s going in your body when someone has anxiety is akin to the fight or flight reflex, but it’s not in the least bit helpful to tell someone having a panic attack that their body is just evolutionarily confused and it’s not related to their current, modern and personal context. Yes, these behaviours could have been ‘advantageous’ in some really specific situations, but the human condition changes and it’s important to not shrug off syndromes as being a left over effect and not contextually legitimate.Gilling’s paper still provides an interesting anthropological and genetic analysis of a current annoyance some people face, despite it framing said annoyance perhaps a bit negligently. Sometimes a broader analysis, more inclusive of frameworks beyond anthropology and hard science, is necessary to properly explore and explain potentially contentious conclusions.