Monthly Archives: August 2014

Is There an Evolutionary Explanation for PMS?

One of the bugbears of our times is PMS, a physical condition that’s used as everything from a punchline to an idiotic reason why women shouldn’t be in charge of something important. Why does PMS exist? Is there any advantage to PMS, one that could have been selected for over the course of our evolutionary history?

A recent paper hypothesizes that the evolutionary advantage of PMS is that it “increased the chance that infertile pair bonds would dissolve, thus improving the reproductive outcomes of women in such partnerships”. Michael Gillings bases this idea around the fact that women don’t get PMS when they’re pregnant, so PMS is a sign of an infertile pairing.

There are three legs of his argument detailed in the paper published in Evolutionary Applications: Genetic variation affects the severity of PMS; PMS is directed preferentially at current partners; and PMS increases the likelihood of changing partners.

He cites studies that show that genetic variation affects the severity of symptoms of PMS, and that these symptoms are hereditary. This variation is normally put down to differing sensibility to the hormones, since “the absolute levels of progesterone, oestrogen and testosterone do not differ between individuals at high or low risk of PMS”. Since this genetic variation is heritable, it could be subject to natural selection.

Gillings cites a number of studies showing that severe PMS has a negative impact on marital relations, which is no surprise, but only one study which shows that it affects family life greater than social, school and occupational life. Specifically, “Functional impairment tended to be highest at home, followed by social, school, and occupational situations.” (source) This could be explained by the tolerance for functional impairment going from highest to lowest in those situations. At work you do your job, even if you’re in pain – at home you leave the dishes for later and just order pizza for dinner, because who’s going to say otherwise.

However, the crux of his argument is that PMS encourages a change of sexual partners, and for this he has little support. Most of his references in this section are of tendency towards risk, whether or not women want to have sex at this point in their cycle, and whether visible signs of menstruation would encourage other males to attempt to mate with a woman (this connection is not only a stretch, but irrelevant to PMS). This section is full of segues and studies only loosely related to what he’s trying to show.

It’s not a strong hypothesis, and ScienceNews interviewed a number of researchers who were generally unimpressed. A very strong point was made by Jane Ussher, a women’s health psychologist at the University of Western Sydney in Australia, who said: “Women are fertile before the premenstrual phase of the cycle…so any function of PMS in terms of repelling males would have no impact on fertility.” She goes on to add that PMS directed at partners is probably a symptom of other issues the woman is unhappy about.

For me, the most compelling argument was made by Mark Elgar, who studies evolutionary biology at the University of Melbourne in Australia. He pointed out that there’s no association between PMS symptoms and how many children a woman has. “In other words,” he explains, “there doesn’t seem to be a very compelling reason to construct an evolutionary explanation of PMS in the first place.”

PregnancyBar

Speculative hypotheses are integral to the advancement of scientific knowledge, but this seems to go off on an unnecessary side tangent. Hormones and their receptors play important roles in a variety of traits that are under selective pressure, while menstruation is a vitally important aspect of human reproduction. Menstruation can be painful, and pain makes people irritable; menstruation also requires a change in the levels of hormones, which naturally changes their other functions. PMS is just a byproduct of these biological aspects. Gillings – who lectures on human biology and the science of sex – seems to be seeking an evolutionary explanation for a trait where none is required. There is an unfortunately common idea that every single trait must have an evolutionary explanation, and must have conferred some sort of benefit that was selected for. In 1979 Stephen J Gould and Richard Lewontin published a paper (pdf) arguing against this position (which I’ve remembered because it has the fantastic title of: The Spandrels of San Marco and the Panglossian Paradigm). They made the point that many traits are simply byproducts of other things that have been selected for, and convey no inherent advantage themselves. This is probably what PMS, since it doesn’t seem to affect the reproductive capabilities of women.

Also (getting input from someone who actually menstruates), my wife told me that PMS is a largely modern and western phenomenon, and is made worse by low levels of exercise and the use of hygienic products made from synthetic materials.

Review: Brutal Imperial Stout

Brutal Imperial Stout    One of my favourite comics of all time is Beautiful Stories for Ugly Children, written by Dave Louapre and illustrated by Dan Sweetman (who also did the cover art for Mr Bungle). I bring this up because I was introduced to this series by one of the collections, What if this were Heaven, wouldn’t that be Hell?, which contained the story The Night they Missed the Donkey Show, which was about a group of Gringos who drove down to Tijuana to see a donkey show and left with nothing except homicidal Elvises. For a long time the donkey show was all I knew about Tijuana, but now I have learned it is the home of Border Psycho Brewery, which I encountered at the first Cuernavaca Beer Festival.

   This is the brewery that makes Brutal Imperial Stout, a fantastic beer which is brewed with cocoa and star anise. This stout is delicious, dark and thick and sort of sweet, sultry would be a good word to use, bringing to mind The Black Cat, one of those anti-villains that Spider-man never really wants to beat. It has a complex taste, but very drinkable, and gives great head when poured into a glass. Like Felicia Hardy this drink is of the night, the shadowed places, a poorly lit tavern wooing a girl with Edgar Allen Poetry.

   It sinks its claws into you, dragging you back for more, but will a surfeit of sultry goodness bring you the bad luck that is synonymous with going against the Black Cat? Well, the alcohol content is 10.3 percent, so…yes.


Black Cat cosplayed by Dalin

Review: Karamawi Belgian Golden Strong Ale

Karamawi   The next beer from the inimitable-without-a-mud-pit 1st Cuernavaca Beer Festival is Belgian Golden Strong Ale by Karamawi.
   For full disclosure, I must reveal that I have in fact been to Belgium, staying a few days in Brugge, where I lived on Belgian beer and Belgian chocolate. I don’t think I would have lasted much longer, to be honest, since man cannot live on beer and chocolate alone…but what a way to go.
   Now, this particular Belgian Golden Strong Ale produced by Karamawi did not originate in Belgium, of course, but in Pueblo, a city famed for taking various ingredients and mixing them together for the best possible results. To a large extent this beer follows that tradition: It is brisk and fruity, or actually more berry than fruity, much like Poison Ivy. That Batman villain has more in common with this beer – she’s got a powerful punch and this beer logs in at 8% alcohol. To my palate, at least, the malt is a bit sour, resulting in a dichotomous reaction in the mouth that’s partly a very nice taste and partly something you don’t really want near you…again, much like Poison Ivy.

   A beer for a fun but challenging time, a garden party full of verbal jousting from amiable people, perhaps.

Poison Ivy photo by Robbins Studios