PMT. What is it good for?

Absolutely nothing? That’s pretty unlikely. Look how common it is. By PMT I’m talking about the crabbiness that some women exhibit in the run up to their period. If you ask women if they suffer from this, then quite a few will say yes. If you ask their husbands or partners, they will probably agree. If you ask them out of their wife’s earshot, you may well get a “Hell yeah!”

YMMV of course. Women vary enormously in their monthly behaviour. Some seem to have little personality change, while some women are  fairly described by PMT memes. Evolutionary psychology suggests that if a behaviour is not in the interests of you passing on your genes, it will become less common over time. Surely crabbiness would impair your ability to reproduce?

There is a very straightforward evolutionary explanation to PMT. It allows people to escape infertility. Infertility is often a result of problems in just one partner. People can also be relatively infertile with one partner, but have no problems conceiving with another. For this reason, prior to the advent of expensive medical interventions like IVF, one of the most effective treatments for infertility was to get a lodger.

If a woman does not get pregnant, she will then experience the hormone shifts which trigger PMT. The mood altering effects of this make it more likely she will behave in a way that either drives her partner away, or makes her want to leave him.  One of three things can then happen. They can find someone else, they can get pregnant, or they can repeat the cycle of mood swings month after month. Because the purpose of this mood is to get people who are infertile together to move on, the vast majority of a woman’s anger will be directed at her partner. Other people are relatively safe.

A woman with severe PMT will not scream “you didn’t get me pregnant you loser!” She may well not consciously want to have children at this point, or even at any point in the future. But evolution has selected for behaviours that do lead to reproduction. So she is experiencing an irrational emotional state which she will then rationalise into a reason to be angry.

If you do not cause her belly to swell, she will find a casus belli to give you hell. She may complain if you don’t get promotion and in the next breath complain you are always at work. She will complain if you are not nice enough to her mother, and if you sleep with her mother. If she’s got it bad, you are not going to win.

If this is the purpose of PMT, what is the solution? Pregnancy is the obvious one. Anybody have any alternative suggestions? Just asking for a friend.

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