Christopher Ryan Ph.D.

Sex at Dawn

Prehistoric PMS?

Were cavewomen moody at that time of the month?

Posted Feb 21, 2010

As the APA (American Psychiatric Association) ponders whether or not to include premenstrual dysphoric disorder (PMDD–severe PMS) in the DSM-V, Newsweek reports on recent research suggesting that the condition may have a genetic component. The research is far from conclusive however, having been conducted on mice (and only sixteen of them).

One of the researchers, Dr. Peter Schmidt of the National Institute of Mental Health told Newsweek: "This is the first time, in the case of PMS and PMDD, that we have very strong evidence that there may be an underlying biological variation, at the level of the genome, that may relay a differential response to a normal change in hormone levels."

I'm reminded of Marjorie Shostak's wonderful book: Nisa: The Life and Words of a !Kung Woman. Shostak asked hunter-gatherer women living in the Kalahari region of Botswana about PMS. None of them had any idea what she was talking about. They thought she was referring to menstruation or pregnancy. So if there's a genetic component to PMS, presumably the gene is very infrequently expressed among this group.

But I tend to be skeptical of these genetic arguments. I find more significance in the fact that the women Shostak spoke with led very different lives than modern Western women do. For example, hunter-gatherer women menstruate far fewer times in their lives than do modern women.

  • Consider that because of their very low body fat content, foragers don't normally begin menstruating until their late teens.
  • Once they become fertile, it's not long until the typical h/g woman becomes pregnant.
  • After her baby is born, she'll typically breast-feed for three or four years, during which time she's unlikely to menstruate (lactational amenorrhea).
  • When she stops breast-feeding and starts ovulating again, she'll soon be pregnant . . .

Add it all up, and according to this scenario, it's likely that ancestral women probably menstruated fewer than fifty times in their lives, whereas many modern women can expect to pass through this hormonal storm over 400 times (12 times approximately 37 fertile years = 444 menstrual cycles). That's a huge difference in the wear-and-tear these hormonal storms presumably leave in their wake.

It's been suggested this difference could help explain why breast cancer appears to be so much more prevalent in Western societies than in populations where women have more children.

But this is not to suggest that Nisa and her friends were unaware of any female ailment related to sexuality. But the principal danger these women feared came from unsatisfying sex, not menstruation. As Nisa explained to Shostak,

All women know sexual pleasure. Some women, those who really like sex, if they haven’t finished and the man has, will wait until the man has rested, then get up and make love to him. Because she wants to finish, too. She’ll have sex with the man until she is also satisfied. Otherwise she could get sick. Because, if a woman doesn’t finish her work, sickness can enter her back.