PMS. WTF.

July 2, 2007 9:35 AM

What is the evolutionary relevance of PMS?
posted by Ambrosia Voyeur to science & nature (49 answers total)

None? It simply isn't maladaptive?
posted by aramaic at 9:40 AM on July 2, 2007

Natural selection only cares if we survive and have kids (which the human menstrual cycle apparently facilitates well enough); it doesn't care if we're happy beyond that.
posted by scottreynen at 9:51 AM on July 2, 2007

It proves that we no longer know how to take care of ourselves emotionally and physically, and serves as a reminder to slow the fuck down and take care of our own needs?
posted by occhiblu at 10:01 AM on July 2, 2007 [1 favorite]

I'm not sure you're thinking about evolution in the right way, although I understand the temptation, given all the foolish "evolutionary psychology" BS floating around to think that everything lasting in the human condition was selected for. In fact, as long as it doesn't interfere with human survival, there's no reason to think that it was ever the target of evolutionary pressure.

Of course, one can concoct a story, again, ala the brilliance of evolutionary psychologists, for why it should have been the subject of evolutionary pressure, but it would be a myth.
posted by OmieWise at 10:04 AM on July 2, 2007

sometimes nonuseful things evolve because they're genetically "tied" to useful things.

maybe the cavewomen with the worst PMS were also the ones who were most receptive to their hormonal swings, and hence they were the ones who were the friskiest and flirtiest when they ovulated?

so the cavemen procreated with the sauciest, most ovulatory cavewomen a few days before the mood swings and bloating... and by then the deed was done.
posted by twistofrhyme at 10:10 AM on July 2, 2007

by "receptive to", i guess i meant "affected by".
posted by twistofrhyme at 10:11 AM on July 2, 2007

Menstruation is unusual in humans and apes. We're one of the only ones with discharged rather than reabsorbed menses, which is itself of unclear 'function.'

It's worth noting that a number of scientists speculate(!) that early humans did not menstruate that often because of pregnancy, lactation, and body fat restrictions on it.

Other than that, I guess I agree with the above posters that unless PMS had a noticeable effect on your survivability or child rearing it would not matter in an evolutionary context, and could easily therefor fix in the (early, small) population if linked to an even remotely desirable phenotype.
posted by a robot made out of meat at 10:16 AM on July 2, 2007

I agree with the others who state that it has little to do with any macro-level evolutionary trends. PMS should be looked at as a stress indicator for the individual organism to seek rest during an intensive hormonal surge. If anything, it seems to be counter to evolution to insist that women try to be as active and emotionally the same as the rest of the month (witness the plethora of advertisements for PMS medication purporting to keep women "normal").
posted by Burhanistan at 10:17 AM on July 2, 2007

It may be like the spandrels in San Marco.
posted by chinston at 10:18 AM on July 2, 2007

To add to unobservable-evolutionary-just-so-story-filter, I will point out that non-actionable pain is in general maladaptive. If you were in pain for no good reason, then it would lessen the value of pain as a signal in other situations, so evolution doesn't ignore your suffering totally. Just mostly.
posted by a robot made out of meat at 10:23 AM on July 2, 2007

Without some actual evidence regarding differences in fitness related to PMS, all anyone can do is spin a pseudo-scientific just so story.
posted by KirkJobSluder at 10:24 AM on July 2, 2007

Natural selection only cares if we survive and have kids

doesn't interfere with human survival

My PMS comes damn close to interfering with these things. I hate to say it, but the best description of the feeling is "suicidal rage." FWIW.
posted by Ambrosia Voyeur at 10:24 AM on July 2, 2007

yeah, but it doesn't on a biological level. i doubt our cro magnon predecessors let moods influence childbearing.

also, i imagine a lot of early females didn't have the final say in procreation. so unless murderous, psychotic pms was so prevalent that females routinely murdered or castrated their mates before becoming pregnant, it probably wasn't selected against.

voluntary childbearing is a relatively recent social phenomenon.
posted by thinkingwoman at 10:28 AM on July 2, 2007

It is important to consider the difference between evolution and selection. Although the terms are widely conflated, selection is but one mechanism of evolution. The phrase "evolutionary relevance" indicates this confusion, and is not used by scientists. I think the question would be better expressed as "What is the selective advantage of PMS?"

As others have already said, one cannot say with certainty that PMS gives a selective advantage. It might even be disadvantageous—even deleterious alleles can carry on through the other mechanisms of evolution such as genetic drift.

In the absence of other data, speculation about whether this particular trait helped our ancestors to reproduce somehow is simply that—unscientific speculation. It is a kind of evolutionary "just so story" that is much beloved by the news media, but shunned by real scientists.

My PMS comes damn close to interfering with [human survival and reproduction].

I know you are joking, but with regard to the evolution of a large population, an individual organism is irrelevant. Billions of women manage to reproduce despite PMS.
posted by grouse at 10:33 AM on July 2, 2007

thinkingwoman: you've raised a point I hadn't really acknowledged: I was thinking of it in terms of "what an ostracizable bitch of a chimp I would be" but if I still smelled in season, I guess calling him useless eep eep bananaskinfucker last week wouldn't matter to a stronger male.
posted by Ambrosia Voyeur at 10:33 AM on July 2, 2007

This is pure speculation on my part (as a major PMS sufferer): I wonder if PMS is part of nature's way of trying to make us want to be pregnant more often (i.e. pregnancy = no period for nine months = no PMS for nine months). But I don't know if cavewomen would have made that connection, so I don't really know what worth it has from an evolutionary standpoint.
posted by amyms at 10:35 AM on July 2, 2007

Early women would presumably have avoided most PMS symptoms through pregnancy and breastfeeding.
posted by yohko at 10:41 AM on July 2, 2007

if I still smelled in season

One of the unusual things about humans and our close relatives is that the males can't tell when the females are most fertile.

I wonder if PMS is part of nature's way of trying to make us want to be pregnant more often

"Nature" doesn't "try" to make you do anything. And while as a male, I've never had a period, I expect that pregnancy and labor are much more painful, and much, much more likely to kill you, especially before modern medicine.
posted by grouse at 10:41 AM on July 2, 2007

also, i imagine a lot of early females didn't have the final say in procreation. so unless murderous, psychotic pms was so prevalent that females routinely murdered or castrated their mates before becoming pregnant, it probably wasn't selected against.

And also, I would imagine that most early females of childbearing age were either continually pregnant or lactating, and had much fewer opportunities to experience PMS in their lives.
posted by gaspode at 10:43 AM on July 2, 2007

To push away potential mates so you won't mate during the unfertile part of the cycle?
posted by happyturtle at 10:58 AM on July 2, 2007

Looooong literature review that (so far) makes some interesting points, including:

* PMS is, to some extent, a culture-bound idea
* There are positive symptoms associated with pre-menstrual hormones, including creativity and increased sex drive, but we have a certain idea of what PMS "means" in our culture so we don't talk about those things as much.
* Severe PMS sufferers tend, on average, to be more anxious than the general population.
* Psychological support for PMS sufferers seems to be universally helpful, which would argue against PMS being only a biological syndrome.

I would add (the article might also; the damned thing's 22 pages) that we've created a society in which women are not allowed to be angry, or excused for it, except if they're pre-menstrual, which I think then skews our perception of what "normal" behavior might be. That is, PMS can give many women (I'm including myself) a culturally-approved way of aggressively confronting people or events that have deserved such all month.

I don't know. Once I started realizing that I suffer PMS (at least the psychological symptoms) only when I'm in stressful relationships, I started looking at the whole thing differently. For me, at least, I really think it's more a sign that I'm dealing with too much stress and unfinished business and need to start addressing what's wrong rather than repressing it. I'm sure other women experience it differently, but I strongly lean toward the idea that it signals we're out of touch with our needs (emotional and physical), not that it's some immutable timeless evolutionary force and women have therefore been bitchy since time immemorial.
posted by occhiblu at 10:59 AM on July 2, 2007 [13 favorites]

I hate to say it, but the best description of the feeling is "suicidal rage." FWIW.

That's pretty extreme to endure once a month; I know you weren't asking for this answer, but if I were you I'd seek some treatment for that, starting with my doc but maybe also seeking psychological responses.

I want to emphatically underscore the idea many are posting that the theory of evolution does not explain every aspect of human experience and behavior. I have heard that some scientists consider menstruation an aberration, since early humans would have menstruated very, very rarely. They most likely would have spent most of their reproductive years either already pregnant or nursing, and would have experienced only an occasional period in between, rather than a monthly cycle. Here is a fascinating discussion I found on theories about menstruation in humans -- suggesting that it evolved because our endometrial tissue is too highly specialized to be re-absorbed without a significant metabolic cost. But you aren't asking about how menstruation may have evolved -- just PMS -- and it doesn't seem that we can be sure that PMS is a product of evolution at all.
posted by Miko at 11:15 AM on July 2, 2007

> the males can't tell when the females are most fertile.

isn't there some sort of study indicating that human males prefer the scent of an ovulating female? i seem to get hit on more when i'm ovulating, too, although i guess my dressing better to show off my flat ovulatory stomach might play into that.
posted by twistofrhyme at 11:18 AM on July 2, 2007

OK, I'm still in the midst of that article I posted, but it's totally fascinating. I love this idea:

Feminist writers (e.g., Laws, 1983; Martin, 1988; Tavris, 1992) have often cast the use of the concept of PMS as part of the backlash against feminism. It is difficult to conclude that the historical time line of interest in premenstrual phenomena and the development of active PMS research programs in the countries in which the women's movement achieved the greatest gains are mere coincidences. Now that it has become unpopular for women in the U.S. to embrace feminism publicly, we may want to consider whether their willingness to embrace PMS serves a similar function in facilitating resistance to cultural demands. Whereas 30 years ago a woman might have said, "I refuse to diet, to achieve a perfectly clean house, to stifle my anger, etc. because I will not collude with patriarchal demands," she now says, "I cannot lose weight, get all of my work done, keep quiet and calm, etc. because I have PMS."

The use of the dualistic discourse (Jekyll & Hyde, "me/not me," "PMS-self/real-self') that permeates the self-help books (Chrisler, 2001), as well as women's explanations of their own behavior (Cosgrove & Riddle, in press; Swann & Ussher, 1995), contributes to the social construction and maintenance of an idealized image of femininity to which women are encouraged to aspire. This image includes the "serene comportment" (Cosgrove & Riddle, in press) described above; women should be calm, patient, and open to others at all times, make others feel calm and safe, be cheerful and content with their lives. PMS allows women to aspire to the ideal without having to admit that it is impossible to achieve (Cosgrove & Riddle, in press; Laws, 1983). Blaming the "unfeminine" parts of one's personality or behavior on PMS can be a survival strategy by making it possible for women to hold onto a self-definition of "good/proper" woman (Laws, 1983).3 The premenstrual week is the only time that some women "allow" themselves to be angry (McDaniel, 1988) because they can attribute their anger to their hormones rather than to any of the many things in the world that could legitimately anger them. Elson (2002) referred to this strategy as "redeployment" of the menstrual cycle to meet women's emotional needs. It is one of the few reasons why women in her study who had had hysterectomies said that they missed menstruating.
posted by occhiblu at 11:22 AM on July 2, 2007 [5 favorites]

isn't there some sort of study indicating that human males prefer the scent of an ovulating female?

You're welcome to post one if you think it exists. But such effects, even if significant, would be marginal when compared to the ability of many other mammals to determine fertility.

it doesn't seem that we can be sure that PMS is a product of evolution at all.

Of course it is a product of evolution. If it weren't, it wouldn't exist. But the question is really whether it gives a selective advantage, and that we can't be sure about. Its mere presence does not indicate that it is advantageous or even neutral.
posted by grouse at 11:24 AM on July 2, 2007

One of the unusual things about humans and our close relatives is that the males can't tell when the females are most fertile.

Actually, female chimpanzees and bonobos - the two closest species of ape to Homo sapiens - have a pronounced swelling of the genital region when they are in estrous. "Some females develop a pale pink protuberance that is fully as large as a three-pint bowl."
posted by i less than three nsima at 11:49 AM on July 2, 2007

This is pure speculation on my part (as a major PMS sufferer): I wonder if PMS is part of nature's way of trying to make us want to be pregnant more often (i.e. pregnancy = no period for nine months = no PMS for nine months). But I don't know if cavewomen would have made that connection, so I don't really know what worth it has from an evolutionary standpoint.

Amyms makes an excellent point, which I would restate as 'PMS is selected for because its absence rewards pregnancy.'

I also think PMS is selected for because its moodiness tends to destabilize relationships which have not resulted in pregnancy. In other words, this one hasn't gotten the job done, honey-- time to move on.
posted by jamjam at 12:23 PM on July 2, 2007

Wow, we are far afield, but I have to toss this out from a recent lecture on bonobo population genetics that I attended: while they have those protuberances, they have it for far longer than their fertile period. Their actual ovulation is still occult to the male bonobo.
posted by a robot made out of meat at 12:30 PM on July 2, 2007

voluntary childbearing is a relatively recent social phenomenon.

Control of fertility through late-marriage and other diversionary practices has waxed and waned through recorded history and across cultures. I see no reason why this should not have been true way back into pre-history.
posted by meehawl at 12:39 PM on July 2, 2007

PMS might not have been as bad, historically. Women who avoided caffeine and got more exercise might have had reduced pain. Or, alternately, if endocrine disrupters are truly as pervasive as they appear to be, then that might result in excess pain and emotional distress.

Me, though, I would have been the one eaten by the sabre tooth tiger.
posted by arabelladragon at 1:12 PM on July 2, 2007

doesn't seem that we can be sure that PMS is a product of evolution at all.

Of course it is a product of evolution. If it weren't, it wouldn't exist.

You misunderstand me there. I was referring to the post by occhiblue which suggested that PMS, as an 'illness', may be a social construction and thus non-biological and not a result of evolution. In other words, PMS itself may not really exist and may not have a biological basis. There are many human phenomena that exist that cannot necessarily be traced to an evolutionary cause (tennis, summer blockbuster movies, birthday parties), unless you believe that all social behavior is determined or constrained by evolution, which is in the EP realm. In general, as you say, if something was neutral or not harmful the possibility of its existence is opened up, but that doesn't mean that natural selection caused it to occur.

I'd also have to suggest that the idea that PMS is an incentive to get pregnant because it's more comfortable could only come from someone who has never been pregnant.

Besides which, the process of becoming pregnant was probably outside cognition for very early humans. It was not necessarily obvious that sex and pregnancy correlated when life was extremely primitive. Once in puberty, one probably had sex frequently, and one had babies every year and a half or so, some of which actually lived. It's not that obvious, when you think about it, that the sex and the having of babies might be connected. So it's not as though you'd be able to recognize any 'reward' factor to getting pregnant. I don't think control of fertility could even be imagined until hierarchical societies emerged with all of their social fallout, including concepts like marriage, virginity, ownership, and a settled agriculturally-based lifestyle.
posted by Miko at 1:48 PM on July 2, 2007

Ah, sorry, Miko, I did misunderstand you. Yes, if PMS is solely a recent social construction, then it can't really be said to be a product of biological evolution. However, biological aspects contributing to PMS are.

if something was neutral or not harmful the possibility of its existence is opened up

Deleterious traits can also be propagated through evolution.
posted by grouse at 2:01 PM on July 2, 2007

You're right.
posted by Miko at 2:07 PM on July 2, 2007

One minor point that may or may not be relevant is that in hunter-gatherer societies, it is normal for women to not have more infants around than they can carry when the tribe moves (ie one) and that a constant pregnancy/lactation cycle such as people are suggesting in this thread may not have been commonplace prior to settlement. Whether PMS pre-dates settled societies, is beyond my knowledge. Do tribal populations around the world all suffer in the same way?
In any case, as everybody else has said, not all aspects of the human condition are the result of natural selection, and there may be no selective advantage to PMS. It may be a side-effect of something else that does confer an advantage, or it may just be bad luck. Or you know, that thing with the snake and the apple and the getting thrown out of the Garden.
posted by nowonmai at 3:37 PM on July 2, 2007

Whether PMS pre-dates settled societies, is beyond my knowledge. Do tribal populations around the world all suffer in the same way?

No. The article I linked says the idea was invented by an American gynecologist in 1931 to cover tearfulness, irritability, and "foolish and ill-considered actions." Then a British endocrinologist picked it up and ran with it for a while, then the whole 80s feminist backlash hit:

Biomedical and behavioral scientists began to pay serious attention to PMS in the 1970s, after the widespread gains brought about by the Women's Liberation Movement. By the mid-1980s, during the era when the politically conservative Ronald Reagan was U.S. President and the politically conservative Margaret Thatcher was U.K. Prime Minister, and there was a backlash against feminism in both countries (Faludi, 1991), PMS had become firmly established in North American culture. The establishment was greatly facilitated by two sensational murder trials in the U.K. in which the courts accepted PMS as a plea of diminished responsibility. One of the accused women had a history of mental illness and a criminal record of previous violent acts; she was arrested for stabbing a coworker to death during an argument. The other, who would probably be described today as suffering from traumatic stress as a battered woman, killed her lover by running him down with her car after they had been drinking heavily and arguing violently. The trials received world-wide publicity, and the journalists who covered them introduced many people to the concept of PMS and to the notion that premenstrual hormonal fluctuations could turn normally placid women into dangerous criminals. The attorney for one of the accused women described his client as a "Jekyll and Hyde" (Nicholson-Lord, 1982, p. 2) and said that without progesterone injections to control her PMS the "hidden animal" in his client would emerge ("'Woman's period' plea rejected," 1981, p. 4). These and other comments made about the women on trial have been documented (Chrisler, 2002; Chrisler & Levy, 1990) to appear in later magazine and newspaper articles about the average woman with premenstrual symptoms.

Shortly after the publicity about the murder trials subsided, a committee of U.S. psychiatrists devised the late luteal phase dysphoric disorder (LLPPD; the precursor to PMDD) and inserted it into the DSM-III-R. During the debate about whether to include LLPPD in the DSM, Paula Caplan was interviewed by a Canadian reporter who wanted to write a story about the debate. Her editor thought no one would want to read it, and he "killed" the story. Soon afterward Kim Campbell was elected head of the Progressive Conservative Party, and it looked like she would become Canada's first woman Prime Minister. The editor instructed the reporter to complete the LLPPD story immediately because the newspaper hoped to prevent Campbell's party from assuming power. He thought that the notion that women behave irrationally once a month would hurt Campbell's chances of political success. This is just one example of the pattern that has emerged: Each time women make substantial gains in political, economic, or social power, medical or scientific experts step forward to warn that women can not go any farther without risking damage to their delicate physical and mental health.

The authors also talk about cross-cultural studies that show symptoms are not anything close to consistent, about the fact that no one's ever really charted headache, fatigue & irritability cycles for men so we have no idea if getting crabby every month is exclusively a female thing, and about the fact that the culturally accepted idea of PMS explaining any negative physical or emotional symptom a woman experiences means that women (Western women, at least) creates a confirmation bias in which both women and men create a "syndrome" out of things that may not have anything to do with a woman's hormonal cycle. There's also the cultural idea that only women have mood swings (or moods at all), and that such moods are not normal:

Industrialization may contribute to the belief in modern societies that one can and should exercise self-control in order to feel and to behave the same way every day (Martin, 1988). American culture encourages people to believe that they have more control over their lives and their bodies than is actually possible (Brownell, 1991; McDaniel, 1988). Landers (1988) has suggested that PMS is a metaphor for the common inability of women to control their life situations. Premenstrual women often complain of feeling "out of control" because they are angry, irritable, exhausted, craving sweets, or unwilling, even temporarily, to put others' needs ahead of their own. Control is so important to some American women that even the thought of being out of control is frightening (Ritenbaugh, 1982). This impossible-to-satisfy need for control contributes to self-diagnosis of PMS and PMDD and to other behavior patterns that are related to depression (e.g., perfectionism, eating disorders, compulsive exercise). Furthermore, because of the preference in industrialized societies for control, order, and stability (i.e., people should behave like well oiled machines), characteristics such as changeableness, rhythmicity, and emotionality have come to be seen as inherently unhealthy (Koeske, 1983).

Most of the research on PMS and PMDD has been done by scientists in a few Western countries (Australia, Canada, Germany, Great Britain, the Netherlands, Sweden, and the U.S.), which share many common cultural beliefs (Chrisler, 1996). The vast majority of participants in studies of PMS and PMDD are European American, middle class, college students or married women. Participants are most often recruited from psychology classes or from private psychiatric or obstetric/gynecologic practices or university hospitals to which lower income women may not have access. This methodological limitation is rarely mentioned in review articles, but it may be important in understanding whose (and how) experience has been medicalized (Chrisler & Johnston-Robledo, 2002). World Health Organization surveys indicate that menstrual cycle-related complaints (except cramps) are most likely to be reported by women who live in Western Europe, Australia, and North America. Data collected from women in Hong Kong (Chang et al., 1995) and mainland China (Yu, Zhu, Li, Oakley, & Reame, 1996) indicate that the most commonly reported premenstrual symptoms are fatigue, water retention, pain, and increased sensitivity to cold. American women do not report cold sensitivity, and Chinese women rarely report negative affect. The results of these studies thus support the idea that culture shapes which variations in mood and physical sensations are noticed and which are of concern. Further support comes from Paige's (1973) survey of women in the U.S. She found that the most severe menstrual complaints came from strict Catholics and Orthodox Jews, both of whom strongly adhered to the traditional feminine gender role.

(Earlier she mentions that women who adhere to strict feminine gender roles tend to report higher instances of PMS.)

But my favorite example of the culture-boundedness (?) of PMS would be this:

We have already considered evidence that women are ready to diagnose themselves with PMS and PMDD. Others are also ready and willing to see women's behavior as pathological. Nash and Chrisler (1997) asked college students to complete a symptom checklist that included the criteria for PMDD and then 2 weeks later to complete it again after having read the diagnostic criteria for PMDD. Half of the 134 students read the criteria as they exist in the DSM-IV under the title "Premenstrual Dysphoric Disorder." The others read the criteria with all references to the menstrual cycle removed under the title "Episodic Dysphoric Disorder." The students also answered questions about whether they or anyone they knew might be suffering from the disorder. Knowledge of the menstrual "nature" of the diagnosis did not affect women's perceptions of their own menstrual cycle-related changes, but it did increase both men's and women's perceptions that menstrual cycle-related changes are a serious problem for women in general. Participants were willing to name female friends, relatives, employers, and professors as likely candidates for the PMDD diagnosis. However, they named both male and female friends and relatives as candidates for Episodic Dysphoric Disorder.
posted by occhiblu at 3:59 PM on July 2, 2007 [3 favorites]

Also related is the study that came out recently showing that lesbians in co-habitating relationships suffered fewer PMS symptoms than straight women co-habitating with male partners, again bringing up the question of whether PMS is in large part a reaction against unrealistic gender-role expectations (either internal or external).
posted by occhiblu at 4:51 PM on July 2, 2007

(Or, as the Daily Mail so sensitively put it: Men to blame for PMS.)
posted by occhiblu at 5:06 PM on July 2, 2007

Awesome detective work, occhi...
posted by Miko at 5:52 PM on July 2, 2007

Also related is the study that came out recently showing that lesbians in co-habitating relationships suffered fewer PMS symptoms than straight women co-habitating with male partners

I think this tends to support the view that one 'function' of PMS is to make it more probable that a woman will break up with a man who has not succeeded in impregnating her.

Which raises the issue of what the most favorable time, from a woman's point of view, to break off a relationship with a man might be. To me it seems clear that it would at least be no sooner than the moment at which it is certain she is not pregnant (and cannot be made so), since it could be disastrous to leave a man when you are pregnant with his child, and you might not be able to refuse sex as you are trying to leave. (In other words, he may rape you. from a game theoretic perspective, it's a good move for him. It might stop a woman from leaving, and if it does not, it is one last chance to produce offspring. I have read several accounts in which the last act of a man who could not stop a woman from leaving was to rape her.)

That leaves the premenstrual period or during menstruation itself. I would argue that the premenstrual period is better for leaving because unless a potential new male partner witnesses menstruation at least once, he has no way of knowing (such knowing might well be unconscious) that a child which results from any sex he might have with a woman is in fact his.

I think this view provides, by the way, one way of explaining the evolution of the hymen. The blood which results from breaking it, by its resemblance to menstrual blood, prevents a man from thinking, consciously or unconsciously, that a virgin whom he impregnates before first witnessing a period is pregnant with another man's child.
posted by jamjam at 5:56 PM on July 2, 2007

Except the evolutionary viewpoint completely ignores the fact that many women outside Western cultures don't conflate irritability or arguments with PMS; "arguing with your partner the week before your period (and no other time) (and only if you're a woman) (and only if your partner is a man)" is not a scientifically validated, cross-cultural phenomenon. Which makes any evolutionary argument for its function quite a stretch.
posted by occhiblu at 11:27 PM on July 2, 2007

I think occhiblu has done a great job of pointing out the ways in which PMS is cultural, and I'd just like to add that even if it is linked to biology, that does not necessarily make it the product of evolution.

If PMS is biological, or partially biological, it is linked very closely to the hormone changes in pre-menstrual period. Hormones are tricky things. The regulation of bodily systems through hormones involves both the production and absorption of hormones, which means that there are several points at which the genetically regulated processes can be disrupted or altered. Diet, stress, immunodeficiency, industrial chemicals, pesticides... a huge host of environmental factors can wreak havoc with your ability to produce or absorb hormones, or with the amount of hormone present in your body. These environmental factors can potentially cause noticeable effects in your body and your mood without indicating anything at all about evolution, and the one you suggest clearly was not.


jamjam, that is a very unlikely reason for the evolution of the hymen. Many cultures prefer women to be pregnant or have had a child before the marriage is contracted, as an indication that she is fertile. In the European tradition from which the Western value placed on virginity derives, semen was thought to be like a seed that, once planted, could grow at anytime. Thus, a simple lack of pregnancy at the time of the marriage was no guarantee that a woman would not become pregnant by her first partner at some time during the marriage. Only virginity could assure that. In order for a moral value to have an impact on evolution, it would have to be very consistently held across many cultures and over a long period of time.
posted by carmen at 6:20 AM on July 3, 2007

make it more probable that a woman will break up with a man who has not succeeded in impregnating her

Also, jamjam, this would be assuming that early humans most often practiced monogamy (otherwise there'd be no need to "break up with" someone), which I'm not sure is the case. And it would be counterindicated by the many cultures down through the history of civilization which insisted on lifelong marriage contracts regardless of fertility.
posted by Miko at 6:28 AM on July 3, 2007

d'oh. Editing weirdness: "and the one you suggest clearly was not" was supposed to be at the end of the second paragraph (in response to jamjam), not in the first, where it makes very little sense. Arg.
posted by carmen at 7:00 AM on July 3, 2007

Wow, that was hard. Hard to mark best answers when there's little consensus among them and with my own feelings!

When I posted, I had recently been blindsided by one of the worst episodes of PMS ever, with no other corrolations in sight other than getting off BCP for the first time in five years. I have lots of experience with stress-monitoring due to my anxiety disorder, so I feel qualified to say that for me there is a hormonal surge driving my PMS experience. However, there is a lot of food for thought here!
posted by Ambrosia Voyeur at 1:52 PM on July 3, 2007

Whereas 30 years ago a woman might have said, "I refuse to diet, to achieve a perfectly clean house, to stifle my anger, etc. because I will not collude with patriarchal demands," she now says, "I cannot lose weight, get all of my work done, keep quiet and calm, etc. because I have PMS."

Again with the generalizations! Who are these bizarre women, where do they find them? I am offended to be lumped into this class of people.
posted by small_ruminant at 3:49 PM on July 3, 2007

Evolutionarily, I think it just means that the hormones that have evolved for fertility can have side effects. I used to believe the cultural argument-- my periods have always been painful but used to lack the pre-period fatigue, irritation, and emotional unpredictability. But as I get older those symptoms have become personal reality. It's disconcerting. I don't doubt that PMS gets blamed for some things that it has nothing to do with, and in that sense can be psychologically useful for individuals, but that doesn't mean it's evolved in the species for that reason.

There have been nicely controlled experiments that showed that sometimes the effects of alcohol are entirely psychological in basis-- people get tipsy when given fake beer they believe is real-- but that doesn't mean that actual drunkenness is all in your head, either. It just means that your expectations can affect a real physiological effect. The effects of alcohol can be individually useful-- you get to act in ways you usually feel socially compelled to restrain-- but its evolutionary significance (why alcohol makes us drunk) is an altogether different question.

In those comparisons across different groups of people, it's usually not mentioned that human populations could vary in physiology as well as cultural norms. Diet, too. I expect a lot of things affect an individual's hormones, and those are likely to vary along with culture and confound the comparisons.
posted by Tehanu at 3:59 PM on July 4, 2007

hormones that have evolved for fertility can have side effects

Hormones did not evolve for fertility or any other reason. They simply evolved and continue to do so. To say otherwise is putting the cart before the horse—it is like saying that the Earth is ~150 million km from the sun so that we can have a year of ~365 days. No, it's the other way around.

Any changes in reproductive fitness caused by changes in hormone expression is a "side effect" of their evolution no more and no less than any other effect.

its evolutionary significance (why alcohol makes us drunk)

The evolutionary significance of ingested alcohol, if it has any, is not why it makes us drunk, but would rather be caused by the fact that it makes us drunk.
posted by grouse at 4:26 PM on July 4, 2007 [1 favorite]

Poor word choice on my part. I meant that a trait can be under selective pressure in one context but have effects in other contexts. People were arguing that PMS itself makes a person more or less fit when it might just be additional effects of the hormones that do directly affect fitness.

Yes, I meant evolutionary origin, not significance.
posted by Tehanu at 4:51 PM on July 4, 2007

To punish women for not breeding, duh. Just kidding.
posted by BrotherCaine at 4:43 AM on August 27, 2007