PMS Evolved to End Bad Relationships, Says Scientist

[Lightknight]

Dude, the fact that you're arguing "PMS is a natural side effect and not a real syndrome"" while mentioning your medical training is really really not cool. Yes, hormones are some heavy-hitters; yes, they've got full-body huge effects, since that's what they do.

Of course it's a syndrome. That's what the S is for in the acronym, I didn't say it wasn't a syndrome but a syndrome isn't a disorder. Syndromes are literally defined as a consistently occurring set of side effect with no comment as to the severity of the side effects. If you'll reread your quote of me you'll see that my issue wasn't with it being a syndrome but with the comment that PMS isn't a typical side effect of the menstrual cycle that the vast majority of women experience. This, however, is clearly something you still disagree with me on so hopefully my next comment will alleviate the issue.

But PMS is specifically when those symptoms become crippling. Like many other disorders, there's a point at which it takes over your life. A natural process pushed to an extreme is when it becomes a syndrome.

Oh, here's the confusion. You are mixing PMS with PMDD. Premenstrual dysphoric disorder (PMDD) is the term for when the symptoms involved with PMS are so severe as to become a disorder.

Yes, PMDD is an actual disorder and can truly impact your life. But please don't confuse it with PMS. This is why I recommended you speak with your physician on the subject when you discussed the severity of your symptoms.

Here's a mayo clinic article I found on the topic if you're interested:

http://www.mayoclinic.org/diseases-conditions/premenstrual-syndrome/expert-answers/pmdd/faq-20058315

If you are suffering from PMDD then there are some treatments and lifestyle changes that can drop the symptoms down to tolerable levels for you. So please don't think that what you're experiencing is just normal nor that there's no hope in alleviating them for yourself. PMS is an almost universally experiences syndrome amongst women, PMDD is not. Just under 10% from what I remember. 8% if Wiki is to be believed, I had thought it was a little higher.

 

[Nieroshai]

Interesting, the presumption that evolution directs itself towards purposes. Any actual benefit from evolution not related to natural selection is serendipitous at best, my friend. PMS does not exist for this purpose. It does not exist for any purpose. It simply exists.

Uhm.. how exactly is the ability to find viable mates NOT a part of natural selection?

This sounds plausible, but who knows... a flat earth sounded pretty damn plausible for a lot of people at one point (and sadly, still does).

The point I'm trying to make, that every honest biology teacher tries to make, is that evolution has no direction. Natural selection weeds out fatal evolutionary traits, albeit inefficiently, but evolution is chaos. Evolution is unbound genetic variation. You don't evolve towards a purpose, you find a purpose for your evolution. Or else die.

 

[Lightknight]

That is a fanciful thing you say. Traits through natural selection are random.

Not really depending on exactly what you mean. New traits (mutations) can be random. But the survival of traits is usually ultimately defined by the beneficial or negative impact they have on reproduction. The reason natural selection is involved is because a beneficial trait will be passed on more frequently than a negative or competing but slightly less beneficial trait.

So, say creatures live in an environment where food is very high up and hard to reach. Over time, the members of the species who are more capable of reaching the hard to reach food are going to reproduce more than the members of the species who are less capable because well fed animals means less deaths by hunger, larger/stronger body, improved health in general, more energy to reproduce, more attractive to the other sex.

An easy example of this is in the bird study from the Galapagos islands called Darwin's Finches in which he observed specialized differences amongst a common type of bird according to region. On one island, a spoon shaped beak for scooping up insects is more beneficial due to the environment so the birds in that region were more likely to have that type of beak while one island over a narrow beak is more beneficial to get at insects found in that type of ecosystem.

So, that a gene mutated to produce a slightly wider or narrower beak was random, but that the gene survived and spread over the subsequent generations was not random but because it made the gene's owners more fit for survival and reproduction than those without it. It's really all probability. A 1% advantage means a 101 children where without it there would be 100 children. Over the generations the 1% advantage starts working with larger numbers and has an exponential increase towards population size.

Though, admittedly, a 1% advantage would be a tremendously advantageous trait.

A great many people like to imagine that only the good survives the process, but many traits are just traits that persist because there is no reason for them to be selected out. Of course, many traits co-exist with other traits (ie. Sickle Cell Anemia is a product of an evolutionary adaption to Malaria. But that is literally the mutation of that same gene. You could not get rid of one without getting rid of the other).

Sure, some things slide past the filter that is time. It is also erroneous to believe that we are the pinnacle of human evolution at this moment. Our physical bodies are rapidly becoming less necessary while intelligence is far more beneficial. That being said, it appears that our societies have largely turned natural selection on its head with the poor (presumably less skilled/educated) having more children and the more wealthy having fewer children. We may actually regress over time which would be weird.

In the thought present behind this theory, a woman would have to be perpetually pregnant to avoid getting PMS. A baby only stops PMS while the woman is pregnant. As soon as she went back to her normal cycle, she would experience the same symptoms again, month after month, until she was pregnant again. If you read my previous posts, I have pointed out that a large body of evidence suggests that larger family units were not the norm until well after civilization came about. Though an adaptation could have come about only in the last 10,000 years that has made the symptoms of PMS appear.

If you read my posts you'd see I've been advocating that this theory is bunk. From the fact that women were things and not able to enter and exit relationships easily to the idea that a pregnant woman often has more regular and even wilder moodswings when pregnant. If PMS scares men away, then pregnancy driven mood swings will f them up, yo!

I see what you and others are doing, you are looking at it solely from the biological perspective, but that is one dimensional. You need to look at evolution from other perspectives as well, such as evolutionary psychology. You cannot look at biology and explain the actions of people.

Eh, no. Sorry. You've earmarked me for the wrong side. I just took a general issue with the way you said what you did. But you are technically correct. But overall the benefits of the menstruation cycle FAR outweigh the negatives of PMS.

 

[Baresark]

snipped for space consideration

I wrote this post and then accidentally closed the tab. So I'm going to try and hit the points I did before.

We are on agreement about most things. We both say this is bullshit. I think some of the points I mentioned may have come up as some kind of counterpoints to some of the things you were saying, but they were not.

We do disagree on the trait selection or lack thereof though. I am saying that traits can just exist without creating some sort of biological advantage, which is my reasoning behind this existing and not having a purpose. It is folly to think that nature is somehow attempting to build the perfect organism. It can't happen because our environmental stressors change all the time. But that does not make new trait not occur.

I am intimately familiar with Darwin's Finches and their beak differences. Darwin had insufficient time with the Finches. They required more study and more study was done way later. Further study has shown that the Finches have an average beak size that is not that different. The smaller beaks were for when seed shells were soft (ie, during seasons of adequate rainfall) and the larger for when they were harder shelled (ie. when there was not adequate rain that year). It shows that every island has an average beak size that the majority of the birds fit into. There were some with smaller than average beaks, and some with larger than average beaks, but most were in an average range. Darwin inferred from his studies that selection is acting on the birds beaks to make birds with either larger or smaller beaks. Only the average beak sized stayed the same from season to season, regardless of rainfall. There may have been an alternating (slightly) occurrence of prevalence of larger or smaller beaks, but the average beak size stayed the same. The environmental stress that caused differences in beak sized changed from year to year, but no one side was at a big enough disadvantage to be prevented from breeding. One year the smaller beaked birds were better off, the next it was the large beaked birds. The bird populations intermingled independent of the available food supply. The issue with Darwin's Finches is that with the short time he had to study them, it only let him take a very small sample of the population from the various islands, and the crew not being aware, only captured samples of birds that were different from average.

 

[KingsGambit_v1legacy]

PMS is something of a sensitive issue,

It is? Since when? Is that a new thing?

a woman in a "bad" relationship would experience PMS much more than other women.

LMAO. Come on, this is a joke, right?

"In the past, women had many fewer menstrual cycles than women in modern societies

OMG, seriously, come on now. Fewer menstrual cycles? Are you talking about Neanderthal women maybe? Or females of another species? 2 weeks, ovulate (and horniness), 2 weeks, menstruate (and PMS). It's pretty straightforward and happens regardless of how nice or big a jerk the boyfriend is.

 

[Lightknight]

We do disagree on the trait selection or lack thereof though. I am saying that traits can just exist without creating some sort of biological advantage, which is my reasoning behind this existing and not having a purpose. It is folly to think that nature is somehow attempting to build the perfect organism. It can't happen because our environmental stressors change all the time. But that does not make new trait not occur.

Yes, they can survive through the filter of time but if they are not somehow tied to a beneficial trait then they also need to not be in competition with a trait that is beneficial and therefore becoming a less fit trait themselves.

But generally speaking, traits will remain rare unless the groups expressing them also have other traits that coincide with it. So people who have two common mutations, one as a basic extra bone in the hand that doesn't help or harm anything and the second as a trait that makes them immune to a disease in the region. That extra bone would start to show up in larger numbers in future generations if that disease spreads only because it is assumed that the group with the extra bone survived to reproduce and expand while other groups contracted and intermarried with them.

But just one mutation with no commonly coinciding element? It should spread by itself in any significant numbers. Some things are random but the ravages of time tears things down to probability.

However, I digress. I think we both agree that neutral traits can persist. I just don't know if you agree with me or not that they would be rare unless tied to something beneficial even if totally unrelated.

I am intimately familiar with Darwin's Finches and their beak differences. Darwin had insufficient time with the Finches. They required more study and more study was done way later. Further study has shown that the Finches have an average beak size that is not that different. The smaller beaks were for when seed shells were soft (ie, during seasons of adequate rainfall) and the larger for when they were harder shelled (ie. when there was not adequate rain that year). It shows that every island has an average beak size that the majority of the birds fit into. There were some with smaller than average beaks, and some with larger than average beaks, but most were in an average range. Darwin inferred from his studies that selection is acting on the birds beaks to make birds with either larger or smaller beaks. Only the average beak sized stayed the same from season to season, regardless of rainfall. There may have been an alternating (slightly) occurrence of prevalence of larger or smaller beaks, but the average beak size stayed the same. The environmental stress that caused differences in beak sized changed from year to year, but no one side was at a big enough disadvantage to be prevented from breeding. One year the smaller beaked birds were better off, the next it was the large beaked birds. The bird populations intermingled independent of the available food supply. The issue with Darwin's Finches is that with the short time he had to study them, it only let him take a very small sample of the population from the various islands, and the crew not being aware, only captured samples of birds that were different from average.

Oh man... I've carried that misinformation for a long time. Middle school even so nearly two decades. The teacher even set up displays with multiple types of spoons that were better at getting the beans out of various containers... I glossed over the wiki section on the followup study. Should have read that.

How Darwin's finches never came up again in all my studies, including multiple courses on biology in university, I have no idea. Were they unaware of Darwin's mistake by the late 90's?

It is fortunate that the principle is still successful. If regions do vary enough then species of similar origin will evolve different sets of traits through natural selection (over significant time periods, of course).

 

[Lightknight]

PMS is something of a sensitive issue,

It is? Since when? Is that a new thing?

a woman in a "bad" relationship would experience PMS much more than other women.

LMAO. Come on, this is a joke, right?

"In the past, women had many fewer menstrual cycles than women in modern societies

OMG, seriously, come on now. Fewer menstrual cycles? Are you talking about Neanderthal women maybe? Or females of another species? 2 weeks, ovulate (and horniness), 2 weeks, menstruate (and PMS). It's pretty straightforward and happens regardless of how nice or big a jerk the boyfriend is.

I thought the same thing you did.

What he was saying, using pretty offensive terminology, is that PMS happens more frequently in an infertile relationship. He substituted the word "bad" for infertile. Something I took offense to. But if you're interested, he did respond to my complaint at the top of this page and was apologetic for the offense.

Additionally, he does define what he meant by "bad" in the article itself.

 

[Lightknight]

Note, most women do not experience PMS, and its actually contested if it even exists in the first place. This theory is illogical.

Indeed. PMS is a fantasy. Women exhibit overemotional, irrational and erratic behavior all the time. It's not just a symptom of some made up temporary condition.

Also, I may be joking, please take that into consideration before lambastic this comment. Then again, I may be totally serious with what I just said, concerning the comment in itself or about the part of it possibly being a joke.

Your joking aside, there is often a clear difference between a woman not experiencing PMS and a woman who is. Any man who has been in a long term committed relationship should have some kind of mental calendar about when to back away quickly from an argument.

Flood a man's system with the same hormone levels and you'll get the same results.

Yes, women are more emotional than men. This has been proven over and over again. But the impact of the progesterone/estrogen cycle is something else. My wife, for example, is extremely level headed. It's one of the reasons I married her for those years back. However, there are those few days a month where her not being level headed lies just underneath the surface. Where comments from me she wouldn't take offensively suddenly become direct insults at her and my tone suddenly becomes a factor rather than my intent. In a few days, I'll usually get an apology, or I would if I hadn't eventually become aware of the timing of events and learned to just quickly drop on my back with my belly exposed in submission to the temporarily dominant beast [/joke].

... please... no one tell my wife.... at least not for about two weeks just to be safe...

 

[Baresark]

We do disagree on the trait selection or lack thereof though. I am saying that traits can just exist without creating some sort of biological advantage, which is my reasoning behind this existing and not having a purpose. It is folly to think that nature is somehow attempting to build the perfect organism. It can't happen because our environmental stressors change all the time. But that does not make new trait not occur.

Yes, they can survive through the filter of time but if they are not somehow tied to a beneficial trait then they also need to not be in competition with a trait that is beneficial and therefore becoming a less fit trait themselves.

But generally speaking, traits will remain rare unless the groups expressing them also have other traits that coincide with it. So people who have two common mutations, one as a basic extra bone in the hand that doesn't help or harm anything and the second as a trait that makes them immune to a disease in the region. That extra bone would start to show up in larger numbers in future generations if that disease spreads only because it is assumed that the group with the extra bone survived to reproduce and expand while other groups contracted and intermarried with them.

But just one mutation with no commonly coinciding element? It should spread by itself in any significant numbers. Some things are random but the ravages of time tears things down to probability.

However, I digress. I think we both agree that neutral traits can persist. I just don't know if you agree with me or not that they would be rare unless tied to something beneficial even if totally unrelated.

I am intimately familiar with Darwin's Finches and their beak differences. Darwin had insufficient time with the Finches. They required more study and more study was done way later. Further study has shown that the Finches have an average beak size that is not that different. The smaller beaks were for when seed shells were soft (ie, during seasons of adequate rainfall) and the larger for when they were harder shelled (ie. when there was not adequate rain that year). It shows that every island has an average beak size that the majority of the birds fit into. There were some with smaller than average beaks, and some with larger than average beaks, but most were in an average range. Darwin inferred from his studies that selection is acting on the birds beaks to make birds with either larger or smaller beaks. Only the average beak sized stayed the same from season to season, regardless of rainfall. There may have been an alternating (slightly) occurrence of prevalence of larger or smaller beaks, but the average beak size stayed the same. The environmental stress that caused differences in beak sized changed from year to year, but no one side was at a big enough disadvantage to be prevented from breeding. One year the smaller beaked birds were better off, the next it was the large beaked birds. The bird populations intermingled independent of the available food supply. The issue with Darwin's Finches is that with the short time he had to study them, it only let him take a very small sample of the population from the various islands, and the crew not being aware, only captured samples of birds that were different from average.

Oh man... I've carried that misinformation for a long time. Middle school even so nearly two decades. The teacher even set up displays with multiple types of spoons that were better at getting the beans out of various containers... I glossed over the wiki section on the followup study. Should have read that.

How Darwin's finches never came up again in all my studies, including multiple courses on biology in university, I have no idea. Were they unaware of Darwin's mistake by the late 90's?

It is fortunate that the principle is still successful. If regions do vary enough then species of similar origin will evolve different sets of traits through natural selection (over significant time periods, of course).

I know what you mean about the followup on Darwin's Finches. For years and years it was brought up and I only found out about the followup myself like not even a year ago. I sat through so many biology classes, read all kinds of books on genetics, evolution and epigenetics, then I was listening to one of the Great Courses like last fall when I heard about the followups. I was like, "did no one ever think this information was important?" I do believe that the followup took place before the 90's. I don't remember the exact decade in question, to be quite honest.

I also learned that in Kettlewell's Moth experiment he pinned them to the tree so they couldn't fly away. For years I was like, "how did he know what moths were what after a night? What about the one's that flew away?" Come to find out that they didn't, because they pinned to the tree, which also made them an easy meal for predatory birds. Though the broad scientific conclusion is that his results wouldn't have varied so much from what they were. Talk about no holds barred science.

 

[PhiMed]

snip

Hmmm... I've heard arguments like this before.

How old do you think the world is, in years?

Ummm, that is a rather strange question. It's 4.3 Billion years old, at least last time I checked. Human remains have been found that place people at least as old as 180,000 years old, in our present incarnation (ie. fully erect when we stand with all of our bits where they presently are). Science has traces about 160 genetic traits that have only occurred in the last 20,000 years or so (estimated of course). Though, secretly everyone loves to think evolution requires millions of years, when thousands do for small things like Lactase production in human adults.

It's clear what you were thinking, and you do little for this educational back and forth by thinking things that were not explicitly said. What part of what I said lead you to that conclusion?

Sorry for the delay in response. I've been too busy to come to the Escapist lately.

The reason I asked is because it wasn't explicitly stated. Asking whether something is true is pretty much the exact opposite of assuming it to be so. I'm sorry if that didn't sit well with you.

The thing that lead me to ask that question is that there are some emerging schools of thought which begrudgingly admit that an intermediate between macro- and micro- evolution is possible, but insist that most species were created with a set number of traits inherent to them.

Your statement that "if a trait is common enough, it doesn't have to convey an evolutionary advantage in order to persist", while true, still doesn't answer the question of how that trait came to be so common within that population in the first place, unless it was in close chromosomal proximity to one that did. A likely answer (though not the only one) is that it might not convey an evolutionary advantage at the point being studied, but did at an earlier point in the evolution of that species, thus explaining its wide prevalence.

A (youngER earth? I don't know if there's even a name for this particular viewpoint yet) creationist would be of the opinion that the reason that this trait was so widespread, and thus did not need to convey an evolutionary advantage at any point in order to persist is that "God did it That population just sprang forth with a particular milieu of traits, and only evolutionary pressure would cause them to change."

I did not assume that you believed this. That's why I asked. Asking questions is still fair game, yes?

 

[PhiMed]

Hmmm... I've heard arguments like this before.

How old do you think the world is, in years?

I know you were asking this to someone else but just the nature of your question caused a bit of a spark of thought for me. How long in human history have women really had the option to leave a male? The entire argument of this article presupposes that women were in control of relationships and were able to easily end the relationship but this still isn't the case in several societies today and certainly wasn't hundreds of years ago in the vast majority of the world.

I don't know if that's really what the hypothesis is claiming.

Quite the opposite, in fact.

It seems that a neurophysiological process that causes cyclic emotional lability and irritability in women with persistent ovulation would cause the MALE in an "unsuccessful coupling" to leave a woman with whom reproduction was unsuccessful. If the reason for unsuccessful procreation lies with the male, then this would allow her to be open to advances from other candidates. Because they had little agency of their own for much of human history, this is a way for feminine biology to "trick" (pardon the anthropomorphism of physiologic processes) males into behaving in a way that is more conducive to the reproduction of the female.

I apologize for the latency in my reply. I've been crazy busy with non time-killing activities, so no time to mess around on the forums.

 

[Baresark]

snip

Hmmm... I've heard arguments like this before.

How old do you think the world is, in years?

Ummm, that is a rather strange question. It's 4.3 Billion years old, at least last time I checked. Human remains have been found that place people at least as old as 180,000 years old, in our present incarnation (ie. fully erect when we stand with all of our bits where they presently are). Science has traces about 160 genetic traits that have only occurred in the last 20,000 years or so (estimated of course). Though, secretly everyone loves to think evolution requires millions of years, when thousands do for small things like Lactase production in human adults.

It's clear what you were thinking, and you do little for this educational back and forth by thinking things that were not explicitly said. What part of what I said lead you to that conclusion?

Sorry for the delay in response. I've been too busy to come to the Escapist lately.

The reason I asked is because it wasn't explicitly stated. Asking whether something is true is pretty much the exact opposite of assuming it to be so. I'm sorry if that didn't sit well with you.

The thing that lead me to ask that question is that there are some emerging schools of thought which begrudgingly admit that an intermediate between macro- and micro- evolution is possible, but insist that most species were created with a set number of traits inherent to them.

Your statement that "if a trait is common enough, it doesn't have to convey an evolutionary advantage in order to persist", while true, still doesn't answer the question of how that trait came to be so common within that population in the first place, unless it was in close chromosomal proximity to one that did. A likely answer (though not the only one) is that it might not convey an evolutionary advantage at the point being studied, but did at an earlier point in the evolution of that species, thus explaining its wide prevalence.

A (youngER earth? I don't know if there's even a name for this particular viewpoint yet) creationist would be of the opinion that the reason that this trait was so widespread, and thus did not need to convey an evolutionary advantage at any point in order to persist is that "God did it That population just sprang forth with a particular milieu of traits, and only evolutionary pressure would cause them to change."

I did not assume that you believed this. That's why I asked. Asking questions is still fair game, yes?

That is absolutely fair to ask. I just wasn't sure what had lead to that question. It's important, when discussing scientific research and evidence, to know that you and the person you are discussing it with have the same understanding of how events occurred. Otherwise it's not reasonable to continue, really.

The only reason I can see it as being so common and yet not giving an advantage is that it shares genes with another trait that may not have been identified as of yet. When you spend the time to think about the nearly uncountable number of traits that make us like we are, it seems that this is the most likely outcome. Though, I do question how common it is. I mean, are we talking about PMS or people who suffer from Premenstrual Dysphoric Disorder. 3-8% of women are affected by the latter, which is not big at all. Normal PMS has very mild and in some cases unnoticeable symptoms for a lot of women. As an example, my girlfriend switched her birth control pill recently. The new one is working terrible. She has horrendous PMS where she will just cry for hours when she is coming up on that time. It's awful. When people talk about PMS though, they are usually referring to what is actually Premenstrual Dysphoric Disorder (ie. uncontrollable emotional states, extreme crippling cramping, stuff like that). This is because of how the chemical makeup of her reproductive systems are changed by this particular birth control pill. Time to change it I would say.

That aside: I just think it's presumptuous for them to make that hypothesis when they clearly have an incomplete understanding of human social evolution. But that is a downfall for a lot of biologists. They only see it from that perspective. They see the genes pass on and that is all that matter, for a lot of them it's the end of the equation. Only genes do not have a direct affect on the survivability of the organism outside the organism itself. That is where social evolution comes into play. Humans are not fully developed until they are about the ages of 18-20, which is one of the longest growth cycles in the kingdom Mammalia. Meaning that PMS would most likely act as a detriment as the only way to avoid it is to be in a state of nearly constant pregnancy, which I have pointed out does not make sense in pre-civilized humanity.

 

[PhiMed]

snip

Hmmm... I've heard arguments like this before.

How old do you think the world is, in years?

Ummm, that is a rather strange question. It's 4.3 Billion years old, at least last time I checked. Human remains have been found that place people at least as old as 180,000 years old, in our present incarnation (ie. fully erect when we stand with all of our bits where they presently are). Science has traces about 160 genetic traits that have only occurred in the last 20,000 years or so (estimated of course). Though, secretly everyone loves to think evolution requires millions of years, when thousands do for small things like Lactase production in human adults.

It's clear what you were thinking, and you do little for this educational back and forth by thinking things that were not explicitly said. What part of what I said lead you to that conclusion?

Sorry for the delay in response. I've been too busy to come to the Escapist lately.

The reason I asked is because it wasn't explicitly stated. Asking whether something is true is pretty much the exact opposite of assuming it to be so. I'm sorry if that didn't sit well with you.

The thing that lead me to ask that question is that there are some emerging schools of thought which begrudgingly admit that an intermediate between macro- and micro- evolution is possible, but insist that most species were created with a set number of traits inherent to them.

Your statement that "if a trait is common enough, it doesn't have to convey an evolutionary advantage in order to persist", while true, still doesn't answer the question of how that trait came to be so common within that population in the first place, unless it was in close chromosomal proximity to one that did. A likely answer (though not the only one) is that it might not convey an evolutionary advantage at the point being studied, but did at an earlier point in the evolution of that species, thus explaining its wide prevalence.

A (youngER earth? I don't know if there's even a name for this particular viewpoint yet) creationist would be of the opinion that the reason that this trait was so widespread, and thus did not need to convey an evolutionary advantage at any point in order to persist is that "God did it That population just sprang forth with a particular milieu of traits, and only evolutionary pressure would cause them to change."

I did not assume that you believed this. That's why I asked. Asking questions is still fair game, yes?

That is absolutely fair to ask. I just wasn't sure what had lead to that question. It's important, when discussing scientific research and evidence, to know that you and the person you are discussing it with have the same understanding of how events occurred. Otherwise it's not reasonable to continue, really.

The only reason I can see it as being so common and yet not giving an advantage is that it shares genes with another trait that may not have been identified as of yet. When you spend the time to think about the nearly uncountable number of traits that make us like we are, it seems that this is the most likely outcome. Though, I do question how common it is. I mean, are we talking about PMS or people who suffer from Premenstrual Dysphoric Disorder. 3-8% of women are affected by the latter, which is not big at all. Normal PMS has very mild and in some cases unnoticeable symptoms for a lot of women. As an example, my girlfriend switched her birth control pill recently. The new one is working terrible. She has horrendous PMS where she will just cry for hours when she is coming up on that time. It's awful. When people talk about PMS though, they are usually referring to what is actually Premenstrual Dysphoric Disorder (ie. uncontrollable emotional states, extreme crippling cramping, stuff like that). This is because of how the chemical makeup of her reproductive systems are changed by this particular birth control pill. Time to change it I would say.

That aside: I just think it's presumptuous for them to make that hypothesis when they clearly have an incomplete understanding of human social evolution. But that is a downfall for a lot of biologists. They only see it from that perspective. They see the genes pass on and that is all that matter, for a lot of them it's the end of the equation. Only genes do not have a direct affect on the survivability of the organism outside the organism itself. That is where social evolution comes into play. Humans are not fully developed until they are about the ages of 18-20, which is one of the longest growth cycles in the kingdom Mammalia. Meaning that PMS would most likely act as a detriment as the only way to avoid it is to be in a state of nearly constant pregnancy, which I have pointed out does not make sense in pre-civilized humanity.

While I agree that the organism as a unit in society must be considered when contemplating human evolution (at least modern humans), is that not what the author of this study was attempting to do? He was examining the trait (which we do not even know is related to one gene) as it might affect the individual in a family unit. He was attempting to explain how the effect of this trait on a family unit which did not produce children might help the female transition to a different family unit which might be more reproductively successful. Also, while we often like to speak of human evolution in terms of how the organism relates to society, we must remember that while we are "special", we're not that special. Especially before the development of civilization, we still need to remember that humans are animals, subject to the same laws of nature as other animals. Many animals have rudimentary societies, but we view their societal pressures as just another environmental competitive pressure. We must keep this in mind with humans.

I've already mentioned that I have some disagreement with your assertion that pre-civilization families only produced an average of two children, so I won't revisit that. As far as "constant pregnancy", ovulation is often halted during milk production, so that wouldn't necessarily preclude a halt in ovulation for extended periods of a female's fertile years. Especially since nursing was likely prolonged in pre-civilization eras due to a complete lack of pulverized baby foods. We see extended nursing in primitive societies even today. There's no reason to believe it would be different for ancient humans.

Additionally, infant mortality rates were much higher during pre-civilization eras than today, so 2 children reaching adulthood doesn't necessarily mean two pregnancies. Also, due to poorer nutrition and shorter life cycles, menopause likely had an earlier onset, which would serve to bolster the author's argument.

And finally, as far as the question of whether the author was discussing PMS or pre-menstrual dysphoric disorder, I think you kind of sat on your own point. If the frequency of PMDD is 8%, for example, and assuming it is a monogenic, somatic, recessive trait (we don't know that is a fact, but we don't know it NOT to be so, either. If genetic, the traits are almost certainly recessive, but they have not yet found a "PMDD gene"), that would mean that Harvy-Weinberg equilibrium would place the allelic frequency of the trait as 8%^.5, or 28%. That's a pretty high allelic frequency.

 

[Baresark]

snip

While I agree that the organism as a unit in society must be considered when contemplating human evolution (at least modern humans), is that not what the author of this study was attempting to do? He was examining the trait (which we do not even know is related to one gene) as it might affect the individual in a family unit. He was attempting to explain how the effect of this trait on a family unit which did not produce children might help the female transition to a different family unit which might be more reproductively successful. Also, while we often like to speak of human evolution in terms of how the organism relates to society, we must remember that while we are "special", we're not that special. Especially before the development of civilization, we still need to remember that humans are animals, subject to the same laws of nature as other animals. Many animals have rudimentary societies, but we view their societal pressures as just another environmental competitive pressure. We must keep this in mind with humans.

I've already mentioned that I have some disagreement with your assertion that pre-civilization families only produced an average of two children, so I won't revisit that. As far as "constant pregnancy", ovulation is often halted during milk production, so that wouldn't necessarily preclude a halt in ovulation for extended periods of a female's fertile years. Especially since nursing was likely prolonged in pre-civilization eras due to a complete lack of pulverized baby foods. We see extended nursing in primitive societies even today. There's no reason to believe it would be different for ancient humans.

Additionally, infant mortality rates were much higher during pre-civilization eras than today, so 2 children reaching adulthood doesn't necessarily mean two pregnancies. Also, due to poorer nutrition and shorter life cycles, menopause likely had an earlier onset, which would serve to bolster the author's argument.

And finally, as far as the question of whether the author was discussing PMS or pre-menstrual dysphoric disorder, I think you kind of sat on your own point. If the frequency of PMDD is 8%, for example, and assuming it is a monogenic, somatic, recessive trait (we don't know that is a fact, but we don't know it NOT to be so, either. If genetic, the traits are almost certainly recessive, but they have not yet found a "PMDD gene"), that would mean that Harvy-Weinberg equilibrium would place the allelic frequency of the trait as 8%^.5, or 28%. That's a pretty high allelic frequency.

It's more than likely the lesser or greater symptoms of PMS (and PMDD) are due some level of x-chromosome cancellation, either greater or lesser degrees of a set of genes. PMDD is just the same symptoms to a much greater degree. Hardy-Weinberg has it's limitations in these discussions though because it only refers to ideal frequency. We can't know at this point what selection pressures are causing or not negating the symptoms of PMS. So few things are reliant on a single gene that it's almost funny that it's a common reference. The safest assumption is always that a given trait relies on a set of genes and their unique interactions, which would also explain why there are so many degrees of effect of the symptoms.

So far as infant mortality and number of offspring is concerned: When we first started this discussion there was a word that escaped me completely. The beginning of civilization started with all societies as Agrarian (the word that I could not think of for the life me, because I'm tired way more often than I wish to be) societies. This is the first instance of people having larger numbers of offspring for a lot of reason. First, infant mortality greatly increased in this society. The reasons were typically that food was more scarce as families outpaced production and common accidents combined with very little medical knowledge, and a prevailing concept of a mechanistic view of human development. Evidence suggest (and I can't emphasize that word more) that in societies that predated these times (ie. pre-civilization) that a smaller number of offspring was the norm. The issue is that the beginning of civiliation is also the furthest back human history safely goes. The main issue is that human knowledge basically starts here. The assumption from a biological perspective has mostly been (from what I have seen) is that it's built with the understanding that more kids is always better and then is reinforced by the knowledge of the bad side of Agrarian Societies (and perpetuated throughout history as increased population drove farmers into cities and into industrialized societies). That has lead to a whole plethora of theories that do not have a place in reality. My favorite among them being polygamy the natural state of being and not monogamy, which makes sense until you look beyond biology and into social evolution... I'm rambling.

You are right, I had not considered the cessation of PMS while breast feeding, which definitely is a spot on point.