HOW THE WOMAN GOT HER PERIOD
April 10, 2014 1:34 PM   Subscribe


 
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posted by mathowie at 1:46 PM on April 10, 2014 [1 favorite]


That was amazingly informative and fascinating explanation of my relationship with my mom.
posted by Brandon Blatcher at 1:52 PM on April 10, 2014 [22 favorites]


So my wife's insistence that the most accurate movie ever made about pregnancy was Alien ... she was right, then?
posted by localroger at 1:54 PM on April 10, 2014 [43 favorites]


Relatedly, Buzzfeed quiz: How metal is your period. Apparently my uterus is a dark storm cloud and once a month it RAINS BLOOD out of my vagina for days on end.
posted by jeather at 1:56 PM on April 10, 2014 [5 favorites]


Researchers, bless their curious little hearts, have tried to implant embryos all over the bodies of mice.

"Bless their curious little hearts" was not at all the reaction I had to visualizing that. This is why I am not a scientist.
posted by mstokes650 at 1:56 PM on April 10, 2014 [13 favorites]


Terrific read.
posted by yoink at 1:56 PM on April 10, 2014 [1 favorite]


In other words, it's just the kind of effect natural selection is renowned for: odd, hackish solutions that work to solve proximate problems.

This is the best description of the process that I've ever heard.
posted by Etrigan at 2:03 PM on April 10, 2014 [61 favorites]


Far from offering a nurturing embrace, the endometrium is a lethal testing-ground which only the toughest embryos survive.

New reality series or YA dystopia?
posted by jeather at 2:03 PM on April 10, 2014 [22 favorites]


I would like to read a genuine attempt to do a Kipling Just-So Story version of "How the Woman Got Her Period" though.
posted by yoink at 2:11 PM on April 10, 2014 [8 favorites]


Fascinating.

... in nature, women would experience periods quite rarely – perhaps as little as 7-10 times in their lives between lactational amenorrhea and pregnancies

Can anyone explain the logic behind this statement? Is it based on the assumption that "in nature" (whatever that means), women would be getting pregnant a lot more often and/or breastfeeding longer?
posted by iotic at 2:13 PM on April 10, 2014 [2 favorites]


When she sticks to science, she has a very interesting article. However-

the father, whose interests align still less with the mother's because her other offspring may not be his.

is more than a bit tendentious. And silly. It assumes both a strange attitude on the part of fathers in general and yet somehow exempts the pregnancy in question from being not his.

And the final paragraph?

We don't really know how our hyper-aggressive placenta is linked to the other traits that combine to make humanity unique

How? We don't even know if.
posted by IndigoJones at 2:18 PM on April 10, 2014


Yes, iotic: exactly.

No Presbyterian mothers shooing their daughters away from lecherous men. No nickle between the knees. Knocked up shortly after first menhorrea, which is too early, causing the body to abort, but lactation follows, delaying maturation of eggs for a few months, rinse, repeat. If the baby survives, nursing encourages further delay of egg maturation.
posted by IAmBroom at 2:18 PM on April 10, 2014 [3 favorites]


> New reality series or YA dystopia?

Marine Corps boot camp. The few, the proud, the infants.
posted by rtha at 2:20 PM on April 10, 2014 [3 favorites]


Both. Modern hunter gatherers breastfeed for much longer than we do, and that suppresses your period. And once they stop breastfeeding, well, they're not on the pill, so pregnancy usually follows.
posted by antinomia at 2:21 PM on April 10, 2014 [2 favorites]


Indigo Jones: the father, whose interests align still less with the mother's because her other offspring may not be his.

is more than a bit tendentious. And silly. It assumes both a strange attitude on the part of fathers in general and yet somehow exempts the pregnancy in question from being not his.


Why? We know as a statistical fact that stepchildren, both in humans and in wild monkeys (when roving bands of single males drive off the established males), suffer a dramatic leap in mortality rates. It's a mathematical fact, not some silly "social engineering" concept.

And why are you presuming that, in our evolutionary past, there was any constraint on the man caring about past children? Paternity tests aren't really a "thing" with chimps and lemurs, AFAIK.
posted by IAmBroom at 2:22 PM on April 10, 2014 [11 favorites]


IndigoJones, the author is not referring to the woman's romantic partner knowing in his mind who fathered the woman's children. The author is saying the biological father's genes don't "know" that this particular woman is responsible for any of his other offspring, so there is less evolutionary pressure for a man's genetics (as expressed in his offspring) to keep his children's mother healthy than there is for a woman's genetics (as expressed in her own offspring) to keep her healthy.
posted by agentofselection at 2:24 PM on April 10, 2014 [37 favorites]


If it makes you feel better, Indigo, think about this from the perspective of an ancestral primate species. Males and females are engaging in polygynous mating, so really it's true that each male doesn't know whether or not he fathered particular offspring, and has no guarantee that he'd father that female's subsequent offspring, either.
posted by ChuraChura at 2:24 PM on April 10, 2014 [3 favorites]


is more than a bit tendentious. And silly. It assumes both a strange attitude on the part of fathers in general and yet somehow exempts the pregnancy in question from being not his.

The data on violence towards adopted or step children is also 'tendentious'. Sadly.
posted by srboisvert at 2:25 PM on April 10, 2014 [2 favorites]


Ravenous Hemochorial Placenta.

I hope she writes more popular science stuff; she's great.
posted by benito.strauss at 2:26 PM on April 10, 2014


is more than a bit tendentious. And silly. It assumes both a strange attitude on the part of fathers in general and yet somehow exempts the pregnancy in question from being not his.

We do know for a fact that "the [hypothetical] father" of the embryo in the "[hypothetical] pregnancy in question" is, in fact, the father of that embryo. You're mistaking a posited fact for a psychological speculation. We also know for a fact that until very, very recently (in evolutionary terms) no father could be 100% certain that any given child was, in fact, his while almost no mother could have a similar scope for doubt as to their relationship to the children they'd borne. These aren't idle speculations about the psychological states of long dead ancestors, these are the epistemological givens of the nature of human reproduction.
posted by yoink at 2:30 PM on April 10, 2014 [4 favorites]



Ravenous Hemochorial Placenta.

I hope she writes more popular science stuff; she's great.


Sounds like a punk rock band.
posted by KaizenSoze at 2:31 PM on April 10, 2014 [2 favorites]


The war between fetus and pregnant woman is the big reason I think selling harvested eggs is such a questionable business-- though I wasn't willing to say that in the recent thread about it for fear some mefites might have been buyers.

For a fetus derived from an egg of the woman carrying it, the conflict is limited by and because of the fact that the fetus and mother share at least half their genes as well as large chunks of the arrangements of those genes on chromosomes etc., but for an egg from an unrelated donor, all such bets are off-- which could and I think probably does make for significantly higher rates of such things as preeclampsia, gestational diabetes, and even lupus, not to mention the consequences for the fetus.
posted by jamjam at 2:36 PM on April 10, 2014 [1 favorite]


Researchers, bless their curious little hearts, have tried to implant embryos all over the bodies of mice. The single most difficult place for them to grow was – the endometrium.
wut
posted by Sara C. at 2:37 PM on April 10, 2014 [4 favorites]


think about this from the perspective of an ancestral primate species. Males and females are engaging in polygynous mating, so really it's true that each male doesn't know whether or not he fathered particular offspring, and has no guarantee that he'd father that female's subsequent offspring, either.

A fact that could just as easily be used to support the idea that males would be more inclined to raise children who weren't theirs, because hey, maybe they are.

I think agentofselection is closer to what the author is trying to say; she is not making any claims about evolutionary psychology.
posted by (Arsenio) Hall and (Warren) Oates at 2:40 PM on April 10, 2014 [1 favorite]


In other words, it's just the kind of effect natural selection is renowned for: odd, hackish solutions that work to solve proximate problems.

What an amazing thing to consider that some aspects of life are just...cobbled together, because, damn it, it just works. This single phrase is inspiring me to stop what I'm doing and take up evolutionary science as a vocation.
posted by kyp at 2:45 PM on April 10, 2014 [9 favorites]


Wow. I used to TA developmental biology and I didn't know half of that stuff. Thanks so much for posting that!
posted by palmcorder_yajna at 2:46 PM on April 10, 2014 [2 favorites]


Mother Nature by Sarah Blaffer Hrdy has a lot about the socio-cultural factors at play in reproduction.

I'm skeptical of the extremely low numberof periods claim. Not every woman is perfectly fertile, even in our plentiful-calorie and rhogam world. Additionally, women can and do space their births/commit infanticide, even in the absence of modern birth control and abortion.
posted by the young rope-rider at 2:51 PM on April 10, 2014 [3 favorites]


Can anyone explain the logic behind this statement? Is it based on the assumption that "in nature" (whatever that means), women would be getting pregnant a lot more often and/or breastfeeding longer?

Breastfeeding much, much longer than most women in affluent Western cultures do, yes.

Back in anthropology class in college I learned that, in hunter-gatherer societies, children are often breastfed until they're 4-5 years old.

Weaning after a year is a relatively recent development associated with sedentary societies, and weaning before a year or not breastfeeding at all is completely counter to how the human body "naturally" is supposed to work.

There's also the fact that, in "nature" (I hate that phrasing, too, but what she's saying is true), much more active lifestyles and potential for food shortage meant that amenhorrea was more prevalent than it is in the modern affluent West. So in addition to having fewer periods due to breastfeeding, it's likely that women were also able to have periods slightly less often than modern Western women do. Certainly women started their periods later in life (later in their teens as opposed to like 11-12 or whatever the average is in the US today).
posted by Sara C. at 2:51 PM on April 10, 2014 [4 favorites]


It's pretty well documented that women living as hunter-gatherers do not menstruate as often as women in farming-based societies, even when not pregnant or breastfeeding. This presumably results from the relative absence of easily storable carbohydrate in the food supply, and as with the endometrial zygote boot-camp it makes little sense for the body to start such a potentially risky and expensive process then the resources to bring it to completion simply aren't available.

Of course, modern humans have foods hunter-gatherers only dreamed of in fantasies of the afterlife 24/7, so there is never a time a modern woman's body would feel sufficiently starved of nutrients to not bother ovulating.
posted by localroger at 2:56 PM on April 10, 2014 [3 favorites]


women would be getting pregnant a lot more often and/or breastfeeding longer?

What everyone has said, plus communal nursing behaviours- you'd probably be nursing your sisters and cousins kids, even more so if there's a higher maternal mortality rate leading to orphaned infants.
posted by Phalene at 2:59 PM on April 10, 2014 [2 favorites]


Great read, love that she tied it up with a reference to the expulsion from Eden.
posted by So You're Saying These Are Pants? at 3:16 PM on April 10, 2014 [1 favorite]


Human reproduction, man. If I've learned one thing about evolution, it's that bearing live young is for the birds!
posted by Eyebrows McGee at 3:27 PM on April 10, 2014 [10 favorites]


Hell, I still remember in the childbirth class we took before I gave birth to my first kid -- we all had these circular nametags that were attached to our shirts with diaper pins, so that we could learn everyone's names. Halfway through the second class, the instructor asked "SO!! Who here has figured out that your nametags are ten centimeters in diameter?"

The look of dawning horror on everyone's face probably would have been more amusing if it weren't mirrored on my own. Never has ten centimeters seemed simultaneously so large and so small.
posted by KathrynT at 3:30 PM on April 10, 2014 [86 favorites]


Never has ten centimeters seemed simultaneously so large and so small

That's a nice encapsulation of the inherent conflict between the mother and the infant.
posted by yoink at 3:36 PM on April 10, 2014 [8 favorites]


In graduate school I must have taken, oh, 7 or 8 semesters of reproductive physiology, including an entire course on immunoreproduction that was awesome. I didn't know very much of this, either, probably because I'm an animal scientist, and humans and livestock are very different reproductively. I really enjoyed reading this!
posted by wintermind at 3:47 PM on April 10, 2014 [1 favorite]


Bats and elephant shrews, sngh sngh snghm.
posted by Joe in Australia at 4:03 PM on April 10, 2014 [1 favorite]


Yeah getting pregnant is still my actual worst nightmare. So much body horror. I don't have a phonetic representation for the full-body shudder noise I made just now.
posted by dogheart at 4:15 PM on April 10, 2014 [8 favorites]


That was much more fun to read now that I am done with both childbearing and menstruation. Viva la hot flash....
posted by St. Alia of the Bunnies at 4:59 PM on April 10, 2014 [3 favorites]


"Bless their curious little hearts" was not at all the reaction I had to visualizing that.

Oh dear, you seem inconversant with the Southern Belle dialect, in which "Bless you" with the proper tone is about the most cutting thing you can say to another person in the second person. If I may offer an approximate translation,

"being psychopathic monsters whose treatment of cute furry animals makes the Nazi doctors look like Bill Nye by comparison," ...

But of course a proper Science Lady would not say that out loud, any more than a proper Southern Belle would outright accuse her husband's mistress. Instead she'd say "Bless you, dear," so that everyone knows she knows but she can't be accused of rudeness.
posted by localroger at 5:10 PM on April 10, 2014 [4 favorites]


agentofselection: "IndigoJones, the author is not referring to the woman's romantic partner knowing in his mind who fathered the woman's children. The author is saying the biological father's genes don't "know" that this particular woman is responsible for any of his other offspring, so there is less evolutionary pressure for a man's genetics (as expressed in his offspring) to keep his children's mother healthy than there is for a woman's genetics (as expressed in her own offspring) to keep her healthy."

QFT. The author should have put the father's "interests" in quotes or otherwise continued the convention she used in the prior paragraph regarding what the mother and embryo "want."
posted by desuetude at 5:13 PM on April 10, 2014 [2 favorites]


Basically, the evolution of childbirth in humans is the story of how our ancestors said "fuck it, walking upright and having big brains is way more important than easy, painless childbirth."

Seriously. The more I study human evolution, the more this is true.
posted by raeka at 5:36 PM on April 10, 2014 [3 favorites]


Emily Martin's The Woman in the Body touches on how charged medical narratives of "nurturing, enveloping" female reproductive systems are, and how little they have to do with the actual science of fertility. We want to believe that wombs are nurturing (just like our culture wants to believe that mothers are automatically and maybe even genetically nurturing), and so we develop ideological framings that match the pre-existing beliefs rather than the science.

(She also talks about how reluctant doctors--especially male doctors-- are to acknowledge that the framing of "active" sperm vigorously PENETRATING the passive, floating egg within a rosy and welcoming vaginal environment is scientifically inaccurate. Most of the sperm get lost, most of them are destroyed by the environment's acidic pH before they can fertilize, etc-- the egg is like the Final Boss for sperm, but you wouldn't know it by most medical texts.)
posted by a fiendish thingy at 5:36 PM on April 10, 2014 [39 favorites]


the egg is like the Final Boss for sperm

I love this.
posted by joseph conrad is fully awesome at 5:55 PM on April 10, 2014 [12 favorites]


Emily Martin!

I read an essay of hers about the penetration thing in college and it changed my life!
posted by Sara C. at 6:13 PM on April 10, 2014 [1 favorite]


How is this not common knowledge? HOW DID I HAVE SIXTEEN YEARS OF SHITTY PERIODS WITHOUT ANYONE EXPLAINING THIS TO ME EVER
posted by you're a kitty! at 6:31 PM on April 10, 2014 [3 favorites]


dogheart: "Yeah getting pregnant is still my actual worst nightmare. So much body horror."

When I was about 8 months pregnant, I had a case of bronchitis, and every time I coughed, my belly button popped from an innie to an outie and then back in. I have video. It was horrifying.
posted by Eyebrows McGee at 6:43 PM on April 10, 2014 [28 favorites]


We're waiting, Eyebrows.

I took a course in feminism and science, which was awesome in the sense that the professor (a biologist, biochemist or microbiologist - I forget which) was fantastic and knowledgeable and horrible in the sense that exactly two of us in the course had studied any science past high school. So sure, we learned about how active the egg is in fertilization -- so interesting! -- and also we had people arguing that the concept that in a chemical reaction with one big molecule and one little one you could imagine it as if only the little one were moving was based on sperm + egg and sexist. It was a very weird course.
posted by jeather at 6:54 PM on April 10, 2014


That was brilliant and answered a lifelong mystery for me. The whole system always struck me as so stupid, and this explanation doesn't make it any less stupid from the point of view of a woman inthe 21st century but it does explain how things ended up that way. Brilliant.
posted by bluesky43 at 7:00 PM on April 10, 2014 [1 favorite]


... in nature, women would experience periods quite rarely – perhaps as little as 7-10 times in their lives between lactational amenorrhea and pregnancies

I am not that surprised. I had five pregnancies (three living children) over a ten year period. Between the pregnancies and nursing I had less than a dozen periods for almost a decade and a half. As someone who passes out because of heavy periods (thank goodness my boss also had horrible periods and my missing work due to Aunt Flo isn't an issue), that was such an awesome time of my life!
posted by saucysault at 7:42 PM on April 10, 2014 [1 favorite]


the egg is like the Final Boss for sperm, but you wouldn't know it by most medical texts.

I'm a medical student (we're doing our reproductive biology unit right now as it happens) and I am pleased to inform you that we are definitely learning the Egg As Final Boss model.* The metaphors of embryo as parasite and/or Machiavellian competitor for Mom's resources are a lot more prevalent in our texts than the warm, loving motherly womb idea, which is great, because the truth is a lot more interesting. And this article just became mandatory reading for my friends in class.

*My personal favourite part of the whole process is how semen temporarily coagulates at the innermost area of the vagina, holding itself in place adjacent to the cervix for a period of several minutes while enzymes in the semen get to work dissolving the protective mucus that seals off the passage into the uterus. Once that time is up, the semen re-liquefies, and if the enzymes haven't done their job, the sperm can't advance and the entire mission is a failure. I cannot but think of this in terms a heist movie.
posted by saturday_morning at 8:19 PM on April 10, 2014 [35 favorites]


in nature, women would experience periods quite rarely – perhaps as little as 7-10 times in their lives between lactational amenorrhea and pregnancies

Here are some of the author's comments about this statement, from the comments on the answer:
So, in hunter-gatherer societies like the ones where modern humans evolved, women typically reach puberty much later than in modern Western ones. 18 would be typical. They also go through menopause much earlier (around 35 I think? Edit: James Pitt is right, that should be 40-45). Each time they have a child, they would lactate for about 4 years, which inhibits ovulation. During times of hardship ovulation also dries up. So all in all, there just weren't that many times in a woman's life when she would ovulate. When she did ovulate, without contraceptives, the chance of conceiving was fairly high.

Link to comment (Some interesting additional comments below this from other Quora users)
In response to a comment proposing a different estimate:
The 1/4 figure was based on sedentary millet farmers, not hunter-gatherers. Hunter-gatherers breast-feed their children for longer, and dietary differences also mean they reach puberty later and menopause earlier, and are more prone to skip cycles than farmers.

The 7-10 periods figure is from my notes on a course, and I unfortunately can't check it definitively as I don't currently have institutional access. But it sort of makes sense when you reason it through.

The Hadza of Tanzania, for example, reach puberty around 18, bear an average of 6.2 children in their lives (plus 2-3 miscarriages), and go through menopause at about 43 if they survive that long (about 50% don't). Around 20% of babies die in their first year; the remainder breastfeed for about 4 years. So this is 25 years of reproductive life, of which about 20 are spent lactating, and 4.5 pregnant, leaving only about 6 months of normal cycling. Amenorrhoea probably ceased some time during the last year of lactation for each child; on the other hand, this calculation ignores the ~50% of women who died before menopause, miscarriages, months spent breastfeeding infants who would die, and periods of food scarcity, all of which would further reduce lifetime menstruation. All in all, whilst I can't prove the 7-10 periods figure, it seems to me it's probably in the right ballpark.

Link to comment
posted by audacity at 8:28 PM on April 10, 2014 [5 favorites]


There's also some interesting exposition from Suzanne Sadedin in the comments on the 'wants' of the different genes involved (the mother's, the father's, and the fetus itself) and what that can actually mean and what complications might arise when say, the mother's genes and father's genes 'want' the fetus to have different levels of a particular hormone.
posted by audacity at 8:38 PM on April 10, 2014 [1 favorite]


though I wasn't willing to say that in the recent thread about it for fear some mefites might have been buyers.

For a fetus derived from an egg of the woman carrying it, the conflict is limited by and because of the fact that the fetus and mother share at least half their genes as well as large chunks of the arrangements of those genes on chromosomes etc., but for an egg from an unrelated donor, all such bets are off-- which could and I think probably does make for significantly higher rates of such things as preeclampsia, gestational diabetes, and even lupus, not to mention the consequences for the fetus.


Actually, I don't think there is scientific evidence for this. I looked into it back when I donated eggs for a friend. And our fertility doctor also claimed that there was no lower "success rate" or higher rate of complications once you get to the point where the embryo has implanted, whether the egg is from a donor or not. There are a few complicating factors when it comes to looking at the statistics: firstly, IVF has higher rates of multiples, which can lead to various problems, but you can compare non-donor IVF to donor IVF with the same number of embryos transferred, so that isn't a problem by itself for the stats. However, the second issue is that donor eggs are usually from a relatively young woman: in their 20s on the whole. Non-donor IVF is more often for women in their thirties or even forties, so the eggs involved are much older. So we would expect higher complication/lower success rates for NON-donor IVF. It's harder to separate that out from any problems that might be due to genetic mismatches.
posted by lollusc at 1:51 AM on April 11, 2014 [1 favorite]


All in all, whilst I can't prove the 7-10 periods figure, it seems to me it's probably in the right ballpark.

Let me be more clear. The idea that there is "nature" that was in the past for "us", and that it was exactly like any given hunter-gatherer culture "we" have happened to study is really...not true. Humans vary, including humans in cultures that have prima facie similar resource acquisition patterns.
posted by the young rope-rider at 3:40 AM on April 11, 2014 [2 favorites]


My other thought is that this is the first time the practice of eating the placenta has made much sense to me. Hippie earth mother getting back in touch with her body? Eh.

But victorious warrior devouring the corpse of her vanquished enemy? THAT makes sense. "You tried, placenta. You stole my blood, you stole the calcium from my very bones, but I AM STILL HERE." That's a feasting motive I get.
posted by a fiendish thingy at 6:19 AM on April 11, 2014 [21 favorites]


This was great. Thanks for posting!
posted by jillithd at 6:20 AM on April 11, 2014


The idea that there is "nature" that was in the past for "us", and that it was exactly like any given hunter-gatherer culture "we" have happened to study is really...not true.

Sort of. There is one major constant difference between all hunter-gatherer tribes ever studied, from the !Kung to the Eskimos, and all farming societies ever studied from those using the most primitive techniques to our modern selves:

The hunter-gatherers do not have access to carbohydrates in the quantities farmers do, full stop. Carbohydrates are fast storable energy, so they are on top of the acquisition list for every animal in any particular environment. As such there is no natural unmodified environment where large quantities of carbohydrate food are continuously and copiously available. If they were, there would be a race (as there is even when we plant a field) among everything from insects to other macrofauna to take advantage of it.
posted by localroger at 7:18 AM on April 11, 2014 [2 favorites]


I'm sending my mom flowers today and she's going to think it's because her birthday is coming up but it's because I read this.
posted by MCMikeNamara at 7:27 AM on April 11, 2014 [7 favorites]


The idea that there is "nature" that was in the past for "us", and that it was exactly like any given hunter-gatherer culture "we" have happened to study is really...not true.

You're getting bogged down in a turn of phrase. The piece isn't really about hunter-gatherer culture, so it's perfectly OK for the author to just use the term "nature" as a quick shorthand for "not modern day affluent sedentary culture".

The "nature" thing is something that would have gotten a few points docked on one of my essays as an Anthro undergrad, but from a zoologist who is otherwise dead on correct, I'll allow it.

Also, while I agree that any given modern hunter-gatherer culture may or may not resemble our ancient human past, for things like how often people menstruate, it's a fairly OK metric. I'd balk at this in an ethnography, but it's perfectly consistent with current scholarship on the matter and for the sake of brevity I think "in nature" is fine.

It is straight up Known that the idea that you have a period every month for the vast majority of your life, from age 12 to age 50, except for maybe a 9 month period while you're pregnant with the one child you're ever going to have, is an extremely recent development.

There are a lot of theories that it is this modern over-active menstrual cycle that is the cause of a lot of reproductive cancers, in fact.
posted by Sara C. at 9:45 AM on April 11, 2014 [3 favorites]


My other thought is that this is the first time the practice of eating the placenta has made much sense to me.

Yup. Also when you consider the way she opened, with the idea that our particular style of childbearing (well, really, the period) is especially wasteful of nutrients.

Get all those suckers back, mom! Delicious protein! You're gonna need it! Especially since it's not like you can get up and go hunt some rabbits right now.
posted by Sara C. at 9:49 AM on April 11, 2014


....there's one thing I don't get from an "evolutionary biology" standpoint, based on a quirk of my own experience.

Some women don't ovulate every month, due to fertility wonkiness; each ovary, I was told, only "fires" every other month, and they take turns; and sometimes something happens to one of the ovaries (like losing one, which is what happened to me). So, in theory, there are some women who only ovulate every other month. And yet menstruation does happen every month, even when you're "firing blanks".

So, if this is a month you ain't gonna ovulate, why invest that nutrient-rich endometrium? Why are the "generate an endometrium" hormones not related to the "I'm gonna ovulate" hormones so you would be spared if you weren't gonna be ovulating that month anyway?
posted by EmpressCallipygos at 5:12 AM on April 12, 2014


I think I'd understand Dr Sadedin's argument better if she didn't anthopomorphise everything. For instance, I don't know what she means when she says
The longer the female can delay that placenta reaching her bloodstream, the longer she has to decide if she wants to dispose of this embryo without significant cost.
Who is deciding here, and on what basis? Do other species consciously think about their fertility? Why do they need time to make up their mind? Is the endometrium actually a successful delaying tactic? Wouldn't it be infinitely more effective to simply not produce any eggs?
posted by Joe in Australia at 7:23 AM on April 12, 2014


Joe I found it perfectly clear what she meant; if she is using the language poorly it's because our language doesn't really provide a clear way to distinguish between conscious decisions and decisions made autonomously by our bodies.

Phrasing it all "correctly," e.g. "her body," "it", "her endocrine system," etc. sounds bloodless and clinical, and the whole point of the article is that it's a very personal war between the interests of the mother, embryo, and paternal genetics.
posted by localroger at 7:43 AM on April 12, 2014 [1 favorite]


So, if this is a month you ain't gonna ovulate, why invest that nutrient-rich endometrium?

Because your uterus doesn't know your ovaries have this medical condition.
posted by Sara C. at 8:12 AM on April 12, 2014 [3 favorites]


Joe, I'm assuming you're taking the piss when you ask if other species "consciously think about implanting embryos" to make your point. Which is a kinda lame way to have a discussion.

I guess I can see some objections to teaching science in this imprecise manner but, I really liked this story, because it was just that, a story. It pulled bits and pieces from different research and told a narrative with it. Assuming familiarity with the basic facts of evolution, (and understanding some subtleties of humor), I think it's pretty clear what she's saying.

I don't think anyone walked away with the impression that any uterus or embryo was "making decisions", but that is part of the risk of putting this out to the sadly, scientifically illiterate public. Even if it helped someone reach an incomplete, but greater working knowledge of evolution, it was better than nothing.

In just about any biology text book outside of grad school, you probably saw a familiar comforting diagram of a cell with a nice big nucleus, some orderly mitochondria and ribosomes, etc. While reality is closer to this, throwing that at someone isn't going to help them reach a working knowledge of the subject. Same with some mangled sentence like "genes that create an endometrium with greater resistance to placental implantation were apparently available to human ancestors..."

To me, (someone with a love of biology, but a different career path), this story really drove home the fact that Evolution, and our resulting state of being, and is really just a giant Rube Goldberg Machine. A shoe kicks a bucket of marbles, because there was a shoe, and it could kick, and when it kicked that bucket of marbles something advantageous happened.

If a female can delay placental implantation until the embryo can prove it is going to survive, its advantageous for the female. Would it be better to submit the embryo to, I don't know, a talent show, before accepting implantation? Sure. But that wasn't in the tool kit. Delay is. So delay it was.

To paraphrase: Evolution is inelegant, hackish solutions to proximate problems.
posted by fontophilic at 2:25 PM on April 14, 2014 [3 favorites]


Because your uterus doesn't know your ovaries have this medical condition.

Sara, that's precisely what I'm asking - I'm asking, from an evolutionary-biology standpoint, why it didn't shake down that way.

Meaning: Okay, the premise is that, because the creating of an endometrium is a physiological cost to the woman biologically, it's something that evolved to happen only when there was a chance that the woman was going to potentially become pregnant; that's why it doesn't happen when you're breastfeeding, or when you're nutritionally deficient.

So - if you think about it, it would have made even more sense for the hormones that control ovulation to also be the ones to control the creating of an endometrium - because without an ovulation, what's the point. But that's not what happened - the hormones that control ovulation and the hormones that control the creation of an endometrium are different. And thus, your uterus doesn't know what your ovaries are doing.

What I'm asking is, is there any kind of biologic reason that things might have shaken down that way.
posted by EmpressCallipygos at 2:39 PM on April 14, 2014


IANAn evolutionary biologist, but I would guess that it works like that because it's good enough. The energy and resources required to create an endometrium that isn't going to end up being useful isn't enough of a cost to the survival of the species as a whole, and so there was no pressure to select for some other way of doing it. Enough women survived to child-bearing age and bore enough children that this was the system that drowned out any other modifications. There's not no cost, but it's not a big enough one to have been selected against.
posted by rtha at 2:49 PM on April 14, 2014 [1 favorite]


It's probably explained via entropy. In the absence of pressure to change, the pre-existing system keeps on keeping on.

If there was a population bottleneck, and suddenly your particular ovarian condition became the default for most women, and we were still facing population pressures from predators, famine, etc. it's likely that there would be a shakeup in how our reproductive hormones worked.

But in the absence of anything that dramatic, where the upshot is "a few women have periods that aren't strictly necessary, but nobody is dying or anything," things just keep humming along as usual.
posted by Sara C. at 2:51 PM on April 14, 2014


Joe, I'm assuming you're taking the piss when you ask if other species "consciously think about implanting embryos" to make your point. Which is a kinda lame way to have a discussion.

No, I'm being totally serious. She's speaking figuratively, I get that, but what's underlying the figure of speech?

Here's what she said:
The longer the female can delay that placenta reaching her bloodstream, the longer she has to decide if she wants to dispose of this embryo without significant cost.
What is her evidence for the assertion that delaying implantation is advantageous? Is it actually true that implantation may be prevented (i.e., not that it merely fails to occur) and what is the process for determining that? Is there some assessment of the embryo? The mother's environment?

The assertion that there is a lengthy decision-like process leading up to the implantation of human embryos is huge. Is it true? I have no idea, but if it were true then wouldn't it be used in morning after pills and so forth? Perhaps it is and I just don't know, but coyly saying "the female ... has to decide if she wants to dispose of this embryo" seems to elide some very fundamental assumptions about fertility.
posted by Joe in Australia at 6:35 AM on April 16, 2014


I apologize for my assumptions then.

I think you might be putting too much emphasis on a difference between "preventing" and "failing to happen". There is no difference evolutionarily speaking. No fetus implanted, no genes passed on, do not pass go, do not collect $200.

When she says "the female" she means the mechanisms of her biology. The "decisions" are natural selection, extrapolated over millions of years. "Failing to occur" happens for a reason. And the "reason" is the happenstance of evolution.

The delay of implantation is advantageous because it is a "test" that the fetus must pass. If you make the endometrium more difficult to implant in, then only the strongest embryo's placenta will attach. Should a fetus have some kind of defect, it won't be as able to implant, the mother won't expend unnecessary energy, time and resources bringing a baby to term that would die.

As many as 1 in 3 pregnancies in women who know they are pregnant end in miscarriage by 20 weeks. The number is far higher when you account for spontaneous abortions/miscarriage before a missed period or pregnancy is detected. (This number is also pretty hard to observe.) This isn't because of some women with fertility problems jacking up the numbers. This is what normal looks like.

Lots of these miscarriages/failure to implant are of embryos/fetuses with defects but some are healthy too. The mechanisms of biology at work in the female place a bias towards ending early pregnancies or preventing them from happening before more resources are expended on non-viable children. The female gets to "decide" to fold her cards early with minimal risk and minimal expenditure.

Morning after pills/emergency birth control do use this basic mechanism. Implantation takes up to 7-12 days after ovulation. If you can trigger menstruation before that window of time is up, you can prevent pregnancy.

So yeah, having babies is pretty fucking cut throat. A narrative of an invading foreign body is perhaps more apt than a cuddly uterus making a fluffy nice bed for Baby.
posted by fontophilic at 7:13 AM on April 16, 2014 [1 favorite]


Babies might cry so much at night in order to delay their parents having more kids to increase their survival chances, says evolutionary biologist.
posted by Eyebrows McGee at 5:38 PM on April 16, 2014


I feel like that story (and the research) is unnecessarily "wink-wink-if-you-know-what-we-mean" about it, when it could just as easily be stated "Babies might eat so frequently in order to keep their mothers from ovulating to delay having more kids to increase their survival chances...".
posted by Etrigan at 6:01 PM on April 16, 2014


I have this theory about why so many evolutionary psychologists are male. It's an adaptation that derives from the behavior of hunter-gatherers. Males were more typically hunters, and traveled widely seeking food. They would often come into contact with other groups of humans, and they used myths of common origin to establish a basis for cooperation. These shared myths drove evolutionarily-costly ritual behavior, but they were advantageous because they reduced inter-tribal conflict.

In contrast to this male behavior, women stayed slower to home, foraging and looking after babies. There was no reason for them to develop these sorts of myths, so the costs outweighed the benefits. This was a classic situation to force a sex-linked adaptation that persists today. So evolutionary psychology isn't actually true; it's just that men are primed to develop evolutionary "just-so" stories and predisposed to believe them.
posted by Joe in Australia at 6:44 PM on April 16, 2014 [3 favorites]


Babies might cry so much at night in order to delay their parents having more kids to increase their survival chances, says evolutionary biologist.

I've been telling my friends this for years, and I've been sorely tempted to mention it in any number of difficult baby threads in AskMe, but all it ever accomplished was to make my friends angry and disgusted with me.
posted by jamjam at 10:26 PM on April 16, 2014


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