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Menstruation is just blood and tissue you ended up not using

The views expressed are those of the author and are not necessarily those of Scientific American.


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I love science, and I love the scientific method. I think that the scientific method is one of the most useful ways of knowing out there. I have devoted my life not only to the study of the science of human evolution and female reproductive physiology, but to increasing science appreciation and literacy in the general public.

So why am I always criticizing it?

Two reasons. First, the process of science can be biased by who performs it.

Second, the results and implications of scientific research can be biased by who tells it.

To demonstrate this, I’m going to tell you a little story about a menstruating nurse.

* * *

Dr. Bela Schick, a doctor in the 1920s, was a very popular doctor and received flowers from his patients all the time. One day he received one of his usual bouquets from a patient. The way the story goes, he asked one of his nurses to put the bouquet in some water. The nurse politely declined. Dr. Schick asked the nurse again, and again she refused to handle the flowers. When Dr. Schick questioned his nurse why she would not put the flowers in water, she explained that she had her period. When he asked why that mattered, she confessed that when she menstruated, she made flowers wilt at her touch.

So, rather than consider the possibility that the nurse was offended that her skills and expertise were being put to use to put someone else’s flowers in water, Dr. Schick decided to run a test. Gently place flowers in water on the one hand… and have a menstruating woman roughly handle another bunch in order to really get her dirty hands on them:

An image of the menotoxin flowers experiment. One vase of flowers is wilted while the other is not.

An image of the menotoxin flowers experiment. One vase of flowers is wilted while the other is not.

The flowers that were not handled thrived, while the flowers that were handled by a menstruating woman wilted.

This was the beginning of the study of the menstrual toxin, or menotoxin, a substance secreted in the sweat of menstruating women.

* * *

This story begins far before Dr. Bela Schick and his menstruating nurse. Because the kind of bias that produces a doctor who can believe that menstrual toxins exist, and launch a field of study on them based on some wilted flowers (if the story really did happen the way he tells it), did not come from one man alone. The cultural conditioning that has produced the idea that women are dirty, particularly during menses, is quite old. The Old Testament of the Bible claims that women are unclean when they menstruate, and menstrual huts exist in some cultures to separate out menstruating women from the rest of their group.

But some mark the beginning of our misunderstandings of female physiology in European-derived cultures with one book in particular written in the thirteenth century – De Secretis Mulierum, The Secrets of Women. This book was written by a man who claimed to be the monk Albertus Magnus, but was most likely an impersonator (which is why most call the author of De Secretis Mulierum pseudo-Albertus Magnus, or pseudo-Albert).

So here are some winning quotes from this book, which was considered a premier text for several centuries, even though it is likely pseudo-Albertus Magnus never treated women and based much of his work on having dissected a female pig:

“Woman is not human, but a monster.”

Menstruating women give off harmful fumes that will “poison the eyes of children lying in their cradles by a glance.”

Children conceived by menstruating women “tend to have epilepsy and leprosy because menstrual matter is extremely venemous [sic].”

De Secretis Mulierum went through at least eighty editions over several centuries (Rodnite Lemay 1992). While it was not a strictly medical text, it is clear that it was both popular and influential. Do doctors refer to De Secretis Mulierum today? Of course not. But this book, to me, represents a broader cultural understanding that menstruation is dirty, that women are powerful, mysterious, dangerous, and sub-human.

* * *

This figure is from a study that did not support the existence of the menotoxin, as there were not significant differences in phytotoxicity in the blood of menstruating and non-menstruating women, under what these authors argued were more rigorous experimental standards (Freeman et al. 1934). Only paper I could find with repeatable methods and data, and interestingly, the only one that rejects the menotoxin hypothesis.

This figure is from a study that did not support the existence of the menotoxin, as there were not significant differences in phytotoxicity in the blood of menstruating and non-menstruating women, under what these authors argued were more rigorous experimental standards (Freeman et al. 1934). Only paper I could find with repeatable methods and data, and interestingly, the only one that rejects the menotoxin hypothesis.

So back to those menotoxins. Dr. Schick decided there was something nasty in the sweat of menstruating women. Others took up the cause. Soon, people were injecting menstrual blood into rodents, and those rodents were dying (Pickles 1979). Others were growing plants in venous blood from menstruating women to determine phytotoxicity; the sooner the plants died, the higher the quantity of menotoxin assumed in the sample.

What’s worse, the presence of the menotoxin in the female body began to expand beyond menstruation. Any woman who was post-menarcheal and pre-menopausal could be found to have the menotoxin in her system. She could not escape it: some reported that the menotoxin could be found in a woman’s menstrual blood, but also venous blood, sweat, and breastmilk. One case study reports that a mother gave her child asthma because she was menotoxic during pregnancy (Perlstein and Matheson 1936), and several contended that colic was caused by menotoxin in breastmilk (Ashley-Montagu 1940; Perlstein and Matheson 1936).

Not only did the idea of the menotoxin become a ubiquitous menace around any reproductively-aged woman, it began to explain pathology. So the menotoxin, which first was an explanation for the presence of menstruation in women, became a way of diagnosing women as ill… and again, since now all reproductively-aged women could secrete it from any bodily fluid at any time, the state of being female essentially made one pathological.

Soon the idea that the menotoxin indicated specific illnesses began to take hold.

“Dr. Schick and I discussed the possibility that the adult female diabetic out of control, the depressed adult female psychotic, and the adult female in the premenstrual phase secreted some common substance in their sweat.” (Reid 1974)

Here, you see premenstrual women compared directly with two pathological conditions: diabetes and psychosis. And all of these relationships, between menstruation and colic, asthma, wilted flowers, are largely observation, case reports, or poorly controlled experiments. When studies do not support the idea of the menotoxin, as with Freeman et al (1934) and two studies cited by Ashley-Montagu (1940) that were not in English, each get dismissed as outliers (even though in Labhardt’s case from Ashley-Montagu, the sweat of men was often as toxic as that of menstruating women).

And this is where I bring it back to my first two points about bias, that science can be biased by the cultural conditioning of those who perform it, and those who tell it. The people who studied the menotoxin really, really wanted to believe in it, to the point that they would ignore negative results and overstate the power of their anecdotes and case studies. The study of the menotoxin spans at least sixty years, maybe ninety depending on which references you consider legitimate, debated in Lancet letters to the editor, and published in several medical journals.

I wish I could say that the menotoxin was dead. But several contemporary hypotheses about the evolution of menstruation still in some way reflect the thinking that menstruation, if not women, is dirty and serves the purpose of expelling toxicity. Clarke (1994) proposed menstruation as a mechanism to expel unwanted embryos. Margie Profet (1993) argued that menstruation helped to expel sperm-borne pathogens, which made men the dirty party. This is why it’s important to recognize that many ideas that seem intuitive to us at first derive from cultural conditioning and bias. (My favorite book on the topic is Emily Martin’s The Woman in the Body (1980).)

Thankfully, the most accepted idea is that menstruation did not evolve at all, but is a byproduct of the evolution of terminal differentiation of endometrial cells (Finn 1996; Finn 1998). That is, endometrial cells must proliferate and then differentiate, and once they differentiate, they have an expiration date. Ovulation and endometrial receptivity are fairly tightly timed, to the point that the vast majority of implantations occur within a three-day window (Wilcox et al. 1999). So it’s not that menstruation expels dangerous menotoxins, but rather that menstruation happens because the endometrium needs to start over, and humans in particular have thick enough endometria that we can’t just resorb all that blood and tissue.

It’s time to dump the idea that menstruation is dirty. It’s blood and tissue that you ended up not using to feed a baby, and that’s all.

 

*I want to credit one of my favorite courses from college for much of the content related to pseudo-Albertus Magnus: Women’s Studies 106a, Bodies and Boundaries, taught by Prof. Katherine Park at Harvard University. I have no idea if it’s still taught (*cough* it’s been ten years *cough*), but if you are a student there, you are missing out if you don’t take a class with her.

**If you are a historian of science and would like to talk over this material with me, let me know! It would make for a great paper.

References

Ashley-Montagu M. 1940. Physiology and the Origins of the Menstrual Prohibitions. The Quarterly Review of Biology 15(2):211-220.

Clarke J (1994). The meaning of menstruation in the elimination of abnormal embryos. Human reproduction (Oxford, England), 9 (7), 1204-7 PMID: 7848450

Finn CA (1996). Why do women menstruate? Historical and evolutionary review. European journal of obstetrics, gynecology, and reproductive biology, 70 (1), 3-8 PMID: 9031909

Finn CA (1998). Menstruation: a nonadaptive consequence of uterine evolution. The Quarterly review of biology, 73 (2), 163-73 PMID: 9618925

Freeman W, Looney JM, and Small RR. 1934. Studies on the phytotoxic index II. Menstrual toxin (“menotoxin”). Journal of Pharmacology and Experimental Therapeutics 52(2):179-183.

Martin E. 1980. The woman in the body. Beacon Press, Boston.

Perlstein M, and Matheson A. 1936. Allergy Due to Menotoxin of Pregnancy. Archives of Pediatrics and Adolescent Medicine 52(2):303.

Pickles VR (1979). Prostaglandins and dysmenorrhea: Historical survey. Acta Obstet Gynecol Scand Suppl 87:7-12.

Profet M (1993). Menstruation as a defense against pathogens transported by sperm. The Quarterly review of biology, 68 (3), 335-86 PMID: 8210311

Reid HE (1974). Letter: The brass-ring sign. Lancet, 1 (7864) PMID: 4133673

Rodnite Lemay H. 1992. Womens Secrets: A Translation of Pseudo-Albertus Magnus’ de Secretis Mulierum with Commentaries: State University of New York Press.

Wilcox AJ, Baird DD, & Weinberg CR (1999). Time of implantation of the conceptus and loss of pregnancy. The New England journal of medicine, 340 (23), 1796-9 PMID: 10362823

Kate Clancy About the Author: Dr. Kate Clancy is an Assistant Professor of Anthropology at the University of Illinois. She studies the evolutionary medicine of women’s reproductive physiology, and blogs about her field, the evolution of human behavior and issues for women in science. Find her comment policy here. Follow on Twitter @KateClancy.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. nthmost 5:22 pm 09/9/2011

    Really fun read. The ability of people who swear by their devotion to reason and logic to convince themselves of the existence objects not found in actual evidence never ceases to amaze me.

    Link to this
  2. 2. seamonkey 6:15 pm 09/9/2011

    I wonder this pervasive belief that menstruating women are “dirty” or “toxic” is based on the idea that they have lost, however temporarily, what some see as the primary purpose of womanhood. Infertile women have also been treated as untouchable pariahs in many cultures as well.

    Now that I think about it, the concept of the “menotoxin” fits right into the history of modern science, if you think about it. The language and practices of science gave people (i.e., white men) the tools to quantify and pathologize the traits that they found distasteful or disgusting in women and “lesser” races. And because menstruation, unlike other waste disposal processes, is limited to reproductive-aged women, it’s that much weirder, that much more disgusting, and therefore incomprehensible without placing it in a dysfunctional context.

    Still can’t shake my personal beliefs that menstruation *is* gross. But I’ve been at war with my uterus since I was 10, so that’s definitely how the whole thing started. I look forward to your ladybusiness posts because they remind me that not every woman’s uterus is out to get her.

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  3. 3. macphile 7:56 pm 09/9/2011

    seamonkey: I’m not sure anyone’s saying it’s not gross; just about everything that the body expels could be considered “gross.” There’s a difference between gross and pathologically unclean or inferior, though.

    These old ideas die hard, like the common joke about not trusting anything that bleeds for days and doesn’t die. Of course, I’ve also seen the extreme examples of women who really “celebrate” this event. There must be a middle ground somewhere between considering it unclean and sharing it with others. At least, I really hope there is.

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  4. 4. mgmcewen 12:22 am 09/10/2011

    I first encountered this lovely ‘menotoxin’ idea among raw foodists. You see, multiple studies have found that a diet of nothing but raw fruits, vegetables, and nuts leads to amenorrhea for many women. In order to explain this away, some of the raw foodists have come up with a rather disturbing explanation http://curezone.com/blogs/fm.asp?i=982094:

    “So why do most women in our society experience such bleeding episodes? A clue comes from animals. Wild relatives of the domestic animals do not menstruate. They have mating seasons – called heat, rut or estrus – which usually happen only once or twice a year. At this time the females ovulate and their genital organs become slightly congested and moistened with mucus in preparation for mating and likely conception (2:36-37). In the wild, nature has tied ovulation closely to the availability of food, and in times of scarcity estrus may not occur.

    What is this connection between diet and menstruation? What is actually happening in the womb to make it hemorrhage? A poor diet, with significant excesses of some nutrients and deficiencies of others, causes a breakdown in the transport of nutrients to and wastes from the cells throughout the body. Blood vessels become more porous, allowing fluids to seep out between the cells of the tissues creating congestion. Residues from improper digestion contribute to a state of body-wide poisoning, or toxemia. Dietary deficiencies and related hormone imbalance combine to increase the fragility of capillary walls so that under the increased pressure of unnatural congestion they rupture when the womb contracts to slough off the unneeded endometrial tissues after the unfertilized egg has passed through.”

    Yikes…

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  5. 5. arunan 12:55 am 09/10/2011

    But, do the ones evolutionary closer to us, like the Chimp or any other animal for that matter, have anything close to bleeding, during its reproductive cycle?

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  6. 6. Kate Clancy in reply to Kate Clancy 3:04 pm 09/10/2011

    I do think it’s good to distinguish between gross and pathologically unclean… though maybe instead of gross I would just call them all waste products. And holy crap Melissa, I don’t even know where to begin with that one. What a mess of misinformation!

    arunan, there are plenty of other animals who menstruate, and chimps and bonobos and, I think, gorillas, have all been observed menstruating. But again, the more important ancestral condition to figure out is endometrial cycling. How often, why, and how thick is the endometrium?

    Link to this
  7. 7. Alvin Phee 4:04 pm 09/10/2011

    Blood generally is dirty right? Would you want blood on your jeans when you go out and walk around your neighbourhood?

    I am guessing no.

    Link to this
  8. 8. twiffy 12:24 am 09/11/2011

    An amusing article on some sad past forays into pseudo-science. However, you do seem rather fixated on the idea that menstruation “ought” not to be dirty. Why would this be the case?

    Menstruation, in that it expels unused material, superficially resembles urination and defecation, which incidentally occur in very proximate regions. Intuitively I agree with the idea that menstruation is the expulsion of unused material, rather than the expulsions of toxins, since the former explanation is more parsimonious and the latter raises new questions. But the toxin hypothesis is not a priori unreasonable; nor does it seem inherently sexist. I don’t see why it’s “thankful” that “expelling unwanted material” is the dominant modern scientific view. Surely the unsubstantiated belief in menotoxins was a product of bias more than a generator. And what about the fact that many women experience mood swings and physical discomfort during PMS? Is this “unfortunate” because it causes some males to joke? It seems to me that we should bemoan any residual sexism, rather than any fact or fiction that is targeted by sexists.

    There are many things about the female body that differentiate it substantially from the male body, and none of these things is justification for sexual discrimination. What difference, then, if menstruation is the expulsion of toxic material, or just non-toxic waste? Menstruation, urination, defecation, expectoration, any release of unnecessary bodily products — by either gender — is culturally unpleasant to us, and that isn’t unreasonable. Sexism based on that perception is unreasonable, but thanks to *proper* science, and the improved standard of education, that seems to no longer occur.

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  9. 9. kclancy 8:48 am 09/12/2011

    Twiffy, here is the section where I write about the sexism of the menotoxin:

    “What’s worse, the presence of the menotoxin in the female body began to expand beyond menstruation. Any woman who was post-menarcheal and pre-menopausal could be found to have the menotoxin in her system. She could not escape it: some reported that the menotoxin could be found in a woman’s menstrual blood, but also venous blood, sweat, and breastmilk. One case study reports that a mother gave her child asthma because she was menotoxic during pregnancy (Perlstein and Matheson 1936), and several contended that colic was caused by menotoxin in breastmilk (Ashley-Montagu 1940; Perlstein and Matheson 1936).

    Not only did the idea of the menotoxin become a ubiquitous menace around any reproductively-aged woman, it began to explain pathology. So the menotoxin, which first was an explanation for the presence of menstruation in women, became a way of diagnosing women as ill… and again, since now all reproductively-aged women could secrete it from any bodily fluid at any time, the state of being female essentially made one pathological.

    Soon the idea that the menotoxin indicated specific illnesses began to take hold.

    “Dr. Schick and I discussed the possibility that the adult female diabetic out of control, the depressed adult female psychotic, and the adult female in the premenstrual phase secreted some common substance in their sweat.” (Reid 1974)

    Here, you see premenstrual women compared directly with two pathological conditions: diabetes and psychosis. And all of these relationships, between menstruation and colic, asthma, wilted flowers, are largely observation, case reports, or poorly controlled experiments. When studies do not support the idea of the menotoxin, as with Freeman et al (1934) and two studies cited by Ashley-Montagu (1940) that were not in English, each get dismissed as outliers (even though in Labhardt’s case from Ashley-Montagu, the sweat of men was often as toxic as that of menstruating women).”

    Link to this
  10. 10. AScientist 1:01 pm 09/12/2011

    Sounds like the sexist “science” that presumes men are unfit parents in divorce, and that men are never victims of domestic violence.

    When will SA do a series on this large body of sexist pseudoscience?

    Link to this
  11. 11. kclancy 4:02 pm 09/12/2011

    Well, AScientist, this is a blog, so SA has no control over my content (you may want to read Bora’s “Blogs: Face the Conversation” post for more on this). You are always welcome to suggest people for the Guest Blog, or topics, by contacting SA.

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  12. 12. poihths 10:54 pm 09/12/2011

    Taking the position that menstruation somehow did not evolve (“Thankfully, the most accepted idea is that menstruation did not evolve at all, but is a byproduct of the evolution of terminal differentiation of endometrial cells”) seems very odd to me. Or at least very oddly phrased. Surely anything directly associated with any evolutionary process is itself a part of that process. Menstruation is a part of concealed estrus, the development of which is certainly an interesting aspect of human evolution.

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  13. 13. kclancy 11:11 pm 09/12/2011

    Actually, this is one of the cool things about evolution, that there can be byproducts. That is, one thing is selected for, and the other thing just happens to come along for the ride because it is associated with the adaptive trait. So menstruation itself didn’t evolve, but endometrial cycling and thick endometria did.

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  14. 14. Diesel67 1:48 am 09/13/2011

    This just goes to show that Tanakh (what you call the Old Testament) must be studied in Hebrew. A menstruating woman becomes temei’ah (adjective) and acquires tum’ah (noun). Tum’ah is also acquired from contact with the dead and with non-kosher animals, and also from childbirth and normal marital sex. A man who is tamei or a woman who is temei’ah may not enter the Temple. Today (i.e. since 70 C.E.) there is no Temple, and the only tum’ah with any significance is that a menstruating woman may not cohabit with her husband until the flow ceases and she undergoes ritual immersion. Tum’ah connotes a kind of spiritual contamination beyond human understanding; we accept it on faith. Somebody long ago translated tamei (fem. temei’ah), perhaps via Greek, as “unclean” or “dirty.” Hence menstruation and the sex act (along with words that describe it) became “dirty,” leading to ongoing neurosis and guilt surrounding both. Jews never physically segregated menstruating women from the general population. That distinction belonged to the metzora. That word is mistranslated as “leper,” but that, says Chaucer, is another tale.

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  15. 15. kclancy 7:34 am 09/13/2011

    Very interesting. Thanks for sharing Diesel!

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  16. 16. Geopelia 10:05 am 09/13/2011

    Menstruation would be uncommon among our primitive ancestors. Females would either be pregnant or breastfeeding for most of their short fertile lives.
    Once our ancestors learnt to speak, something unusual and frightening would give rise to all sorts of rumours and legends.
    There were still some weird ideas around among working class girls as late as the 1940s.

    Link to this
  17. 17. madaboutmenses 8:49 pm 11/7/2011

    I agree with “poihths” that to claim that menstruation “did not evolve at all” is bizarre, if not oddly and misleadingly phrased, regardless of what one thinks about the existence of menstruation.
    Does Professor Clancy mean to imply that a supernatural agency intervened in the otherwise naturalistic process of evolution and bestowed upon humanity and some other mammals the “non-evolved” trait of menstruation? Much as many people today still believe that “God” intervened at the end of the process of evolution and bestowed upon humanity a non-evolved “soul”? I think not, but to the casual reader, this is what she seems to have written. Presumably, Professor Clancy merely means the more mundanely materialistic claim that menstruation is not an adaptation that has evolved directly through the process of natural selection. She thinks that menstruation is merely a byproduct – fair enough, some scientists today do think this, perhaps in way not dissimilar to those scientists who used to believe in menotoxin – but non-adaptive characters also evolve, just not as a direct consequence of natural selection, as anyone familiar with the copious anti-adaptationist writings of Stephen Jay Gould will appreciate. It is not apparent that there are many evolutionary biologists who think that because a trait is non-adaptive it “did not evolve”.
    In her insistence that “menstruation itself didn’t evolve”, Professor Clancy seems to be confusingly conflating two different terms for rhetorical effect, but the term “evolution” is not synonymous with the term “natural selection”: the latter is but one of the processes through which the former occurs. The word “evolution” has many connotations, and interpretations, but from the narrowest gene-centric views of evolution as “merely changes of gene frequency in a gene pool”, to the broadest conceptions of evolution as “the entirety of material existence unfolding from the Big Bang onwards”, the term “evolution” does not equate with “natural selection”. Assuming that one is a naturalist, and not appealing to a deus ex machina or some other such intervening supernatural entity, byproducts also evolve, just not directly through natural selection. Indeed, in a naturalist framework, all the traits of an organism “evolve”, whether they are adaptations or byproducts or something else – and regardless of the process(es) that brought them into being.
    Professor Clancy’s claim that menstruation did not evolve also misrepresents Finn (1998), who understood that evolution and natural selection are not synonyms, and claimed no such thing: he wrote that menstruation “needed no adaptive value to evolve” (p. 163). In his own words, therefore, Finn clearly believed that menstruation was a byproduct and that it had evolved, just that it had not done so directly through the process natural selection.
    In summary, it’s okay to claim that “a trait has not evolved by natural selection”, but, within a naturalistic framework, it’s plain wrong – indeed, nonsensical – to claim that “a trait has not evolved, period”. Within a naturalistic framework, everything about life has evolved, just not necessarily as a direct consequence of natural selection. As Professor Clancy says, evolution is indeed cool, but enthusiasm – and popularization – is not a sufficient justification for conceptual carelessness.

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  18. 18. kclancy 9:43 am 11/8/2011

    Madaboutmenses, endometrial cycling evolved. Menstruation is a byproduct of the fact that in some species there is more blood and tissue left over than can be absorbed by the body — the rest comes out as menstruation. This isn’t a value judgment on menstruation, this doesn’t imply it isn’t natural, and it doesn’t imply it isn’t important to the broader evolutionary framework around understanding female reproductive physiology. You’re running away with your own ideas here.

    I think you are the one who might be a little careless, my friend. Also, this is a comment on a blog. So, you know, feel free to talk to me directly.

    Link to this
  19. 19. madaboutmenses 4:37 pm 11/8/2011

    Kate: No, I don’t think I am running away with my own ideas here. I am sorry if my previous blog caused personal offence – it was not intended to do so – but you have not answered our criticism, and I still do not understand why you think it is acceptable to claim that byproducts do not evolve. I never thought that you thought menstruation was anything other than a natural phenomenon – but that is my point… Haven’t all natural phenomena “evolved”? You seem to believe not, which some of us find odd. Even Finn believed that byproducts evolved. If you are genuinely committed to increasing science appreciation and literacy in the general public, please define for us what you mean by the word “evolve” and explain to us why you think that it is not appropriate to describe byproducts as evolving when most evolutionary biologists apparently think otherwise. We don’t understand your position. On matters epistemological, you seem to be very certain of your own objectivity, which seems paradoxical given that you believe that other scientists are not. Why are you different from other scientists? Do you think that the scientists who believed in menotoxin felt any less certain of their own objectivity than you do? I will leave it to any readers of your blog to decide for themselves which one of us – or neither or both – is being careless…

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  20. 20. kclancy 12:09 am 11/9/2011

    madaboutmenses: So, here’s the thing. I don’t think a comment thread in a blog post about the history of the study of menotoxins is really the place to expound on the differential merits of whether byproducts evolve or not, whether this makes one an adaptationist or not, etc etc. Add to that your tone, which is hard to read, even with a generous eye, as anything but sexist douchebaggery, and I just didn’t feel like getting into it.

    And so my response to you was hasty.

    So, since apparently it is so important to you that I take time out of my evening to address your questions, even though you already seem to know the answers to your own questions:

    -Did Finn believe menstruation evolved? Perhaps, but he’s the one who first said it was a non-adaptive consequence of uterine evolution.

    -The term “evolve” in its most general sense means change over time. I suppose that means menstruation has evolved. However I find it important to parse out where natural selection acts, which in this case in on the endometrial cycle of growth, decidualization and regression. On a blog for layreaders, this seems like a decent distinction to make, and the way I made it is not necessarily inconsistent with “most evolutionary biologists,” but actually reflects my own training. Feel free to look up my credentials.

    -I am not certain of my objectivity and have in the past and continue to welcome constructive criticism, here on the blog, in my teaching, and in my research. I am certain, however, that I occasionally attract commenters who want to swipe at me in a way that almost always questions my abilities, my credentials, or my expertise. I wonder why that is?

    -I don’t think I can comment on the state of mind of researchers from several decades ago, but based on their tone and use of language, they did seem fairly certain in the existence of the menotoxin in sweat and menses.

    Now that I have answered your excessively rude questions, I won’t be responding to any more. But I won’t shut you down. Feel free to carry on about how great you are.

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  21. 21. madaboutmenses 3:06 am 11/9/2011

    Kate: Yes, the precise and careful use of language is important to me. So, thank you for taking the time to reply, even if the response was not exactly gracious. Perhaps I should defend myself against your accusations and innuendo, but again I think our blog entries speak for themselves. Take care.

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