Tuesday, July 31st 2012
Thursday 26th July saw the launch of SciLogs.com, a new English language science blog network. SciLogs.com, the brand-new home for Nature Network bloggers, forms part of the SciLogs international collection of blogs which already exist in German, Spanish and Dutch. To celebrate this addition to the NPG science blogging family, some of the NPG blogs are publishing posts focusing on “Beginnings”.
Participating in this cross-network blogging festival is nature.com’s Soapbox Science blog, Scitable’s Student Voices blog and bloggers from SciLogs.com, SciLogs.de, Scitable and Scientific American’s Blog Network. Join us as we explore the diverse interpretations of beginnings – from scientific examples such as stem cells to first time experiences such as publishing your first paper. You can also follow and contribute to the conversations on social media by using the #BeginScights hashtag.
Over the course of my training to become a biological anthropologist with a specialty in women’s reproductive ecology and life history theory, or ladybusiness expert , I have learned a lot about miscarriage. Only it wasn’t miscarriage, it was spontaneous abortion. Except that some didn’t like the term spontaneous abortion and used intrauterine mortality (Wood, 1994). Or fetal loss. Fetal loss is probably the most common.
There is also pregnancy loss (Holman and Wood, 2001). You can use that term, too. Oh, or a-conceptions (a for abortion), compared to l-conceptions (l for live birth) (Wood, 1994).
A large number of these fetal losses are before or close to the time of implantation. For many of those, unless the mother is measuring her hCG levels via a pregnancy test because she’s trying (or not) to get pregnant, she is at most going to notice a day or two longer cycle, maybe a slightly longer but lighter period. Most women with very early fetal loss will never even know they were pregnant.
So fetal loss, while important to my research, never seemed like a big deal to me from a cultural or emotional perspective. And there are a lot of ways to talk about it, plenty of terms to choose from.
They’re all inadequate.
* * *
The first time I talked to someone about her miscarriage was only a week or two after she told me she was pregnant. “I know the convention is to wait twelve weeks, but it seems silly to keep it a secret that long.” I was maybe twenty five, still uninterested in children enough to be perplexed that she wanted one, but thrilled for her. We hugged over the stick shift of her car.
Then, later, she shares that the fetus hadn’t grown since the last ultrasound, and almost certainly was dead. We hug again, and I don’t know what to say. I never found out if she had to get a D&C or whether she miscarried on her own. A few days later, we’re in an important meeting in a local cafe. She hasn’t gotten some key things done. I don’t know what to do: is the right thing to do to push her and act like nothing’s happened, or give her time to grieve? Asshole that I was, I ask her about her piece of the work.
She pauses. “I just feel… lost.”
And she begins to cry.
The third person in our meeting, our boss and friend, says, “We are not pushing a woman who just had a miscarriage.” And so the three of us just sat in that cafe, in the uncomfortable semi-silence of trying to hold back tears. And none of us knew what to do next.
* * *
A few years later, I found myself a very different person, no longer remotely perplexed by the idea of wanting a child. I loved the smell and feel of babies. I wanted to carry a baby in my belly. And thankfully, after a little help, I was pregnant.
Shortly after implantation, I had about a week of almost continuous menstrual cramps. I felt as though I would get my period at any moment, and spent almost every day semi-working from home, in a panic that I was about to miscarry. In a follow-up call with my nurse, she told me the cramping was actually normal in a healthy pregnancy and that my hCG concentrations – that’s the signal the fetus sends to the mother to let her know it’s there – were quite high. For about the millionth time that week, I sobbed like a baby.
For the rest of that first trimester I was so nauseous that I could barely eat. I lost six pounds, unheard of for a big eater like me. Yet as awful as I felt, I relished every second of that nausea, because I knew it meant the fetus was most likely alive and thriving.
As far as I know, I have never miscarried.
Miscarriage still terrifies me.
* * *
There was the woman who was having twins, until one stopped growing. There was the one who didn’t tell anyone until she was twenty weeks into her next pregnancy for fear of jinxing the one that seemed to be sticking. There are the ones where the woman shrugs it off, where tears prick at the corners of her eyes, where the shoulders slump even as she tries to smile.
The beginning of pregnancy, which if you want to be pregnant is a joyous moment, is also fraught with tension. Most of the advice newly pregnant women receive is about denial: no caffeine, no alcohol, no raw fish or raw milk or tuna or swordfish or deli meat or unwashed fruits or vegetables. No cleaning kitty litter. Don’t let your heart rate get too high. No heavy lifting. Don’t gain too much weight, or too little.
And don’t stress out, of course. It can hurt the baby.
The majority of factors that influence fetal loss are likely out of the mother’s control, meaning they have little to do with any of the above factors. Genetic abnormalities comprise the majority of very early fetal losses, as far as we can tell. These are embryos that probably would not develop properly into fetuses. When this happens, the body can reject an ill-formed embryo, or the embryo itself simply fails to grow. But this is a mechanism we know very little about.
Maternal age also matters, as the risk for fetal loss increases with age (more so after thirty-five years). There are at least three factors contributing to this: the eggs, the ovaries, and the endometrium. Aging eggs probably contribute to the genetic abnormality issue. And aging ovaries and an aging endometrium could have an increasingly hard time supporting a fetus, and so lower hormones or a thinner or less-nourished endometrium could help explain some fetal losses (there’s a lot more I could say on this, so let’s just assume I’ll elaborate in a future post). For instance, low progesterone concentrations, which is the hormone the ovary and then placenta secretes to maintain pregnancy, is associated with miscarriage risk (Arck et al., 2008). After thirty, progesterone concentrations begin to decline, but are still in the peak range through about thirty five years of age (Ellison et al., 1993; O’Rourke et al., 1996). Another study found that maternal age decreases the chance of conception, but donor’s age increased the risk of miscarriage in women undergoing IVF (Levran et al., 1991). These are women who are undergoing progesterone supplementation, so my best guess is that their endometria become less responsive to hormonal control as they age (Clancy, 2009). Yet, a mother cannot control her own age and can only partially control her chances of getting pregnant.
Figure 1. The straight line represents the increase in the number of fetal losses over a woman's lifetime, the curved line her ovarian hormone concentrations.
The controllable factors still probably have little to do with all the things a pregnant woman is supposed to avoid during pregnancy. Across a few clinical samples, researchers have found that spontaneously conceiving, underweight women are at a greater risk for miscarriage (Arck et al., 2008), overweight and obese women are not (Turner et al., 2010), but obese women with recurrent (three or more) miscarriages are (Metwally et al., 2010) and overweight women conceiving with IVF are as well (Dokras et al., 2006). There is a sweet spot that reduces risk the most in terms of maternal weight. Yet weight is a potent mix of genetics, socioeconomic status, and nutritional status that rests on top of the supposed biggest culprit of willpower.
Of all the things a pregnant woman is supposed to avoid, stress is the one with a growing body of evidence in its favor. One prospective study – meaning they began to study participants before they were pregnant – found that women from a rural Mayan sample who experienced very early fetal loss had higher cortisol concentrations (Nepomnaschy et al., 2006, who happens to be a collaborator on a different project). Cortisol is often mistakenly called a “stress hormone” in our popular interpretation of psychological stress. But cortisol is a signal of physiological, or constitutional stress. It indicates that our hypothalamic-pituitary-adrenal axis has been activated, which means the body is at minimum trying to allocate towards maintenance effort or the stress response. So this study – one of the first of its kind and, I think, performed to a high technical standard – shows us that freeliving women who happen to have miscarriages also happen to have an elevated stress response. Whether that is causal is unclear.
Fig. 2. From Nepomnaschy et al 2006.
In efforts to get at stress from a different angle, some researchers have explored inflammation, which I review in a chapter in Building Babies, out in September (Clancy, 2012). Systemic inflammation, often measured via C-reactive protein (CRP), is correlated with psychological stress (Danese et al., 2009; Miller et al., 2005; Miller et al., 2002). And there are indicators that both systemic and local inflammation impact pregnancy. But here’s the funny thing: you actually need some inflammation to support pregnancy. So very high and very low concentrations of CRP are both correlated with an increased risk of early fetal loss (Sacks et al., 2004). There’s that sweet spot again.
To make it all extra confusing, many of these studies employ different methods to understand fetal loss. Prospective or retrospective study designs, different ways of determining pregnancy, different cutoffs for what constitutes early fetal loss, very early fetal loss, and so on. So actual estimates of how much these factors influence fetal loss varies. The safest overall estimate for any given pregnancy is probably about 30%, though one study, even with conservative estimates of pregnancy and fetal loss puts it at 60% (Holman and Wood, 2001). This means, though, that for every two live births a woman has, she’ll have at least one miscarriage. And that’s not because she’s done anything in particular to deserve it.
The randomness, the lack of control, the fact that it can even happen a few times in a row in a woman and just be poor luck, that is the terror of miscarriage. Trying to give it a different name, or restricting women’s intake or movements, these are just ways to try and establish control in something largely uncontrollable.
So, beginnings are wonderful. But beginnings can be brutal, too. And there are no words I can say that will make the experience of miscarriage less raw or inexplicable.
References
Arck PC, Rücke M, Rose M, Szekeres-Bartho J, Douglas AJ, Pritsch M, Blois SM, Pincus MK, Bärenstrauch N, Dudenhausen JW. 2008. Early risk factors for miscarriage: a prospective cohort study in pregnant women. Reproductive biomedicine online 17(1):101-113.
Clancy KB. 2012. Inflammation, reproduction, and the Goldilocks Principle. In: Clancy KB, Hinde K, Rutherford JR, editors. Building Babies: Primate Development in Proximate and Ultimate Perspective. New York: Springer.
Clancy KBH. 2009. Reproductive ecology and the endometrium: physiology, variation, and new hypotheses. Yearbook of Physical Anthropology 52:137-154.
Danese A, Moffitt TE, Harrington H, Milne BJ, Polanczyk G, Pariante CM, Poulton R, Caspi A. 2009. Adverse Childhood Experiences and Adult Risk Factors for Age-Related Disease: Depression, Inflammation, and Clustering of Metabolic Risk Markers. Arch Pediatr Adolesc Med 163(12):1135-1143.
Dokras A, Baredziak L, Blaine J, Syrop C, VanVoorhis BJ, Sparks A. 2006. Obstetric outcomes after in vitro fertilization in obese and morbidly obese women. Obstetrics & Gynecology 108(1):61.
Ellison PT, Panter-Brick C, Lipson SF, O’Rourke MT. 1993. The ecological context of human ovarian function. Human Reproduction 8(12):2248-2258.
Holman D, Wood J. 2001. Pregnancy loss and fecundability in women. In: Ellison P, editor. Reproductive Ecology and Human Evolution. New York: Aldine de Gruyter.
Levran D, Ben-Shlomo I, Dor J, Ben-Rafael Z, Nebel L, Mashiach S. 1991. Aging of endometrium and oocytes: observations on conception and abortion rates in an egg donation model. Fertil Steril 56(6):1091-1094.
Metwally M, Saravelos SH, Ledger WL, Li TC. 2010. Body mass index and risk of miscarriage in women with recurrent miscarriage. Fertility and Sterility 94(1):290-295.
Miller GE, Rohleder N, Stetler C, Kirschbaum C. 2005. Clinical depression and regulation of the inflammatory response during acute stress. Psychosomatic medicine 67(5):679-687.
Miller GE, Stetler CA, Carney RM, Freedland KE, Banks WA. 2002. Clinical depression and inflammatory risk markers for coronary heart disease. The American Journal of Cardiology 90(12):1279-1283.
Nepomnaschy P, Welch K, McConnell D, Low B, Strassmann B, England B. 2006. Cortisol levels and very early pregnancy loss in humans. Proceedings of the National Academy of Sciences 103(10):3938-3942.
O’Rourke MT, Lipson SF, Ellison PT. 1996. Ovarian function in the latter half of the reproductive lifespan. American Journal of Human Biology 8(6):751-759.
Sacks GP, Seyani L, Lavery S, Trew G. 2004. Maternal C-reactive protein levels are raised at 4 weeks gestation. Hum Reprod 19(4):1025-1030.
Turner MJ, Fattah C, O’Connor N, Farah N, Kennelly M, Stuart B. 2010. Body Mass Index and spontaneous miscarriage. Eur J Obstet Gynecol Reprod Biol 151(2):168-170.
Wood JW. 1994. Dynamics of Human Reproduction: Biology, Biometry, Demography. Hrdy SB, editor. Hawthorne, NY: Aldine de Gruyter.
Thursday, July 26th 2012
Yesterday:
- I submitted an NSF CAREER proposal on the reproductive ecology and life history of peri-menarcheal girls
- I submitted a manuscript on transvaginal ultrasounds and stress to a gynecology journal, and
- I submitted an IRB (Human Subjects Committee) proposal.
Since I may never be that productive in a single day ever again, I figured I would catch up on some of my reading.
Summer reading
This summer has been the Summer of Connie Willis. After reading Doomsday Book a year or so ago (heartbreaking, beautiful, a necessary part of your life), and then one of her short story collections Impossible Things, I temporarily forgot about her (to be fair, I was reading Kristin Cashore and George R. R. Martin). Then this summer I’ve read Lincoln’s Dreams, To Say Nothing of the Dog, and yesterday finished The Passage. The Passage may be my favorite yet, the most unexpected, scary, sad, re-emergent book I’ve read in a while. It was a challenging read because it put me in a morbid state of mind, which is something I already found myself in after my birthday, which was last week (this has to do with me worrying about how long I will be able to play high-level roller derby before someone hands me a cane and kicks me off the rink). But Willis has proven herself to be one of the handful of writers of adult science fiction that writes the kind of difficult but beautiful, hopeful even as it’s terrifying novels that will ensure that I read every single short story, novella and novel she writes.
But, what do I read in between all the Willis novels and collections? Fellow professor and derby athlete Steph Davidson (well, I call her Snarker Posey) recommended some great young adult fiction, as I am a fellow lover of all things YA: Divergent by Veronica Roth (I’ve just started), Unwind by Neal Shusterman, and Emergence by David R. Palmer. I’ll be taking these to California for some family time and Sci Foo.
Other books I am considering: Barbara King’s science-y summer read recommendations, and Alyssa Rosenberg’s vote for Alif the Unseen.
Not novels, but other things worth a read:
Academia
The “snake fight” portion of your thesis defense (I believe I have a faculty meeting next month to incorporate this into our graduate curriculum.)
Notes from the #ProfGrind: Having it all (the remix)
Dual Career Challenges
Has Higher Education Become an Engine of Inequality?
Becoming a “Stylish” Writer
Thoughtful, kick-ass science writing
How bacteria in the vagina change during pregnancy
The Life Engineers: Prometheus Asks, Is a Culture as Stupid as Ours Ready to Create New Life?
Written in Stone, one year later
Are warnings about the side effects of drugs making us sick?
One Molecule for Love, Morality, and Prosperity? Why the hype about oxytocin is dumb and dangerous. This might be one of my favorite pieces by Ed Yong ever. Ed identifies exactly what has infuriated most people I know who study behavioral endocrinology about oxytocin fever, and does it with confidence and care.
Some LOLs
Barber Lab Quartet – The Longest Time (Coral Triangle Edition) (maybe not bringing the LOLs, exactly, but they sure are bringing the adorable, and sharing very cool science to boot)
36 Terrible Sex Tips for Men (maybe NSFW, but also rather hilarious)
Always Label Your Axes
What are you reading this summer?
Tuesday, July 10th 2012
The idea for this post came from a question I received when a guest on Skeptically Speaking: is menstrual blood an attractant to bears? Scicurious has since covered that paper in her usual delightful way, and I’m going to focus more on cultural issues and deer. Yes, deer.
* * *
That’s right ladies, it’s time to set up your red tents and enjoy the great outdoors. A whole world awaits you without limits! You can do anything!
Awesome, let's fist pump to celebrate! Image by leuwam via Flickr Creative Commons.
Wait, you did say you were a lady, didn’t you? Of the menstruating variety? Not now though, surely? Oh, you are? Menstruating, I mean?
Danger! Caution, you menstruating fools! Image by mjtmail via Flickr Creative Commons
A world of dangers awaits you with many limits! If you go in the water, sharks may bite you! Bears could attack you in the forest! And don’t expect to enjoy nature (or eat it), because the deer will run from your very scent.
Why don’t you just crawl back into that tent and wait for it all to be over, k?
* * *
This post was supposed to be about menstrual odor and wild animals, really it was. But the more reading I did on the topic, the further the material lead me to think more deeply about the cultural meanings around menstruation, particularly related to the idea of menstrual blood as polluting.
The concept of female pollution is one I’ve covered before from a medical perspective. And this idea pervades many cultures, across many contexts. The situation is complicated: some populations have a more mixed rather than negative perspective, and some seem to see menstruating women as downright powerful. Or, as Balzer (1985) suggests regarding the Khanty (an indigenous Russian population), men tend to find menstruation uniformly negative, where women may often describe it in positive terms and use menstrual confinement to their advantage.
Balzer also contends that the concept of female pollution is prevalent in populations where male dominance is “significant but not secure (given contrasting values of female worth, cooperation, and autonomy)” (1985:128). If I’m understanding this correctly, she is suggesting that patriarchal populations that have at least some aspects of equality or female power are the ones who are going to work hardest to define menstruation as bad. And it seems like these same populations are also ones with strongly defined male and female roles – or at the very least, that men have something at stake in maintaining these roles.
This all ties back into whether menstruating ladies make deer skedaddle in an important way: if we can document that deer do not like menstrual blood, we can provide a biological explanation for cultural divisions of labor. Most people understand humans to divide our labor in a gendered way: men hunt and women gather, men provision and women care for the kiddos, men look to the outside world and women to the domestic one.
Since we like to think this is all biological because it exempts us from thinking about any cultural issues that may create this division, having a potential food source run away from women would be a nice way to justify men as the sole hunter.
There are two problems with this: first, the scant evidence doesn’t support deer being afraid of menstrual blood, and second, there are populations where women hunt and contribute to hunting activities in contexts that directly contradict some early hypotheses for the conditions that support man-only hunting.
The evidence for deer fear
There are several older papers that maintained not only that women don’t really hunt (at least, not when it really matters) and that the main reason for this is the deterrent menstrual and other female odors serve for prey.
One hypothesis is that when meat is a very important part of a population’s diet, menstrual taboos against hunting should be stronger (Dobkin de Rios and Hayden 1985). This is not necessarily mutually exclusive with the first hypothesis mentioned on patriarchal culture (Balzer 1985). The rationale of the menstrual taboo hypothesis is that a population should do everything it can to maximize its chances of hunting success. Since, to their minds, menstrual, pregnant and lactating odors are all rather noxious, that means developing taboos against menstruating women touching men, their weapons, or even casting a shadow over a man as he prepares to bring home the bacon (or antelope). Of course, if the taboo is primarily towards menstruating women, but all of these odors can turn away game, it is hard to see how they are related. But hey, lumping many more reproductively aged women into this category of stinky sure is fun!
But what about male odor? I think my husband’s workout clothes contribute (almost) equally to our laundry hamper’s stink! The authors anticipate this, and contend that even though men’s sweat tends to smell more, AND they are more hairy and thus trap more smell, it is easier to disguise men’s smells compared to those of a woman (Dobkin de Rios and Hayden 1985).
None of this was actually tested, of course. But the burden of evidence wasn’t nearly so high in the 80s as it is today, so perhaps that’s why they felt it appropriate to leave these odor differences as untested assumptions.
A few authors did test the deer avoidance hypothesis, however. March (1980) contaminated the feed of deer on a game reserve with menstrual blood and human urine (which was a mix of “nonmenstruous” female – thank you, March, for introducing me to a new word – and male urine). She found that the deer approached the menstrual blood feed first, but fed only from the urine feed. They sort of replicated this by trying to hand-feed the deer apples with menstrual blood or urine on them, to the same effect.
The problems with this study are many, though the author does state the work is preliminary. No male scent was used as a control (Kelly 1986 also notes this). The sample was on a game reserve with partially domesticated deer who are presumably used to the scent of humans. Not many hunters lure deer with feed, that I know of. Oh, and the deer actually approached the menstrual blood feed FIRST. Maybe they didn’t eat it, but being aversive to eating menstrual blood isn’t the same as being aversive to it being in one’s presence. Heck, I don’t mind menstruating but I certainly wouldn’t eat it.
Nunley (1981) repeats the experiment with a bit of a twist: the feed is contaminated with men’s venous blood, versus nonmenstruous/male urine, versus cow blood. The deer were quite inquisitive (again, this doesn’t strike me as aversive!) but fed only from the regular feed, or the cow blood- or urine-contaminated feed, depending on the herd and the day. Nunley concludes that male veinous blood has no lesser effect on deer than menstrual blood, though he did not actually test menstrual blood.
Finally, Kelly (1986) makes an important observation about menstrual taboos that puts the final nail in the coffin regarding whether deer avoidance of menstrual blood explains labor divisions. As it turns out, the menstrual taboos in some populations are POST-HUNT, not pre-hunt (related to how the game is brought back to the household or group). Menstrual contamination after the animal is dead probably has little influence over the hunter’s previous success at killing it. Unless you own a time machine or something.
So why do men hunt?
Men nearly universally hunt more. But what conditions drive variation in labor divisions? Waguespack (2005) uses the early Paleoindian archaeological record to test this question and understand where our assumptions about Man the Hunter came from. This is a useful sample because they were large game hunters (including Pleistocene megafauna, cool!), and so it’s likely a large portion of their diet came from meat. However, the author describes significant archaeological remains for hunting and almost none for gathering, which has led past researchers to assume men were hunters (ethnographic evidence in modern American Indians corroborates this instance) and women largely absent or invisible from any important work in that culture. It’s easy to forget what women do if we have little record of their work, and easy to create strong gender divisions when information is this incomplete. Without archaeological remains that help us understand gathering behaviors, we won’t always know if past populations relied more on hunting versus gathering, and who was more likely to practice these skills.
Waguespack (2005) also makes another important point: the activities of women in populations that rely most heavily on meat are often unknown. What are women doing with all that time that, in other groups, they would fill with gathering? In a cross-populational comparison, Waguespack (2005) found that many women are actually helping with the hunting, by making weaponry, participating in driving game to hunters, and helping with the transportation issues like making and moving houses so important to game-driven populations.
If that’s not good enough evidence that women are hunters too, consider this: among Aka foragers in Central Africa women do more net-hunting than men (Noss and Hewlett, 2001). Noss and Hewlett (2001) also point to another thorough account of women hunters in the Agta of the Phillipines, and descriptions of women hunters among the Woods Cree, Matses of the Peruvian Amazon, and the Ache of Paraguay. The authors also mention the Ju/’hoan (!Kung) of northeastern Namibia, who not only have occasional joint tracking and gathering outings, but husband-wife hunting pairs (Biesele and Barclay, 2001). Other examples can be found of women who frequently hunt small game, and occasionally large game, in the Western Desert of Australia (Brightman, 1996).
An evolutionary imperative for humans, predators or prey?
At the end of the day, there is little mechanistic or evolutionary support for the hypothesis that deer avoid menstrual odor, or that the gendered division of labor seen in forager societies has anything to do with it. Menstruation is far too infrequent – 50 to 100 times across the reproductive life span of a forager woman, compared to the 400 of industrialized women (Strassmann, 1997) – for it to make sense as a pheromonal signal to predators or prey of humans in the first place.
Men certainly hunt more than women among hunter-gatherers, but the simplest and most common biological explanation – that women, being the childbearers, are more likely to be busy with pregnancy, breastfeeding, and the raising of small children – is the best one. This explanation also allows for variation – it is possible for women to choose the hunt if they aren’t poisoning it with their lady stink. Further, the variation we see in how much women hunt seems to be environment- and culture-dependent. If more hands are needed, women step up. And if men are clinging to their higher status, they might push women down.
References
Balzer MM. 1985. On the Scent of Gender Theory and Practice: Reply to Child and Child. American Anthropologist 87(1):128-130.
Biesele M, Barclay S. 2001. Ju/’hoan women’s tracking knowledge and its contribution to their husbands’ hunting success. African study monographs Supplementary issue 26:67-84.
Brightman R. 1996. The sexual division of foraging labor: Biology, taboo, and gender politics. Comparative studies in society and history 38:687-729.
Dobkin de Rios M, Hayden B. 1985. Odorous differentiation and variability in the sexual division of labor among hunter/gatherers. Journal of Human Evolution 14(3):219-228.
Kelly R. 1986. Hunting and menstrual taboos: A reply to Dobkin de Rios and Hayden. Human Evolution 1(5):475-477.
March KS. 1980. Deer, Bears, and Blood: A Note on Nonhuman Animal Response to Menstrual Odor. American Anthropologist 82(1):125-127.
Noss AJ, Hewlett BS. 2001. The contexts of female hunting in Central Africa. American Anthropologist 103(4):1024-1040.
Nunley MC. 1981. Response of deer to human blood odor. American Anthropologist 83(3):630-634.
Strassmann BI. 1997. The biology of menstruation in Homo sapiens: Total lifetime menses, fecundity, and nonsynchrony in a natural-fertility population. Current Anthropology 38(1):123-129.
Waguespack NM. 2005. The organization of male and female labor in foraging societies: Implications for early Paleoindian archaeology. American Anthropologist 107(4):666-676.
Additional reading
Blood Magic: The Anthropology of Menstruation, edited by Thomas Buckley and Alma Gottlieb. (Prof. Gottlieb is in my department, and this is a simply lovely book.)
Oh, hey, you’re still here, that’s awesome! Why don’t you leave a comment while you’re here? You only need a valid email address and only I see it, so pseuds are fine.
