Wednesday, April 6th 2011
When I was younger, periods were not a fun time, and I was plagued with dysmenorrhea, which is a fancy term for really bad cramps. In high school, I would often take 1000 mg of ibuprofen every four hours to alleviate symptoms to get through all my classes, band, sports practice, and homework (what, it took you this long to realize I was, and am, a dork?).
After having my daughter in 2008, and the thirteen months of lactational amenorrhea that followed it (lactational amenorrhea means absence of periods due to lactation), my periods resumed. Pain during my periods has almost totally ceased, but I have noticed more cycle-related variation in emotion. In particular, my patience and tolerance for rude behavior, and my tendency to cry sentimentally at even the lamest greeting card, skyrocket in my premenstrual phase. I already have low tolerance for rudeness, and I already cry easily. But something about progesterone decline — which is a normal process towards the end of ovulatory cycles — seems to make it harder for me to repress these behaviors in order to fit in culturally with those around me.
I tell this to you to say, I don’t doubt that hormones, and hormonal variation through the cycle, plays some role in variation in female behavior and emotion. And I find this kind of work inherently interesting. I hate to repeat myself, but you will find echoes of my structural and methodological concerns with evolutionary psychology in this post as well.
* * *
Durante et al (2011) observe that women spend more money on their appearance than men, and claim that this sex difference is cross-culturally consistent (I wonder, is this consistent across cultures without money?). In order to understand this sex difference, they wish to see whether spending or shopping behavior is dependent on cycle phase. Therefore the authors hypothesize that women choose sexier clothing during ovulation — “even if the women themselves are not consciously aware of this biological fact” (Durante et al 2011: 922), a problematic turn of phase if I ever saw one, but I’ll get to that later. They also consider the effects of priming a shopping woman with images of attractive women and hypothesize there is a greater effect of this priming on high-fertility women.
Methods
The participants were female undergraduates and were compensated with course credit or money. The authors claim the participants had no idea the study had anything to do with the menstrual cycle, but the participants had to use LH strips at midcycle to see when she was ovulating (this is a urine test to check for a luteinizing hormone peak, which comes before ovulation).
Here’s the important part, for me:
“The first urine test was scheduled 2 days before the expected day of ovulation. If an LH surge was not detected, women came back each day until an LH surge was detected or six tests had been completed, whichever came first” (Durante et al 2011: 924).
Here are my questions: what is 2 days before the expected day of ovulation? The follicular phase — that’s from menstruation to ovulation — is the most variable phase of the menstrual cycle (Fehring et al. 2006; Lenton et al. 1984). I wonder how many ovulations they missed because of this. Perhaps even worse, how many participants had six LH tests and didn’t have a detectable LH surge? It sounds like they were included in the project. But, they either ovulated before the authors started testing, or they had an anovulatory cycle. That means the authors were including participants in their study that weren’t ovulating… in a study of behavior during ovulation.
Participants viewed a made-up shopping website on a high-fertility (near the LH surge) and low-fertility (about eight days later) day, where they had to select ten items they would like to buy that day. They were randomized into two groups: one shown a site featuring casual clothes, the other featuring clothes and accessories. The clothing on these made-up sites were “pretested to be sexy” (Durante et al 2011: 925). While that is a phrase I never expected to write on this blog, the separate validation they did to determine sexy versus nonsexy clothing seems fine.
Results
Hypothesis 1: Near ovulation, women should be more likely to choose sexier and revealing clothing and other fashion items rather than items that are less revealing and sexy (Durante et al 2011: 923).
Women chose a greater percentage of sexy clothing and accessory items near ovulation: 59.8% ± 21.6 during ovulation, 51.3% ± 22.4 during low fertility. This was a statistically significant difference, but they did a repeated measures ANOVA, and I don’t understand why they didn’t do a paired t-test. Further, statistically significant or not, I question how meaningful it is when the averages are so close and the standard deviations almost completely overlap.
H2: Ovulation should lead women to be especially likely to choose sexier products when women are primed to compare themselves to attractive female rivals (Durante et al 2011: 924).
H3: There should be no differences in product choice between ovulating and nonovulating women when women are primed with unattractive women or men (Durante et al 2011: 924).
Follow-up studies primed sub-sets of participants (so a different cohort, same recruitment methods as above) to think about 1) attractive local women, 2) unattractive local women, 3) attractive local men, 4) unattractive local men. They did this by showing photographs of people who they claimed to be local and asking participants to rate their attractiveness.
When primed with attractive women, the percentages of sexy items chosen were 62.7% for ovulating women and 38.2% for low fertility women (I could not find standard deviations for these values so have no idea how much the two groups overlap). Priming with unattractive women, attractive men, or unattractive men produced no significant difference between low and high fertility women.
H4: Ovulation should lead women to choose sexier products when primed to think about local attractive women who constitute potential direct rivals. However, ovulation should not influence product choice when women are primed to think about women from distant locations because such women do not constitute direct rivals (Durante et al 2011: 924).
The authors used a different method for assessing fertility this time; they asked women their normal menstrual cycle length and counted back from menses to estimate when ovulation would be. So AGAIN, we don’t know how many women actually ovulated in this study, and we don’t know whether a significant portion of women were then grouped in the high-fertility group who shouldn’t have been.
This study is like the previous one in terms of photo priming, but this time the photos were said to be local or distant, and were of women only (so the four groups were local attractive, local unattractive, distant attractive, distant unattractive).
The authors claimed that the relationship between fertility, photo attractiveness and location was “marginally significant,” but the p-value was 0.09. That is, in fact, not significant, as significance is generally only considered under 0.05 unless you cheat and say your study is special and should consider a different limit (they don’t say this in their study).
That said, the only significant effect found of photo priming on high versus low fertility women was in the local attractive women group: high fertility women chose 65.8% sexy items versus low fertility’s 39.1% (I could not find standard deviations for these values so have no idea how much the two groups overlap). These results are almost identical to those found when priming women with attractive women without saying if they are local or not.
How biological are we talking here?
The authors claim a biological cause for the differences found above. And maybe there is, to some extent. But there are two major issues with the authors’ conclusions.
First, there is the major methodological flaw of including women who probably aren’t ovulating in their high-fertility group. Heads up to people who don’t study female physiology: women, even healthy women with “normal” cycle lengths, don’t ovulate every cycle. So if understanding a behavior during ovulation is important to your hypotheses, you need daily hormones on top of that LH test. Then, you know, if you can’t document ovulation, you need to exclude those women from your sample. Oh, and while we’re discussing methods, the authors don’t mention whether the participants were in a relationship or not, or what their sexualities were, or their races or socioeconomic statuses. These are all important to understanding variation in female-female competition (Campbell 2004). And since ornamentation is likely related to honest signals of health, it would be good to know waist to hip ratios, or BMI, or facial symmetry (Streeter and McBurney 2003) (hello, I’m handing someone a dissertation here! Just remember to cite me correctly).
But the second issue relates to the theme I saw throughout this paper, that changes in mood or choice behavior due to ovulation or presence of attractive women is a “biological fact.” Female-female competition is certainly found within human behavior, and behavior changes through the menstrual cycle. But is it fair to call these behaviors strictly biological, or should we have a more nuanced understanding of the interaction between biology and culture?
There are alternative cultural theories out there. Objectification theory proposes that there are consequences to living in a culture that sexually objectifies women: when women are continually appraised based on their looks, it leads to a disconnect between their body and individual (Moffitt and Szymanski 2011). This disempowers women and leads to them feeling as though their bodies exist for the pleasure of others. And if this is what women learn they have to offer others, and they seek affirmation, praise or attention from those around them, it makes sense for women to compete around attractiveness, particularly sexiness.
I would posit that shopping, particularly when primed with the image of an attractive woman, is a kind of objectification. So really, what Durante et al (2011) are measuring are the results of objectifying their study participants. Under these circumstances, a woman is more likely to start treating herself as an object to be evaluated on the basis of her appearance, so it makes sense that she would choose sexier clothing, in an effort to produce a culturally-appropriate, attractive body.
As the study stands, there is no way to parse out the impact of biology or culture — and many cultures encourage objectification, female-female competition and female attractiveness towards men. As for how that interacts with high versus low fertility samples… that’s the interesting part of this paper. If we can trust how the women are parsed. Which we can’t, since some of the high-fertility sample might not have been ovulating.
These high heels are made of deer antlers
The authors also seemed enamored with the idea of comparing their female participants to male animals. Twice they mention the idea that they want to determine whether sexy clothing is analogous to a peacock’s tail, a deer’s antlers, or a lion’s mane (really). These three examples, according to the authors, reflect a courtship function, a same-sex competition function, or both functions respectively. The authors go on to say that their results suggest that sexy dressing in women is like deer’s antlers, or, a same-sex competition function.
First, since when are a deer’s antlers only a same-sex competition function? Second, doesn’t it say something that they couldn’t find any examples of this kind of display in a female animal? This begs the question of why female humans do so much more displaying and maintenance of their appearance compared to other female animals, and again, this suggests interactions between biology and culture (Smuts 1995).
We can spin all the stories we want to explain why many human females make efforts to be physically attractive. And I do think Durante et al (2011) are on to something here as, despite methodological concerns they did find differences in high- and low-fertility choices. But if we continue to do this research on undergraduates in western contexts without sufficient hormone analysis, I’m unsure that its meaning extends beyond the participant pool.
References
Campbell, A. (2004). Female competition: Causes, constraints, content, and contexts Journal of Sex Research, 41 (1), 16-26 DOI: 10.1080/00224490409552210
Durante, KM, Griskevicius, V, Hill, SE, Perilloux, C, & Li, NP (2011). Ovulation, female competition, and product choice: hormonal influences on consumer behavior Journal of Consumer Research, 37 (6), 921-934
Fehring, R., Schneider, M., & Raviele, K. (2006). Variability in the Phases of the Menstrual Cycle Journal of Obstetric, Gynecologic, Neonatal Nursing, 35 (3), 376-384 DOI: 10.1111/j.1552-6909.2006.00051.x
Lenton EA, Landgren BM, Sexton L, & Harper R (1984). Normal variation in the length of the follicular phase of the menstrual cycle: effect of chronological age. British journal of obstetrics and gynaecology, 91 (7), 681-4 PMID: 6743609
Moffitt, L., & Szymanski, D. (2010). Experiencing Sexually Objectifying Environments: A Qualitative Study The Counseling Psychologist, 39 (1), 67-106 DOI: 10.1177/0011000010364551
Smuts, B. (1995). The evolutionary origins of patriarchy Human Nature, 6 (1), 1-32 DOI: 10.1007/BF02734133
Streeter, S. (2003). Waist–hip ratio and attractiveness New evidence and a critique of “a critical test” Evolution and Human Behavior, 24 (2), 88-98 DOI: 10.1016/S1090-5138(02)00121-6
Wednesday, March 16th 2011
My blogging mojo has been channeled almost entirely towards a book project I’ve undertaken with Julienne Rutherford of UIC and Katie Hinde of UCLA (though shortly to be of Harvard). The book is called Building Babies: Primate Development in Proximate and Ultimate Perspective and it will be published by Springer in 2012. Each co-editor has a chapter in there, and then we have a number of other rather fancy-pants contributors as well.
The first drafts of the chapters were due yesterday. I did not submit my chapter (er, to myself). I’m running about a week late. I thought I would come clean with this, because there are a number of elements of the writing process that I think remain obscure for students and other junior scholars. And after I share a few thoughts about academic writing, I thought I would show you some of the draft I’m working on.
First drafts suck
They really, really do. If you think your first draft is amazing, give it to someone else, and that someone else can’t be a pet, spouse or parent. First drafts suck because we write the most obvious things in them, the most vague. First drafts don’t have enough context. First drafts are where you use cliches because you haven’t figured out how to say what you’re saying in a sophisticated way. They are often under-cited. They are out of order. And, they aren’t that compelling.
This is why so much student writing is bad — but it’s not their fault. Close together deadlines, ones that align with other projects, and little teaching of time management means most students start writing projects just before they are due. So they essentially submit first drafts of papers, with a little copyediting if you’re lucky. Plus, somehow a lot of students have picked up this idea that first drafts are better or more authentic than revisions. This is patently false. They are simply the place our favorite worst stuff goes to die (this is why revision is so often called killing our darlings, to use a term from scio11, though its origin is much older).
But everyone has bad first drafts, so it is absolutely useless to feel bad about them. Give them to your advisor or your colleague if they have said they will read a first draft (otherwise, revise it after consulting with someone else first). They write bad first drafts too. You have to write a first draft in order to get to the revision, and to me, this was a liberating realization. Get it all out now! Don’t worry about using the right word! Just get the words on the page, get about the right content in about the right order, and if something is repetitive, just leave it for now. Because after a little breather away from it, or a look from a trusted colleague or advisor, you will hack it up and remake it into something far better.
Revising only sucks sometimes
Revising sucks when you get your first comments back from a colleague, because it is terrifying to share that vulnerable, bad first draft with another person (ever had that moment after you print it out or hit send when you realize your prized metaphor was a trembling nod to your failed attempt as a fiction writer?). It sucks at those moments when you feel at cross-purposes with the thesis of your paper. And it’s frustrating, also, that revising is the most important yet under-taught skill in academic writing.
But here’s the thing. Revising can be glorious. If you abandon any sense that you own your words, and remember only to own your mind, it allows you to be merciless in cutting out all the badness of that first draft: the cliches, the vague repetition, the jargon. If you return again and again to your outline, or abstract, or data, or whatever materials you keep to help you remember what the paper is about, you will start to see the right shape of the piece. And then you can also build in the context.
The best moments of revision are when you remember why you were writing the piece in the first place. Do you want to produce a fundamental review that will be useful to other practitioners in your field? Do you have an amazing piece of data to share? A well-grounded hypothesis that you want to articulate? What was surprising or compelling about that work when you first set fingers to keyboard?
One last thing I’ll say about revising is that owning your mind is not the same as owning your ideas. You need to be willing to let go of being right, and you need to be willing to change if the evidence is against you. Accepting reality and working with it in an interesting way is the mark of a good scientist, and a good revision.
My first drafts suck
The title of my chapter is: “Inflammatory factors that produce variation in ovarian and endometrial functioning” (eventually, I think, I will need to change the title to better reflect the manuscript). I thought this would be an easy piece for me, since I have been doing a lot of work on C-reactive protein, a biomarker for systemic inflammation, and I have been studying the endometrium and ovaries for many years.
I was wrong. Oh, so wrong.
A few quick searches pulled up an embarrassingly large number of citations for chemokines and cytokines, for toll-like receptors, natural killer cells, and other immunological terms I barely remembered from high school and college. So I re-drafted my outline, set aside a lot of time for reading (as in, several days straight), and then finally set to work.
The problem with the literature on this topic is that it is wholly mechanistic. I can now tell you what interleukins are expressed in the periovulatory phase versus the implantation window, or which ones are suppressed or overexpressed for certain pathologies, but I can’t tell you what that means in a broader sense, or what produces variation in any of these immunological factors in a systemic way that might impact local inflammation in the female reproductive system.
Here is my section on normal endometrial functioning (alas, given the literature, the section on pathology in the endometrium is far, far longer). First draft ahead! Remember, I am sharing this embarrassingly bad prose for the good of SCIENCE.
The endometrium is composed of the functionalis and basalis layers; the functionalis comprises two thirds of the endometrium and is the part that proliferates and sheds each reproductive cycle. The basalis is adjacent to the myometrium, and is the place from which the endometrium regenerates after menses. The proliferative (also known as follicular) phase is when estradiol promotes proliferation of endometrial tissue, where the secretory (also known as luteal) phase is characterized by progesterone control of decidualization and menstruation. The endometrium typically proliferates with narrow, straight glands and a thin surface epithelium, and angiongenesis continues as ovulation nears (King and Critchley 2010). After ovulation and during the secretory phase, the endometrium differentiates: endometrial glands become increasingly secretory, and by the late secretory phase spiral arterioles form. If implantation does not occur, the corpus luteum degrades, progesterone declines, and this triggers a cascade of events to produce menstruation.
Menstruation is a key inflammatory process of the endometrium. Menstruation is when the functionalis are shed at the end of the human reproductive cycle. The basalis regenerates over the course of the next cycle. The demise of the corpus luteum and the associated withdrawal of progesterone precipitate inflammatory mediators that cause tissue degradation. For instance, progesterone inhibits nuclear factor κ B (NF-κB), which increases the expression of inflammatory cytokines like IL-1 and IL-6 (Maybin et al. 2011). The withdrawal of progesterone is also associated with an increase in endometrial leukocytes and IL-8, which regulate the repair process (Maybin et al. 2011). At this time other inflammatory factors promote MMP production to break down endometrial tissue (Maybin et al. 2011). Further, it is thought that progesterone withdrawal, not an increase in estradiol concentrations, leads to the repair of the endometrium so that it can resume activity for the next cycle (Maybin et al. 2011). Thus, variation in progesterone concentrations may lead to variation in inflammatory activity, degradation, repair and cycling in the endometrium.
First question: why should I care about any of the above? So what if any of this happens? Then, you might not know this, but I do: the only two citations in these two paragraphs are both review papers, and one of the authors overlap between them. Therefore, it’s quite under-cited. To be fair, in this section it is less important that I demonstrate the depth of the literature, but a review that only cites two other reviews isn’t doing its job.
Do I inspire excitement in my field? No. Do I provide an appropriate context for this material in order to situate the reader? Not so much. Right now, these two paragraphs contain the exact information I wanted them to contain, based on what was in my outline. That is, I’ve described the basic functioning of the endometrium, and menstruation. It’s flat because that’s all that I did.
My job in this chapter is to take this vast reproductive immunological literature, pair it with what little we have in anthropology and ecology that helps us understand the way genes and environment might produce this variation, and then describe the necessary context in future work to understand these mechanisms. In some places, a lack of context may help me make my case, because it will demonstrate why anthropologists need to be in the field. But if my whole manuscript looks like the two paragraphs above, it will be an unreadable yawnfest that doesn’t contribute a thing to anthropology.
So, I guess I would expand the “kill your darlings” advice. First, accept your darlings. Accept that you have them like everyone else, and that darlings aren’t just turns of phrase but entire ideas, hypotheses, fields of thought. Then, once you have accepted that your darlings make you just like every other academic writer out there, from the middle schooler to the full professor, kill them. With fire. Finally, make sure you provide what is left with context or else there is no reason to read what you wrote.
And now, I have been sufficiently inspired to go finish my bad first draft.
References
King, A., & Critchley, H. (2010). Oestrogen and progesterone regulation of inflammatory processes in the human endometrium The Journal of Steroid Biochemistry and Molecular Biology, 120 (2-3), 116-126 DOI: 10.1016/j.jsbmb.2010.01.003
Maybin JA, Critchley HO, & Jabbour HN (2011). Inflammatory pathways in endometrial disorders. Molecular and cellular endocrinology, 335 (1), 42-51 PMID: 20723578
Friday, March 4th 2011
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Figure 1. My apologies to Baby Jaguar
for not finding a picture that included
him. |
My daughter will be three in just a few weeks. She loves telling stories. These stories have the same, uncomplicated arc every time: she and her friends Dora, Diego, Boots and Baby Jaguar go on an adventure to rescue Mommy from the giant condor. Or sometimes Mommy and Dora and Diego and Boots and Baby Jaguar are rescuing her. Or sometimes Daddy does the rescuing.
There is almost always a net, then a pair of Rescue Scissors needed to cut the captive free. But the variation in these stories is very small, the framework borrowed heavily from one of the few mythologies known to my little girl: Dora the Explorer.
Evolutionary psychology is often a kind of story-telling, and instead of borrowing from a preschool cartoon they borrow from the concept of anisogamy. Anisogamy is sexual reproduction formed by unequal gametes, in our lineage a big egg made by females and little sperm made by males. This provides the foundation for differential reproductive investment, where females often put in the time and effort of gestation, lactation and care. From here, proponents of EP see essential differences between what men and women want in relationships, and the kinds of relationships that are optimal, and a model this broad makes it possible to shoehorn any behavior into its adaptive framework.
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Figure 2. The actual image that
accompanied Tierney’s column. |
Enter John Tierney, my (not) favorite journalist for the New York Times. This is the man who thinks that sexism is a radical act (I am referring to his charming articles on gender disparities in science). So I suppose I shouldn’t have been surprised when he outed himself as an EP fanboi in his most recent piece, “The Threatening Scent of Fertile Women.”
Tierney covered the work of Jon Maner and others who have studied relationship maintenance – the suite of behaviors that keeps a couple together. In particular, Tierney focuses on the problem of the wandering eye, or rather, the possible mechanisms that prevent it in a monogamous couple. The idea here is that relationship maintenance is evolutionarily adaptive, because when a couple stays together it is easier to raise offspring and increase reproductive success.
The range of explanations
The study that frames Tierney’s column is Miller and Maner (2010). Thirty eight undergraduate men rated the attractiveness of a woman with whom they interact, at several points over her menstrual cycle. The authors found NO relationship between where a woman is in her cycle and how attractive a single man finds her, but a negative relationship between the chance a woman is fertile and how attractive a partnered man finds her.
What do Miller and Maner (2010) discuss, and what is the idea Tierney is so enamored with?
“It’s possible that some of the men in Florida were just trying to look virtuous by downgrading the woman’s attractiveness, the way a husband will instantly dismiss any woman pointed out by his wife. (That Victoria’s Secret model? Ugh! A skeleton with silicone.) But Jon Maner, a co-author of the study, says that’s unlikely because the men filled out their answers in private and didn’t expect the ratings to be seen by anyone except the researchers.
“It seems the men were truly trying to ward off any temptation they felt toward the ovulating woman,” said Dr. Maner, who did the work with Saul Miller, a fellow psychologist at Florida State. “They were trying to convince themselves that she was undesirable. I suspect some men really came to believe what they said. Others might still have felt the undercurrent of their forbidden desire, but I bet just voicing their lack of attraction helped them suppress it.””
This conjecture is unconnected to the study’s methodology and results. Nowhere in that study did they assess the participants’ state of mind or ask them how they felt about this. How do we know they were trying to convince themselves of anything? This finding, while interesting, does not test their hypothesis for an evolutionary framework for relationship maintenance that includes adaptively suppressing attraction to others.
Maner et al (2009) studied the attention people pay to images of attractive people of the opposite sex when first exposed to sexual words like “lust” and “kiss.” They recruited 120 straight undergraduates, thirty six of whom were in committed relationships. Individuals in committed relationships paid far less attention to the attractive images than those not in relationships. Tierney titters,
“The subliminal priming with words related to sex apparently activated some unconscious protective mechanism: Tempt me not! I see nothing! I see nothing!”
I’ve done my own share of human subjects research, and subjects will often tell you or do what they think you want, or they will just not be honest if they don’t want you to know the truth. What if, as originally posed by Tierney himself, the respondents weren’t warding off temptation but wanted to look virtuous? What if, now bear with me because this might seem crazy, the people in these studies were in love with their partners and genuinely uninterested in anyone else? Too often EP wants to provide a single explanation for a behavior, when the range of possible explanations far exceeds their hypothesis.
An anthropological perspective
Jamie Jones, Associate Professor at Stanford and blogger at Monkey’s Uncle describes anthropology like this,
“…[A]nthropology is the science charged with explaining the origin and maintenance of human diversity in all its forms. To achieve this end, anthropology must be unapologetically grand in its scope. How can we explain human diversity without documenting its full extent, through both time and space, and across cultures? … Where does the tapestry of human diversity come from and how is it that we continually manage to resist powerful homogenizing forces and hang on to our diversity? What commonalities transcend local difference to unite all humanity? How is it that civilizations rise and fall? And what is the fate of humanity?”
Jamie beautifully depicts the importance of documenting and understanding diversity even in the face of efforts to simplify human nature. Thus, to me, an anthropological perspective is often at odds with EP explanations for behavior.
An anthropological perspective asks, what happens if you take these basic observations and, instead of deciding on a favorite explanation and applying it to everyone, put them into a model in which you can vary context (age/sex specific mortality rates, distribution of resources, what have you) and see what range of strategies actually give fitness benefits? That is, when you actually throw some variation into the equation, is this still the best strategy for the partnered men with whom Tierney feels simpatico?
Right now we don’t know. Much psychological empiricism rests on undergraduates who participate in studies for course credit. When one wants to make connections to evolutionary adaptedness, they may be a place to start, but not end.
I have a real problem with continuing to use this population to make statements of universality for all humans. Undergraduates usually are trying to avoid pregnancy and build their financial and social capital, so relationship maintenance for the sake of reproductive success rarely exists. Until we can show that relationship maintenance, and the particular behaviors Miller, Maner and others study within that are shown across many populations, and particularly across reproductively-aged folks, their argument for adaptation fails.
 |
| Figure 3. Celebrations of marriage. |
Another problem is that most work on relationships in EP tends to be heteronormative, meaning that they think nothing of assuming that either everyone is straight, or the universally best behavioral strategy is to be straight. They also tend to assume that the best strategy is to be monogamous, with occasional sneaky infidelity permitted if one can get better genes or more offspring that way (keep in mind that there is a difference between what might be biologically advantageous in a certain context, and what is culturally appropriate – the argument here is not against the culture of monogamy).
But heterosexual monogamy is only one reproductive strategy of many that humans employ. Depending on how you measure it, monogamy and polygyny (single male, multi female marriage) vie for the most frequent strategy – in fact, polygyny occurs in about 80% of modern human societies (Murdock and White 1969). There are even a few rare populations that practice polyandry, which is the marriage of a single female and multiple males. And, even in those populations where monogamy is practiced, serial monogamy is far more frequent than lifetime monogamy: this means that individuals have a series of monogamous relationships rather than find one mate for life (so no, divorce is not a modern human invention).
When taking an even broader, comparative perspective, monogamy isn’t practiced by our closest relatives at all. Chimpanzees and bonobos, both equally related to us, are promiscuous. This is a scientific term for a reproductive strategy that involves females and males making reproductive decisions to mate with many individuals at each fertile period. Bonobos are also promiscuous, but they also use heterosexual and homosexual sex to reduce stress and aggression, and form bonds among one another. Gorillas, our next closest relative, are polygynous. Orangutans are very solitary, but essentially promiscuous. It’s only once you delve into the lesser apes, the gibbons, that you see any monogamy, and they are far less monogamous than we first thought (Brockelman et al 1998).
Maintaining a heterosexual, monogamous relationship is certainly advantageous at certain times, in certain contexts. But it is not universally adaptive, even within humans. Without anyone studying these behaviors in populations that use different reproductive strategies, and in the absence of comparative data to support these assertions, we are at an impasse.
Conclusion
In the words of a friend, EP is plugged into evolutionary theory with little more than a ratty old extension cord. EP takes some very basic, ancestral conditions, like differential costs of reproduction, and uses it in a sufficiently vague way that any behavior can relate to females generally being the ones to put in all the time and effort into making babies. Yet EP often ignores the three conditions necessary for natural selection, the mechanism for evolution. For natural selection to act on a trait, the trait must be variable, heritable, and produce differential reproductive success. Rarely does EP understand variation in a trait, rarely does it examine whether said trait has a genetic component, and rarely does it test whether their trait confers a reproductive advantage.
Are fertile women a threat to partnered harmony, their scents providing a temptation that noble men must suppress? I can’t rule it out, but I also think it is one of the least likely of many possible explanations.
Unfortunately for readers of the New York Times, Tierney loved this idea more than he loved interrogating it.
Acknowledgements
I’d like to thank Charles Roseman, friend, faculty curmudgeon and Bastard Colleague from Hell, for taking a look at an early draft of this post and providing commentary crucial to its improvement. Any rhetorical or scientific errors are my own.
References
Brockelman, W., Reichard, U., Treesucon, U., & Raemaekers, J. (1998). Dispersal, pair formation and social structure in gibbons ( Hylobates lar ) Behavioral Ecology and Sociobiology, 42 (5), 329-339 DOI: 10.1007/s002650050445
MANER, J., GAILLIOT, M., & MILLER, S. (2009). The implicit cognition of relationship maintenance: Inattention to attractive alternatives Journal of Experimental Social Psychology, 45 (1), 174-179 DOI: 10.1016/j.jesp.2008.08.002
Miller, S, & Maner, J (2010). Evolution and relationship maintenance: Fertility cues lead committed men to devalue relationship alternatives Journal of Experimental Social Psychology, 46, 1081-1084
Murdock, G., & White, D. (1969). Standard Cross-Cultural Sample Ethnology, 8 (4) DOI: 10.2307/3772907
Image sources
Dora picture: http://www.doratheexplorertvshow.com/dora/dora-explora-pics.htm
Lady magnet: http://www.nytimes.com/2011/02/22/science/22tier.html?_r=2&ref=johntierney
Same-sex marriage: http://markusisthedrug.onsugar.com/date/2009/05/07
