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Apr 07 2011

Skepticism and Rape Adaptations

ResearchBlogging.org
It isn’t terribly difficult to find well-written, skeptical pieces on evolutionary psychology. In fact, several have come out quite recently. They examine current evo psych theorizing in the light of scientific requirements for proof of any such theory.

Kate Clancy wrote a post on the variety of human behavior that evo psych studies attempt to represent by using mostly college undergraduate research subjects. In addition to her concern over undergraduates’ WEIRD (Western, Educated, Industrialized, Rich, and Democratic) demographics, she notes other ways in which these research participants aren’t representative of the whole of humanity they’re being used to study:

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).

And that’s not even getting into the nonhuman primates with whom we share a fair amount of evolutionary history. In short, Clancy makes the case that if we wish to describe a behavior as evolutionarily adaptive in humans as a whole, we need to consider more than a subset of the behavior in a single culture.

Also looking at the challenges that evo psych must meet in order to scientifically determine the adaptive value of a behavior is Jeremy Yoder. In a multipart series examining the evidence that homophobia is an evolved trait, he breaks down the multiple lines of evidence required:

When evolutionary biologists say a trait or behavior is “adaptive,” we mean that the trait or behavior is the way we see it now because natural selection has made it that way. That is, the trait or behavior is heritable, or passed down from parent to child more-or-less intact; and having it confers fitness benefits, or some probability of producing more offspring than folks who lack the trait. Lots of people, including some evolutionary biologists, speculate about the adaptive value of all sorts of traits—but in the absence of solid evidence for heritability or fitness benefits, such speculation tends to get derided as “adaptive storytelling.”

A few particularly interesting points were brought up in these posts. One, which should be obvious but often seems not to be, is that evo psych is talking about biological mechanisms for behavior, which means that a demonstration that the behavior is widespread is not enough to support claims that a behavior is evolved.

To recap: Gallup proposed that homophobia could be adaptive if it prevented gay and lesbian adults from contacting a homophobic parent’s children and—either through actual sexual abuse or some nebulous “influence,” making those children homosexual. In support of this, he published some survey results [$a] showing that straight people were uncomfortable with adult homosexuals having contact with children.

I pointed out that all Gallup did was document the existence of a common stereotype about homosexuals—he presents no evidence that believing this stereotype can actually increase fitness via the mechanism he proposes, or that it is heritable.

The next item of interest didn’t come from Yoder, but from Jesse Bering, who wrote the article to which Yoder was responding. Bering described his affection for research that is done “without curtseying to the court of public opinion.” Yoder points out that a study providing a rationale for homophobia didn’t exactly run counter to public opinion in 1983, when it was done.

Later, in a response to Yoder’s first post, plus those of others, Gallup himself suggests that his critics “tip-toe around the fact that my approach is based on a testable hypothesis” and “go out of their way to side-step the fact that the data we’ve collected are consistent with the predictions” because the hypothesis is “politically incorrect or contrary to prevailing social dogma.” Given that Yoder specifically discussed the relevance of his data to his theory, it’s difficult to award Gallup the mantle of abused maverick he and Bering both claim for him.

Earlier this year, Jerry Coyne wrote (in response to another Bering article), a caution about building strong evo psych edifices on slim foundations. In this case, he examined the idea of the “rape module”–a genetic, inherited predisposition among human men to commit rape–and of specific, genetically programmed, inheritable behaviors in women designed to avoid this “rape module.”

Well, one can debate whether reading a story about rape is the same thing as being sexually assaulted, or whether a marginal increase in handgrip strength would have been sufficient in our ancestors to fight off a rapist. But the important part of these studies is that they were apparently one-offs—they have not, as far as I know, been replicated by other researchers. Do we accept single results, based on surveys of American undergraduates at a single university, as characterizing all modern women?

As we know, many studies in science, when repeated, fail to replicate the initial results. Think of all the reports of single genes for homosexuality, depression, and other behavioral traits that fell apart when researchers tested those results on other groups of people! And if an author did an initial study (not a replication) of handgrip strength that didn’t show the relationship with ovulation, would that even be publishable? I think not.

I suggest, then, that the results of evolutionary psychology often reflect ascertainment bias. If you find a result that comports with the idea that a trait is “adaptive,” it gets published. If you don’t, it doesn’t. That leads to the literature being filled with po
sitive results, and gives the public a false idea of the strength of scientific data supporting the evolutionary roots of human behavior.

In addition to critiquing the studies themselves, Coyne also notes that this is not the first time the “rape module” idea has been criticized.

Thornhill and Palmer’s book was controversial, with many critics claiming that the authors were trying to excuse or justify rape. Bering takes after these critics, properly noting that “‘adaptive’”does not mean ‘justifiable’,” but rather only mechanistically viable.” But what he doesn’t mention is that there were strong scientific critiques of the “rape module” idea as well. I produced two of them myself, a long one in The New Republic and a short one with Andrew Berry in Nature, pointing out not only scientific weaknesses in the evolutionary scenario but Thornhill and Palmer’s unsavory fiddling with statistics, distorting what the primary data on sexual assault really said. Bering doesn’t mention the scientific controversy, noting only that “it’s debatable that a rape module lurks in the male brain.”

The New Republic article is itself a strong skeptical look at the science used to bolster the concept of the “rape module.” I recommend reading it in its entirety. Coyne discusses the various versions of the idea that rape is a product of evolution (one trivially vague enough to be meaningless–but intuitively acceptable–and one stronger and requiring proportionally more evidence) and how they are played against each other in such a way that they could describe any evidence. He also applies a broader understanding of crime to provide alternate explanations that don’t require a biological predisposition to explain patterns of victimization, and he explains how the evidence in three studies used depend on statistical manipulation. He also examines claims that rape can only be prevented properly using an evo psych framework for understanding it.

Given the availability of people like these, with the tools and inclination to turn a skeptical eye on the topic of evolutionary psychology, it is perhaps no surprise that Center for Inquiry Michigan is promoting a speaker tomorrow night on the topic of evo psych and rape. What is surprising, however, is the identity of the chosen speaker. Dr. Todd Shackelford is the director of the Evolutionary Psychology Lab at Oakland University.

Dr. Shackleford will present a talk on the competing theories of rape as a specialized rape adaptation or as a by-product of other psychological adaptations. Although increasing number of sexual partners is a proposed benefit of rape according to the “rape as an adaptation” and the “rape as a by-product” hypotheses, neither hypothesis addresses directly why some men rape their long-term partners, to whom they already have sexual access. He will present the findings of two studies that examined these hypotheses, discuss the limitations of this research and highlight future directions for research on sexual coercion in intimate relationships.

Now, the problem is not that Dr. Shackelford is an evo psych researcher. There are people doing good work in evo psych. The problem is that Dr. Shackelford isn’t doing good work on this topic. In particular, the work he is presenting, relating female infidelity to rape of female partners by male partners, doesn’t tell us anything that the already robust scientific literature on rape hasn’t already told us.

In the 2006 paper that Shackelford will be presenting tomorrow, “Sexual Coercion and Forced In-Pair Copulation as Sperm Competition Tactics in Humans,” (pdf available) Goetz and Shackelford demonstrate a correlation in heterosexual couples between the likelihood of female infidelity (past or present, rated by the male or female partner) and the likelihood of male sexual coercion, up to and including rape via physical assault. This isn’t news. We already know that men who endorse rape myths and the acceptability of sexual violence against women under certain circumstances are more likely to rape. One of the common attitudes that predicts rape is that “sluts” lose the right to say, “No.” (“Nice girls don’t get raped.”) Non-monogamy is used to excuse rape, and not merely rape by prior sexual partners.

Non-monogamy also isn’t alone among excuses for rape (Scully and Marolla, 2005, pdf available). The idea that women secretly want the sex is common. Rapists claim that the circumstances of the rape were beyond their control due to drugs, alcohol, or emotional problems. People see demands for sex as more reasonable in circumstances where financial contributions to a date or relationship are uneven. None of these, however, are examined whether they similarly contribute to rape within an existing relationship. Without that, the 2006 paper tells us nothing about whether potential female infidelity triggers “sperm competition tactics.”

Nor is this Shackelford’s only study that ignores our broader knowledge of crime in a way that selectively supports evo psych explanations for violence against women. In the 2002 paper, “Understanding Domestic Violence Against Women: Using Evolutionary Psychology to Extend the Feminist Functional Analysis,” (pdf available) Peters, Shackelford, and Buss note the trend toward fewer domestic assaults of post-menopausal women as support that domestic assault is evolutionarily selected as a means of controlling fertile women. They do this using New York City police incident reports for assaults against women only.

They don’t use data from the National Crime Victimization Survey, despite the fact that they cite the survey in the paper. Nor do the results for female victims don’t look substantially different than those they do use. From the NCVS:


Then there is the NCVS data for males:


There are fewer assaults overall, but the pattern isn’t much different. In fact, the pattern isn’t much different if you look at other types of crimes, either.


Given this information (the report on the age of crime victims dates to 1997), the challenge isn’t to explain why the rates of domestic assault fall off near menopause, but to explain what is common to all crime experienced by females in the U.S. that produces that age curve, whether the crime is sexually motivated or not. This study, by again ignoring the data on the broader topic, fails to tell us anything about what it purports to be studying.

In order to actually present a skeptical view of a topic, it is not enough to assert, as some evo psych advocates do, that yours is the minority viewpoint or not widely accepted. That is simple contrarianism. Skepticism and honest inquiry require that one deal with all the information available on the topic. They also require that we not use the absence of information that would allow us to choose between explanations to argue for only one of these explanations.

The studies produced on this topic by Dr. Shackelton don’t meet either criteria. That is what makes it disappointing that CFI Michigan has chosen to uncritically promote his work. [ETA: This topic is discussed at some length in the comments. They're worth reading.]

Citations

Goetz, A., & Shackelford, T. (2006). Sexual coercion and forced in-pair copulation as sperm competition tactics in humans Human Nature, 17 (3), 265-282 DOI: 10.1007/s12110-006-1009-8

Peters J, Shackelford TK, & Buss DM (2002). Understanding domestic violence against women: using evolutionary psychology to extend the feminist functional analysis. Violence and victims, 17 (2), 255-64 PMID: 12033558

30 comments

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  1. 1
    bug_girl

    Thank you for writing what I could not.

  2. 2
    Stephanie Zvan

    Any time I can, bug.

  3. 3
    Jason

    CFI Michigan does not "uncritically promote the work" of speakers at our events. We provide a forum for people to address controversial topics and our audiences are extremely critical. We often host speakers whose beliefs and ideas are diametrically opposed to those of most of our members. A Christian speaker once told our audience that atheists have a "God-shaped hole". The Q&A is often the best part of our lecture events!Jason PittmanAdvisory Board ChairCenter For Inquiry Michigan

  4. 4
    Stephanie Zvan

    Jason, for many subjects, allowing the audience to supply the skepticism is an approach I whole-heartedly endorse. Those subjects are generally well-aired within the skeptical community, and most audience members are familiar with at least some of the details of the debate.That doesn't work so well for this topic. Misconceptions about rape are appallingly common. If you want your audience to be able to tackle this topic skeptically, someone will need to provide them with the background to do that. That background isn't in the announcement. This is specialized knowledge. Will there be another, unanounced speaker at the event to add the context that otherwise only comes from being familiar with the rape literature? If not, who will be equipped to provide, not merely doubt, but actual skepticism of your speaker's claims?

  5. 5
    Emily

    You have a very poor understanding of evolutionary psychology, evolutionary theory, and human origins. I suggest going to Shackelford's talk or contacting him for more information and explanation. I would not consider him a "rape expert" nor do I think he considers himself as such either, but he is a very well-respected evolutionary psychologist. You are misinterpreting his research and related research.

  6. 6
    Stephanie Zvan

    Emily, would you care to be more specific about my poor understanding? And the fact that Shackelford is designing, conducting, and publishing experiments on the nature of rape without a thorough knowledge of the literature on the topic is exactly the problem here.

  7. 7
    Jennifer

    I would like to clarify that Center for Inquiry Michigan is not hosting this event, nor did we have any say in the choice of the speaker or the topic. We were asked by the student group – Evolution for Everyone at Grand Valley State University – if we would inform our members of this presentation – which we have done. http://www.gvsu.edu/psychology/evolution-for-everyone-141.htmOur participation in promoting this event DOES NOT mean that we endorse or promote any of the views presented by the speaker. Also – I would encourage you to re-read the talk abstract of Dr. Shackelford – I think there might be some misunderstanding of what he will be presenting.Talk Abstract (scroll down to additional details): http://www.cfimichigan.org/events/event/w-e4e-040811/

  8. 8
    Stephanie Zvan

    Jennifer, I didn't claim that CFI Michigan chose or hosted the speaker, but it is a point worth reiterating, particularly as Jason's comment refers to "our events". As for the talk abstract, that is a description of the 2006 paper that I discuss in this post.

  9. 9
    Jason

    Stephanie, the final sentence in your post is: "That is what makes it disappointing that CFI Michigan has chosen to uncritically promote his work." This sentence is clearly incorrect and it is misleading to anyone who reads your post. I would appreciate it if you would address this point.

  10. 10
    Stephanie Zvan

    Jason, CFI Michigan is promoting the event at which Dr. Shackelford is presenting his work. There is no criticism or facilitation of criticism or encouragement of criticism presented with that promotion. I asked in an earlier comment whether CFI Michigan is doing anything to facilitate critical inquiry on the topic at the talk itself. You haven't answered. I see the promotion. Where is the criticism?

  11. 11
    Jason

    Stephanie, we have encouraged and facilitated criticism of Dr. Shackelford simply by promoting the event. CFI has provided info about the event so that you and others can provide the criticism. Your post about Dr. Shackelford proves my point. We promoted the event. You have provided criticism. When we promote an event, we are encouraging critical thinkers to attend (sometimes to the detriment of the speaker at said event!) Skeptical criticism of ideas is what CFI is all about.

  12. 12
    Stephanie Zvan

    Jason, I understand that that's your goal, and I understand that it may happen sometimes. However, it's worth thinking about this: How would your promotion of the event look different if you wanted everyone to come and just listen without being prepared with enough background knowledge to effectively engage with the topic? If there aren't any differences, you're not actually doing what you think you're doing.

  13. 13
    Jason

    Stephanie, the difference is that our members are very different from the general public. They do not "come and just listen". I realize that this isn't one of our events, but the more of our members who attend, the more like our events it will be. You should be happy about that! Also, it is entirely possible that more people will read your post on the CFI MI website than will attend the actual event to hear Dr. Shackelford. CFI MI has provided you a forum for your views by promoting the event. This is partly why I take issue with your criticism of CFI.

  14. 14
    Stephanie Zvan

    Jason, I'm glad CFI Michigan has decided to include my information as context. However, that still doesn't change the fact that there was nothing done with this announcement to encourage discussion on the topic. In fact, it's my understanding that Bug girl inquired about the announcement, and the response to her was simply that your organization wasn't responsible for the event. She wasn't encouraged to challenge the material, although she ultimately did.I understand that you don't appreciate my criticism. On the other hand, how hard would it be to put a note on any event that says something like, "CFI Michigan doesn't endorse any speaker or their views. In the spirit of open inquiry, we encourage anyone interested in the topic to participate in the event by asking questions. We particularly encourage those with knowledge of and different perspectives on the subject to participate."? How hard would it be to do explicitly what you hope you're doing now?

  15. 15
    Jason

    Stephanie, I have heard Jennifer read a similar (but less unwieldy) disclaimer before speakers address our regular lecture events. I don't see why such a statement would be necessary when we are promoting a non-CFI event but I will bring this up at our next CFI Michigan advisory board meeting. Would you be willing to make some sort of a statement modifying your criticism of CFI? I'm ok with criticism but not when it is inaccurate and misleading.

  16. 16
    Stephanie Zvan

    Jason, when I'm someplace where I can do it without messing up the post format, I'll add a note referring people to the discussion in the comments.

  17. 17
    Jason

    Stephanie, your note directing readers to this comments thread helps a little but you would be better off removing your erroneous statements about CFI altogether. They call the veracity of your entire blog post into question.

  18. 18
    Stephanie Zvan

    Jason, it's time to knock that shit off. Now.

  19. 19
    Jason

    Stephanie, I'm sorry, I was under the impression I was communicating with a reasonable person. It's clear I've been wasting my time. Cheers!

  20. 20
    Stephanie Zvan

    And I'm unreasonable because (1) I thought there was a problem, which we've since discussed fixing? (2) I don't believe that a single sentence that accurately represents my views but with which you disagree is going to destroy a post packed full of science? or (3) I told you your strong-arm tactics were unwarranted and unwelcome? Jason, I don't really think the problem here originates with me.

  21. 21
    Jason Thibeault

    Jason @CFI: What erroneous comments? Seriously, what comments has she made that are in any way demonstrably erroneous?Despite your assertion that merely presenting the speaker allows for criticism, you're defending CFI on the one point Stephanie made about the organization that she has you cold on — this talk, which your organization promoted and yet claims it has nothing to do with, does not provide a forum for criticism. It provides a one-way communication dump by Shackelford. It does not even go so far as to call his works "controversial", because they haven't stirred any controversy until now, when CFI started promoting him and Stephanie rightly dissected his claims.Again I ask: What part of what Stephanie has posted is incorrect? Please be specific, and include some evidence.

  22. 22
    Jason Thibeault

    Silence from the crowd at my request, but sneers from the sidelines here: https://www.facebook.com/notes/jeremy-beahan/when-skeptics-behave-like-thought-police/10150154389614586 Lovely thought, that those of us who are upset that no opposing viewpoint is being presented are accused of trying to enforce a lockstep mentality. Not sure how you can get around the cognitive dissonance on that one.But what do I know? I am beneath contempt and have obviously never darkened the door of a lecture by a guy presenting hypotheses with no supporting evidence — err, sorry, I meant "scientific conference".I appreciate that you CFI MI folks have to dig in your heels and defend yourselves against a number of ridiculous comments, and on other days I will defend you as a stalwart defender of skeptical thinking, but honestly, you communicated poorly on the first part, and the real point of this post was to show Shackelton's academia in the subject to be questionable at best. The fact, as Stephanie said, that you disagree with her on one point does not call the rest of the science into question, especially when you can't damn well present any evidence for your counterassertions.

  23. 23
    KBHC

    I still don't understand, after reading Stephanie's post and this comment thread, what she did that was remotely misleading or erroneous. I'd love for the CFI folks to be specific in their criticism — Stephanie certainly was, and righteously so.

  24. 24
    daedalus2u

    One of the things not mentioned is that during pregnancy violence against women by their intimate partner (the father of the fetus she is carrying) increases. Here is a pretty good paper, that shows that violence against women by the father of her fetus increases during pregnancy. http://ajph.aphapublications.org/cgi/content/full/93/7/1110That is of the women who experienced violence during pregnancy, not all of them experienced violence before pregnancy. Look at table 1. Physical violence, sexual violence, emotional violence all increase during pregnancy (for those who experienced violence during pregnancy) and the severity of emotional violence increased. This directly contradicts the hypothesis that it is “sperm competition” that is driving the violence. If the partner is already pregnant, sperm competition can't happen. There is also violence against women by their male relatives, either their father or brothers. That can't be due to sperm competition either. That violence also tends to increase during pregnancy, many “honor killings” occur when the woman is pregnant. When I was thinking about this, I looked for examples in non-human mammals where a male was violent toward his mate while she was pregnant with his fetus and couldn't find any. My hypothesis is that the violence against women while she is pregnant is to epigenetically program the fetus into a more violent phenotype, starting the cycle of violence, and/or to induce miscarriage to prevent cephalopelvic disproportion. Typically the male relatives of a woman are more abusive toward her during pregnancy than is her male partner. In an evolutionary sense, her brothers want to maximize her reproduction over her lifetime (more miscarriage to prevent her death via cephalopelvic disproportion), her male partner wants this particular pregnancy to be successful (less miscarriage at the expense of more cephalopelvic disproportion).

  25. 25
    Marina S

    I've been following the developments in popular (rather than academic) evo-psych and its representations in the media for a good decade now; and what astonishes me is how rarely we hear reports of evolutionary explanations for majority adaptive behaviours – and how often about minority ones.To clarify, what I mean is that most men, for example, don't rape; rape is a minority – maybe "cheating"? – behaviour against a background of a majority strategy of peaceful cooperation, paternal investment in childrearing and so on. It's tempting to say that explanations for cooperative, collectivist behaviour are simply obvious and commonsensical, and don't really need to be explained in detail. Still, one of these days I'd love to read some big splash in a weekend magazine, or a book by some high-profile science writer, about the precise prehistoric evolutionary pressures that have lead humanity to be able to cooperate enough to e.g. build the Pyramids.But no: from outside the scientific community at least, it looks like all evolutionary psychologists are interested in is providing adaptationist explanations to minority behaviours, some rare enough to potentially be dismissed as maladaptive aberrations. It's weird to me that we're so obsessed with proving that rape is "natural", rather than revelling in how natural care for the elderly is, or love of art, or communal singing.

  26. 26
    Stephanie Zvan

    Marina, a lot of work on cooperation is being done in other fields, particularly primatology. If you enjoy reading about it, you might want to (if you haven't already) check out The Primate Diaries: http://primatediariesinexile.blogspot.com/

  27. 27
    Stephanie Zvan

    I think part of the issue some CFI folks have with this post is a confusion on their part between criticism and condemnation, both as applied to them and to Shackelford. There may also be some issue in my thinking of them as an outreach group, where they may think of themselves as more of a club. Might be worth another post.

  28. 28
    Stephanie Zvan

    Another post, but this one a follow-up on some comments addressing the science: http://almostdiamonds.blogspot.com/2011/04/more-on-science-of-rape-adaptations.html

  29. 29
    Bryant

    This was quite a nice discussion. Sorry there was so much ad hominem in there. (and ad organizationem, if you will). However, that adds a little zing. I am not previously familiar with the full scientific literature on this subject, so much of the analysis was very interesting. This topic obviously attracts a lot of interest. And it is important to the quality of our society that we find a way to learn more. Even this erudite discussion has not even begun to scratch the surface of prevention. I suggest that CFI look into sponsoring more speakers on this subject, particularly those with divergent views so that we can begin to assimilate a more detailed picture of the literature and current understanding, limited though it clearly is.

  30. 30
    Stephanie Zvan

    And a follow-up post regarding CFI's responses to this post. http://almostdiamonds.blogspot.com/2011/04/skepticism-is-how-not-who.html

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