ResearchBlogging.orgThis came up a while ago and I assumed the idea would die the usual quick and painless death, but the idea seems to be either so fascinating or so irritating to people (mainly in various blog comment sections) that it still twitches and still has a heartbeat, but only as a result of the repeated flogging it is getting.


The research was reported in Science and quickly popularized in a post by Brian Alexander. Please read this review of the tear research and a critique of Alexander’s post by Christie Wilcox. The idea that tears are a mechanism to avoid rape is mainly proffered in comments in various posts. Also, please have a look at this post by Mike the Mad, which is not about tears but about the evolution of rape avoidance mechanisms in general.

Here’s the idea. It appears that a steroid hormone found in human female tears reduces sexual arousal in human males when they are exposed to those tears. Is this a mechanism to stave off rapists?

Let’s start out by giving the idea the best chance we can. Rape matters. Female hominids in a semi-pair bonded or monogamous species who are raped will give birth to young that will not garner the normal level of male parental investment because the male parental unit is not the father. The female that would be raped is better off not being raped for this reason and thus we would expect adaptations to arise to avoid it. Any rap-avoidance mechanism would be strongly selected against. Bla bla bla.

OK, that’s about as good as I can do. Now, rather than making a cogent argument against this hypothesis (which I could do, honest) I’m simply going to list a number of questions I would ask about this idea before deciding anything.

1) Does this work with male tears? Do man-tears make heterosexual men less aroused? If so, then the steroid hormone is just something in tears.

2) Does this work on the females? Do woman-tears make the woman herself less aroused? Does this work with male tears for homosexuals? Do gay men have reduced arousal when their partner cries? This may not mean much, but would also indicate that this is not really an adaptation, because the production and delivery of a hormone is only part of the process. Receptors matter too. If the tears are working in any of these ways to reduce sexual arousal, then that means that the recipient of the putative signal is responding as the hypothesis predicts, inappropriately or non-specifically, and thus, both the hormone delivery and the reception of the hormones is incidental.

3) Do rapists have reduced sexual arousal when exposed to these hormones? I.e, does the adaptation work in this way? (See below.)

4) Does reduction in sexual arousal in rapists lead to a reduction in likelihood of rape? How does this vary across different kinds of rape?

5) Do rapists who get cried at become safer or more dangerous?

6) Does the presence of the hormone vary with who is getting signaled to?

7) Is the tear-born steroid hormone level in the same range across females, or is it tied to each female’s baseline? Hormone amount is not the factor that matters in their function; What matters is receptor site frequency and distribution and relative hormone amount. Hormone signaling within an individual works because hormone production levels and hormone receptor site frequency and distribution co-develop. This is one of the reasons why those who study endocrine systems establish individual baselines and measure hormone levels in relation to those baselines. Using steroid hormones set to internal baselines to signal between organisms would be difficult, though not impossible.

8) Yes, pheromones exist and work, and these limitations can be compensated for, but they remain two-way devices. A female animal may send out a scent to attract a male, and the male may get attracted, but both parties benefit from this communication and the communication serves a common interest. Why would male rapists have a mechanism for getting “turned off” as it were? If rape is of evolutionary significance, it would be trivial, I would think, for male rapists to avoid a “don’t rape me” pheromone interference mechanism (such as simply not developing the receptor sites for it).

9) Why does the effect happen even though the tears used in the study were not from frightened about to be raped women, but rather, women who were watching Bridget Jones’ Diary or something?

The Science study does show an effect. Perhaps something is going on here. The evidence that it is an anti-rape adaptation is very poor, and reason suggests that it is not. The idea that one facies of emotional state (sad/happy/etc) is linked to another (aroused/not aroused/etc) is reasonable, and we may be seeing that here.

One problem is that human tears are a unique human trait. And, human rape is probably unique as well, though forced copulation is not (human rape is so very much more, in a bad way, than that). This makes it difficult to do the sorts of comparative work that helps to parse out the adaptive from the incidental.

Christie, in her post, discusses a more nuanced hypothesis that does involve communication of emotional states in a way that is probably more reasonable given that tears occur in a much wider range of social settings than either the intercourse-related or the rape-related. In fact, to narrow down her idea a bit, tears in infants may be a powerful way of eliciting care-taking behavior. That alone could cause tears in adults to have similar effect for no particular adaptive reason, but rather, as a ride-along and incidental effect. (Christie discusses all of this).

Finally, while rape is important in human affairs, I’m not so sure how important it is in long term evolutionary history. Most tropical and subtropical foragers are relatively monomorphic in body size, and there is little evidence of rape being important. Rape is much more common in so-called “middle range societies” which a lot of modern evolutionary psychologists lump in with foraging societies. They are wrong to do this, and I find it very annoying. So annoying that I’ve started to write about it a few times but my keyboard burst into flames every time. Eventually, I’ll address that issue, but I may have to skin a few colleagues.

Gelstein, S., Yeshurun, Y., Rozenkrantz, L., Shushan, S., Frumin, I., Roth, Y., & Sobel, N. (2011). Human Tears Contain a Chemosignal Science, 331 (6014), 226-230 DOI: 10.1126/science.1198331

Comments

  1. #1 Brent
    January 21, 2011

    Another good question may be something along the lines of what kind of contact does the rapist need to have with the tears? Is ingestion the only method to limpify the rapist? If so, it is hard for me to imagine a rapist trying to slurp up his victims tears while (or before) raping them.

  2. #2 Warren
    January 21, 2011

    Brent @!:

    “[I]t is hard for me to imagine a rapist trying to slurp up his victims tears while (or before) raping them.”

    But you gotta admit, that wold be one creepy-as-hell serial rapist/psycho thriller story.

    I’ve been functioning for some time under the supposition that rape isn’t really about sex, so much as humiliation and debasement. In that light, I would expect tears to arouse the rapist, not deter him.

  3. #3 Stephanie Z
    January 21, 2011

    “Increased physical injury was associated with pleading, crying, or reasoning indoors.” http://onlinelibrary.wiley.com/doi/10.1111/j.1471-6402.1993.tb00674.x/abstract

  4. #4 CherryBomb
    January 21, 2011

    You can summarize almost everything that Evolutionary Psychology has to say about rape in one word: “Bullshit.” OK, crying deters rapists; so do other things, like kicking the rapist in the nuts or yelling for help. My money says that NONE of these behaviors is an adaptation that evolved to deter rape. Like you say, Greg, tears have a lot of other uses in human interaction. A woman trying to avoid rape is just going to use whatever tools she has available.

  5. #5 gwen
    January 21, 2011

    What is to prevent the victim from dropping off the infant, once born, into the nearest field to die? I can’t imagine the product of such violence triggering ANY feelings of maternal love in ME.

  6. #6 Samantha Vimes
    January 22, 2011

    It would really make more sense if (assuming there was a purpose rather than an accidental effect) one looked into whether men knowing when NOT to make annoying passes at their upset beloveds improves the emotional bond between them, making it more likely they will raise children together rather than her kicking him out of the shelter for being clueless.
    But it seems just as likely that a sorrow-stress hormone, when smelled, would induce a dampening effect on mood, just because it would be a little bit like having some of that chemical in your own bloodstream. No purpose, just a simple biochemical recognition.

  7. #7 Phinneus
    January 22, 2011

    The study done on the effect of female tears on the arousal of males was done with fairly nomral male humans I imagine.
    A rapist could hardly be categorized as a ‘fairly normal male’, and would be unlikely to be influenced by the faint chemicals in the tears of the victim. A nice small bullet would work so much better.
    Brent above is accurate when he states that rape is not so much about sex as humiliation and debasement and power, and a sexual ‘turn off’, would matter little.

  8. #8 natural cynic
    January 22, 2011

    The study done on the effect of female tears on the arousal of males was done with fairly nomral male humans I imagine.
    A rapist could hardly be categorized as a ‘fairly normal male’, and would be unlikely to be influenced by the faint chemicals in the tears of the victim…

    The key word is normal. Rape, in our society, is normally a solitary situation committed by someone who is decidedly not normal. In a more primitive situation, namely in a tribal society, occasions of rape may have been more communal situation, as in to the victor go the spoils in the case of tribal warfare. In that situation, tears may have had some effect on some the winners. Did all of the Serb soldiers commit rape in Bosnia and Kosovo?

  9. #9 Greg Laden
    January 22, 2011

    In a more primitive situation, namely in a tribal society, occasions of rape may have been more communal situation, as in to the victor go the spoils in the case of tribal warfare.

    Uh oh.

    [anthropological rant]

    Ah… when I read a sentence like this, many bells go off, such as the use of the word “primitive” (I promise you it has a rich meaning that simply does not apply in this case at all no matter what you happen to think it means) and the term “tribal society” .. that’s a little like saying “Well, we’ve got your raccoons, and we’ve got non-raccoon members of the order of Carnivores, and the raccoons are one thing and the carnivores are this other thing” … Then there’s the fact that non-Western societies, being very very diverse, have very very different patterns of rape, and I’m sure you will find many such societies where rape is rare or virtually does not happen.

    There are three very famous social settings where rape of one form or another occurs more often than many other societies. 1) Lots of variation in economic disparity, women’s power, etc. in the context where individuals (men or women) are very often alone. That would be rural and urban areas in the US; 2) Western armies in combat settings; and 3) that whole period of time from the “rise of civ” through the “dark ages” and the middle ages and so on, including the prior lat Bronze Age and Iron Age, in Europe. I mean, really, Vikings were more typical than not.

    I’ve listed these three in ascending order of liklihood that a woman will at some time in her life be raped, and we can probably reverse 2 and 3 locally for prolonged occupation or if we want to ask a slightly different question: Chance of cause of death being linked to rape.

    None of that is about “tribal” or “primitive” … I lived for years in “tribal primitive” societies and the only rape that happened was by westernized people, such as regular army soldiers. There is virtually no rape among Pygmies and almot no rape among the horticultural villagers I lived with in two totally different regions of Central Africa.

    [/ anthropological rant]

  10. #10 Wow
    January 24, 2011

    Rape also often has a component of projection.

    Lots of rapists are *seriously* religious in a religion that deems sex immoral. Therefore, since this person is getting a buzz, it must be the victim’s fault, ergo THEIR (the victim’s) lust.

    It also gets easier to justify in a religion that has Original Sin: if all humans are basically wicked, then it’s not your fault, you just backslided for a bit and maybe being EXTRA virtuous for a week will even it out.

  11. #11 Wow
    January 24, 2011

    Greg, I like T Pratchett’s definition of “primitive culture” that Rincewind has found by actual experience.

  12. #12 Bekkah
    June 9, 2011

    As a woman who has been raped (more than once), I would like to add that some male rapists are definitively not “turned off” by tears. Tears may arise from both the physical pain and emotional terror. Some rapists progressively escalate the intensity of physical pain they inflict specifically to produce the desired response (including tears, screaming, pleading) in their victims.

  13. #13 StevoR
    June 10, 2011

    @5.gwen | January 21, 2011 11:36 PM :

    What is to prevent the victim from dropping off the infant, once born, into the nearest field to die?

    Religion?

    In some cases the rapist himself and /or his gang / tribe?

    A patriachial cultural context where women’s bodies are seen as male property and they not allowed to control what happens to them? :-(

  14. #14 HenryS
    USA
    November 29, 2014

    It’s in a weak, semi-feminized patriarchal society that the exploitation of females by males, which is necessary for the continuation of kind and tribe, continues while the protection that a male “owner” of his females is largely eliminated. The worst feature of patriarchialism is continured while its best feature is disabled.

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