Sunday, October 31, 2010

Getting Savage on evolutionary psychology

Now, I love sex advice columnist Dan Savage. I have been a faithful purveyor of his columns, podcasts and blogs for some time now. And sure, I don’t agree with him on every bit of advice, but he bats a solid .900 and articulately calls out many forms of B.S. But right now, I have a beef with Mr. Savage over his love affair with the new evolutionary psychology-inspired book Sex at Dawn by Christopher Ryan and Cacilda Jethá. This is an example of the all-too-common use of science-y thinking as justification for a particular belief, in this case, the use of evolutionary psychology to endorse the “naturalness” of polyamory.

My contentions are the following: 1. while I am all for the promotion of reading and scientific literacy, we need to be especially vigilant against accepting poor science that confirms what we already believe; 2. that we need to critically examine whether science can inform social policy discussions; and 3. we need to divorce the notion that the “naturalness” of an act means that the act is desirable.

Problems with evolutionary psychology
I need to point out in the spirit of full-disclosure that I have not read Sex at Dawn. However, from Mr. Savage’s multiple interviews with Dr. Ryan, it is evident that the apple of this book does not fall far from the tree of Buss and Baker.

Evolutionary psychology offers only post-hoc fits of theory to data
            In evolutionary psychology, one asks how human evolutionary history can explain aspects of current human behavior. Functionally, it amounts to doing thought experiments on questions such as “how did a cave man’s life influence the shape of the human penis”? The problem with this kind of problem statement is that you are looking at some data (in this case the shape of human penises) and looking for a model that fits this data. You can come up with many such models, because you are fitting the data after the fact, but you have no guarantee that your model is correct.

Let’s take a case in point of an issue brought up in the latest interview with Dr. Ryan on the Savage Lovecast. The question: why are human penises larger than gorilla penises when gorillas are larger than men? The given answer: because they were designed as plungers to remove the semen of rival males from the reproductive tract of a female. The larger theory behind this answer lies in the idea of sperm competition, the notion that females practice selective non-monogamy as a means of maximizing genetic quality in the offspring. The male, worried that he might be cuckolded into investing resources into offspring not genetically related to him needs adaptations to keep his partner from being impregnated by rivals. Therefore, it is to his advantage to have a “plunger penis” that will reduce the probability of pregnancy from a rival.
It’s kind of like an intellectual Rube-Goldberg machine, isn’t it? Or perhaps more fittingly, like one of Kipling’s “just-so stories”.

The “scientific data” for this claim come from this paper, which might be the most hilarious scientific study I’ve ever read (and this includes the smoking pot in the fMRI scanner study). From the abstract:

Inanimate models were used to assess the possibility that certain features of the human penis evolved to displace semen left by other males in the female reproductive tract. Displacement of artificial semen in simulated vaginas varied as a function of glans/coronal ridge morphology, semen viscosity, and depth of thrusting. Results obtained by modifying an artificial penis suggest that the coronal ridge is an important morphological feature mediating semen displacement.
Yes, kids… this is research with dildos and masturbation sleeves. Other great sound bites from the article include the “recipe” for artificial semen: 

Simulated semen was created by mixing 7 ml of water at room temperature with 7.16 g of cornstarch and stirring for 5 min. After trying different mixtures of cornstarch and water, this recipe was judged by three sexually experienced males to best approximate the viscosity and texture of human seminal fluid.

And in addressing limitations of the current paradigm:

A limitation of our attempts to model semen displacement was the greater rigidity of the prosthetic as compared to real genitals. The artificial vaginas did not expand as readily as real vaginal tissue nor did the phalluses compress, and, as a result, semen displacement was assessed on the basis of a single insertion. The effects, however, were robust and generalized across different artificial phalluses, different artificial vaginas, different types of simulated semen, and different semen viscosities.

…Sigh…. My own research seems so vanilla in comparison! But in all seriousness, extraordinary claims require extraordinary evidence, and this is not that evidence.
Evolutionary psychology does not make uniquely falsifiable claims
The hallmark of actual science is that it makes predictions that can be falsified and separated from other possible explanations. Evolutionary psychology does not do this. For example, the fact that men who have spent more time away from their partners find their partners more attractive and desirable, and ejaculate semen with higher sperm counts during copulation are taken as evidence for the sperm competition hypothesis. The argument is that as the man has not observed his partner, he is threatened by sperm competition, so it is to his advantage to copulate often and with… uh, greater virility. Although these studies control for time since last copulation, it doesn’t take much creativity to come up with alternative explanations.

Another example: the sperm competition hypothesis would predict that men would be more concerned with sexual infidelities of a partner (as this could result in cuckoldry) and women would be more concerned with emotional infidelities (as this could result in him leaving her without resources, or diverting resources into another partner). To test this prediction, David Buss conducted many surveys with many different groups asking them whether they would theoretically be more upset by a sexual or emotional infidelity. As nicely shown in David Buller’s critique of evolutionary psychology, although more men than women say that sexual infidelity is more upsetting, half of the men are still choosing emotional infidelity as more upsetting, so this model is far from complete.

Evolutionary psychology assumes that we know what psychological pressures existed for our ancestors in the Pleistocene.
We don’t

A closely related problem is that evolutionary psychology assumes that the mind evolved to the problems of the Pleistocene and then remained static for over 12,000 years. This seems implausible as large species-wide shifts have been observed in as little as 18 generations (less than 500 years for human generations).

However, many people who hate evolutionary psychology do so for irrational reasons
Evolutionary psychology is fine for intellectual masturbation, but we should strongly question its place as an actual science. However, many of its loudest critiques are based on emotional and political responses, rather than on the quality of the academic content.

Consider Megan McArdle’s critique of Sex at Dawn for The Atlantic. She writes:

“For example, like a lot of evolutionary biology critiques, this one leans heavily on bonobos (at least so far).  Here's the thing:  humans aren't like bonobos. And do you know how I know that we are not like bonobos?  Because we're not like bonobos.
(Emphasis in original). 

Although I am sure Ms. McArdle is more articulate in other matters, it is true that when our beliefs are challenged, we are quick to say that scientific inquiry into the matter in question is useless.

Evolutionary psychology stirs up a political hornet’s nest. If we believe that our minds evolved to solve problems of the Pleistocene and have remained largely unchanged, this suggests that our minds have little capacity to change. Therefore, we can do little about real social problems such as war, racism and rape.

As Steven Pinker points out, ignoble tendencies do not have to lead to ignoble behavior. In other words, what “is” is not the same as what “ought”. The confusion between these two concepts comes from a fallacy confounding what is natural with what is good. Which leads me to my last problem with Dan Savage’s promotion of this book…..

Things that are natural are not necessarily desirable
Let’s step back and assume for a moment that the science of evolutionary psychology was solid, and that Ryan’s hypothesis about the polyamorous nature of humans was true. There would still be a major problem with Dan Savage’s use of this book to endorse polyamorous relationships: just because some behavior is fundamental to the nature of human beings does not mean that it’s a desirable state for current human beings.

Let me be clear on this point - I am not saying that humans shouldn’t be polyamorous. I believe consenting adults should do whatever they like. However, I am saying that the “naturalness” of polyamory does not inform its desirability.

Savage and Ryan are implicitly stating that since polyamory occurs throughout animal species and in human evolutionary history, it is natural. OK, but so are war, conquest, exploitation and rape and we do not condone these.

Dan, you are a smart guy…. Don’t get sucked in to poor science just because it tells a compelling story that you want to believe!


  1. Really well put! I hope he reads it.

  2. Thanks - I emailed him with the link. I'll keep you posted. :)

  3. I love the research which shows the various ways in which humans have evolved since agriculture. Evolution hasn't stopped. The Stone Age diet ceased to be the "right" diet soon after we started farming.

    Of course we aren't the same as we were 10,000 years ago.

  4. Indeed. Hasn't stopped people from claiming otherwise though:

  5. Michelle,

    Great post but I do take issue with you on a couple of points.

    First, while I will agree that EP has an affinity for just so stories, that is no excuse to dismiss the entire field.

    Second, The basic premise of EP is not that are brain stopped adapting it is that there has not been enough time for our brain at a fast enough pace to keep up with cultural and technological evolution. As a result we as humans engage in activities which on the surface seem strange but when viewed through the lens of EP start to make sense.

    Finally, no one is saying that poly relationships are ok because they are natural but that the arguement against them cannot be one based on its unnaturalness. Many civilizations through time have practiced the tradition of more than one wife. And, most of them have faired ok.


  6. Hey B,

    Thanks for keeping me honest. :)

    I do agree with you that I was a bit hyperbolic by characterizing EP as assuming that brains don't change. My point was that they consistently underestimate the degree of change that can exist (though I don't think there's a reliable measurement of this).

    As for the third point, I was trying to express that any argument of naturalness is orthogonal to any argument about the desirability of a trait. Any argument using poly-as-unnatural is flawed because many desirable things are unnatural (antibiotics, eye glasses) and many natural things are undesirable (war, famine). In some sense, I'm arguing against the people that Dan Savage is arguing against.

    As for dismissing an entire field, it depends what we want to call the field. EP is fine as philosophy, but it is not an experimental science. (This is not the fault of EP, it isn't possible to see many possible evolutions of humans to test hypotheses).


  7. Funny that you write a post critical of others' unsound argumentation that includes the rather HUGE fact that you haven't even bothered to read the book you're dismissing. In fact, they trash Buss quite savagely (no pun intended) for precisely what you point to (just so stories) and talk quite extensively about the controversy over Baker's overblown claims. Their book is really a critique of EP more than an iteration of it. If you want to set yourself up as the judge of good science, maybe you should familiarize yourself with the data before rendering judgment.

  8. That's fair. From 2 podcasts worth of interviews, I had not heard anything new in these arguments, but you are right to point out that I should really be more informed before shooting my mouth off.

  9. This comment is a little late, and I see you've stepped back slightly from the more absolute position you asserted in your post (which was well-written, by the way), but I think you may simply be a victim of selective news. The tragic fact of the world is that the more sensationalist news tends to be what makes the headlines, even if it's not entirely true or, in the case of science, even if it's based on bad research.

    You said: "As for dismissing an entire field, it depends what we want to call the field. EP is fine as philosophy, but it is not an experimental science. (This is not the fault of EP, it isn't possible to see many possible evolutions of humans to test hypotheses)."

    Firstly, I'll just point out that I have major problems with evolutionary psychology too and it infuriates me most of the time, so I'm not exactly a "supporter" of EP.

    The main problem with the above quote is that you've automatically (and perhaps accidentally?) assumed that "psychology" is the study of humans, when this is untrue. Obviously, a lot of the research is brought back around to how information can be applied to humans, but at its core it is simply the study of behavior (and some will argue the study of the "mind" as well).

    The importance of pointing that out is that although you are correct in being skeptical over the possibility of doing good science in human evolutionary psychology, the same is not true of animals. In particular, I think the work done on tool-use in New Caledonian crows is amazing evidence of the power that evolutionary psychology can bring to science. The work of Hunt, Gray, Taylor and more, is touched upon here:

    You might also be interested in this book chapter on the two approaches to evolutionary psychology: (sorry for the messy link, I don't know the codes to fix it). The first approach being as you describe; adaptationist, filled with just-so stories and unfalsifiable/untestable assertions, and the second being a more scientific and useful approach, although arguably less exciting than the "explanation" for why men are attracted to lipstick...

    I've only recently stumbled onto your blog so I'm sorry if you've covered any of this information before. I'm enjoying reading through your posts though!

  10. I'd like to add to what Mike has said by mentioning that even within that podcast, they spent a lot of time talking about human groups that live in pre-agricultural circumstances, and the aforementioned bonobos of course, which all present falsifiable claims: if pre-agricultural humans were monogamous, societies closer to that model would be likely to have more monogamy. They don't.

    Just because EP theory/speculation with no backing in evidence is bullshit, doesn't mean all EP theory is bullshit. I'm feeling a little confirmation bias in the way you're listening to the podcasts :P

    That aside, I think one of the reasons Savage et al have got your hackles up is that he in particular is really, really defensive about polyamory. Considering how overwhelmingly it gets attacked, I really can't blame him, but it's true that it all sounds a bit unreasonable if you view his argument as starting from a blank slate, rather than as a mere rejoinder to the monogamy-enforcing status quo.

  11. No doubt it will be very useful for my future projects. Would like to see some other posts on the same subject!