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Robert Kurzban

The Evolutionary Psychology Blog

By Robert Kurzban

Robert Kurzban is an Associate Professor at the University of Pennsylvania and author of Why Everyone (Else) Is A Hypocrite. Follow him on Twitter: @rkurzban

Two Sides of the Same Coyne

Published 10 January, 2011

A well known biologist, and author of Why Evolution is True, Jerry Coyne recently blogged about a really interesting new paper about fruit fly wings.

In the new paper, the authors show that fruit fly wings have really pretty patterns when viewed against a black – but not a white – background. As Coyne says, the work is described well over at Discover; it’s worth checking out, if for no other reason than the patters of color really are striking.

My interest is in Coyne’s remarks. Discussing the finding, Coyne asks, “What are these patterns for?” He goes on to discuss evidence regarding the function of these patterns.

But that simple question is interesting and caught my attention. In it lies the implicit assumption that the patterns are for something. Coyne seems to be assuming that these traits are adaptations. (He ventures some guesses, in part based on the fact that the trait is sexually dimorphic, having to do with mating and species recognition.)

Now, the thing is that this reminded me of some stark criticisms leveled by a well known biologist, and author of Why Evolution is True, Jerry Coyne. In his book, he talked about how traits should emphatically not just be assumed to “reflect genetically based adaptations.” Now, true, in that quote there he was talking about behaviors, not physical traits, but the argument he makes does not, as far as I can tell, as a logical matter apply only to behavior. Indeed, he cautions about rushing to conclusions about a physical trait — interestingly enough, one that is, just like the wing patterns, sexual dimorphic –  writing that, for one particular species – readers may guess which one –  you can’t infer that because males are larger, this is necessarily due to male-male competition; there could be another reason for the difference, given what we know about the natural history of the species in question.

That said, it’s clear that he thinks that one can, in principle, identify adaptation in the context of behavior, more generally. He discusses lots of behavioral adaptations in the book, including, for instance, the “adaptive behavior” (p. 112) of honeybee defense against hornets. (As an aside, he refers to the hornet as “designed for mass slaughter,” p.112, his italics.) (By the way, this is really, really cool. When a hornet comes into the nest, the bees swarm the intruder, vibrate, and cook the hornet to death. See Coyne’s description for a bit more.)

In any case, Coyne (author of the book) says that the problem is that it’s just too easy to make up “just so stories” like the ones that Coyne (blogger) makes up in his post. Discussing some functional hypotheses, Coyne (author) reiterates that these ideas “come down to untested—and probably untestable-speculations,” adding that “it’s almost impossible to reconstruct how these features evolved (or even if they are evolved genetic traits) and whether they are direct adaptations or…merely by-products…” (p. 250 his emphasis). In short, he cautions: “We should be deeply suspicious of speculations that come unaccompanied by hard evidence.”

So my worry here is that Coyne (blogger) in his very nice blog post has made the sort of error that Coyne (author) would criticize, assuming the traits are functional and speculating about what the function might be. I hope that the one doesn’t become aware of the other. It might set off quite a fight.

It’s probably obvious, but in case it is not, I agree with the blogger not the author. Yes, one ought not simply assume any observed trait is an adaptation, but well specified guesses regarding adaptive function can be tested. Coyne (author) actually endorses this inference, saying: “Every time we see an obvious adaptation, like the camel’s hump or the lion’s fangs, we clearly see evidence for selection.” (p. 135). So he is saying that one can infer the function (rending) from form (fangs), given the right sort of evidence. And in his blog post, he discusses some relevant evidence in terms of the fly wing patterns. The question is, why is it that when discussing humans, the logic of identifying adaptations changes, such that the problem of the ease of generating ideas of function means that developing a hypothesis about function in non-human animal behavior is just fine, but a hypothesis about function in humans is “not science”? (p. 228).

So, in all seriousness, I want to say that I only just discovered this blog, and so far I have enjoyed it. I might also note that with the exception of a few pages, I actually liked the book, too, though I haven’t read all of it cover to cover.

But I do believe that it’s worth thinking about why Coyne thinks honeybee behavior can be characterized using the framework of adaptationism but worries about applying these principles to human behavior, so much so that hypotheses of function in humans cease to be science. Why is the claim that humans have, say, cheater detection devices different from saying that bees have hornet-defense systems? Why is he an enthusiastic adaptationist about fly wing pattern coloration while condemning hypotheses about the function of human traits as merely a “parlor game?”

In short, shouldn’t we do “species-neutral biology,” to Coyne a phrase?

(Note that Liddle & Shackleford address some of the ideas here in their review of the book, as well as Coyne’s (incorrect) reading of the field as endorsing genetic determinism.)

  • http://vertebratesocialbehavior.blogspot.com Clara B. Jones

    Note that Coyne received his Ph.D. under Richard C. Lewontin; although, to be fair to Coyne, his published views have not been as extreme or, apparently, politically based as those of his major professor.

  • David P.

    I love Jerry Coyne’s book, and his blog is fantastic. But his negative knee-jerk reactions to evolutionary psychology are purely the product of his “emotional dog” wagging his “rational tail” (to steal a phrase from Jon Haidt). Jerry Coyne’s essay in an Edge compilation on the question “What’s Your Dangerous Idea?” pretty much says it all.

    (You can read it here but you need to scroll down: http://www.edge.org/q2006/q06_9.html )

    Coyne’s dangerous idea (and boy is it dangerous) is that the tenets of evolutionary psychology… (cue thunder strike) are true! The horror! Could you imagine what it would do to our society if people found out that “many behaviors of modern humans were genetically hard-wired (or soft-wired) in our distant ancestors by natural selection”? It would be total anarchy!

    This line is particularly telling:

    “So, why do I see evolutionary psychology as dangerous? I think it is because I am afraid to see myself and my fellow humans as mere marionettes dancing on genetic strings. I would like to think that we have immense freedom to better ourselves as individuals and to create a just and egalitarian society.”

    And therein lies the “emotional dog.” Coyne is afraid of what he sees as the political implications of an apolitical field of inquiry. I would comment on this pervasive and irrational fear, but Steven Pinker has already given it a book-length treatise entitled The Blank Slate: The Modern Denial of Human Nature. I couldn’t recommend this book highly enough, especially for those with a Coynean bent. Somehow, I get the impression that this “emotional dog” is wagging the tail of many of EP’s critics.

    • Robert Kurzban

      Thanks for the comments. Interestingly, Coyne blogged about The Blank Slate over the weekend, and even recommended the book (with an exclamation point, no less). I hadn’t seen the Edge piece before, but it seems to me essentially the same as what he said in the book, including “mere marionettes dancing on genetic strings” and the usual, if these ideas are right, then we have “excuses for behaviors that seem unacceptable.”

    • http://helian.net/blog/ Helian

      It never seems to occur to these people to wonder why they have an emotional response to the notion of a “just and egalitarian society” to begin with, or why they have any values at all for that matter. They seem to have this notion that “justice” and “equality” are things that float out there in the ether as things in themselves. They need to read Plato’s Euthyphro and get a grip.

      As for Pinker’s “Blank Slate,” Robert Ardrey described it as the “Romantic Fallacy,” and referred to it in most of his books. His analysis of it in “African Genesis” is similar to Pinker’s, but much more entertaining to read, with much less ancillary and dubious stuff about how this philosopher begat that philosopher who begat the Blank Slate. Ardrey was unquestionably the number one proponent of what is now known as evolutionary psychology and consequently the greatest bete noire of the blank slaters throughout the 60’s and early seventies. For thus resisting the prevailing obscurantism in the behavioral sciences he was dismissed by Pinker, acting in this instance as Dawkin’s poodle, as “totally and utterly wrong,” because he had spoken approvingly of the group selection hypothesis. Of course, group selection seems to be making a comeback, but in any case, it was only a hypotheses mentioned as one among many in “The Social Contract,” and of no more central importance to his ideas than Pinker’s equally idiotic reference to Konrad Lorenz’ “hydraulic hypothesis,” which, to the best of my knowledge, Ardrey never even mentioned. The central tenets of Ardrey’s philosophy were that there are such a things as innate predispositions, that they do not “determine” our behavior but their expression is profoundly influenced by culture, and that therefore the “blank slate” is wrong. By far the most important and effective opponent of the blank slate in the 20th century, he was dismissed by Pinker, who was supposedly writing about the blank slate, in a few lines, and has become an unperson today. That’s sad, because if anyone ever personified Wilson’s concept of consilience, Ardrey was it.

      Yes, EP is an interesting science. It’s impossible to grasp what’s going on in the field by reading all the recommended textbooks and journals. You have to know something about its history. If ever there was a science that simply cannot be left to academic chauvinists as their untouchable domain, like so many popes and cardinals of holy church before the days of Luther, EP is it. It’s much too important for the rest of us ever to leave entirely to the mercies of future Richard Lewontins.

  • Jason Meltzer

    While there is clearly an emotional reaction to the idea of EP (seems odd among scientists, though), there is a deeper problem that may plague even the most hard-nosed among us: complexity (the ultimate frontier in all scientific and technological understanding). While it’s very easy to determine certain adaptive physical traits (camel’s hump, etc) and even possible to find the genetic bits that govern them, it’s a far more complex and delicate matter to tease apart human behavior. Among humans it is even more-so than animals, as one cannot raise a pristine human being in captivity from birth, as we do with animals.

    That’s not to say it cannot be done or should not be done. But the complexity of the problem is certainly a barrier to credulity — I’m sure you’re aware : )

    • David P.

      Good point, Jason. Human behavior may well be more complex than most other species. But if the barrier to credulity lies in the complexity of human behavior, then all approaches to the study of human behavior should be met with equal degrees of credulity, or lack thereof. Yet there exists a huge asymmetry between the evolutionary approach and other approaches, even though evolution is the only process we know of that can generate the type of complexity you refer to.

    • Robert Kurzban

      I agree it’s mysterious that there is such emotion surrounding EP. On your second point, I think you’re saying that raising people in captivity allows control over the organism, but I don’t see the fact that we can’t as fatal. We know a lot about various species from studying wild populations. On your other point, complexity, as David P indicates, is a problem independent of what approach one takes. Studying humans with the added tools from biology, it seems to me, should only help matters. That is, the complexity of human behavior shouldn’t make evolution-less psychology more appealing than evolutionary psychology, it seems to me. So I guess I just don’t see the credulity gap. Why does a hypothesis about a complex creature (like us) become less plausible as more theoretical tools are brought to bear on it? I find that puzzling.

      • Jason Meltzer

        As complexity increase, it is harder to estimate causality. While you say that your hypotheses are derived from evolutionary principles, that conception can be quickly misunderstood or twisted into thinking you are seeking evolutionary causes for human psychology. No doubt, many aspects of human psychology are adaptive (or, er, maladaptive at this point), but given such complexity and the inability to control innumerate variables, it’s very hard to pin down cause.

        The real misunderstanding and dispute, from what I can discern, is the actual question EP is trying to answer. From my understanding of your work, you are not looking to prove “behavior X is an evolved adaptation to environmental variables y,z,w…” but rather using evolutionary principles to guide discovery of and experimentation about the fundamentals of human psychology. Nobody should have a problem with the latter, so long as the evidence holds up!

  • David P.

    Interesting exchange. Not to drag this on too much, but I’d like to note that regardless of whether EP is or should be in the business of proving adaptations, there is clearly a double standard in the field between proposed evolutionary “causes” and proposed cultural or folk psychological “causes” for human behavior.

  • http://www.umsl.edu/~carrolljc/ Joseph Carroll

    The question is, why is it that when discussing humans, the logic of identifying adaptations changes, such that the problem of the ease of generating ideas of function means that developing a hypothesis about function in non-human animal behavior is just fine, but a hypothesis about function in humans is “not science”? (p. 228).

    Very shrewd, incisive. That is the question. I’m reminded of a passage in Donna Haraway. She acknowledged that she used a double standard. For any scientific findings she thought potentially contrary to her favored political positions, she applied, she said, a much higher level of proof than to findings that seemed to support her favored political positions. That higher level of proof is, in effect, a level so high that it could never be met.

    Haraway is unusual in being so explicit. Coyne is more typical in evidently not being aware that he has two distinct identities, Coyne the blogger an Coyne the author.

    One way this kind of political bias enters into polemical discussion a la Lewontin is tacitly to require an impossibly high level of “proof” for the ideas that you dislike while simultaneously giving a free pass to the ideas you do like. And it isn’t just discussions of human evolution in which that pattern appears. It comes very close to being a human universal: let’s hold our own beliefs at a level of subliminal certainty beyond all challenge or doubt, and let’s exercise the most stringent skepticism against any belief that might tend to undermine our self-affirmations, either as individuals or as groups.

    Who was it who said that evolution had not designed our minds for truth but for survival? Science is the institutionalized, collective effort to overcome a universal tendency toward using our minds as defense mechanisms, rather than as instruments of objective knowledge.

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