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

PZ Myers Clarifies Criteria For Distinguishing Genuine Hypotheses from “Just So Stories”

Published 28 December, 2011

PZ Myers recently wrote a blog entry about the answer to the question, “Why Do Women Menstruate?” In the piece, he went through a number of candidate answers and summarized a recent paper that addresses this question. My interest after having read the post was how to reconcile Myers’ discussion of the possible evolved function of menstruation with his dim view of evolutionary psychology, since it seemed to me that the structure of the arguments he entertained was the same in the menstruation case as in evolutionary psychology.

A commenter (bromion, #23) on Myers’ site had the same question, writing:

I’m wondering why you support this kind of evolutionary explanation of a phenomenon that is difficult to prove directly (we can’t observe an evolutionary fossil record here), but dismiss the entire field of evolutionary psychology as “just so” stories.

Myers (#32) answered as follows:

This hypothesis has the advantage of being based on actual comparative data and the physiology of decidualization. It has an explanation based on the cell and molecular mechanism, not just derived from a phenotype. And it makes a specific, testable prediction about how the shift could have been made.

It isn’t about looking up the fossil record (fossils suck for evaluating most evolutionary hypotheses), but about using the molecular evidence to evaluate the answer. We have molecular evidence. We can also get more much more readily than we can dig up a fossil uterus.

This is really useful because Myers has made explicit his criteria for distinguishing a legitimate scientific hypothesis from a “Just So Story.” (The “Just So Story” label, for the uninitiated, is meant to imply that the hypothesis in question cannot be shown to be false, and therefore is not a legitimate scientific hypothesis.) Myers seems to have committed to what appear to be three reasons having to do with 1) comparative data (which I think is the same as “actual comparative data”), 2) cell & molecular mechanism, 3) predictions about “the shift,” which in context I believe refers to the evolutionary pathway from the ancestral condition to the present condition.

I thought I would apply these three criteria to some hypotheses to see how they fare on the Myers Story Scale (MSS). Let’s take a hypothesis Jerry Coyne proposed in a blog entry some time ago, about why sloths come down to the ground to defecate instead of doing so in the tree. His favored hypothesis seems to be that this is to attract mates; the dung pile is a signal to potential mates that a sloth is present in the dung-adjacent tree. Does it satisfy the three criteria Myers points to?

Comparative data. Nope. The post was just about sloths.
Based on the cell and molecular mechanism. Fails. Just poop.
Makes a prediction about evolutionary course. Fails. No discussion of this.

This hypothesis, then, is 0 for 3 on the MSS, and so is an untestable Just So Story, according to the Myers criteria. Coyne, however, thinks this is a perfectly fine hypothesis, writing that “in principle these theories are testable. We could see, for example, how sloths manage to find each other at mating time. We could also do mock-defecation studies from branches, using model sloths, to see if the noise attracts predators.” From this conflict, we can see either that the criteria are wrong, or Coyne is wrong. I don’t see another option.

To take a second example, in Myers’ post, he entertains and rejects one explanation for female menstruation, writing that one possibility is that “humans have rather aggressive embryos that implant deeply and intimately with the mother’s tissues, and menstruation “preconditions” the uterine lining to cope with the stress. There is, unfortunately, no evidence that menstruation provides any boost to the ‘toughness’ of the uterus at all.”

He rejects this hypothesis, clearly, but he doesn’t reject it because it’s an untestable Just So Story. He accepts it as a legitimate hypothesis because he (implicitly) reasons as follows. If the function of the trait is coping with future embryos, then the trait should have properties (toughness) that contribute to this function. From the observations of toughness (however that is measured), he rejects the hypothesis. The key idea to note is that the claim about the function is, in itself, enough to render the hypothesis testable. The hypothesis did not seem to need comparative data, etc.

Finally, at the end of the post, in a postscript, PZ Myers tried to become an evolutionary psychologist, trying his hand at understanding one aspect of human social behavior, why some people are pro-choice and others pro-life. Here is his explanation:

The maternal-fetal conflict is also a conflict between males and females: it is in the man’s reproductive interests to have his genes propagated in any one pregnancy, while it is in the woman’s reproductive interests to bail out and try again if conditions aren’t optimal for any one pregnancy. This conflict is also played out in culture, as well as genetics — pro-choice is a pro-woman strategy, anti-abortion is a pro-man position. Sometimes, politics is a reflection of an evolutionary struggle, too.

First of all, it’s obviously very interesting that Myers seems to be trying to explain a psychological phenomenon – here, moral variation – by thinking about the relevant fitness interests. It’s a bit surprising that the people commenting on his blog, many of whom roundly condemn evolutionary psychology, seem not to have had a concern about his proposal here.

It’s not precisely clear, but this remark seems to me to be proposing that the reason for variation in views on abortion has to do with reproductive interests and, in turn, the key variable that underlies these differences is one’s sex, with women gaining an advantage by adopting the pro-choice position. Now, the proposal does poorly according to the MSS — no comparative data, no cellular mechanisms, and no word about the evolutionary trajectory of the trait – but the proposal does seem to make a prediction, that a person’s sex will be the key predictor variable for views on abortion. As it happens, there are a large number of datasets that Myers could have consulted in making this proposal, nearly all of which would have shown that there is no sex difference, and, when there is one, it accounts for a tiny amount of the variation in abortion views.

Now, the part that Myers might be right about is the idea people’s views on sexual issues can be systematically predicted by considering their strategic reproductive interests. But the crucial variable isn’t sex, it’s reproductive strategy. In my opinion, the best work on this is by Jason Weeden, who has gathered and analyzed a tremendous amount of data to interrogate his explanation for variation on abortion views. (Weeden’s dissertation is, with respect, one of the only dissertations I’ve even come across that’s actually worth reading. Note that in the spirit of disclosure, I should mention that I’ve collaborated with Weeden and we have made a similar proposal regarding views on recreational drugs.)

In terms of the broader theme here, my guess is that Myers doesn’t really believe that those three criteria distinguish a testable hypothesis from a Just So Story. As I’ve shown here, he himself produces hypotheses which fare poorly according to his own criteria. It is easy to find other hypotheses from the animal and human literature, measure them against the MSS, and show that hypotheses that fail on this measure are treated as perfectly legitimate hypotheses. The reason is that functional claims entail predictions about the structure of traits, whether physiological or behavioral, as illustrated by the three cases above. The criteria Myers enumerates are not required for making a hypothesis falsifiable, and from his own writing, it seems that he implicitly believes this.

In short, Myers’ proposal shows that he thinks that evolutionary reasoning can form the basis for hypotheses about the human mind and human social behavior. Yes, I wish that he would police himself a bit more, and dip his toe in the pools of data available to evaluate the claims he makes before writing about them, but I’m very happy to look past that because I think it’s encouraging that he’s starting to write about how evolutionary ideas can inform hypotheses about human behavior. He didn’t do all that well this time, but I’m confident that, with helpful policing from others, he can do better.

Reference

Weeden, J. (2003). Genetic interests, life histories, and attitudes towards abortion. Dissertations available from ProQuest. Paper AAI3087480.

http://repository.upenn.edu/dissertations/AAI3087480

http://behavecology.wordpress.com Steven

Myers’ comment – as quoted – doesn’t state that the criteria he stated are the only possible criteria. He might argue that the criteria he proposed are sufficient but not necessary (or that only one or more of them are necessary). Thus, it’s not certain that Coyne’s blog post would have failed to satisfy Myers. It might fail to satisfy him, but you don’t know that, and the web that you’ve constructed out of a couple of isolated examples doesn’t tell us much about what either man would say about it.

I also have doubts about your construction / usage of the third criteria. As I read it, Myers was talking pretty explicitly about the evolutionary history of menstruation, while Coyne is clearly talking about the current adaptiveness of the trait of ground-pooping. These are not the same thing. Laland and Brown (2006, p. 25) state:

“An adaptation is a character favored by natural selection for its effectiveness in a particular role. It is something that has evolved to fulfill that function, and it may or may not be adaptive in the current environment. Adaptive behavior is functional behaviour that increments reproductive success, and it may or may not be an adaptation.”

As far as I can see you conflate the two, and then end up claiming that Coyne fails because he’s not talking about adaptation, and later fail Myers on his own criteria about adaptation because he’s not using addressing adaptiveness with abortion data sets.

———
K. N. Laland and G. Brown. An introduction to evolutionary models of human social behavior. In J. C. K. Wells, S. Strickland, and K. N. Laland, editors, Social information transmission and human biology., Society for the study of human biology series, chapter 2, pages 19–37. CRC Press, 2006.
- Robert Kurzban
  
  On the issue of what he intended as the criteria, all I have to go on is what he wrote. I would welcome any clarification he has to make of the logical necessity/sufficiency of the criteria.
  On your second point, yes, history and function are different, but I disagree that Myers is talking only about history because he explicitly talks about candidate functions for menstruation in the text. (Similarly, Coyne is talking about the function of ground-pooping.) Generally, I endorse the distinction L&B are trying to make (though I prefer Don Symons’ rendering of these issues); to clarify, my view is that abortion datasets are relevant insofar as they speak to the function of the underlying psychological mechanisms, not the issue of RS in modern environments.
David P. Schmitt

Comparative data, physiological data, phylogenetic data, experimental data…too bad real evolutionary psychologists don’t use such things (and evaluate such adaptation evidence in terms of breadth and depth; cf. Schmitt, D.P., & Pilcher, J.J. (2004). Evaluating evidence of psychological adaptation: How do we know one when we see one? Psychological Science, 15, 643-649.)
Nietzsche

It seems to me that one of the largest difficulties facing evolutionary psychology, as things currently stand, is overcoming the rhetorical propaganda being fed on the matter of adaptationist methodology and epistemology.

In line with contemporary philosophy of science, it is folly to try and dictate a priori what specific methodological or epistemological criteria should apply in any given branch of the sciences. The picture these days is to allow such criteria to emerge from the actual practice of the various sciences by their various communities. What you end up with are cluster-class views where often there are little or even no necessary conditions for what should be included as evidence; a given theory is corroborated proportional to its depth and breadth of evidence. (A similar move is often made by philosophers of science when addressing the so-called ‘demarcation problem’ [more plainly, the question of what determines science from non-science])

However, in light of this picture, something strange happens when it comes to adaptationism, and particularly sociobiology and evolutionary psychology: Even some philosophers of science start playing tricks (when presumably they should know better).

For instance, the philosopher Robert Richardson’s recent book, which is an all-out assault on what he perceives to be a flagrant abuse by evolutionary psychologists of the methodological and epistemological ‘standards’ in evolutionary biology, is one case of this.

Richardson pretends that there is an established, stringent standard for assessing adaptationist hypotheses in evolutionary biology. He argues this by selectively pointing to a few studies, in so doing seemingly ignoring the very different impression one gets by just looking through the textbooks and journals, where one finds adaptationist conclusions on the basis of very different and varying evidentiary ‘criteria’.

Another philosopher of science, Sheldon Davies, enthusiastically approves of Richardson’s elucidation of such make-believe standards. Philosopher of biology Elisabeth Lloyd has offered up much the same analysis. Philip Kitcher is similarly of a like mind. They seem to set the bar extremely high. It makes you wonder what’s going on here.

In the case of Richardson’s recent book, he oddly begins not with a direct entry into the methodological and epistemology arguments, but rather first makes the Kitcherian move to appeal to what he feels is a sort of pragmatic ‘danger’ of adaptationist reasoning as applied to human cognition and behavior. This is odd considering the thesis of his book, which is an attempt at demonstrating what he thinks are the epistemic and methodological shortcomings of evolutionary psychology. Ultimately, I think he is wrong on that score. But — and even though it ultimately doesn’t matter what one’s motivations might be for promulgating a certain view — it does make one wonder whether it is the horse or the cart doing the pulling.

Is it Richardson’s belief (misleading, in my view) that stringent and specific standards exist in evolutionary biology? Or is that he thinks evolutionary psychology is ‘dangerous’, and so should be put to bed for good, even if that entails a rhetorical Gouldian/Lewontonian-inspired assault, designed to proffer an impressive appearance of validity, analytical sophistication, and accurate appraisal of such standards to readers (who more or less wouldn’t know any better)? And if it were really about the standards, why would he also try to criticize the reverse engineering perspective of so many biologists, given that he doesn’t take reverse engineering to figure as a part of the so-called standards that he disinters to exist in biology? Did he think a shot-gun approach was the best strategic move to make if the goal was to decapitate his target (evolutionary psychology)?

So yes, one perhaps cannot help but wonder from afar just what the critics’ motives are…
Nietzsche

Your comment about Myers’ evolutionarily-oriented thinking on pro-choice/pro-life — and the apparent lack of concern about this style of thinking by his blog commentators — is rather interesting as well.

It often appears — to me anyway — that the degree to which many folks are accepting of evolutionary hypotheses is contingent on the content of those hypotheses. In the Myers case, it seems as if the specific hypothesis put forth doesn’t raise any flags because it does not obviously have any politically incorrect connotations or inherent ‘dangers’ associated with it. (Compare, for instance, the way David Buss’ work is still often received negatively.)

If a given theory or hypothesis triggers people’s moral and political buttons, there often seems to be a reflexive backlash (i.e., “this is evil;” “sloppy standards;” “just-so storytelling,” etc.). This unfortunately seems to apply as much to academics as to laypersons. All too many academics, it seems, operate under the assumption that politics determines good scholarship (or at least anecdotally I and others find they unwittingly operate under this assumption). So far as normative epistemology goes, placing politics as the key criterion for assessing the merit of empirical assertions is obviously a bad thing.

But the short answer to these problems is to try to make clear to critics what the actual evidential and methodological standards in evolutionary psychology are; and to this end, perhaps it would be most effective to point to actual research programs and scientists in the field which are the best exemplars (e.g., depth and breadth of evidence).
- Anonymous
  
  Thanks for your both your comments, N. As you say, I think it’s worth asking, as you put it in the first comment, whether it’s the horse or the cart doing the pulling. My view, which I think is also yours, is that there are certain conclusions certain critics want to reach about the field, which explains a certain amount of what we observe. (This raises the prior question about why critics want to reach those conclusions, which I think is also interesting.) On this comment, I take your point, but I’m curious if you think that the critics you have in mind would be interested in studying the papers coming from the programs you’re referring to. That has not been my experience. In any case, thanks for your insights here.
  - Nietzsche
    
    In Robert Richardson’s case, he is effectively forced to concede agnosticism, for instance, regarding whether language is an adaptation. He cites the Bloom & Pinker paper, for example, and finds their conclusion of language being an adaptation for language as being simultaneously unjustified and trivial. Richardson’s conclusion, in my view, is absurd, and most any adaptationist would (and I think should) call him out on this. Though of course his whole methodological and epistemological argument contra evolutionary psychology basically forces his hand in this way.
    
    You know something has gone terribly wrong when you are forced to tell adaptationists that they must remain agnostic about whether the eye is adaptation, lest you rigorously test the hypothesis to the most strictest of standards. I recall Daniel Dennett once referring to cladists as biologists who tie one arm around their back, unnecessarily prohibiting themselves of evidential and methodological resources in inferring adaptation. I agree. And more to the point, I might even argue that evolutionary scientists like cognitive ethologists and evolutionary psychologists could be well placed to even demonstrate how adaptive hypotheses of cognitive traits are best pursued, methodologically and evidentially. That would perhaps be an instance of evolutionary psychology ironically feeding back into evolutionary biology proper, extending the adaptationist armamentarium (at least with respect to cognitive adaptations).
    
    It can also be argued that Richardson misconstrues the cheater-detection work by Cosmides & Tooby. He construes their position as one proffering an adaptive account of reasoning in some broad sense; but as I’ve always understood Cosmides & Tooby on cheater-detection, they approach the phenomenon in strictly domain-specific terms.
    
    On this note, it is perhaps troubling that even philosophers of science, who typically evince a sharp acumen of their subject matters, are not immune to poorly understanding and having a less than adequate grasp on the field they criticize. As Philip Kitcher has noted, ‘local critique’ — focused critique on some specific area or question — is time consuming; it requires an extensive investment of time to become acquainted with the material to be critiqued. And time and again we see even critics like Buller, who have made at least a reasonable, extended effort to engage directly with the field, fail to fully understand it adequately. Buller bit off much more then he could possibly have chewed, and that much is obvious, I think, to those that really know the work he tried to ‘dethrone’. The danger with Buller, though, is that it is all too easy to read his book or papers, as an outsider or a dabbler, and come away thinking that he really has done a lot of damage.
    
    I’m actually in the process of writing a response paper to another critic who wrote a scathing indictment of work done by high profile evolutionary psychologists. The troubling aspect of that particular paper is that it was published in a relatively prominent philosophy of science journal, and certainly had more than a patina of being theoretically sophisticated; but in fact it is woefully inaccurate and biased. The fact that such a paper — replete with strawman representations, critical omissions, and even flagrant misunderstandings — got by the peer-review process in that particular journal certainly does not help to quell the feeling that criticisms of evolutionary psychology have an easier time getting by the quality-control filters. (Of all things, you’d think that being intellectually honest would be relatively easy to enforce.)
    
    So perhaps the shortest answer to your question is that there does, unfortunately, seem to be a lot of corner-cutting by the critics.
    
    Also, on a more pragmatic note, I should mention that researchers might helpfully make good use of the notion ‘inference to the best explanation’ (sometimes referred to as ‘abduction/abductive reasoning’), something which various philosophers have claimed is what science is arguably ultimately about. (For a psychologist’s take on it, check out one of papers on the issue by Brian Haig.) Thornhill & Gangestad’s work is a clear example of how it can be used in a very compelling way. (Gangestad, in fact, makes explicit mention of a similar point in his paper on adaptationism in the Handbook of Evolutionary Psychology edited by Crawford and Krebs — he raises it in connection with Wesley Salmon’s notion of “damn strange coincidences.”)
    - Nietzsche
      
      Edit: Richardson’s view on language is essentially that he is agnostic as to whether it is an adaptation, but moreover believes that it is trivial to say that it is ‘for communication’.
- http://www.facebook.com/rob.brooks.the Rob Brooks
  
  Spot on!
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Anonymous

I understand the frustration of feeling that EP is held to a different standard. However, as it is focused on a specific kind of evolution in a highly exceptional species, I think it should be. Biology is a science with few theories (some say one), and it is not expected that models are stable across the variety of life. Maybe you’ve discussed it elsewhere, but I think where you fall down comparing the Just So-ness of EP arguments to other arguments in evolutionary biology is that for nearly all organismal traits we can exclude the possibility that the trait is learned. Obviously, women don’t learn to menstruate, and they do menstruate under most (but not all) environmental conditions. Likewise, your recent example of flies and irises supports the idea that the white arrows are a proboscis extension cue for flies and maintain the fitness of the iris. We know of no plausible mechanism for irises to have white arrows other than developmental genetic mechanisms.

For human psychological traits, there is a powerful and omnipresent force that is nearly always a highly plausible source of the behavioral traits and therefore always has to be addressed – social learning. EP has a special barrier to pass: show me why the obvious answer (we’re a highly intelligent and neurologically plastic species that is masterful at behaviorally conforming to our social environment) is wrong. We do not have even a basic understanding of how nervous system architecture produces psychological traits or how genes, environment, and the interaction between the two produce variability in the relevant nervous system architecture. Even for human psychological traits with high heritability, it is more than plausible that a neurological endophenotype of unknown function is the “real” trait while the psychological feature of interest is a manifestation of neurogenetic x environment interaction.

An analogy…. if I submitted a cell biology paper where I kept Strain A at 35 degrees and Strain B at 38 degrees, and then I argued that an observed difference in mitochondrial function was because of genetic differences between the strain, I would rightly be told by the reviewers to sod off and do the right experiment. No one argues that male and female human children are treated the same in our society. That’s why when I see arguments for adaptive evolved differences in behavior in men and women, for example, it’s not that I feel that it’s not plausible or even likely in some cases, it’s just that I feel the first hurdle is to provide evidence that it is not culturally acquired. This hurdle does not exist for sloth defecation (or it’s at least a lot lower). Cross-cultural comparison means nothing if the relevant independent variable is “patriarchy” and all the cultures examined are patriarchal. Humans are exceptional learners and human culture is biologically unprecedented. This is not just a caveat of EP, it is its overriding problem.

All that said, obviously our brains and our behavior evolved. What is also clear is that societies are more than the sum of a bunch of interacting brains (just as brains are more than the sum of a billion neurons in a bowl). Others have argued that it is the enormously receptive plasticity of our brains that allows this rapid social change to occur. Teasing apart the aspects of our behavior that are relevant to our evolutionary past and those that are dependent on our enculturated present is a mind-boggling task, and I admire those who take it on substantively. However, EP usually comes off as halfhearted plausibility, stripped of complexity and nuance, and craving of credibility and attention it doesn’t (yet) deserve as science. Maybe that’s unfair, but that seems to be a fairly broad consensus impression from biologists. Take a little bit of the blame. Look at how much half-assed EP goes out to the popular media, or the barely polite criticism of EPists themselves (“…many evolutionary psychologists make broad and unwarranted claims about the positive identification of human adaptations.” Schmitt & Pilcher 2004). I mean, oof, right? The most obvious impact of EP I’ve seen is capturing the imagination of pseudo-intellectual cranks like David Brooks, and that’s nothing to be proud of.

Finally, regarding the “political correctness” thing. Yes, talking out of your ass is objectively worse when it has social/political implications than when it is about, say, a kinase or sloth poop. In any case, cell biologists DO sit around accusing each other of talking out of their asses about kinases (and in terms as denigrating and insulting as those directed at EP), it’s just that it doesn’t happen in the public domain / blogosphere. Most people don’t care about your favorite kinase, and the latest controversial results about protein phosphorylation aren’t in the New York Times every Tuesday. Everyone cares about politics, so expect a little blowback when assertions with political implications are made. Nut up – the “different standards for EP is unfair” is both wrong and whiney.
- https://sites.google.com/site/pleeplab/ Robert Kurzban
  
  It’s clear from your remarks you’ve read a number of posts, for which I thank you. The brief answer to your question about why the obvious answer – social learning – is wrong is the inability of domain general content-independent mechanisms to overcome the problem of combinatorial explosion. These ideas have been addressed and laid out extensively, probably best in Tooby & Cosmides chapter, “The Psychological Foundations of Culture,” available online. I very strongly encourage you to read it (see on this especially pp. 100-123). Most of the rest of your remarks are non-sequiturs; of course if you change one independent variable and claim a causal role for a different variable, you have made the incorrect inference, and of course no one claimed that societies are the sum of parts, given that there are always interactions beyond additivity. Similarly, the consumption of the primary literature by the press is irrelevant to the issue of the soundness of the inferences drawn by scholars in the discipline.
  
  You provide no evidence regarding the consensus of biologists, but if it’s true, to judge from my experiences and the bloggers who write about the field, this is primarily due to the fact that there has been no serious attempt to understand the field. My experience is that biologists seem to reason that because they know biology (true) and because psychology is “easy” (false), they know enough to pass judgment on the entire field without having bothered to credit that the people doing it might be sufficiently bright to be able to distinguish science from non-science and that the area requires careful study. That is, in my view, a substantial mystery: why are scholars such as yourself willing to write, in public, that an entire discipline doesn’t deserve credibility as a science? I find this very interesting, particularly juxtaposed with the ample evidence that the bloggers I quote and cover, for instance, have not taken the time to study and master the field.
  
  On this point that EP doesn’t deserve credibility as a science, suppose I claimed that cell biology, presumably your field, was not a science. Could you adduce evidence that it was? What would that evidence be? Where people in the field publish? The grants and awards they receive? Statements about the epistemology that underlie the field? Citation counts of important papers? (By the way, these are not intended as rhetorical questions. What evidence counts in favor of this claim for you?)
  
  In any case, I appreciate your reading my posts, and I hope despite the fact that we seem to disagree – or even because we do – you will continue to do so. Given your interest, I encourage you to “nut up,” as you say, and read the primary, or at least the secondary literature in the field. I would welcome hearing your reactions to the chapter I mention above.
- Robert Kurzban
  
  It’s clear from your remarks you’ve read a number of posts, for which I thank you. The brief answer to your question about why the obvious answer – social learning – is wrong is the inability of domain general content-independent mechanisms to overcome the problem of combinatorial explosion. These ideas have been addressed and laid out extensively, probably best in Tooby & Cosmides chapter, “The Psychological Foundations of Culture,” available online. I very strongly encourage you to read it (see on this especially pp. 100-123). Most of the rest of your remarks are non-sequiturs; of course if you change one independent variable and claim a causal role for a different variable, you have made the incorrect inference, and of course no one claimed that societies are the sum of parts, given that there are always interactions beyond additivity. Similarly, the consumption of the primary literature by the press is irrelevant to the issue of the soundness of the inferences drawn by scholars in the discipline.
  
  You provide no evidence regarding the consensus of biologists, but if it’s true, to judge from my experiences and the bloggers who write about the field, this is primarily due to the fact that there has been no serious attempt to understand the field. My experience is that biologists seem to reason that because they know biology (true) and because psychology is “easy” (false), they know enough to pass judgment on the entire field without having bothered to credit that the people doing it might be sufficiently bright to be able to distinguish science from non-science and that the area requires careful study. That is, in my view, a substantial mystery: why are scholars such as yourself willing to write, in public, that an entire discipline doesn’t deserve credibility as a science? I find this very interesting, particularly juxtaposed with the ample evidence that the bloggers I quote and cover, for instance, have not taken the time to study and master the field.
  
  On this point that EP doesn’t deserve credibility as a science, suppose I claimed that cell biology, presumably your field, was not a science. Could you adduce evidence that it was? What would that evidence be? Where people in the field publish? The grants and awards they receive? Statements about the epistemology that underlie the field? Citation counts of important papers? (By the way, these are not intended as rhetorical questions. What evidence counts in favor of this claim for you?)
  
  In any case, I appreciate your reading my posts, and I hope despite the fact that we seem to disagree – or even because we do – you will continue to do so. Given your interest, I encourage you to “nut up,” as you say, and read the primary, or at least the secondary literature in the field. I would welcome hearing your reactions to the chapter I mention above.
  - Anonymous
    
    “the inability of domain general content-independent mechanisms to overcome the problem of combinatorial explosion”
    
    I don’t buy this… it is analogous to Chomsky’s oft-cited but neuroscientifically unsupported theory that language is too complicated to learn, therefore there is an “innate” organ, whatever that means. See Deacon’s refutation of this assertion. Languages (and cultures) also evolve, in a manner which is both different from but dependent on human brains. Thus, languages can evolve into the complex and diverse entities we see today as long as they conform to the prior cognitive/learning capacities of human children, which though not necessarily language-specific are complex enough environments for a rich language ecology to emerge. Likewise it is easy to imagine broadly tuned cognitive mechanisms (if not fully content-independent) that are for all intents and purposes “generalist” in the context of human culture, because human cultural evolution is itself constrained (indirectly) by our cognitive structure. The “combinatorial explosion” is both contained and shaped by what is cognitively possible. So, when we say humans are “general learners”, we mean they are general learners among the large-but-limited subset of social environments humans can produce. There is little evidence from neuroscience for and much against the kind of modularity in higher cognitive functions proposed by EP. Worryingly, and, if I may say so, typically for the theoretical constructs of psychologists, this doesn’t seem to bother anyone
    
    I don’t think all of my other comments are non sequitors. You seem put out that EP is held to different standards for inferring adaptive evolutionary function. I was trying to offer a variety of reasons — both scientific and social — why it should be. I also explained that critiques of EP are not much different than critiques biologists make of any discipline, it’s just that EP gets a lot of popular public attention and therefore the criticism is more public as well. I think 80% of computational biology is so unmoored from empiricism as to be useless (to biologists), and I say so. I don’t think Scientific American really cares either way. My impression of biologists’ attitudes toward EP is based on the blogosphere and the biologists I know, I have not conducted surveys. It is my impression that, like psychology, EP actively and almost perversely insulates itself from neuroscience and behavioral genetics (which are my fields, not cell biology). Again, it’s an impression. People like Deacon who I think do engage across these fields do not self-identify as EPists, I don’t know how they feel about it.
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