The Colour-blind Leading the Colour-blind …

So, as he had promised, P.Z. Myers has continued on to discuss the failings of evolutionary psychology. And as I promised, I’m going to comment on it.

This post is entitled “The fundamental failure of the evolutionary psychology premise”, and at this point it seems like a good idea to remind you of the things that it would be disastrous for a New Atheist to do while going after any fundamental failure of evolution:

1) Describe a fundamental failure that would cast doubt on the evolutionary explanations for altruism and morality that New Atheists love so much.

2) Describe a fundamental failure of evolutionary explanations, not just ones that are applied to psychology.

Does Myers do either of these? He seems to do both. But let’s start with what he thinks is the fundamental problem in evolutionary psychology:

I have a real problem with evolutionary psychology, and it goes right to the root of the discipline: it’s built on a flawed foundation. It relies on a naïve and simplistic understanding of how evolution works (a basic misconception that reminds me of another now-dead discipline, which I’ll write about later) — it appeals to many people, though, because that misconception aligns nicely with the cartoon version of evolution in most people’s heads, and it also means that every time you criticize evolutionary psychology, you get a swarm of ignorant defenders who assume you’re attacking evolution itself.

That misconception is adaptationism.

In a forlorn attempt to forestall the buzzing mob that will immediately accuse me of creationism and of denying natural selection, that does not mean that I think selection is unimportant or not essential. It does not mean that I think other modes of evolution are more important. It means that there is a large collection of mechanisms that all play a significant role in evolution, and that you can’t simply pretend that one is all that matters. Not appreciating the importance of these other mechanisms is a bit like being an electrician who thinks that voltage is all that matters, and resistance and current can be ignored.

So, basically, the objection here seems to be that evolutionary psychology relies too much on a naive view that selection is an incredibly important factor in evolution, so much so that all you have to do is find a selective advantage for a trait and you can then spin out an entire story that explains exactly why we have that trait. And you don’t even need to go back and look at other factors like population size, drift, specific environment or anything else. This naive view, then, is what Myers seems to be attacking.

Isn’t this basically what Fodor and Piattelli-Palmarini criticized evolution/natural selection, as a useful theory, for? I don’t recall too many people telling them that they were basing that on a wrong or naive idea of evolution; instead, most seemed to tell them that they were underestimating the power of natural selection.

In particular, random genetic drift, the variation in a population caused by sampling error, is far more significant than most people (including most evolutionary psychologists) assume. Most of the obvious phenotypic variation we see in people, for instance, is not a product of selection: your nose does not have the shape it does, which differs from my nose, which differs from Barack Obama’s nose, which differs from George Takei’s nose, because we independently descend from populations which had intensely differing patterns of natural and sexual selection for nose shape; no, what we’re seeing are chance variations amplified in frequency by drift in different populations.

And if evolutionary psychology in particular — and psychology in general — were interested in explaining individual traits like the specific shape of a nose, then random genetic drift would be an excellent counter to that. Unfortunately for Myers, evolutionary psychology in particular — and psychology in general — is far more interested in explaining traits like “Why do we have noses?”. Which, by his own discussion here, is not going to be impacted by drift comments. It is clear that evolutionary psychology is after strong tendencies, and not particularly interested in outliers. Drift, as least as described here, is all about producing minor outlying differences, and so traits like nose shape can be produced by chance variations that were amplified in frequency by drift. It is unlikely that fundamental portions of our cognition that hold mostly universally could be, and it is those that evolutionary psychology is after.

Why? Because selection is blind to small differences. Chance dominates, unless the selection coefficient is relatively large.

And this, again, seems to be most of Fodor and Piattelli-Palmarini’s objection: a lot of traits may survive not because they had specific adaptive value, but because they were associated with a trait that had it or the deficiency associated with them was not strong enough to be selected for and so on and so forth. The conclusion, then, was that you can’t simply take a trait, find that it has a benefit, and insist that that is why we have that trait. A fair criticism, then, but it would seem to apply to the explanations for altruism and morality as well, and seems to be a shot at evolutionary explanations themselves, and not just a fundamental assumption in evolutionary psychology. Can he save himself with his examples?

I’ll skip the gambling metaphor, except to point out this:

One rule of thumb is that for selection to be effective,

|s| >> 1/Ne

What that means is that selection works best in large populations, while chance dominates in small populations — you need a very large s to make the selective advantage rise above the noise generated by chance variation.

What it also means is that in any population there will be a range of variation that is effectively invisible to selection, a range that will be rather narrow in an immense population of bacteria, but will be relatively wide in small populations…like, for instance, a large, slow-breeding population of Pleistocene primates.

Which would mean that any trait in humans where the selection was supposed to start around then should have the same objection … and altruism and morality were claimed to be necessary as we started to build societies around groups, which would be around that time. So, doesn’t that strike against them as well?

Again, that does not mean that selection did not apply to our Paleolithic ancestors. Being born with a heritable heart defect meant you were strongly selected against, and that trait would be gradually eliminated from the population; being born with testes that produced voluminous robust sperm, or having an immune system that made you more resistant to a common virus, would still give your offspring an edge. But keep in mind that even the most wonderfully advantageous allele that arose by a de novo mutation in you has a good chance of being lost by meiotic segregation (1 over 2 to the number of children you have, to be precise), and even if your children do inherit that one trait, there’s a significant probability that one of the multitude of other factors that constrain survival and reproduction can work against it.

Well, other than the fact that heritable heart defects weren’t eliminated (and need not be), this seems to apply to altruism and morality as well, doesn’t it? Are they really heart defect level adaptations? Noting that Myers et al likely can’t rely on group selection — ie the group is stronger even if the individuals aren’t — to pull that off?

But the important example is the one that makes up the title of my post: colour-blindness.

Here’s a specific example: color blindness. Being unable to discriminate differences in a particular range of wavelengths is a disadvantage — probably a very small one, but it’s clear that having trichromatic vision swept to near-fixation in old world monkeys and apes fairly rapidly, and fairly thoroughly…and not having it is a step backwards. So why hasn’t natural selection culled it from our populations? This isn’t a recent innovation that hasn’t had time to be corrected; trichromacy arose sometime after the split between the old and new world monkeys, 30-40 million years ago. It’s X-linked in those other primates, too. Shouldn’t this defective allele have been long gone from the primates?

No, and there’s a simple explanation: color blindness is a defect that’s below the threshold for a strong selection pressure to work against it (all you colorblind readers can heave a sigh of relief—Nature isn’t going to come gunning for you).

And if color-blindness is invisible to selection …

Let me reintroduce you to our old friend, the peppered moth, the ultimate example of adaptation and natural selection in action. Recall that the predominance of white colour in peppered moths was posited to be the work of selection pressures; the moths were harder to see and so survived more, while the darker coloured ones were easier to see and so were preyed on more. And then England decided to pollute their atmosphere with soot, and researchers noted that the percentages started to shift, because the white moths stood out more against the soot and so were preyed upon more than the darker ones. When the pollution levels went down, the numbers returned to their previous ratios. The peppered moth, then, became the poster child for selective pressures.

Has anyone ever asked why the darker coloured moths weren’t completely eliminated? Well, except myself, and I only used it as an example of how you couldn’t take a specific trait — in this case, the darker colour — and posit that the moths that had that specific colour must have gotten an advantage from it and so it had an advantage. That colour was an accident of genetics that didn’t have a strong enough selection applied to it to eliminate it completely (so we would agree there), and that’s why it still exists. But if I have ever doubted that the white colour was selected for — and I don’t think I have — then I will happily concede here that I am likely wrong (barring other objections like the ones I raised in my review of Fodor and Piattelli-Palmarini’s book).

The same thing applies to colour-blindness. It is not, in fact, invisible to natural selection, because even Myers seems to admit that the reason it is dominate in humans is because of its selective benefits. The benefits are not so strong as to eliminate it completely, and also there are likely recessive genes that exist in those that do not have colour-blindness that explain why it keeps cropping up in children. To claim that if a trait is not eliminated completely then it could not have been produced primarily by selection is to claim that the peppered moth example is not an example of natural selection, since darker coloured moths were never eliminated and it is unlikely that the white moths would have ever been eliminated completely by it. And so when Myers moves from colour-blindness to evolutionary psychology:

And if color-blindness is invisible to selection, I’m going to be pretty damned skeptical when an evolutionary psychologist tries to tell me that girls’ fondness for pink colors is or was a functional adaptation: a product of a 100,000 years of natural selection. It’s not impossible that pink preference could confer a benefit, but the idea that a pink preference was so strongly selected for that we can infer that it must have had a selective advantage is so unlikely that it can be dismissed as totally bogus, in the absence of exceptionally strong evidence for such an improbable circumstance. Furthermore, even if a pink preference existed as a heritable trait (which I doubt), the most likely explanation for its presence in a population is drift, not selection.

Well, all evolutionary psychologists want is peppered moth status for the fondness for pinks and reds, that this fondness conveyed an advantage that made it be a dominate inherited trait. Colour-blindness is, in fact, obviously a trait with peppered moth status, and so if that’s the case then it’s hard to see how he can use that to criticize another evolutionary psychological trait. And if colour-blindness is invisible to selection for him, it seems unlikely that altruism and morality are going to have stronger benefits, and so there go those theories, leaving New Atheists unable to explain those traits in any way except by appealing to conscious assessments of benefit … and if they do that, they don’t actually have altruism and their morality is Ethical/Enlightened Egoism mixed in with a Hobbesian Social Contract, which most of them don’t really seem to like too much.

So, at the end of the day, Myers seems to take out natural selection explanations for traits in a manner that’s stronger than what some critics of natural selection as a theory do, and also eliminates the evolutionary psychological explanations for altruism and morality. Thus, he does the things that he absolutely could not do to maintain New Atheism. Excellent.


8 Responses to “The Colour-blind Leading the Colour-blind …”

  1. Crude Says:

    Any comment on the dustup over at Coyne’s with regards to Paul Nelson and the centrality of natural selection in evolutionary theory? Seems rather on this topic.

  2. verbosestoic Says:

    When I read Myers’ posts, it does seem to me like Myers is doing what Coyne derides others for doing. However, I don’t know enough about it to say whether Myers really is taking that strong a take or whether he’s just being reasonable about the importance of natural selection. But the fact that Myers in two posts now keeps saying that natural selection isn’t that important should raise alarm bells for those who agree with Coyne.

  3. Crude Says:

    A few other comments.

    * Myers’ comments about how, if you attack evolutionary biology, you get a ‘swarm of ignorant defenders acting as if you’re attacking evolution itself’ is pretty funny, considering the freak-outs that occur whenever ID proponents make the most marginal criticisms of evolution. I think most of what, say… Mike Behe says is extraordinarily tame. But people still absolutely lose it when he questions the power of Darwinian mechanisms. Either way, the fact that Myers even jokingly talks about how he’ll be accused of ‘creationism and denying natural selection’ should illustrate to a reasonable person just what the state the world is in with regards to discussing evolutionary topics in anything approaching a critical manner. And you can’t tell me Myers and others haven’t played their role in setting this tone. (Actually, Coyne was pretty much doing very close to what Myers was complaining about.)

    * Myers does seem to be saying that if a trait is still present in a population, it is/has been invisible to natural selection. I imagine Myers would qualify this to mean ‘in a significant way’, but that still seems like a fairly weighty statement to make. I have the feeling that if pressed on this, he’d back off and say that color blindness isn’t invisible to selection – it’s that it’s ‘weakly selected’ against. At the moment I’m not quite sure what that would do to his argument.

    * Maybe someone will bring up Myers’ statements about the power of natural selection to Coyne. It’s posts like these that make me wonder if there’s not more people in the field who essentially agree with guys like Fodor, etc, but who don’t want to say as much because the creationist bogeyman under the bed may hear them.

  4. verbosestoic Says:

    I just made a post about Myers’ latest post, and in it he very much seems to be making the point that Fodor et al made about how selection can only work on traits that already exist, and so isn’t an explanation for the origin of traits. And I know that their “Pigs don’t have wings because wings were selected out, but because the genetics never formed them” was bashed by Coyne and others massively. So I’d be interested in seeing what the difference here is.

    As for colour-blindness being only weakly selected against, that seems unlikely … and if the criteria for “strongly selected for/against” is “eliminated all alternatives/eliminated by other alternatives” then it’s hard to see what could meet that criteria. Even his example of “heart defects” have not been eliminated, and even BLINDNESS has not been eliminated genetically, and it’s hard to imagine a trait more detrimental than that.

  5. Crude Says:

    Fascinating reading – glad I stumbled on this site. I know I’ve seen you around in the comboxes before.

  6. verbosestoic Says:


  7. windy Says:

    Hi, came across this only now, but your analysis seems correct. Myers is (unintentionally?) casting doubt on adaptive explanations in general, not just evolutionary psychology. The attack so far is so sloppy and inconsistent, though, that it’s no cause for alarm bells in relation to any serious debate about the role of natural selection.

    The color-blindness example alone has several problems. As you correctly note, deleterious alleles often aren’t completely eliminated by selection. For example, recessive alleles are visible to selection only in homozygotes (and males, in case of X-linked traits). For color blindness, it’s not clear how deleterious it’s been during recent human evolution (probably detrimental for foraging, but some studies indicate that it could even be beneficial for spotting prey in some environments). It’s not clear where he’s going with the primate information: the human allele for color-blindness could be a lot more recent in origin than the Old World primate split, and if trichromatism “swept to near-fixation rapidly”, that contradicts the claim that color-blindness is “invisible to selection”! (Maybe he just means in humans, but it’s very unclearly written, and he hasn’t actually demonstrated the absence of selection.)

    • verbosestoic Says:

      Yeah, that’s how it seemed to me, and that was my worry — well, not much of a one, I guess — when he started: that he’d end up either attacking evolution or the evolutionary psychology he needs while attacking this. And the fact that this argument here looks a lot like what Fodor et al were blasted for seems to confirm that.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: