Uh oh. Now I have some inkling of what Orac goes through. Which is an oblique way of apologising for the length and tone of this post.
A couple of years ago Jerry Fodor (a
psychologist philosopher of mind) wrote a piece in the London Review of Books arguing that evolution was wrong. I had some fun with it, back on my old blog. Now he and Massimo Piattelli-Palmarini have a whole book called What Darwin Got Wrong, and New Scientist has given them a platform to outline their argument. Fodor & Piattelli-Palmarini raise what they see as problems with evolution, but they basically reveal their own ignorance of the subject.
Unfortunately it looks like Fodor’s thinking hasn’t evolved in the last two years, and I could just lightly edit what I wrote before to critique their latest piece. But that would be boring.
Fodor & Piattelli-Palmarini start off by showing their ignorance of the opposition to Darwinism:
The possibility that anything is seriously amiss with Darwin’s account of evolution is hardly considered. Such dissent as there is often relies on theistic premises which Darwinists rightly say have no place in the evaluation of scientific theories. So onlookers are left with the impression that there is little or nothing about Darwin’s theory to which a scientific naturalist could reasonably object.
To the extent that intelligent design and modern Creationism say anything sciency, they don’t rely on theistic premises – they try to critique evolutionary theory using evidence and models that attempt to prove that some or all of evolution is impossible. There’s even a website that outlines all their arguments, along with rebuttals. So there are non-theistic challenges. It’s just they’re not very good1.
Fodor & Piattelli-Palmarini do make it clear that they accept common descent, but their argument is that natural selection isn’t enough to account for what we see. To the extent that they are correct, it’s something that’s hardly controversial. But then their arguments aren’t again evolutionary biology, only a straw man that reveals a basic ignorance.
We can see their confusion even where they are trying to agree with evolutionary biologists: they are even ignorant of what fitness means. This is how they define it:
we’ll follow the current consensus according to which an individual’s relative fitness co-varies with the probability that it will contribute its phenotypic traits to its offspring.
This is not just wrong. To see why, imagine an individual that passes on its phenotype to every one of its offspring. According to Fodor & Piattelli-Palmarini, it has maximal fitness: transmission is 100%. But imagine that the trait is for only having two offspring. Compare that to an individual who half the time passes on the trait of having 10 offspring, and the rest of the time the offspring are sterile. Fodor & Piattelli-Palmarini may think that these individuals are less fit, but if these are the only two phenotypes in the population, the “fitter” phenotype will be lost. For the rest of us fitness is defined in relation to the population (and the environment!), not transmission within a family.
Once we get on to Fodor and Piattelli-Palmarini’s criticisms, it’s no surprise that they show off their ignorance again? They have two lines of criticism; the first is that there are constraints on evolution:
In our book we review a large and varied selection of non-environmental constraints on trait transmission. They include constraints imposed “from below” by physics and chemistry, that is, from molecular interactions upwards, through genes, chromosomes, cells, tissues and organisms. And constraints imposed “from above” by universal principles of phenotypic form and self-organisation – that is, through the minimum energy expenditure, shortest paths, optimal packing and so on, down to the morphology and structure of organisms.
Which we already knew. But in the very next paragraph they turn up the stupid:
Over the aeons of evolutionary time, the interaction of these multiple constraints has produced many viable phenotypes, all compatible with survival and reproduction. Crucially, however, the evolutionary process in such cases is not driven by a struggle for survival and/or for reproduction. Pigs don’t have wings, but that’s not because winged pigs once lost out to wingless ones. And it’s not because the pigs that lacked wings were more fertile than the pigs that had them. There never were any winged pigs because there’s no place on pigs for the wings to go. This isn’t environmental filtering, it’s just physiological and developmental mechanics.
What? OK, let’s help these guys:
That might seem silly, so let’s imagine what a pig with wings would look like. Perhaps like this:
Of course, it’s a long way from a pig to a flying bat, but is it really much further than this:
Protungulatum, a few days before yesterday (piccie from the NHM)
evolving to swim around in the deep ocean sifting the waters for its food? And yet it, or rather one of its close relatives, evolved into this behemoth:
Now, there is a sense in which Fodor & Piattelli-Palmarini are correct: it would be difficult for pigs to grow a third set of limbs: they would need considerable anatomical changes to accommodate them. There are constraints, but I find it difficult to see how this is an argument against evolution. It is pretty basic that evolution is a cumulative process, with present forms being built upon. This does indeed limit how a species can evolve, and if the anatomy of an animal is to change, this means the pattern of development – the bauplan – has to be changed. This is certainly well known: it was one argument put forward in Gould and Lewontin’s celebrated Spandrels paper:
[The argument that natural selection is constrained by the bauplan] also acknowledges conventional selection for superficial modifications of the Bauplan. It also denies that the adaptationist programme (atomization plus optimizing selection on parts) can do much to explain Baupläne and the transitions between them. But it does not therefore resort to a fundamentally unknown process. It holds instead that the basic body plans of organisms are so integrated and so replete with constraints upon adaptation (categories 2 and 5 of our typology) that conventional styles of selective arguments can explain little of interest about them. It does not deny that change, when it occurs, may be mediated by natural selection, but it holds that constraints restrict possible paths and modes of change so strongly that the constraints themselves become much the most interesting aspect of evolution.
This is not an obscure backwater of a paper: it’s arguably Stephen Jay Gould’s biggest individual contribution to evolutionary theory, and is required reading for students. With the recent resurgence in evo-devo (evolutionary development), it has become more important and perhaps better appreciated, but the idea has been kicking around for some time.
Fodor & Piattelli-Palmarini’s other main argument in their New Scientist article is this:
Darwinists say that evolution is explained by the selection of phenotypic traits by environmental filters. But the effects of endogenous structure can wreak havoc with this theory. Consider the following case: traits t1 and t2 are endogenously linked in such a way that if a creature has one, it has both. Now the core of natural selection is the claim that phenotypic traits are selected for their adaptivity, that is, for their effect on fitness. But it is perfectly possible that one of two linked traits is adaptive but the other isn’t; having one of them affects fitness but having the other one doesn’t. So one is selected for and the other “free-rides” on it.
We should stress that every such case (and we argue in our book that free-riding is ubiquitous) is a counter-example to natural selection. Free-riding shows that the general claim that phenotypic traits are selected for their effects on fitness isn’t true. The most that natural selection can actually claim is that some phenotypic traits are selected for their effects on fitness; the rest are selected for… well, some other reason entirely, or perhaps for no reason at all.
It’s a main claim of our book that, when phenotypic traits are endogenously linked, there is no way that selection can distinguish among them: selection for one selects the others, regardless of their effects on fitness. That is a great deal less than the general theory of the mechanics of evolution that the Darwinists suppose that natural selection provides. Worse still, there isn’t the slightest reason to suppose that free-riding exhausts the kinds of exceptions to natural selection that endogenous structures can produce.
This just sets up a straw man, and shows that Fodor & Piattelli-Palmarini are still ignorant of how we now explain selection. Certainly, one can’t say that the free-riding trait is selected “for” but this isn’t a counter-example to natural selection, only to a naïve and teleological version of it. Natural Selection has no fore-thought. In his earlier article, Fodor complained that we didn’t have the language to describe selection. I guess he didn’t read my blog post, as I explained that, indeed, we do: it’s called mathematics.
The crucial insight ame in the 1960s, and was built on by George proce to produce his famous Price Equation. For our purposes the simpler version suffices, and what this says is that a trait will evolve through selection if it is correlated with fitness. We normally think that this correlation is direct: being fire resistant makes straw men fitter because they don’t burn so often. But if more fire resistant straw men also tend to soak themselves in oil, then oil soaking can also be favoured. I don’t think there is anything controversial about this (although I suspect most people don’t think about it much), indeed almost everyone is taught an extreme example of this: sickle cell anaemia. The trait of having sickle-shaped red blood cells cells is actually less fit than normal cells, but the trait is favoured because it is linked to the trait of malaria resistance. Odd that nobody sees this as a problem for evolutionary theory.
I worry that the rest of What Darwin Got Wrong is just as bad: naïve and ignorant of what modern evolutionary biology says. I have quoted Gould and Lewontin’s Spandrels paper above, and it seems that Fodor & Piattelli-Palmarini have not studied it. Had they done so, they would realise that even the title of their is misleading. For Gould and Lewontin quote Darwin thus:
As my conclusions have lately been much misrepresented, and it has been stated that I attribute the modification of species exclusively to natural selection, I may be permitted to remark that in the first edition of this work, and subsequently, I placed in a most conspicuous position-namely at the close of the introduction-the following words: “I am convinced that natural selection has been the main, but not the exclusive means of modification.” This has been of no avail. Great is the power of steady misinterpretation.
Great indeed is the power of steady misinterpretation.
1 Of course, the people making the arguments are motivated by theistic ideas, but a lot hide God out of way where they hope the US courts won’t see Him.