A link from a recent blog by The OFloinn led me to this old article by Jerry Fodor. Only on following it up did I realise the link (authorial and thematic) with the somewhat notorious book that followed it, What Darwin Got Wrong. I shan’t be reading the book, partly because it is written in analytical philosophy-speak, but the core ideas are clear enough in the article. I’ll look at them a bit today in “idiot’s guide” manner, and at the equally instructive reaction to them in another post.
The appeal of Darwinian evolution is its simplicity and self-evidence. All regular readers here know it has complications, but we are all aware that if doubts are raised, it’s the simple tale that is retold to reassure us. Organisms vary non-purposefully, but quasi-purpose and therefore intelligibility are added by natural selection. Sorted – what we see around us is explained. It’s easy to comprehend that the taller giraffes get more food, so that’s why giraffes got taller.
Strictly, this is the adaptationist view of evolution, but its rivals are less intuitively attractive to ordinary people, and are seldom raised in evolutionary apologetics because they might give the impression that the theory encompasses controversy – a widespread fear, as we shall see in the next post, though hotly denied in the academy. Nevertheless adaptationism is what Darwin put at the forefront in Origin of Species. Fodor attacks adaptationism, and through it the importance of natural selection itself, by looking at what are called spandrels.
Build two arches and a lintel, and the triangular space between is a spandrel – you didn’t plan it, but it emerges from what you did design. However, in churches they end up full of carving and decoration though, arcitecturally, they’re just a leftover space. Religious belief is often dismissed as a spandrel getting a free ride from, perhaps, the gene for intelligence. Fodor describes the breeding of silver foxes for tameness over 40 years:
On the one hand, foxes that were bred for tameness also tended to share a number of other phenotypic traits. Unlike their feral cousins, they tend to evolve floppy ears, brown moulting, grey hairs, short curly tails, short legs and piebald coloration (in particular, white flashes). Inbreeding for tameness also had characteristic effects on the reproductive cycles of the foxes and on the average size of their litters. And these are all traits that other domestic animals (dogs, cats, goats, cows) also tend to have. An adaptationist might well wonder what it is about dogs, cats etc that makes curly tails good for their fitness in an ecology of domestication. The answer, apparently, is ‘nothing’. Curly tails aren’t fitness enhancing, they just happen to be linked to tameness, so selection for the second willy-nilly selects the first.
One possible reason for this is that you’re actually selecting for some hormone with multiple effects. In other cases it might involve the recent realisation that most genes are multifunctional. The “tameness” gene or genes also directly mediate these other effects. So if you bred for floppy ears or a curly tale, you’d get tameness thrown in.
The problem is this. Suppose you accept, say, the familiar link between melanotic peppered moths and industrial pollution. It may well be (and how could you know?) that linked to the melanocytes is a high level of melatonin in the nervous system that, say, reduces disease. For all you realise, it could be disease resistance that is being selected, not blackness.
If you suspected this problem, you might be able to envisage how to unhitch the two traits experimentally, eg by suppressing a downstream gene that only affected the colour. But you still wouldn’t be able to make any general inference from a trait to its selective value. An argument like this explanation of the evolution of human hairlessness, for example, would be insupportable. Even in the case of the giraffe, the old adaptationist tale is (in this case easily) debunked by the fact that female giraffes are always smaller – yet they survive. So eating higher leaves wasn’t the reason for tall giraffes at all. Perhaps male giraffes evolved long necks to fight rival males better, and the females simply tagged along. Or perhaps, worse still, giraffes were actually selected for brown and white patches, and tallness just happened to be on a linked gene and not be too deleterious. Giraffes would then be tall because … they happen to be tall. Just think how many just-so stories in evolution (especially human evolution) would become even more speculative were this to be taken into account.
It gets no better when you realise that, though careful research might give us a clue as to what aspect of variation favoured survival, no such discriminatory mechanism is available to natural selection itself. After all, NS is nothing but the brute fact that some animals produce more offspring than others. Stripped of teleology, Fodor asserts that to say an organism is “selected for” something is plain meaningless. A curly tail is, actually, precisely as much a cause as tameness or white flashes, if that variety of silver fox dies out in the wild, seen in natural selection terms.
That doesn’t mean natural selection isn’t occurring, or even that it isn’t a big player. But in practice, Fodor claims, it does tend to make it a nebulous concept of limited scientific use. What use is it to be assured that evolution works by the survival of the fittest organisms when you’ve no way of knowing which bit of the environment is selecting for which bit of the organism (because in the end it’s not selecting any specific traits)? It’s just a faith foundation.
Though in the article Fodor seems not to major on it, neutral theory is an additional confounder of selection. According to many accounts, neutral evolution is responsible for most change in higher life-forms, with selection being primarily a purifier that weeds out grossly unfit variants. Which being interpreted means that selection is a force against major change in existing species suited to their environment, because innovators won’t do so well. Our giraffe might not even be tall because it was linked to selectable patchy colour, but simply because tallness and patches were survivable. Giraffes, in the end, just happen to be that way.
Once again, there are established ways of distinguishing genes subject to selection from those subject to drift. But even if those are entirely valid, it means there are no shortcuts to the detailed examination of each and every case, no way of saying what selected genes were selected for, and nothing useful to be said about selection in fossil forms where genes are not available.
So did feathers evolve for flight, for insulation, to stabilise running or what? All one can really say is that they didn’t cause extinction, and eventually got useful enough to be selected – ie when you tried flying with bad feathers you died. Did your carnivore evolve sharp teeth to eat meat, or did it eat meat because it found itself with sharp teeth that were rubbish for chewing plants? How could you tell? This links to another of Fodor’s points, about Evo-devo. The core of evolutionary change, he points out, is what possibilities are already present in a species. Hence his title about flying pigs – pigs with 4 legs and wings don’t exist because “there’s nowhere to put them”. Natural selection, then, only gets whatever organisms choose to give it to play with – and that has teleological and Aristotelian overtones in keeping with the article I linked to in the previous post. The diminution of natural selections universal importance begs the question of how that internal evolutionary potential got there in the first place.
Some years ago I saw a nature documentary about hammerhead sharks and their unique way of life. The marine biologist involved, seeing, I think, no plausible gradualist scenario for their evolution, proposed that hammerheads appeared in one saltational event. In order to survive, the animals had to learn to cope with their new rearranged bodies PDQ. At the time I thought what an absurd view of evolution that was. But some of the recent advances, including Fodor’s viewpoint (as I said, to be critiqued next time) suggest it’s not as ridiculous as it seems. At least it seems a bit more concrete than natural selection in the light of people like Fodor.