Phew, this chapter—"Constraints on Perfection"—was a bit difficult for me. I took my time reading it and I might just read it again for clarification. I'm reading this book as a layperson and I think Dawkins assumes a certain level of familiarity with some of these concepts. This chapter seems to be devoted to outlining the limitations of "adaptionism" an idea that organisms are "perfectly optimal" for the environmental niche they inhabit.



It's probably a good idea to understand something about Neutral Theory too:



I think it's possible Wikipedia has it wrong about Dawkins being a devotee of adaptionism, per se. As he clearly states up front here:

"Bitter experience warns that a biologist who shows a strong interest in functional explanation is likely to be accused, sometimes with a passion that startles those more accustomed to scientific than ideological debate, of believing that all animals are perfectly optimal—accused of being an 'adaptionist.'" (pg. 30)

I've noticed that Dawkins at times is reacting to criticisms of his work. It turns out, there is something of a controversy related to "adaptionism" or, at least, was. Here's an article by Stephen Jay Gould, called Darwinian Fundamentalism which has contains some pretty harsh criticism of both Daniel Dennett and Dawkins. It was published in the NYTimes Book Review in 1997 so this is well after The Extended Phenotype was published in 1982; I don't know if this controversy is still going on today.

http://www.nybooks.com/articles/1151

An excerpt: "Daniel Dennett's 1995 book, Darwin's Dangerous Idea, presents itself as the ultras' philosophical manifesto of pure adaptationism. Dennett explains the strict adaptationist view well enough, but he defends a miserly and blinkered picture of evolution in assuming that all important phenomena can be explained thereby. His limited and superficial book reads like a caricature of a caricature—for if Richard Dawkins has trivialized Darwin's richness by adhering to the strictest form of adaptationist argument in a maximally reductionist mode, then Dennett, as Dawkins's publicist, manages to convert an already vitiated and improbable account into an even more simplistic and uncompromising doctrine. If history, as often noted, replays grandeurs as farces, and if T.H. Huxley truly acted as "Darwin's bulldog," then it is hard to resist thinking of Dennett, in this book, as "Dawkins's lapdog."

And . . .

The generally accepted result of natural selection is adaptation—the shaping of an organism's form, function, and behavior to achieve the Darwinian summum bonum of enhanced reproductive success. We must therefore study natural selection primarily from its results—that is, by concentrating on the putative adaptations of organisms. If we can interpret all relevant attributes of organisms as adaptations for reproductive success, then we may infer that natural selection has been the cause of evolutionary change. This strategy of research—the so-called adaptationist program—is the heart of Darwinian biology, and the fervent, singular credo of the ultras.

Also read the letters in response to the article: http://www.nybooks.com/articles/1070

Makes for interesting reading.

Thanks, Geo, for laying out this important difference among respected scientists. It doesn't look as though I'll be able to carve out the time for The Extended Phenotype (and frankly I haven't even absorbed all the lessons of The Selfish Gene), but if it helps in moving yourself through the book, I'm very interested to hear what an informed and judicious reader has to say about it.

This issue of "fundamentalism" in science is interesting. I think it's an unfortunate and too provocative choice of words on Gould's part, though. It implies that the scientists holding firm to the adaptationist theory are rigid and willfully ignorant of other facts and points of view (like religious fundamentalists), which I don't think is the case.

Just on emotional appeal, I like the idea that evolution is is more neutral and not what we may think of as strictly law-like. That evolution is not as precise as adaptationists would make it out to be also makes sense to me, since creatures only have to be "good enough," not perfectly adapted to a niche. Maybe there is more art in evolution than we think.

Thanks, Dwill. I'm going to plow through this book and get as much out of it as I can. So far it's more difficult than The Selfish Gene but I'm sure some extracurricular reading will ease the way. Now that I have a better idea of what adaptionism is and what neutral theory is, I think I'll reread this chapter and get a lot more out of it. Anyone else reading the book? Robert? Interbane? Colin?

By the way, i think you're right that Gould was getting carried away with his Darwinian fundamentalism rant. I mean, Gould seems to suggest that Dawkins and Dennett don't accept the possibility that an asteroid such as that that wiped out the dinosaurs can provide a new pathway for evolution. In essence he seems to be guilty of the kind of fundamentalist tactics he's accusing them of using.

By the way Gould's article was actually published in two parts. For some reason, part two is not available for free, but it only costs $3 to read it.

http://www.nybooks.com/articles/article ... le_id=1139

(Or, ahem, PM me).

Rereading this chapter has helped me a lot. Some of my confusion stemmed from Dawkins' ongoing arguments with Gould, Lewontin, etc. who have taken issue with the "adaptionist" or "neo-Darwinist" perspective. These critics argue, for example, that there is a an adaptionist tendency to make up “Just So” stories to explain such novelties as long-necked giraffes. Dawkins begins the chapter by countering some of the arguments, acknowledging that "adaptionist" thinking has "virtues as well as faults" and has also led to some important discoveries. "Cautious adaptionist reasoning can suggest which of many physiological hypotheses are most promising and should be tested first." (pg. 32)

The first part of the chapter is really a digression. I think Dawkins is a "cautious" adaptionist who is arguing that life gravitates towards the optimal. However, there are six basic constraints on perfection. Here are my bastardized, oversimplified summaries of the first two constraints (obviously poor substitutes for Dawkins' book, but I thought I would post them anyway.)

1) Time lag - This is the idea that evolutionary adaptions are optimal for past conditions. "The animal we are looking at is very probably out of date, built under the influence of genes that were selected in some earlier era when conditions were different." (pg. 35)

We've talked about this before, that evolution works on a very large scale, but humans are changing the environment so quickly as to make it difficult for some species to adapt. ". . . since modern man has drastically changed the environment of many animals and plants over a time-scale that is negligible by ordinary evolutionary standards, we can expect to see anachronistic adaptions rather often." (pg. 36) Dawkins uses the example of the moth that flies into candle flames (I would also suggest sea turtle hatchlings that become disoriented from artificial lights and as a result sometimes fail to find their way to the sea).

"We asked 'Why do moths fly into candle flames?' and were puzzled. If we had characterized the behavior differently and asked 'Why do moths maintain a a fixed angle to light rays (a habit which incidentally causes them to spiral into the light source if the rays happen not to be parallel) we should have not been so puzzled." (pg. 37)

As in The Selfish Gene, Dawkins explains how it's useful to think in terms of saying there is a gene for this and a gene for that, although it's really more complex than that. The moth has evolved an adaptation that prompts it to fly at a fixed angle towards parallel light rays's, which likely gave it survival value in older times but in the modern era this expression can be problematic for the moth due to relatively recent human activities that produce artificial lighting and candle flames. The point is that a gene for 'A' environment X may well turn out to be B in environment Y. Dawkins brings up the subject of male homosexuality which is a problem for Darwinians (only if there is a genetic component to it). For the sake of argument, he suggests there is a genetic component to homosexuality, but that the gene that produces homosexuality in today's environment might have produced something completely different in the Pleistocene era. And the question, Why is there a gene for homosexuality is as puzzling as the question, Why do moths fly into candle flames?

2) Historical constraints - Dawkins uses an analogy of a jet engine which superseded the propeller engine due to its superior design. "The designers of the first jet engine started with a clean drawing board. Imagine what they would have produced if they had been constrained to 'evolve' the first jet engine from an existing propeller engine, changing one component at a time, but by nut, screw by screw, rivet by rivet. A jet engine so assembled would be a weird contraption indeed. It is hard to imagine that an airplane designed in the evolutionary way would ever get off the ground. Yet in order to complete the biological analogy we have to add yet another constraint. Not only must the end product get off the ground; so must every intermediate along the way, and each intermediate must be superior to its predecessor." (pg. 38)

Dawkins uses the example of the recurrent laryngeal nerve which is present in all mammals. The shortest path for this nerve is not via the posterior side of the aorta, but this is the path taken by the recurrent laryngeal. "Presumably there once was a time in the remote ancestry of the mammals when the straight line from the origin to end organ of the nerve did run posterior to the aorta. When, in due coarse, the neck began to lengthen, the nerve lengthened its detour posterior to the aorta, but the marginal cost of each step in lengthening of the detour was not great." (pg. 38)

Evolution, Dawkins explains, doesn't have the benefit of foresight, but ambles along blindly. "As a river takes the line of least resistance downhill, thereby meandering in a route that is far from the most direct one to the sea, so a lineage will evolve according to the effects of selection on the variation available at any given moment. Once a lineage has begun to evolve in a given direction, this may in itself close options that were formerly available, sealing off access to a global optimum." (pg. 45)

I love this line: "When looked at in this light, far from expecting animals to be perfect we may wonder that anything about them works at all". For someone who is a perfectionist, it is great to hear that.

Dawkins has a few good one liners.

When discussing the 'recurrent laryngeal nerve,' Dawkins also mentions the flatfish: "The Picasso-like face of a flatfish, such as the sole, grotesquely twisted to bring both eyes to the same side of the head, is another striking demonstration of a historical constraint on perfection. The evolutionary history of these fish is so clearly written into their anatomy, that the example is a good one to thrust down the throats of religious fundamentalists."

Not only is the sole's face all twisted up, Dawkins says, but the circuity of its eye seems to be backwards so that light-sensitve photocells are at the back of the retina.

" . . . Presumably it would be possible to write down a very long sequence of mutations which would eventually lead to the production of an eye whose retina was 'the right way around' . . .but the cost in embryological upheaval would be so great that the intermediate stages would be heavily disfavored by natural selection in comparison with the rival, patched up job which does, after all, work pretty well." (pg. 39)

Great work again on this book, Geo. Dawkins said that The Extended Phenotype is the book he's proudest of, and it sounds as though you think as highly of it. The ideas above remind me of those in Your Inner Fish by Neil Shubin, which we read here a couple of years ago. Dawkins' book sounds much more densely packed than Shubin's, though. Dawkins does always do a good job of putting complex ideas in language that's as simple as possible, but he certainly doesn't dumb anything down, and he demands that the reader work hard to hang in with him. As you noted, he also has a talent for the memorable phrase, which helps to keep me on board.