KC

Pz writes:

I remember reading Gould and Lewontin's 'Spandrels' paper for the first time some years ago.. A simple, elegant argument that hit me right between the eyes.


Cheers,

KC

Doubting Didymus

Hmmm. I want to see 'adaptation' clearly defined. Is an adaptation specifically a change in a population that is a direct result of environmental pressures, or a more general 'anything' that improves the prospects of replication? This may seem a no brainer, but I strongly get the impression that I have been talking past people when I use the word.

If you could be so kind, might darwins terrier and pz please elucidate exactly what each of you mean by adaptation. I must confess that I may have been using the word to mean 'any heritable change in a population that improves the prospects of replication'. Is that right, or the term adaptation more specific?

pz

The meaning is implicit in the word: an adaptation is a feature that is a consequence of selection acting on a population. It also implies something that improves the accommodation of an organism to its environment.

A feature that becomes fixed in a population by drift is not an adaptation unless it confers some selective advantage.

Doubting Didymus

Tricky. But wouldn't selection act on each and every change for the better, regardless of how it got there? Wouldn't that mean that every feature that improves survival is an adaptation, given that selection will act on it?

Doubting Didymus

A more pertinent question: if, for example a beneficial change arose as a result of an alteration in a pleiotropic gene, selection is bound to act on it, true? So is that not an adaptation, even though selection acts on it, because its origins are not related to selection?

Autonemesis

I'm a pan-galactic-gargle-blasterist, myself

Or was that supposed to be pan-galactic-gargle-blastocyst? I can never keep them straight.

Doubting Didymus

Embryonic bar studies research? How immoral!

Secular Pinoy

(This is written in the office, so I cannot give an in-depth response, nor can I give proper citations, so please bear with me. BTW, I have to correct myself, Eldredge used the term "ultradarwinians" not ultradarwinists.)

Ok I think I have to explain myself. I do not have anything new to offer in Evolution. I accept the basics of Genetic Variation and Natural Selection as an engine of Evolutionary Change. It's just that I feel that it does not tell the whole story. Despite DT's assertion, I have read almost all of Dawkins' books (except Climbing Mt. Improbable). I have not read the primary literature or any advanced books(not for the lack of trying mind you), so you know where I'm coming from.

If I am faulted for reading primarily the popular literature, not the technical ones, then I apologize. I have read mainstream evolution books by orthodox darwinists(gene-centric/adaptationist), paleontologists (who comprise a major part of the naturalist position), by a cladist (Henry Gee), by anthopologists, and various other strands of evolutionary thought. The picture of evolution that these eclectic groups hints at is that there is really more to evolution than what Dawkins' would have us believe.

As to my original post, I have to admit that it is much hyperbole. It's a shameful tactic in science, but I felt I had to. If I merely said that I felt that Gould et al had something important to say, there wouldn't be much impact in this board. Most will, and have, just ignored me. So again, I apologize for it.

But now for the naturalist position(s), it is pluralistic. Eldredge/Gould are just a part of it. It comprises the rest of evolutionists who feel that a narrow, gene-centered view of Mathematical Population Geneticists™ is wholly inadequate to explain the diversity of life, with the pattern of evolution based on the fossil record and other concerns. Eldredge's/Gould's position in particular is process structuralism. They see evolution acting on a hierarchal level, with different evolutionary effect on distinct hierarchies, such as individual organisms, populations, species and (probably) higher taxa.

Now it has been alleged that I am setting up a strawman. Is my characterization a strawman? It might be, but it is not terribly far from the truth.

All talk of environmental fators from the likes of Dawkins is just lip service. Find me a few discussions by Dawkins where he gave more than a glancing reference to environmental factors on Evolution. I didn't find it in his discusions on birds' tail length, his discussions on the cheetah's arms race, in his discussion on army ants, and his myriad examples on animal behavior (his favorite, since he is after all an ethologist; from the thought-school of Lorenz-Tinbergen). Reading Dawkins, it just seems that evolution is just genes, genes, genes.

The problem with Dawkins is that he discusses evolution as gradually incremental, and extrapolating that without explaining whether the tempo of change is more or less constant, or jerky. Let me give an example of the perils of extrapolation. Fossil whales, while primitive compared to modern whales, is still fully whale-like. They have bodies that evolved for living in water, with locomotion that is similar to semi-aquatic mammals, but different from fishes. Whales evolved around 50 million years ago (I think that's right, from what I remember from Zimmer's book Fish with Fingers). From that time until now whales did not undergo any "great transformation" into something else. There are a lot of extant whale species, but none differing greatly, morphologically speaking, from the basic body plan of whales. If we extrapolate that backwards, we end up with slightly whale-like creatures about 100 million years ago, before the advent of placental mammals!

So we can see that simple extrapolation just does not work. Yet that's what we get when we take Dawkins' argument and apply it to the fossil record. Dawkins provides no context for the pace of evolution. Throughout the fossil record gradual, incremental, "Climbing Mt. Improbable-type" change is more of the exception than the rule. Rather the fossils show prolonged stasis, of evolutionary stagnation (though not the complete absence of evolution), punctuated by rapid (geologically speaking) macroevolutionary change. I'm not advocating saltationism (I assume that saltationism refers to sudden macromutational change in a single generation), but microevolutionary change leading to macroevolutionary innovation in brief spurts of speciation events, and trivial microevolutionary change during stasis.

And why is it that people seem to think that the naturalist positions are averse to Allopatric Speciation? They refer me to it, assuming that it's some kind of refutation of the Gould/Eldredge paradigm. But Punctuated Equilibrium is the application of Allopatric/Geographic Speciation (and the related Founder Effect), coupled with species stasis, to explain the anomalies found in the fossil record. Most major speciation events are allopatric (with some exceptions of sympatric speciation and others). Isolation of populations not only leads to genic isolation, but a change in environmental setting as well. The complex interplay between populations with their environment on the outside, coupled with the isolation of their unique genic history on the inside is what fuels speciation. Of course, I don't seem to find that in any of Dawkins' books. It's simply a rehashing of Ronald Fisher's mathematical calculations of the genic environment in a population's genotype. And that's the only environment that seems to matter to Dawkins.

In Dawkins' first two books, TSG and TEP, he unabashedly tries to convert us all to his view of gene-centeredness in evolution (which answers DT's question about Dawkins' purpose in writing popular works). That's fine by me. But then he goes around saying that it's the only proper interpretation of it. Whoa! But surely this fundamentlistic outlook is much too narrow? Nay he says, and he shows that he means business, by attacking the dominant paradigm of his time, group selectionism and organism-centered evolution. The naturalists, on the other hand, does not feel the need to fully overthrow the dominant paradigm, only to ask for plurality of outlooks, each serving his own domain of specialization. Gene-centrism's main domain is in microevolution on the population level, with cautious usage in evolutionary history. And Punctuated Equilibrium's domain is the pattern of evolution over geologic time, using Gene-Centrism as one of the tools. One must not dominate over the other, but to have a pluralistic synthesis of differing, yet mostly compatible outlooks.

For furthur reading, I suggest people read Eldrege's book Reinventing Darwin and The Pattern of Evolution. The edited anthology The Dynamics of Evolution has some essays concerning the naturalist-ultradarwinian debate. Richard Dawkins first two books is a good place to start on the other side of the debate. Henry Gee's In Search of Deep Time will be of some help, as he will pull us back to reality, charging us with making unfounded ancestor-descendant conclusions with little evidence. And for online resources, Ernst Mayr's essay is a start, while the rest of the website is also good reading.

There's a lot more to be said, but I have work to do. I hope we can furthur discuss these issues, such as the concept of discontinuity of species; speciation as the major event in achieving macroevolution; the importance of the biological species concept with regards to evolutionary history; Dr. Pangloss/Pan-adaptationism and just-so evolutionary scenarios in modern evolutionary discourse, habitat tracking as a possible explanation of some instances of stasis, and much more.

Finally let's keep it light and fun, ok? We're all trying to learn here. I hope to learn a lot from you guys (I've learned a lot already just by lurking here). Remember: Punctuated Equilibrium vs. Phyletic Gradualism = "Evolution by jerks" vs. "Evolution by creeps."

Secular Pinoy

/me waves hello to pz. Wow, so I'm not alone after all!

Doubting Didymus

Dear Pinoy. Dawkins accepts punctuated equilibrium. If you have a copy of the blind watchmaker, you need to read the last few chapters again. Your whale example is a strawman of dawkins' position. He would accept it as much as you and I do.

In fact, a great great deal of your post that you seem to think contradicts dawkins does not. He would agree with almost all of it, and so do I. The only thing that I immediately disagreed with was the idea that "group selectionism and organism-centered evolution" did not need overthrowing. Group selection is an extremely weak idea in my opinion and is desrvedly ignored by most theoreticians in the feild. The level of the fundamental unit of selection is a livelier debate, which only recently had a good run on these very boards. I will find the link for you.