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whoneedsscience wrote
Yes, I've read much of Dawkins's work. I was trying to simplify a bit, but seeing as I was jumping in to be anal-retentive, I suppose it is fair that you did the same to me. My understanding, however, is that theories of group selection, and even individual selection to an extent, are unorthodox, apart from being extremely weak next to genetic-based arguments like those of Dawkins. It is the process of crossing over that separates the gene from the individual. In species that undergo direct cloning, natural selection has little to work with, as beneficial mutations depend entirely on the success of the line of individual descendents. In sexual species, however, new mutation has only to survive a few generations of being dependent on its "survival machine" before it is established, unless there are significant selection pressures against it, in the gene pool, among individuals of many diverse lines. I don't quite see how it makes sense to say that selection occurs at the individual level through sexual repreduction, then.
Oh, and may I add that anything that makes baby Jeebus cry is more than worthwhile to read.
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I personally tend to go the Dawkins route. However selection acting on genes is a little dodgy. Genes aren't really visible to selective processes - it's individuals which get selected out or in, breed or fail to, etc.
Dawkins does quite a good metaphor in "SG" about genes being connected to phenotypes via bungee cords or similar, but the effect of genes is strongly modulated by environment, especially in the womb. I'm not sure about gene selection then, although personally I like the idea. It's interesting that Dawkins' next step is to try to blur the boundaries between phenotypes (in "extended phenotype") thus giving credence to his vision of phenotypes as the terrain on which genes compete. it's an interesting argument. Mayr comes out very strongly in favour of individuals as the prime targets of selection ("What Evolution Is", chapter six, has a strong refutation of gene selection).
Replication certainly takes place at gene level - genes are the only true replicators (even bacterial clones can be different phenotypically due to environmental factors and plasmid swapping, so I'm with you there). I don't follow your point about sexual species - selection doesn't take place with "a few generations later" in mind, although obviously the
effects of selection can be concieved that way.
Species selection is something I don't go with, but I thought Brad should be aware that the theory is not quite dead - Gould makes an extensive (but flawed IMHO) case for species as Darwinian entities in "the structure of evolutionary theory". He argues that they are stable (remember Gould came up with punctuated eqilibrium), give birth to "daughter species" and that these daughter species inherit some of their traits, thus demonstrating heritability, and that species can die out due to environmental factors, thus demonstrating selection. The flaw is, I think, that the heritable characteristics and effects of selection are all on "individual level" charateristics not "species level" ones. The one example he gives of a species level characteristic is variability, which may well affect the chances of a species surviving a catastrophic event or not, but by definition is not in this case heritable as such catastrophes cause genetic bottlenecks. "Structure" is quite valuable though in that it shows that all Gould's ideas do in fact fit together and aren't the confused mish mash that Dawkins claimed they were in "Unweaving the Rainbow". Some of the ideas are pretty good, and Gould's take on history is valuable. Gould was in fact, I think, trying to create a Darwinian theory out of anti Darwinian components - catastrophism, PE instead of gradualism, contingency rather than survival of the fittest, and group selection. I suspect he did it out of pure contrariness, but since catastrophes did in fact happen, contingency seems about right, and a lot of fossil evidence supports PE, I'm kinda glad he made the effort.
PS Anal retentive? Me? Surely not.....