It's my understanding that evolution functions within the entire gene pool of a population. Variety within that population provides the first level of defense against environmental changes. Diversity is the key to survival of any species.
What entity does evolution act on?
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Evolution must start with a genetic change within an individual so I agree with Dawkins. I see no difference between genetic level and individual level apart from that two individuals with the same genetic change can be more or less successfull due to the circumstances.
I think that it depends partly upon a given population size. If you start with isolated populations of a given species, then within an isolated population, you will be more dependent upon genetic changes to occur before natural selection will have sufficient raw material to act upon. An example would be Darwin's finches in the Galapago islands. But if you are discussing the current population of humans, then the chances are good that even if the mutations that occurred when I was concieved introduced variety into my family, they may or may not have introduced variety into the human population as a whole. So currently, the rate limiting step in the evolution of humans is not the raw material of genetic mutation, but is instead a function of the differential change in the frequency of genes and groups of genes that are undergoing not only natural selection, but sexual selection, and now cultural selection. Even Dawkins was not dogmatic about the locus of evolution being at the gene level, but in his book "The extended phenotype" he viewed it as being as valid as holding to evolution happening at the individual level. What Dawkins was "against" so to speak was Gould's identifying evolution as primarily or at least also happening at the species level. I don't believe that these views are necessarily contradictory, and I believe there is value in both approaches. Asking "at what level does evolution act upon" beggs the question "evolution of what?". Since evolution is a term for the changes and not the mechanism, I would phrase it "at what level does natural selection act upon?" I think that natural selection acts upon the gene level and /or the individual level if you are observing changes during the course of individual lifetimes. But if you are studying the changes that occurred over the course of geological ages, you are unable to observe these kinds of changes, but will have fossilized evidence that represents not discrete genetic changes (although these did occurr), but instead that represents speciation. This is explained in "The structure of evolutionary theory" by Stephen Jay Gould and is know as "punctuated equalibrium". It is important to keep in mind, because at that level of time, you would not expect to see fossilized evidence of very minute changes. So the worn out and frustrating "missing link" arguments that you were afraid I'd bring to the discussion wouldn't apply if you don't expect to have that level of gradualness in fossil form.
This should be a good topic.
What entity does evolution act on? The gene? The individual? A population? The species or perhaps some higher taxonomic level?
Most of my reading on the subject has been by Richard Dawkins and as most of you probably already know he is a proponent of evolution acting at the level of the gene, so this is the view that I am most comfortable with.
I know that there are other points of view on this, even among professional biologists, I am just not too aware of who the supporters are and what evidence they have to support their point of view.
What say you everyone?