Talk origins has a list of so-called "beneficial" mutations but beneficial and gain of function mutations are not the same thing.
I know. Since we were discussing beneficial mutations, not gain of function mutations, I'm not sure why you bring the latter up. How about we settle one question before we start on another. Do you agree that beneficial mutations have been observed or not?
Got any examples of mutations causing a completely new function that didn't exist before?
Yes, but first we'd better settle the question under debate.
I didn't see where he made that assumption:
"all nucleotide sites have selection coefficients within this range"
You mean this sentence: "If substitutions at 10% of all nucleotide sites have selection coefficients within this range"? Leaving out the "if" makes a bit of difference to the meaning of the sentence, no? He's saying that, if his model is correct, there's an issue that needs to be understood. I'm questioning his model. Clear?
As for where he makes that assumption, he makes it when he treats the deleterious mutation rate as being independent of the population's fitness. In a more realistic evolutionary model, populations do indeed arrive at a state where there are many very slightly deleterious mutations that can't be weeded out by selection: it happens when the population size has decreased. (Similarly, the number of mildly deleterious alleles decreases when population size increases.) After such a decrease (and all other things being equal), the number of deleterious alleles in the population will increase. As it does, however, the deleterious mutation rate drops, since there is a smaller target remaining unmutated, and the rate of compensating mutations increases.
I think other shortcomings to his analysis may be more serious, however. First, while he does allow for the possibility of soft selection (not in his model, but as a way of evading the problem seen in the model), his model of soft selection is more attractive mathematically than it is a good representation of common kinds of soft selection; specifically, it is not represent competition for resources or mates. More generally, I am quite dubious about making any kind of meaningful comparison between the fitness of populations millions of years apart. It's quite possible for a later population to have far more mildly deleterious alleles and still have greater absolute fitness (i.e. be able to sustain a larger population size) than an earlier ancestor, since the two populations are likely in different environments and may be filling quite different ecological niches.
I think it comes down to whether you believe beneficial mutations outnumber deleterious mutations or not. I think his model is correct because there are more deleterious mutations then beneficial mutations.
I'm quite certain that there are more deleterious mutations than beneficial ones. That has no bearing on my problems with the model. I'm quite doubtful that there are many more deleterious than beneficial mutations with selection coefficients (s) less than 10[sup]-7[/sup], and I think the number of compensatory mutations with s in the range of 10[sup]-5[/sup] - 10[sup]-7[/sup] is larger than he supposes.
Another example of using the micro- to infer the macro-. We can jump a foot so given enough time we can jump 30 foot. Those positive selections did not produce a new species so there was no violation of genetic homeostasis.
I said nothing at all about macroevolution. For me, genetic homeostasis simply means stabilizing selection. If you have some other process in mind, please spell it out.