The End of Evolution By Means of Natural Selection

That's not quite right. Yes, selection reduces variation. As far as I know, genetic drift does not affect variation. And mutation increases variation.You are correct, that if there were only processes that reduce variation, then eventually evolution would run out of variation and would stop. But as long as there are also processes that increase variation, there is no reason to expect evolution to stop.As far as I know, what is mostly noticed is that variation stays fairly constant. A bottle neck, such as caused by isolation of a small population, can result in reduced variation. But the variation is rebuilt during succeeding generations.The type of argument you are making could perhaps be used to suggest that the theory overemphasizes selection and underemphasizes the production of new variation. But you won't be able to refute evolution this way, because the empirical evidence shows that variation does build up again if it has been reduced - unless, of course, that particular line goes extinct.

That's a misunderstanding right there. Variation is a property of the population as a whole, not an individual. The mutation replaces another allele in an individual, but the chances are that the allele is still present in the population. So the result of the mutation is an increase in variation within the population. I'd say that you are reading too much into that demonstration. It is giving an exaggerated example as an illustration. The complete removal of an allele in 5 generations of drift is improbable, even with a population size of only 20. With larger populations it is even more improbable. Generally, you would expect drift to show up as a slow change in frequency, rather than complete elimination. I'm not a biologist, but I think it is still controversial as to whether genetic drift is significant enough to even be important. Most traits are the result of a combined effect of many genes, rather than a single gene. The near elimination of particular combinations can still leave the same variation in the population, and for a species with sexual reproduction (or other ways that depend on meiosis), crossovers can recreate combinations that had been eliminated by selection. So the loss of competing alleles and of combinations of alleles will not be nearly as complete as you suppose. The case of complete isolation is where you do see a reduction in variation. But you won't see a complete elimination of variation, at least in sexually reproducing species, because crossovers can recreate combinations that were removed by the isolation. Moreover, empirical evidence shows variation building up over subsequent generations. So evolution does not stop at that point. The isolated population is in a precarious situation, and more likely to go extinct than the original group from which it was isolated. But if it survives long enough to build up more variation, it might become the founding group for a new species. Hardy-Weinberg is a theoretical principle when there are no mutations and there is no selection. That's not what I was referring to. Under ordinary conditions, I would expect the loss of variation due to selection to pretty much match the amount of new variation produced by mutations. Under conditions of severe selection pressure, I would expect a decline in the amount of variation. Under favorable conditions (very low selection pressure), I would expect an increase in the amount of variation. As far as I know, that is what is actually observed. There is concern for the cheetah for two reasons. Firstly, it is still in a precarious situation due to reduced variation. Secondly, it is under heavy selection pressure due to habitat destruction in Africa.Likewise, the concern with the salmon is that they are still under heavy selection pressure due to overfishing and habitat destruction.Under a more normal selection pressure, I would expect the variation to be recovered over a number of generations. Under the heavy selection pressure that exists in these cases, the risk of extinction is significant. I don't think we know that (particularly the "one iota" part). We have not been recording DNA variation for long enough.We do have good reason to believe that the domestic dog is a result of selection - probably artificial selection by human populations. There is still plenty of variation such as allows further artificial selection to produce many different breeds.I am as interested in the evidence as you are. If some of our biologist members can produce relevant evidence, that would be useful. It is almost certain that the experiment has been done with drosophila - that is, severe selection to reduce variation, and then observation of the increase in variation over future generations.In any case, we do have natural experiments with antibiotic resistance arising in bacteria. It is pretty much expected now that any new antibiotic will, after a while, lead to bacteria that are resistant to that antibiotic.

To be fair to Faith, I think she is making a different point.She is arguing that as the biosphere branches out, producing more variety, eventually it will reach dead ends where no further evolution is possible beyond those dead end points.Looking at it in terms of a tree analogy, Faith is saying that as the tree branches out, it will reach the point where the peripheral twigs have lost their ability to sprout new twigs. You are responding "but there are lots of twigs as a result of prior branching" and that seems to miss her point.I do think her point is mistaken, and I have said so in earlier posts in this thread.

I am inclined to doubt the "eliminate everything that tends to smallness" part. Breeding reduces the frequency with which those genes appear in the population, but it does not eliminate them. That is why you get atavism (or reversion). Dog breeders have to continue with their program of artificial selection to avoid this problem.

Oh, yes, I have met her before - online, but not in person.She has freshly been reinstated as a member here, so I'm for giving her a fresh start. That is, I treat her as asking honest questions and wanting to learn. I don't doubt that she is still a firm creationist, and wanting to refute evolution. Yet, I do think she deserves straightforward answers that don't refer back to her history at this forum. Hmm, no. I am just being polite and responding to what she asks, rather than responding to what we might assume to be her ulterior motive.

First, I'll comment that it won't bother me if you choose not to reply to my posts. I do hope you at least read them.A second comment: the argument you are making is similar to that made by Fred Hoyle I am confused about what you are saying there. I always thought that the thing about ring species was that there is no "last in a series". And I'm not sure that it is necessarily true that different species in the ring cannot interbreed - what makes them separate species is that they do not interbreed, which is different from saying that they cannot interbreed.Another point about ring species, is that the different species live in slightly different environments. Presumably there is still selection going on, due to these different environments. It seems entirely possible that different species in the ring could all have the same alleles present in the population, but just with different probability distributions. That is, some alleles might be common in one species in the ring, and rare in another. The different probability distributions could be maintained by the continuing selection pressures resulting from differences in the environments.Edited by nwr, : fix typo

Hi Faith. I initially did not respond in order to minimize the "piling on" problem. I assumed others would adequately cover most of the points. However, you requested response in Message 129, so I am complying.Note that some of my responses might differ from those of the biologists. I have been researching the principles of learning, and I am influenced by that research, as I do consider evolution to be a kind of learning system. To "get" a breed, you select dogs with the desired characteristic, and breed them. Yes, you then breed within type. But, as far as I know, that is not sufficient. You also have to continue selection, for the dogs are not guaranteed to "breed true". Yes, but I would prefer to say it is to increase the probability that the pups will have the desired characteristics. Any individual dog contains limited diversity, compared to the total population.The breeding pool also has less diversity than dogs as a whole. But much of that is due to it being a far smaller group. Some of the alleles that the breeder wants to suppress will still be present, but at a lower frequency.And some of the traits being bred for are the result of combinations of many alleles, rather than due to single alleles. In that case, the alleles might be very similar to what is in the general dog population, but the probabilities of particular combinations will be different and will favor the traits the breeder wants. The effect of the breeding is it increase the probability of the desired traits, and reduce the probability of undesired traits. The breeding pool has been selected to produce those changes in probability. But that does not require the complete elimination of the alleles responsible for undesired traits. The genetic diversity of the breed might not be much different from that of a similar sized population group, but the probability distribution will be different and that is what leads to a successful breeding program. No. Some of his ideas came from his knowledge and experience with domestic breeding, but the initial insight came from his voyage on the HMS Beagle, and was particularly influenced by the biota of the Galapagos islands. No, I have previously expressed disagreement with that. Evolution depends on selection and on variation. In my opinion the generation and maintaining of variation within the population is at least as important as selection. As others have indicated, evolution has no goals. However, I think it fair to say that living things have a "drive" to survive and persist, perhaps by producing future generations. And this biological "drive" is an important part of what drives evolution.

Can you post a link to your blog, or enter it in your profile as your home page. Thanks. I find it better to avoid the political threads, or at least to be very minimalistic about what I post there. Those threads usually generate far more heat than light.

It seems that Blue Jay has initiated a thread. If the thread is promoted, then I encourage you to participate. You can treat it as a discussion, rather than as a debate.You can treat it as a way of learning how evolutionists think about how evolution works. You don't have to agree, but it should surely be valuable to better understand the positions you oppose. I think you will find that Blue Jay will treat you fairly, and with patience.

Clearly, you are not understanding how a Young Earth Creationist thinks.

The YEC believe that they have a direct pipeline to the truth, and therefore potentially know more than mere experts.

You are not going to find much evidence of that. Generally speaking, the increase in genetic diversity precedes the speciation, and is part of what makes speciation possible. If you are looking for the increase in diversity to happen at the time of a speciation event, then you are looking in the wrong place.Increase in genetic diversity is mainly a gradual process that is always going on. Speciation occurs as speciation events that depend on contingencies in environment that alter the selection forces. Evolution, itself, includes both processes that increase diversity and speciation events.

I'll suggest that the discussion here is quite misleading.In a way, Faith is correct that beneficial mutations are rare.Take the example of a mutation that gives antibiotic resistance to a bacterium. That mutation is likely either deleterious or neutral. For a bacterium in its normal environment, where there is little antibiotic present, the antibiotic resistance provides no benefit. What that mutation does do, however, is it allows that bacterium to move to a different environment where there is a significant amount of antibiotic present. And that mutation is beneficial in the new environment, but not in the old.The term "beneficial" is not properly applied to a mutation. Rather, it should be applied to a mutation with respect to a particular environment. What might be beneficial in one environment can be deleterious in another. You cannot understand evolution without taking into account the change in environmental niches that accompanies the evolution."If humans evolved from apes, why are there still apes?"
"If motorcycles evolved from bicycles, why are there still bicycles?"Adding a motor to a bicycle is not a beneficial change. It makes the bicycle heavier and less maneuverable. But it does change the bicycle into something different that can be used in ways that are different from the ways we use a bicycle.Evolutionists are quick to point out that evolution is not progress. It is change, but there is no direction. If we deny that evolution is progress, we ought to also deny that mutations are beneficial. If we insist that evolution is change without implied direction, then we should talk of mutations as agents of change, instead of saying that they are beneficial.

This was not a technical scientific discussion. This thread is a discussion with and for the general public.

I have not suggested that. Those are not the terms that are feeding the wrong ideas that many people have. It's "nice" of you to include unnecessary and inappropriate insults in your posts.