The End of Evolution By Means of Natural Selection

The reply to ZenMonkey just above. Message 364 I thought that it was pretty obvious that it had to be a recent post.Edited by PaulK, : No reason given.Edited by PaulK, : No reason given.

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Yes, good example, and it's also possible that a recessive allele whether a mutation or not could be selected against to the point that it is reduced to just a few in a large population,

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Not really. selection operates on the phenotype. A recessive allele will not be expressed in the phenotype of many individuals who carry the genes, so it cannot be strongly selected for or against.

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So in my scenario, if, say, 20 individuals from that population, including 2 of these recessive formerly unexpressed alleles, migrate to a new geographic area where they become isolated from the former population, then the odds of this allele becoming expressed increase a great deal and it should appear pretty soon,

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That could happen, although it must be pointed out that a population of 20 is small (on the limits of viability), and the odds of two having a rare recessive allele is not that high - and it must be very rare if it is never expressed.

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Its homozygotes would have been selected against -- their phenotype. Couldn't that cut back on the number severely?

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Unless the allele is very common heterozygotes will outnumber homozygotes. And if it is that common there will still be a lot of heterozygotes left. So unless there are some special conditions which somehow change things the answer must be that it is very difficult to make a recessive allele rare through selection. If there is really severe selection against the homozygous individuals then it might decline slowly, but it will be slow. (Genetic diseases are usually recessive because those that aren't are eliminated by selection.)

Granted that Faith's view is theoretically possible it still seems unlikely to me to be the case every time. And don't her Flood beliefs make it even more unlikely ? If you take the standard YEC view of the Ark carrying representatives of Creationist "kinds", each of which produced a number of species, all these alleles must be carried in a single breeding pair, in many cases. Obviously that pair must successfully interbreed, and it wouldn't be good if their offspring suffered interfertility problems. And yet, somehow we must get - from a single pair - multiple populations incapable of interbreeding. Without mutation playing a role at all ? Does this sound plausible to anyone ?

In fact I said it in Message 46 and Message 111. But In this case I was raising a specific point about interfertility. If it is down to incompatible sets of alleles, and if we accept the standard YEC view that a pairs of an original species on the ark could give rise to a whole taxonomic family we do have to wonder how this could be plausible without seriously compromising the fertility of the original pair or their early offspring. Remember at the start, no alleles can be rare, since each must be represented at least once in half the population !

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Picture much greater genomic capacity, "packed" -- meaning the vast majority of the genes now gone to junk DNA were then functioning as originally intended.

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That's a few more genes but no more alleles. And, of course, that means that species would be losing genes while remaining viable.

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With that much built-in fertility you don't get rare alleles...

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You mean with no extra fertility and nothing to affect the proportion of the alleles in the population ? With only 4 alleles, total, it's impossible for any allele to be less than 25% of the total !

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Reduction of genetic diversity with a reduction in population numbers ought to be the case every time.

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That's not what I was talking about. I was referring to the loss of interfertility without mutations.

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I have not been using my Flood beliefs in this argument and don't see the relevance. I have some tentative theories about the relation between the two but that's all.

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Obviously YOU aren't using them because there are major problems reconciling your arguments with a standard YEC flood view. That doesn't stop us pointing out that the problems are there.

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OK, I guess I do have to bring in my tentative thoughts to answer this. IF all the alleles WERE carried in a single breeding pair I have to suppose a much more "packed" genome, with thousands more functioning genes where now there is only junk DNA and the alleles all somehow contained in that format.

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That doesn't seem to make sense. If we are talking about alleles for a single gene for a single species how would the assumed historical presence of other genes be relevant ?

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I also have to assume many MORE alleles than we see today

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Which is the problem, since you have FEWER.

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Someone had suggested polyploidy at one time so I consider that a possibility for how their genome was different from ours.

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That would increase the size of the genome, not provide extra alleles.

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OR I have to consider the possibility of some form of "mutation" that followed some sort of chemical law that it no longer follows, that reliably produced compatible alleles in gene duplication.

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That doesn't seem exactly likely.

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he point is that today's genetic situation is different by a long shot than that at Creation and in Noah and his family and all the animals on the ark. The Flood would have had to reduce it dramatically which would show up in the generations soon after them, but there also had to be enough genetic potential available to make ALL the species we see today. It starts from a packed original genetic set and runs out over time.

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In other words you just assume that you are correct. Despite the problems caused by your own arguments. Isn't it more likely that your arguments are just plain wrong ?

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That's my view based on the Bible, but as far as my argument here goes, none of that has to enter into it. If reduced genetic diversity occurs with population splits, and population splits are how we get to speciation, and speciation is essential to macroevolution, all this can be discussed without reference to the ark or the Flood or Creation.

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Sure it could be. But we can also point out, that if it is true, it makes the whole YEC Flood scenario even less plausible. We're under no obligation to cover up that fact.

And most of them are even sillier than the standard. There are good reasons for trying to minimise the number of animals taken on to the ark !

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Yes, but he's saying I'm contradicting YEC views and I know I'm not contradicting that one.

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In fact what I am saying is that genetic diversity is already too high to be easily explained if the YEC Flood story is assumed - even if we assume that the Ark carried modern species rather than Creationist "kinds". And your insistence that genetic diversity is continuously decreasing makes that problem far worse. This is so clearly true that I cannot see how you could even hope to deny it.

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I don't think I deny that it's hard to explain, do I? I know it's hard to explain, I'm simply trying out some possibilities, and I don't think this has to be resolved in order to pursue my current argument.

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In other words what I am saying IS true, contrary to your assertion.

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To try to explain it I have to start with the obvious fact that whatever the genetic situation was on the ark it wasn't anything like it is today, and try to imagine possible genetic scenarios that could have been the case. I assume a geneticist would do a better job of it than I do if he could accept the premises for the purpose.

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By which you mean that your Flood scenario REQUIRES radical differences to the genetics of the animals on board, differences which somehow produced the diversity we see today. And you don't know enough to construct an answer that is in the least bit plausible. Yet you don't see the need to invoke such massive ad hoc assumptions as a problem in your position ? Since you haven't got any real evidence that genetic diversity is decreasing maybe you should reconsider that assumption instead.

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Sorry, I guess I still don't know what you're saying.

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I am saying that if you already have a problem that genetic diversity is too high because of an assumed past bottleneck, arguing that it must also decrease over time only makes the problem worse.

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Thought a "packed" genome was a pretty good start myself.

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Since it only gets you extra genes, not extra alleles for the genes that are retained it doesn't seem to be very helpful. Maybe it would account for related species having some different genes, but that's all. And of course it is pure speculation.

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Not in my current argument. It's a completely separate issue. I'm trying to stick to what I understand to actually occur in the present, whether anybody here thinks I'm right about that or not, I'm not speculating about an utterly different situation in the distant past.

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I don't think that it is a separate issue. If genetic diversity can't increase then it cannot have been lower in the past. And, of course, the only reason why you are saying that it is completely different is because there is a clear problem with current genetic diversity. There's no direct evidence of this alleged difference.

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It's logical that it's decreasing. There isn't anything else it could do. Even with mutations.

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No, it's not logical. It's an unevidenced assumption. Especially as it relies in not counting the increases in diversity from mutation.

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But I don't have a problem that genetic diversity is "too high." A bottleneck when the diversity was enormously higher than it is today, and the genome had all functioning and no junk DNA, wouldn't have the drastic effect it does now because of the lower diversity in species now. It would have a drastic effect by comparison with what existed before but not anything like it would today.

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If you didn't have a problem you wouldn't be trying to explain it away with these wild speculations. Which don't even work.

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As I said, it's a good start, a good start for a hypothesis, which of course IS speculation. And then there's polyploidy to add to it, which WK just confirmed can supply more alleles, up to quite a large number it appears. And there's still also the farther-out possibility of an ACCURATE and LAW-following sort of "mutation." Yes, it's all speculation.

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In fact polyploidy - highly unlikely as it is - is the BEST of the explanations offered. At least it allows for different alleles at the loci where genes are today ! And it doesn't require any implausible and unevidenced mechanisms either.

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But I don't expect it to be lower in the past, I expect it to be higher in the past.

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But without your wild speculations it SHOULD be lower in the past if the Flood story is true.

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And it is a separate issue because it can be discussed completely separately. I don't have to explain how the genetic situation on the ark could have had enormously higher genetic diversity in order to discuss whether genetic reduction is going on in population splits today.

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If you are looking for actual EVIDENCE that genetic diversity really is declining and is not being replenished by mutations then past diversity does need to be considered.

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No, it's completely different because if the Flood account is true, genetic diversity has to have started out larger and been running out ever since, which contradicts current assumptions, but it doesn't contradict the argument I am making.

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That is completely false. There is NOTHING in the Flood account which requires a higher diversity immediately following it. And in fact it strongly suggests that genetic diversity was far lower at that time. Your speculations are an attempt to counter that fact, they are not part of the Flood story at all.

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It doesn't rely on ignoring mutation, it includes the possibility of mutation even though I don't think mutation does what you all think it does. It still decreases with the processes of reduction even with mutation.

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As I said your argument relies on assuming that the increases in diversity from mutation do not count. Because if you did count that you would have to compare the rate of loss with the rate of gain to know whether diversity was increasing decreasing or staying the same. That point was raised in the original thread and you haven't yet dealt with it (and please don't refer me to the OP, because that DOESN'T answer it).

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Both the Flood scenario and the argument about reduced genetic diversity rule out macroevolution.

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Since your argument assumes that speciation happens - and I've no reason to believe that your Flood scenario doesn't assume it as well - that is pretty obviously untrue. Speciation IS macroevolution by the scientific definition which is the only viable definition we have.

So, if I understand correctly your idea is that each species has an "essential character" which natural selection, acting like a human breeder strives to maintain. For this reason all mutations are removed from the gene pool, so that no increase in genetic diversity can occur.Have I got it right ? If not can you explain why adding variation WON'T counteract loss of variation ? It seems odd that such a counter-intuitive claim, central to your argument should be left so vague, especially given the length of the thread.

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I don't think of it in those terms myself -- "for this reason" and "strives to maintain" -- or in terms of preserving the "essential character" of original species. I really do not start from such presuppositions although it could easily be assumed by someone knowing I'm a YEC I suppose.

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No, I got it from your assertion that mutations would "blur the character" of the species Message 541 as if that were somehow an objection.

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I've been trying to do just this all through this thread, and am not doing a very good job of it apparently.

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Can you point me to something that is even an attempt at an explanation ? Because I don't remember seeing one.

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I've tried many times to think up a way to graphically represent it and can't come up with one, certainly not one I could actually do myself using the Paint program. I did post a few back at the beginning to demonstrate a simplified idea of how selection and drift work to reduce alleles, the one on drift from Wikipedia, and included mutations as the source of variation as well. That was the best I could do at the time, not nearly specific enough about what I'm trying to argue.

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The Wikipedia diagram in the OP begged the question. It only showed 1 mutation and therefore implicitly assumed that alleles were lost faster than they arrived. Without that assumption it showed nothing.

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Just by your calling it "counter-intuitive" I know you are getting at least partly what I've been intending, and that is a relief. It IS counter-intuitive. It isn't just a matter of addition and subtraction offsetting one another.

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You said that early in the thread too - but with absolutely no explanation.