A barrier to macroevolution & objections to it

This is a general response to what I understand Faith and MJ's argument to be in regards to speciation generally causing a reduction in allelic diversity that mutation cannot/has not been shown to make up for and that the new phenotypes seen after speciation are only a result of "rare" alleles coming to the fore.I propose a scenario showing that despite initial loss of diversity, previously "neutral" mutations or rare phenotypes/alleles can be affected by further mutation and selection, precipitating a speciation event, but conferring enough of a benefit to make the loss moot. This is a wholly speculative and over-simplified scenario, but I believe it "logically" shows the possibility that a single mutation can more than make up for a severe loss in diversity after a bottleneck/speciation event. Here goes.We begin with a population of rodent-like creatures about the size of a rat that dwell in treeholes. They are largely insectivores, preying on the insects that fly about and those that crawl on the trees, but they also often risk ground dwelling predators to go down out of the trees to eat fallen fruit (the fruit on these trees are very hard to reach) and ground dwelling insects. The population of about 5000 consists of one dominant color (Black) and one rare recessive color (brown). The Black (BB/Bb) phenotype has a fairly short tail, while the brown (bb) phenotype usually has a longer tail (sometimes just a bit longer, but it varies). They both have very good grasping claws to climb the tree trunks with ease and without the threat of falling.Now, the brown allele carries on it an immunity to a lethal disease (when homozygous) that has not yet presented itself to the population, so it is, as of yet, neutral. One day, the disease to which the bb are immune sweeps over the creatures and wipes out all of the BB and Bb. We are left with about 500 bb. This is a severe population and diversity loss. Slowly, the population rebuilds itself (with some genetic defects from some inbreeding popping up at first, but with population growth nipping them in the bud eventually). The new population again stabilizes at about 5000 with a similar diversity as before (due to allelic shuffling and mutation). Some previously rare traits emerge over time as dominant in the population (as Faith proposes occurs), but the species remains generally the same in behavior and basic phenotype (although the differences may be enough to allow them to be called a separate species from the original population before the disease and, therefore, speciation).Fast forward many years (hundreds, thousands, milions...doesn't matter) and a dominant mutation occurs that allows for the prehensility of the tail and it slowly spreads through the population. This is only beneficial to some of the bb because, remember, the tail length varied (the tails of the Black phenotype were all too short for it to be any good and it would have merely been a neutral mutation for them). Also, this mutation only confers a benefit once it is realized that those with long, prehensile tails can reach the fruit on the trees by hanging from certain branches. Sexual selection comes into play, as those with the mutation begin selecting mates with longer and longer tails.Eventually, those with the mutation start to outnumber those that don't (and those still with short tails as well) as they have a new, easy food supply and they don't have to risk predators on the ground anymore. They even learn to swing from branch to branch and sometimes tree to tree combining their tails and their grasping claws, even more greatly increasing their range and food supply. As their numbers increase, diversity, through both allele shuffling and mutation, also increases. They start spreading out to other areas (due to population size and availability of food) through the benefit of their increased mobility and mostly leave behind the other group. This probably causes more allele loss, but the gained advantage from this highly beneficial new mutation, plus the ever growing population from which new allele combinations and mutations come forth, far outweighs the comparatively small loss in diversity. Eventually, the two populations do not or cannot interbreed anymore due to either location and/or drift and/or incompatible mutations.And the process begins again.This mutation and the speciation that followed could have occured without the loss of the Bb and have had a similar effect, but it illustrates that such a huge loss can be overcome with one single beneficial mutation (and one which was only beneficial when combined with a neutral pre-existing trait/previous mutation) which confers enough of an advantage to allow for great population growth and, therefore, increased diversity.PS I know I didn't think of everything necessary for this particular scenario to play out, but, like I said, it is pure speculation.Edited by Jaderis, : No reason given.

Faith, can you make it clear, are you claiming that new alleles don't arise in nature? Or just that they don't arise at a rate fast enough to recover from events such as population bottlenecks?ThanksMick

Is anybody really thinking about the processes that reduce genetic diversity? You can't be!! They DO this, it is a REALITY that I've documented. Thank you Percy for acknowledging it. That is a FIRST.I KNOW mutations happen. But the fact is that populations that get reduced as described DO NOT recover. IN REALITY. They DON'T.It is over and over CLAIMED but it is not PROVED! The mutations that occur have NOT been SHOWN to bring about this ASSUMED result. WHERE IS YOUR EVIDENCE THAT THEY DO THIS, as opposed to your ASSUMPTION that they do simply because they occur?????You are ASSUMING the role of mutations as I've said. You THINK they MUST do the trick but you have NOT shown it.

I am really not claiming anything about mutations at all except that everybody has been SAYING they power macroevolution but they have not SHOWN that they do.It has been shown that mutations occur, in fact that they occur frequently, that "new alleles" are formed. I have no idea whether it is because they aren't enough, beneficial ones aren't enough, or there are too many deleterious ones that become a threat in a population -- one of the links I posted in Message 100 said that each individual dog in a breed has something like 5 "lethal" alleles -- NO MENTION OF mutations in any of that discussion.So, I don't know why or how, all I know is thatIT HAS NOT BEEN SHOWNthat mutations do or even could possibly do what is claimed for them.The assertions, the hypotheticals, the analogies, have been thick, but NOT ACTUAL EVIDENCE!You'd have to count alleles carefully before and after a population split or bottleneck -- not of bacteria, not even of fruit flies, but of mice or salamanders or something on that order -- to begin to show what mutations do or do not do in combination with all the reducing processes that are inexorable.Edited by Faith, : No reason given.

Ah, but we do know that populations do go through severe bottlenecks and do recover. Humans have done so. Even under the Flood fantasy humans recovered and in fact ALL species not just recovered by underwhen hyper-macro-catawumpus-look-out-here-it-comes-again diversity gains. In the real world we know that there have been several such bottlenecks for humans, one about 143,000 years ago and another only about 60,000 years ago.So both in the real world and in the fantasy world of the flood, diversity recovery after a severe bottleneck is a given.

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Aslan is not a Tame Lion

You deny the Flood even happened, jar.But the Flood did not cause the extreme kind of bottleneck we see now, which we see now because species are already much genetically reduced from what they were then. There had to be something different about the genome then, bigger, more genes, something, not what we see now.

You do NOT "know" this. This is pure THEORY, merely being asserted as fact as usual. No more evidence than your silly money-adding analogy is evidence.Edited by Faith, : No reason given.

That is not a matter of belief but rather a conclusion based on all the evidence.BUT...even if the the Flood myth were true, then EVERY species was reduced to only the genetic base of a handful of critters and the total number of critters reduced to the few that would barely crowd one or two little football fields. Yet in the blink of a eye compared to what the evolution model uses, life went from that handfull of genetic material to all of the diversity we see today.As to the bottlenecks in humans, the same basic evidence you use to support your cheetah example is what is used for humans. And there we do see two genetic bottlenecks where the number of humans was reduced. Yet humans recovered from both of those events to the diversity we see today.Of course the TOE requires far less drastic a rate of increase in diversity than any of the Biblical fairytales like the Flood.So where is this barrier that stops macroevolution over long periods of time but also allows it to happen in a blink of an eye when the Biblical Creationists and Floodist want to use it?I put some money in a pile every day for the rest of my life.All of my descendants put money in the pile every day of their lives.Each of their descendants continue the tradition by putting money in the pile every day of their lives.What limits how much money is in the pile?

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Aslan is not a Tame Lion

There are actually contemporary observable bottle-neck situations within the human species, though not due to speciation but to isolation. We have the example of Pitcairn Island where the decedents of the Bounty mutineers have lived for 216 years in more or less splendid isolation. The original population in 1790 was 27, today they are 47 (due to emigration) but the population have in periods been up over 200. So here we have a bottleneck situation where a much limited population and thus a small generic material can be interbred for well over 200 years without the limited genetic variation doing great harm.There are of cause other examples but Pitcairn is one of the most well documented where the pedigree has been kept minutely clean. But other examples such as Iceland that were colonized in the 900 century by a small group of Norsemen and have had very little immigration are another.Though, more important is to realise that speciation, under natural circumstances, isn’t an instantaneous event but at process that takes tens of thousands of years to occur. If two species branch of from a common ancestor this mean that the interbreeding between them are dwindling over time until it come to a stop, not that it stops right when mutation X first occur.

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/jerker

It can happen, but it certainly represents a situation of extreme allele scarcity that could eventually bring about harm. It's similar to the situation of the Amish, who are now producing some terrible diseases, a situation from which there is no recovery without the introduction of alleles from other populations. Mutations, though we are told they are very frequent, are not bringing about this recovery, are they? Are there more alleles being expressed in this population now than there were 200 years ago? Alleles that are bringing about changes in the direction of strength or longevity or anything good like that? Great, they lucked out. But they are certainly allele-poor even if they are doing OK. It depends. It can happen in a few generations of a small population that is constantly inbreeding. At least it can develop an identifiable phenotype that can be differentiated from its original population, which is a step in teh direction of speciation. I think speciation is a somewhat artificial concept myself, the point being that all the processes that tend toward speciation all reduce genetic diversity along the way as new phenotypes are developed. Not sure what you are saying. Two species may branch FROM EACH OTHER, two populations going their own way and developing their own characteristic phenotypes (and genotypes) from their own portion of the once-shared allele pool, now divided between them. Interbreeding or gene flow between the two populations may or may not stop soon or late. If gene flow continues it will slow the processes of divergence; but sometimes due to geographic isolation interbreeding stops very soon. Mutation need have no part in this at any point. Edited by Faith, : No reason given.

Faith, you have to understand that your wants and desires do not control reality.

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Is anybody really thinking about the processes that reduce genetic diversity? You can't be!! They DO this, it is a REALITY that I've documented. Thank you Percy for acknowledging it. That is a FIRST.

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What is in fact happening is that this is not a point of contention. Nobody is talking much about it BECAUSE NOBODY DISAGREES ! You would like people to be arguing with it because you can provide support for that part of your argument. But that doesn't control what happens and that fact is that doing so is just pseudo-argument which doesn't advance the discussion one little bit.

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I KNOW mutations happen. But the fact is that populations that get reduced as described DO NOT recover. IN REALITY. They DON'T.

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But this is not a fact. That is just what you want to be true. That has no bearing on whether it is true or not. You haven't produced a single good reason to think that it is true.

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It is over and over CLAIMED but it is not PROVED! The mutations that occur have NOT been SHOWN to bring about this ASSUMED result. WHERE IS YOUR EVIDENCE THAT THEY DO THIS, as opposed to your ASSUMPTION that they do simply because they occur?????

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You may want an absence of evidence either way to be considered proof that you are correct but that doesn't make it so. The mere fact that mutations happen is evidence that some allele loss will be made up. The fact that allele loss will tend to decline as the number of allelles decreases indicates that we should expect loss and gain to balance in a dynamic equilibrium. This alone is better evidence than you have produced.So to sum up:The arguments your opponents make are not controlled by your desires. Instread of going over and over hammering on points settled long ago you need to deal with what your opponents are really saying, not what you wish that they said.The realities of nature are not controlled by your desires. That you assert that mutation cannot replace allele loss does not make it so no matter how much you wish otherwise. If you wish to convicne others you need to provide evidence and sound argument.The realities of debate are not controlled by your desires. You must support your claims, like everyone else does. Your desire to be excluded from that when you cannot do so is understandable but does not make it so. Simply repeating the assertion or claiming to have "logical arguments" when you have none is not adequate.

Faith, I'm trying to follow your logic, I promise. But I think you are labouring under some misapprehensions regarding the processes of evolution that reduce allele diversity.First let's deal with the idea that populations having undergone population subdivision or bottlenecks are unable to recover the allelic diversity that was lost during those events. If you were to take a single bacterium and place it in a petri-dish, this would represent the severest possible bottleneck event for that bacterium and its descendants growing in the petridish. Now, if you left the petri-dish for a week and came back to sequence the DNA of the bacteria covering the gel, you would find alleles that were not present in the initial founder bacterium. The allelic diversity in the petri dish would have increased over the week. I don't think that this is seriously disputable. Allelic diversity can and does increase within populations due to mutation.Second, you seem mainly to be talking about mutation as a source of novelty versus drift as a remover of novelty. Your view seems to be that drift, as a process removing allelic diversity from populations, is going to always predominate over mutation. But you are wrong if you think that the rate of removal of alleles due to drift is independent of the rate of origin of novel alleles due to mutation. The rate of both processes are correlated with each other. When new mutations are happening very frequently, there are lots of novel alleles that might be removed from the population by stochastic events (such as bottlenecks, or what have you). But when new mutations are happening very infrequently, there are not many novel mutations available for drift to remove! This is basically because the rate at which drift removes alleles and the rate at which mutation introduces alleles are both proportional to population size. They covary with each other. It makes no sense at all to imagine that "stochastic events prevent the origin of allelic diversity" or anything like that. Because if the origin of allelic diversity occurs at a low rate, then the stochastic removal of diversity will also occur at a low rate. Drift does not "limit" the rate of origin of new alleles.I hope this makes sense!MickEdited by mick, : No reason given.

Indeed it is. Where? We've been waiting for evidence for it for over 100 posts. Edited by RickJB, : No reason given.

Faith, I ask again, Faith, please provide evidence of a barrier to macroevolution. I expext you to meet your own standard and have the evidence be so conclusive that we "know" that such a barrier exists.Mark

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There are 10 kinds of people in this world; those that understand binary, & those that don't

Faith writes: A new phenotype does not necessarily mean that the alleles for a previous phenotype are lost. There are mechanisms which help to preserve genetic diversity within a gene pool such as diploidy, balancing selection and neutral variation. I'm sure that these mechanisms would have been discussed on this board before, but I can go into detail if you like.Population bottlenecks do reduce alleles but the above mechanisms help to stabilise those left in the pool, with mutation increasing the diversity.