Natural Limitation to Evolutionary Processes (2/14/05)

I'm not sure Faith but it appears to me that you may have a slightly off picture of what is going on.If a selective "event" -- the death of an individual carrying a gene producing a less fit phenotype than those around it occurs it removes that particular copy of that gene from the gene pool. It may remove at the same time other unique alleles of course.However, the gene pool as a whole may well contain almost all the alleles of that individual. The reduction in variability may not be as drastic as you seem to think.In addition, the differential breeding and survival of those carrying another gene such that the gene spreads to the entire population may only supress other alleles at the site of that particular gene not all the other 1,000's of genes. The selection process may be more subtle than you are imagining.Since all individuals of an animal species carry several new mutations the selecting out of a few isn't likely to keep up with the creation of new ones.When an event occurs that is "catastrophic" and overwhelms the fitness differences of individuals the survival becomes "random" and then the variability may drop dramatically -- e.g. the Cheetah.If the event is dramtically selective that too, of course, my reduce variability dramatically.If there is a separation of a founder population the very occurance of the separation has produced a population of limited variability. If the population is small enough chance events my reduce variability further.In the more "normal" case the rate of mutation is pretty darn high. You carry several mutations yourself. This rate in a large population makes it hard to see how your idea of continued reduction of variability makes any sense.You have yet to do more than say it happens. I've seen no support for that.

Faith, isn't this a very odd way to come at this?You've jumped into the kind of details that researchers like to deal with: thinks that might be called "computational evolution". (I'm makin g that up.).You've jumped in while admitting you know pretty much nothing about the topic at all. Why would you do that? Why not build a base of understanding before you dive into the deep end? There is no pedagological approach that I'm aware of that suggests that yours is a good way to go at it.There may be many other things that you need to clarify first. You haven't as yet made it clear what else you understand or accept.For one thing, separate from the theory of how evolution occured, there is the fact that evolution has occured. If you wonder if the current theory can explain how you need to come up with another one explaining that it has.If, on the other hand, you think that it hasn't happened at all. You need to forget about the theory and get back to the underlying evidence that shows that it has occured (by whatever mechanisms). At the extreme this means backing up and recognizing what has been called "deep time". The evolution of life on earth has occured over a period greater than 3 billion years. You willingness to accept that evolution could happen is bound to be affected by your acceptance of the time scales. If you don't accept them then why would you worry about mutation rates? Or even if evolution occured. All you have to do is show that the 3 billion years value is wrong.How about one step at a time.If you wish to stick to this then you need to show the math that shows that various selective pressures will reduce variation under specific mutation rates.This kind of work is done by evolutionary theorists (though I don't know enough to be able to point to the publications). If you want to suggest that your ideas are right then you have to start with numbers. Produce models showing what happens with various rates of mutation and selection.It seems you haven't the tiniest bit of reason to support what you are suggesting. The only reason you are bringing it up is because you don't like the idea of evolution itself. How about being a bit honest and admit that you are not either going to believe what you are told or do the enormous amount of work necessary to understand the science at the level of detail you are attempting to discuss.

Here is an example of numbers being applied. I'm not spending long at it but I'm throwing it out to allow others to attack it and hopefully produce a better model.Here is my scenario:I have a population of 1 million individuals. This is the carrying capacity of the available resources.These animals live 5 years producing two surviving pups per female per year from the end of their first year.They have 30,000 genes. There is no junk DNA. There are therefore 30,000 alleles in the whole population.Each individual has 10 mutations randomly scattered in it's genes.Half of these are fatal and the pups carrying them are still born or not even carried to term. This gives 5 mutations per individual.The entire population has exactly the same genome at the beginning of the process.What happens?Since there are 1,000,000 new individuals born per year and only 200,000 dying of old age in a year a stable population requires that 800,000 individuals die either by selection or randomly each year.Assume half are randomly killed and half are selected against.In each generation there are 5 million new genes. One way or the other 4 million do not get passed on. This gives us 1 million new alleles added each generation.This means about 1 out of 30,000 genes becomes new in a generation per individual on average. At first, the new ones will be scattered and probably not be on top of a previous one. As the generations go by this will start to happen and there will some of the so-called new ones will be replaced at random.In one year we go from 30,000 alleles in the gene pool to 1,030,000 alleles. Then to 2,030,000 and so on. This is before we allow for selection.The assumptions above have about 100,000 alleles being selected for in some way. Now we have to apply the degree to which they are selected. Let's assume very strongly so they will become fixed very quickly. This means that they drive out all the alleles that are at the some location. At first there aren't many collesions so the number of alleles goes up sharply.Now what I need to do is figure out what the equilibrium diversity will be.

I'm sorry I even hinted at you discussing in bad faith. (and excuse the hint of a pun as well ). I think it has been clear from the beginning (but maybe no one was absolutley unequivocal) that we agree that selection is a reduction in variability much of the time (not all the time but much of it).Yes, selection (particulary to fixation in a population) is a reduction of variation in a gene.Clearly, you have also been shown that mutations aupply variation. Only calculations can settle the question as to when they supply enough and when they don't. One can obviously construct scenarios where the rate of mutation can be overcome. The idea of the flood and ark is one of them. The fact that there isn't a consistent bottleneck for all the animals that were supposed to be on the ark is just one of the more minor falisfications of that idea. Ok, as long as you're willing to understand it is a bit more messy than some areas of discussion; why shouldn't you discuss what you want? It also needed a separate thread since it is one of the rare topics that hasn't been discussed to death. Well one reason is that a good discussion is fun. You should note that when you say that the limit is at the species barrier (which is not where many creationists now but "kind" -- while they work very hard to avoid defining it ) that has been discussed in many threads around here. The occurance of speciation has been documented a rather large number of times. We all hope that a creationist with some scientific knowledge will come along. That is when it is most fun. However, they don't seem to appear and if they do it is with very, very little knowledge. Then they avoid the simple, most obvious issues like the age of the earth one. Personally I keep trying to point YEC'ers at it but they shy away or give up very early.If you hang around for a few months you might begin to suspect that there are not any creationists with the requisite knowledge. You might find that, search as you might, you won't find the creationist sites making arguments that we haven't had fun with several times over here. You might even begin to wonder what all of that is telling you. Not being an evolutionary biologist I can't be sure, but I think you have a good point. I'm pretty sure that the issue of variability and viability of gene pools in the long term is actually examined and modeled by researchers. It is looked at just because you have, at the base, a valid point. However, it isn't the big giant killer you think it is.You should also note that in the process of science it is those same researchers who do the most rigorous digging into such issues. You seem to think that a bias will blind them but that is why we don't relay on the thinking of just few individuals. Oh good! This is one that has been discussed at some length. However, we have had no good explanation that stands up to scrutiny.

Wow! and I thought our texts were a bit medicure and out of date. My daughter 6 years ago in elementary school had a text which, while simple and short, got it right. Then last year in grade 11 they went into a bit of detail discussing how this works.All of it still pretty simple compared to what she will get into at the university level but that is what you have to do when there is very limited time and a group of students not all of whom are as interested as some are.Of course, if evolution isn't discussed well I might refer you to the article in the NY Times of a couple of weeks ago that points out that, while the court cases are stopping the fundamentalists from officially tampering with a descent education, they are coming in the back door by causing so much hassle for educators that a discussion of evolution is curtailed in practice. If there is a problem with the popular understanding it may not all be blamed on poorly written texts and poorly trained teachers. Perhaps it is just the sort that maintain AIG and ICR that can be blamed.

Guess what. A number of people here actually go out to find the best that the creationists have to offer (not all, some don't like supporting them by buying their books). We would, of course, welcome the most knowledgable here.However, we can't find any that show much knowledge of the subjects they attack. Perhaps you can find the writtings of the "most knowledgeable creationists". That would be helpful indeed.As for respect, that has to be earned. Show us someone who has earned it.

In the focus on mutation I've noticed that the meiotic recombination has only been mentioned a little. It is a source of genetype variation of course. However, over the long term new alleles aren't introduced that way. I think you started focussing on the very long term which is why the mutations became focussed on.

Thanks, that is the kind of stuff I figured was out there. Still simple but we don't want to write a book on the topic.Faith can now supply the calculations that show that the loss of variance is a problem. Or maybe that isn't an issue any more? Have we finished with the topic of this thread now?

Thank you, inkorrect. You just destroyed the creationists (and Faith's) arguments against macroevolution. Thanks for being on our side.

This has been explained over and over. It is a simple example of what we are talking about.There is no place for this magic genetic potential to hide. This is understood in many of the cases discussed. In the nylon bacteria case it is easy to show. This has already been explained to you.

In the very controlled case of the nylon bacteria (as in the cases of antibiotic resistance). The population is grown by the natural cloning of a single individual. The population then does not contain the particular genetic sequence of interest.However, bacteria (paricularly) do not reproduce very accurately and very quickly all sorts of new sequences arise. It is shown that it was not anywhere in the originals.Nowadays it is possible to determine the exact sequence and the change that happened. We know that these kind of changes can occur in the reproduction process.There is no where for the built in diversity to hide.

Your problem here is using words like "mistake" or "broken" in this context.It is, as you say, perfectly predictable that there will be novel sequences from the reproductive process. It is by it's nature imperfect. It is even clear that some changes will be more likely to occur than others by the nature of the chemistry.But this is exactly what mutations are. They are changes that produce novel sequences. One may label them mistakes if we think that the gene reproducing process MUST produce perfect copies. It is clear that this would be a VERY BAD thing. These "mistakes" are what makes it possible for ongoing populations of organisms to deal with environmental changes (of all types). The overall population doesn't care that many billions of individuals die because they have changes that are not useful. It is a successful population because it contains these "mistakes". With that view they are not "mistakes" they are simply trails that weren't such a good idea at the current time and place. When they arise again and again they may well happen in the right time and place.It is fair to apply the word "broken" to some (when a gene ceases to function for example). However, this is looking at it from our own immediate and anthrocentric point of view. "Broken" or a "mistake" is simple a change that happened to come along in an environment for which it was less suitable.Antibiotic resistance is "broken" or a "mistake" (generally, I don't know about all cases) in an environment for which the antibiotic is not present. (One suggestion for preserving useful antibiotics is to stop using a specific one for some years. The mutations conferring resistance apparently are less "fit" in this environment and would be selected against thus producing a complete population of non-resistant individuals (other than the rare, now-and-again, new mutation bearing individual). It resets the clock on the development of resistance.)However, in todays antibiotic soaked environment the mutation is not a "mistake" or "broken" at all. It is a darned good and useful trick that has been stumbled over.

The question makes perfectly good sense. It is just a detail that isn't all that important in the big picture we are discussing.Not all mutations can happen as easily as others. That doesn't change the fact that they arise and produce novel sequences. That is the point of the current discussion.