The End of Evolution By Means of Natural Selection

Hi Faith,Genetic diversity can go in any direction after reproductive isolation. For example, consider a relatively homogeneous population that becomes divided in two when a river changes course. There are now two populations, both with pretty much the same alleles and allele frequency. Mutations experienced in one population will no longer be shared with the other and the populations will evolve along different paths. If this continues for a sufficient period then they could lose their mutually interfertile quality and become two species.If both populations thrive then diversity could increase in both. But if one or both populations suffer some disaster such as flood or famine or an invasive predator or disease that greatly reduces population size, then diversity would be reduced. It all depends upon what happens to the populations.--Percy

This argument couldn't be more wrong. The alleles for a gene are not involved in a competition where only one is left standing. If that were the case then extinction would be an extremely common event because a species ability to survive across changing environmental landscapes is dependent upon variability. Great variability increases the likelihood that at least some subset of a population will survive an environmental change.If it were really true that more beneficial alleles eliminate those that are less beneficial or even deleterious then alleles for genetic diseases would have disappeared long ago, and yet genetic diseases like cystic fibrosis persist.You need to find solutions consistent with both your religious views *and* reality.--Percy

This isn't the way it works. For Darwin's 15 different tanager species there were not 15 different alleles for the shape of beaks, one for each species. Bird beaks are controlled by the expression of the Bmp4 gene. All the different beak shapes are the result of different timing and spatial controls on the expression of the Bmp4 gene. Expression of the Bmp4 gene is under the control of regulator genes with names like Shh and Fgf8.In other words, beak shape is under the control of more than one gene and more than one type of gene, and bird gene pools of any species possess a great deal of variation. This is why beak expression is so plastic under the influence of changing environmental pressures.--Percy

Hi Faith,I don't know why you went so far back and responded to Message 15, but what you were saying at the time and what I was responding to was that any evolution can only result in reductions in variation. As everyone's been telling you, variation can increase or decrease. The reason I mentioned mutation is that the sum total of all alleles in a population is the amount of variation, and only mutation can increase the number of alleles. Natural selection can affect allele frequency, and indeed one way to define evolution is as changing allele frequency over time, but only mutation can increase the number of alleles and thereby increase the amount of variation.The reason people are bringing up mutations isn't because they think it is the source of all evolutionary change, because obviously it isn't the only source. They're bringing it up because it is the only way to increase variation. Mixing and remixing the same set of alleles can create unique combinations of alleles that didn't previously exist, but it doesn't change the pool of existing alleles at all.Almost no reproduction is perfect. Even people have mutations. The average number of mutations per person is usually estimated at between 10 and a hundred. Ignoring mutation might make it easier to claim that variation can never increase, but the real world has spoken.--Percy

So am I. I defined variation as the sum total of all alleles in a population. I defined an increase in variation as an increase in the number of alleles in a population. If you're defining variation differently let us know. Yes you did say that variation cannot increase. This is you from Message 1: I just saw your answer to Subbie, so here's another quote from your Message 1: People who make many simple errors draw many responses because everyone rushes to reply thinking, "This confusion should be a simple matter to clear up." Many people are responding to the exact same points. Responding to every reply under such circumstances isn't realistic.There's a simple alternative available now. If you look at the bottom of any response to one of your messages you'll see that it says either "Faith has not yet responded" or "Faith has responded." This text is actually a link, and if you haven't yet replied to the message then if you click on this text it will change to "Faith acknowledges this reply." This lets the person know that you've read his message but don't feel it necessary to respond.--Percy

Faith, as long you continue to assert that mutation plays no role in speciation there will be no peace for you in this thread. People would not find it outrageous to argue that changing allele frequencies and permutational recombinations of alleles are a more significant factor over mutation in speciation. That would actually be a very interesting discussion. But to just declare that mutations have no role at all is once again to simply deny the real world, and assertions denying what is obviously true tend to draw many responses.--Percy

Every allele in existence today had its origin as a mutation to an already existing allele. Given that all alleles begin as mutations, how can you hope to prove mutations have no role in evolution? Alleles that have been around a while are really just old mutations, but we call them alleles. New mutations are alleles, too, but because they just happened we give them the special name of mutations. Do you understand that this is the same as saying that a new allele, one that isn't the same as any other allele in the newly isolated population or in the original population, hinders the emergence of a new phenotype? If so, you realize this makes no sense, right? You do understand that mutations make the newly isolated population even more different from the original population, right? Why not, Faith? You said you were going to prove this. So go ahead and prove it. Mutations happen all the time, Faith, it isn't an assumption. You yourself probably have somewhere between 10 and 100 mutations because the average mutation rate for humans is around 2.5 x 10^-8 errors per base pair and there are around 3 billion base pairs in the human genome - do the math. The DNA copying process for 3 billions base pairs is not perfect and makes occasional mistakes. Errors are inevitable. Yes, Faith, precisely, that's exactly what happens given enough time, though breeders would tend to hinder this process by simply choosing not to breed individuals with mutations they didn't like. All species breed almost but not exactly true. Change is inevitable. Evolution never comes to a halt. Remember, reproduction is almost never perfect. It isn't an issue of whether or not there is change. The issue is how in the world would you ever stop it?Evolutionary change is happening (very slowly) in all species everywhere all the time. The rate of change is a function of the organism itself and the degree of environmental pressure. All existing species are transitional, on their way from the species they were to the unknown and unknowable species they will be, unknown and unknowable because evolution has no direction.--Percy

Faith, a mutation *is* an allele - a new allele. The only way a new allele has ever been observed to form is through mutation, i.e., through copying errors as part of reproduction. If you're imagining that some alleles come from some other source then it is one that has never been observed in either nature or the lab.You said you could prove your view of how evolution works, so you can start any time now.--Percy

First you say you've been "proving it all along," then you say the necessary tests haven't been performed yet. Does the contradiction need to be explained? What you really want is references to research that supports your position.--Percy

Hi Faith,You've been arguing that evolutionary processes can never increase variation, only reduce it, but mutations contribute new alleles to a population, so obviously variation can increase. Rahvin described the simplest experiment yielding increasing variation, and the process this illustrates takes place at all levels of complexity.--Percy

Hi Faith,Discussion has moved on from what people wrote two days ago. If you truly want clarity to emerge then my advice is to respond to all the relevant points made, not to all the messages posted. Switching your responses back and forth between current and old posts is fragmenting your thread and causing it to lose continuity.Tanypteryx in Message 93 and Dr Adequate in Message 96 both posted excellent explanations just last night that were right on target for where the discussion was at that time. The best thing you could do is respond to them. Stop worrying about responding to everybody. As Emerson said, "A foolish consistency is the hobgoblin of little minds."--Percy

Dr Adequate raised a very relevant question about your claim that two individuals of a species possess a great deal of variation. The reality is that variation in a sexual species can not get any less than two individuals. One non-pregnant individual doesn't count since in a sexual species that means the species is effectively extinct.--Percy

Hi Faith,There were no insults in my Message 112, just advice. I'm sure I'm not alone in finding the discontinuity unpleasant and a barrier to clarity. I again suggest you focus on the current discussion by responding to Message 93 and Message 96.--Percy

Hi Faith,As long as you understand that two individuals represent the least variation possible in a sexual species then there's no need to respond.But it does raise the question that if you believe that giraffes today have many fewer alleles now than giraffes thousands of years ago, and if you also believe that reducing variation is how speciation happens, then how could giraffes today with their greatly reduced genomes be the same species as giraffes then?--Percy

The last sentence of my post, and you quoted it, was, "This is why beak expression is so plastic under the influence of changing environmental pressures." It is "environmental pressures" that are responsible for natural selection. When an individual fails to survive because of insufficient adaptation to the pressures exerted by its environment, then that's natural selection. So to answer your question, it would be wrong to say that natural selection is not a key factor in changing finch beak shapes, and in fact I said the exact opposite.--Percy