Hi Faith. Welcome back.What are you looking at? If you are looking at the phenotypic variations you may very well see lots of variance. That's microevolution, that's phenotypic microevolution. But if you look at the DNA you should start to see fewer alleles for the selected traits or even population-wide homozygosity for some traits.
The problem behind your theory is that it's contradicted by real-world observations. Your predictions are invalidated, because observed evolution has not been reducing genetic capacity for variance.
The confusing thing is probably that in most cases you don't get any appreciable reduction in genetic diversity. That is, new gene frequencies from a population split just means that you get more of a different kind of allele for a given trait than the other population had, and less of the kind that dominated in the first population, it's mostly a reshuffling. But the fact is that you DO need to reduce or eliminate alleles that produce the "wrong" trait in order for a new trait to become characteristic of the new population, and over a number of selection events and population splits this will show up as a reduction in genetic diversity along with the production and establishment of the new phenotypic trait. IN THE NEW POPULATION. The old population, assuming it's appreciably larger, will no doubt retain the higher proportion of the "wrong" alleles that are lost to the new population because there they aren't "wrong."
It's down any specific line of variation of the phenotype that you are going to encounter this loss of genetic diversity, but since it is down any specific line of variation that you are seeing the production of new traits, that is, evolution, it ought to be clear that the process of production and maintenance of new phenotypic traits, or variation, or evolution, requires this loss of GENETIC diversity.
Even a population split in which the new population is appreciably smaller in number is going to show a lot of phenotypic change along with the genetic reduction, but ANY actual selection of a trait could completely eliminate some alleles and that is where you will REALLY see this formula in operation. Selection definitely reduces genetic variability. Selection is how evolution proceeds. Put two and two together.
Year after year, undergraduate students directly observe evolution in action as they show changes in allele frequency in fruit flies. Other students observe the case of drug resistance spontaneously forming in a population of bacteria.Are you really looking at the DNA to see the changed allele frequencies or are you inferring them from the "evolution in action" that you are observing, which would of course be the usual microevolution. Drug resistance is the phenotype, what's going on in the DNA?
The process doesn't stop. Variation continues, unimpeded.And so it may. VARIATION may continue and continue a long time. You are talking about PHENOTYPIC variation here. In some species you can get lots of new variations of the PHENOTYPES, but my claim is that you will eventually reach a point where you can't get any more because the process requires genetic reduction. REQUIRES it. If you are only looking at the phenotypes you aren't necessarily going to be aware of this. But also, since you are dealing with fruit flies and bacteria you may be getting a lot more phenotypic variation for more generations just because they are likely to be genetically more variable than higher animals. Bacteria have a lot less junk DNA for instance than higher animals, which suggests a lot more genetic variability. It's really not a valid comparison with dogs, cats, mice, and humans.
There is no reduction in the possibilities derived from mutation guided by natural selection. At no point to we reach an evolutionary "endpoint" where no more change is possible.You have apparently not reached it in the laboratory with fruit flies and bacteria (though I suspect you have), but it is reached every day in the wild, with the elephant seals and the North American bison and the cheetah as the most extreme examples. Yes, they are examples of this process, they are not exceptions. Limiting the numbers of a population is what one does to produce a new phenotype, though it doesn't always happen to the extreme of a bottleneck which of course can threaten the survival of the whole species. But even in these cases they seem to be thriving. Nature does this to many degrees all the time, and nearly depleted genetic variability is the result in the case of a bottleneck or founder effect. Again, this is not merely an extreme, it also demonstrates the pattern I'm talking about.
It's based on the well-known observation that you get new species with reproductive isolation and altered gene frequencies. But what is generally overlooked is that altered gene frequencies NEVER means an increase in variability. It may not change the variability much at any given point, but it certainly does not increase it. For that you would need, yes, mutations, but for many reasons that doesn't happen except as an interference, and even if it did happen it wouldn't change anything outside the parameters of the Species, it would only alter the character of the built-in pattern of traits, it isn't going to produce new traits, new genes themselves.
Preserving a breed, preserving a species, requires reduction in genetic possibilities.
And that's just the examples that we directly observe. The fossil record and the other extant life we see today has variety beyond comprehension.You are talking about PHENOTYPES, and yes you get phenotypic variety "beyond comprehension" -- especially back before the Flood, which is what the fossils are a record of -- but you get it within the Species and you get it only along with reduced genetic variability. Again, the reduction may be quite minimal in a genetically rich species, which is perhaps what you are looking at, and which must describe all species before the Flood, and even many still, but it is still a reduction.
The genetic and morphological evidence for common ancestry of virtually every living thing on the planet is overwhelming,You are looking at similarities and ignoring the differences and not thinking about what would have to happen genetically in order to produce those differences. You are looking at patterns and imposing your belief that genetic inheritance is the explanation, you do not actually have evidence of that inheritance. Again, look at the differences between one species and another and genetic inheritance isn't going to be the explanation.
to the point that it's better established than the Theory of Gravity. Given that this is the case, and populations continue to diversify into distinct sub-groups before our very eyes,Yes POPULATIONS continue to diversify, that's the PHENOTYPE. What I'm talking about is something that happens way down the road in most cases, or suddenly when populations are severely reduced. It isn't going to happen in populations that have a great deal of genetic variability and where population splits occur in great numbers -- you'll get some change and you'll get some reduction in genetic variability but it will be negligible in those cases -- it WILL occur, however, just minimally. Many population splits as in ring species, migrations of small numbers -- this is where what I'm talking about will become apparent.
Whenever you get SPECIATION for instance you should see the genetic reduction I'm talking about, certainly NOT the genetic variability that would be necessary if speciation were the springboard to macroevolution you think it is.
it would seem that your premise, that evolution should grind itself to a halt through some sort of genetic entropy, is falsified.It is happening every day, you are just looking at the wrong end of the phenomena and you are looking where it is occurring least obviously. Conservationists see it every day and so do breeders, it's what they are both working against all the time, trying to prevent it from happening because it is so often accompanied (in this fallen world) by disease -- disease caused by mutations I dare suppose.