The End of Evolution By Means of Natural Selection

Hi Faith. Welcome back.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.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.The process doesn't stop. Variation continues, unimpeded. 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.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.The genetic and morphological evidence for common ancestry of virtually every living thing on the planet is overwhelming, 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, it would seem that your premise, that evolution should grind itself to a halt through some sort of genetic entropy, is falsified.

You seem to have an odd understandong of what natural selection entails. The Theory of Evolution predicts that extinctions will happen. Endangered species are the result of a set of adaptations that no longer apply in a changing environemnt. Since mutation is largely random, the process of developing new traits is slow, and changes in the environemtn can be relatively rapid, there will always be cases where changes in the environemnt will occur too rapidly for a population to adapt effectively, and they will either be killed outright or gradually out-competed for resources by better-adapted species.None of it has anything to do with some sort of reduced potential for adaptation. You certainly haven't provided any evidence that there is any finite limit for genetic variance over long timescales. You've simply asserted it to be so.Reductions in the numbers of a given population does indeed result in a "genetic bottleneck" where extant genetic diversity is lost. If families A B and C die out while family D lives, certainly the currently available genetic diversity inthe total population has been reduced. But that says absolutely nothing about the potential of mutation.The only real problem with a reduction in genetic diversity as in a non-extinction die-off is the danger of recessive traits being passed around and expressed, not some "mutation barrier." If a population is shrunk to a sufficient degree, the lack of genetic diversity can threaten the population's longevity because of those rexcessive traits until reproduction allows natural mutation to restore diversity. Human beings had an extreme population bottleneck some thousands of years ago, yet look at our diversity today. What's your criterial for a "significant change?" We can easily get child populations that no longer interbreed, change the color of their eyes, etc.But remember, Faith: in any observed "branching" of populations into divergent and distinct subgroups (whether actual speciation has occurred or not), total genetic diversity has increased, even if each indivdual subgroup now has less diversity than the parent population. It's both. The experiment involves growing a large population of bacteria from a single cell. All of the child bacteria should be identical clones of the original. The population is then exposed to an antibiotic, which drastically reduces the population - in effect, it eliminates all genetic diversity except for those organisms which include a resistance to the antibiotic. It's used to demonstrate the fact of mutation (since a new trait that was not present in the original parent forms; it's a new trait that was not inherited, the very definition of a mutation)...But it also works well to discount your assertions. When the population is allowed to continue to grow with regular exposure to the antibiotic, the resitance trait remains expressed by the vast majority of the population because those without it are quickly killed off. But when the antibiotic is removed (an environemntalchange) the resistance no longer confers any survival advantage, and will slowly decrease in representation among the growing population.In other words, even after genetic diversity is reduced in a population reduction, diversity will continue to increase.HIV treatment is particularly sensitive to this fact. Believe me, I wish HIV had a "mutation threshold" that could not be passed. Unfortunately, that;s not the way it works. Once a strain of HIV develops resistance to a given antiviral drug, it can and will continue to mutate rapidly, and can develop resistances to new drugs as well. This is why HIV treatment usually involves two or more completely different antiviral medications right from the beginning - if resistance to Drug A develops, the retrovirus should still be susceptible to Drug B, and so on. It;s effective so long as the selective pressure is continued by continuing to maintain a high level of all of teh medications in teh patient's body...but as soon as the pressure is lessened (say, within a month or two off of the meds), the viral population will have grown and diversified to the point that the patient now risks resistance even to both drugs. Not a single allele. A single cell. Very different. Essentially, yes. See above. Populations that have been reduced to a single member (in other words, zero genetic diversity) will spawn populations with lots of diersity, even to the point of acquiring resistance to medications. Evolution never stops. So long as mutations are passed down from parent to child, natural (or artificial, in teh case of lab experiments) selection will continue to increase the frequency of beneficial traits while decreasing the frequency of traits that are not beneficial.In the bacteria experiment, mutation increases diversity. The antibiotic exposure selects, by eliminating non-resistant bacteria and thus reducing total current diversity. The population, when allowed to grow again, will again increase in diversity due to mutations - such that a subgroup of the main population may develop resistance to a different drug, and so on. Wrong. Evolution is not reactive. The resistance trait (in our example) must already exist in the population before the antibiotic is used. The population does not generate resistance as a response. Until the antibiotic is used, the resistance is simply a random mutation that confers no benefit and thus enjoys no greater representation in the population as a whole than any of the other uncounted mutations ina diverse population. Only when theselective pressure of the antibiotic is introduced does the already-existant mutation suddenly confer a survival advantage to the subgroup, and the trait will rapidly increase in freqency as the competition is killed off by the antibiotic. The selective pressure reduces extant genetic diversity by killing off large numbers of a diverse population. But mutation continues to increase diversity even after the population ahs been reduced (just like it did when we started with zero diversity in a population of one). Not all. Some. Natural Selection is not some rampaging genocidal agent running around killing everything.Natural selection is simply the process by which beneficial traits tend to increase in a population because those who possess those traits will survive to reproduce more often than those with non-beneficial traits. More often does not necessarily mean to the exclusion of. In a given environment, animal A may be "better" adapted than animal B, but that doesn't necessarily mean B will go extinct. False. COmpeltely false.Evolution happens when an existing population diversifies and branches off into distinct sub-populations. That doesn't necessarily involve the extinction of any of the child populations or even the disappearance of the parent. Diversification typically happens due to environmental changes, as random inherited mutations suddenly become beneficial or detrimental. Often this happens when some of a given species migrates to a new area, and thus a new environment with different selective pressures. In this case, even though the migratory population will end up distinct from its parent, the parent population still exists, and thus diversity is increased.Provide evidence that other species do not possess the capacity to be bred as dogs have or retract.I'll do one better though: we can breed all manner of plants and animals with a very great degree of diversity. Do you have any idea how different the corn, banannas, grapes, cows, pigs, or really any domesticated animal or plant has diverged from the original natural stock? How much diversity we still have amongst those populations while retaining the ability to interbreed?Which organisms, precisely, lack the potential to be bred to extreme degrees of diversity, and how do you know this? Reduction in the frequency of one trait does not necessarily reduce the frequency of all other traits in teh same organism, Faith. Just look at all of the "small" dogs we have, their differences in fur, coloring, temperament, intelligence, etc. You can breed for a specific result ("bigness" or "smallness") and still increase total diversity. You mean a sub-population will have less diversity than the total population?Why would we ever assume otherwise, Faith?If A = B + C, B and C will always each be less than A. This is really a case of you not understanding genetics. You can reduce the frequency of a single trait without affecting the frequency of other traits, including the appearance of new traits.You can reduce a population of bacteria to one individual, meaning zero diversity, and end up with a highly diverse population that has even developed new traits like antibiotic resistance.Your premise is utterly false. Indeed it would have to be rethought. Fortunately for biology, you've presented no evidence or argument that challenges the Theory of Evolution in the slightest.

But you haven't provided any evidence at all, Faith. None. You haven't offered any type of proof for your assertions.And trying to exclude mutation and "sources of variation" from a discussion about proposed limits on variation is the equivalent of discussing YEC without Genesis, or Jesus' sacrifice without Original Sin, to put it into terms more familiar to you.

Because it's already been falsified, Faith.IF we have a single bacterium, that is a single cell with a single genetic code, then we have zero diversity.Upon allowing that individual cell to multiply into a population of many individuals, variety appears via mutation. In other words, variety spontaneously appears through the process of mutation, even when you bottleneck a population tot he absolute minimum number required to continue reproduction.If you can re-establish genetic variety even after the complete and total removal of all diversity, then your assertion is completely falsified, end of story, do not pass Go, do not collect $200.And since that's exactly what we see in often-repeated experiments, you're just wrong, Faith.

Faith, you seem to want to focus on dogs because you feel like you know something about them.But the fact is, a very simple experiment already falsifies your assertions. I'm just going to quote myself:

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IF we have a single bacterium, that is a single cell with a single genetic code, then we have zero diversity.

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Upon allowing that individual cell to multiply into a population of many individuals, variety appears via mutation. In other words, variety spontaneously appears through the process of mutation, even when you bottleneck a population tot he absolute minimum number required to continue reproduction.

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If you can re-establish genetic variety even after the complete and total removal of all diversity, then your assertion is completely falsified, end of story, do not pass Go, do not collect $200.

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And since that's exactly what we see in often-repeated experiments, you're just wrong, Faith.

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Respond or don't, Faith, you're still wrong.

As odd as it sounds, speciation is rather more of an occasional side effect of evolution than anything else. Remember, evolution is simply the change in allele frequency in any given population of organisms over multiple generations. Evolution happens all the time without speciation. It's only when subgroups of a total population are reproductively isolated under different selective pressures that you really see them differentiate to the point where we identify them as new species.If you want to focus on speciation, perhaps you should look into cladistics? It's a modern form of taxonomy, and it's very easy to see how evolution results in an increase in diversity when you look at it a bit.

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Cladists use cladograms, diagrams which show ancestral relations between species, to represent the monophyletic relationships of species, termed sister-group relationships. This is interpreted as representing phylogeny, or evolutionary relationships. Although traditionally such cladograms were generated largely on the basis of morphological characters, genetic sequencing data and computational phylogenetics are now very commonly used in the generation of cladograms.

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A "clade" is a group of species classifications ("taxa") consisting of an ancestor taxon and all of its descendant taxa. For instance, all vertebrates and their descendants form a clade. All mammals are also a clade, and all members of the mammal clade are also members of the vertebrate clade.What happens in speciation is essentially that a segment of the total population accumulates sufficient differences in their features that we need to identify them specifically rather than simply as members of the whole. A new clade is created, which is still a member of all of the clades the parent population was also a member of (for example, all dogs are still mammals, all mammals are still vertebrates, etc). A "new species" is just a way of saying "a subset of the population that has become sufficiently distinct from the rest of the population that we need to identify it differently so that everyone knows what we're talking about."Is there any part of that that you don't understand? That you disagree with?