"Best" evidence for evolution.

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You are not following my reasoning as you claimed, you are as usual just insisting on the view of the ToE over anything I say.

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I think that the problem is that you don’t understand the concept of following your reasoning. We can certainly recognise and understand your reasoning - what little you present - without agreeing with it’s conclusions.

Correct, there are several mechanisms for evolution. But the thing that you deny - mutation - is proven to have happened. And the second mechanism of evolution - natural selection - was proven to be the cause of the fixation of the mutation in the population.What's more it did it twice. Sheesh indeed.

NO NO NOYou do NOT get to redefine science terms to suit your delusions. This is the basics of evolution (once again): The first box is breeding, including mutations in the population,The second box is natural selection survival, some do, some don't,Arrows from the first box are the results of breeding, including individuals with new mutations andThe Arrow from the second box is that portion of the population that survived to breed.That is ALL natural selection is -- the survival and breeding of individuals in the population.It is NOT population isolation and speciation, that is a different process. Nature and natural selection are not the same thing. Natural selection occurs within nature, but nature does not occur within natural selection. Mutation and natural selection within isolated populations will cause genetic divergence as new mutations in one population cannot be transmitted to the other population, because gene flow has ceased.And it seems it takes at least two mutations for form genetic incompatibility:

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Population Dynamics, Sexual Incompatibility

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... how can we tell when this point has been reached?

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The population genetics of speciation: the evolution of hybrid incompatibilities.

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THE BASIC MODEL

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The central assumption of the DOBZHANSKY-MULLER model of speciation is that alleles cause no sterility or inviability on their normal "pure species" genetic background. Instead, an allele can lower fitness only when brought together with genes from another species. Any particular hybrid incompatibility might cause partial or complete hybrid sterility or inviability. For most of this paper, I assume that hybrid incompatibilties involve interactions between pairs of genes, as in DOBZHANSKY and MULLER'S verbal models. Later, I consider three-locus and higher interactions. I also assume that multiple substitutions do not occur at the same locus, an assumption that is reasonable during the early divergence of taxa. I assume nothing about the evolutionary causes of substitutions. The DOBZHANSKY-MULLER model of speciation requires only that substitutions occur and assumes nothing about whether they are brought about by natural selection or genetic drift.

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Because I consider the cumulative effects of interactions between many loci -- which quickly gets complicated -- it is useful to picture this process diagramatically. Figure 1 offers a simple way to picture the accumulation of complementary genes between two haploid populations. Each of the two heavy lines represents a lineage descended from a common ancestor. The two allopatric populations begin with identical "ancestral" lowercase genotypes at all loci (a b c . . .). Time runs upward, with the first substitution occurring at the a locus, the second at the b locus and so on.

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The first substitution involves the replacement of the a allele by the A allele in population 1 (uppercase letters indicate only that an allele is "derived"; no dominance is implied). The A allele cannot cause any hybrid sterility or inviability: because A is obviously compatible with the genetic background of population 1, it must be compatible with the identical background of population 2. The second substitution, at the B locus (in population 2), could be incompatible with only one locus: A, as the B allele has not been "tested" for compatibility with A. The third substitution, at C, could be incompatible with the B or a alleles. As we continue this process, it is clear that we can identify all possible (i.e., evolutionarily allowed) incompatibilities by drawing an arrow from each derived allele to each "earlier" (lower) allele carried by the other species. Thus D can be incompatible with c, B, and a. This arrow-drawing device will repeatedly prove useful.

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Note that the possibility of two ancestral alleles being involved in incompatibility is

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... because they were the same allele in the parent population.

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And it should be readily apparent that speciation -- defined as sexual incompatibility -- depends on mutations occurring in the sub-populations.

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Nope. I followed your "reasoning" into the garbage can of failed concepts because it was faulty. That failure of your "reasoning" has nothing to do with the ToE, rather it has everything to do with bad logic and failure on your part to include ALL the evidence. Nope. It is an observed biological process, a FACT, not theory.The ToE is that natural selection (an observed process, FACT) and mutation (also an observed process, FACT) are enough to explain the diversity of life on earth. Theories build on facts, faith.Maybe you should actually read Message 559 slowly and attempt to understand your errors detailed in paragraph after paragraph, and not cherry pick one you think is somehow wrong, but actually show it is wrong. But I did, you just don't like the result. Sad? You should be glad that you just got some free education so that you can improve your arguments ... if you wanted to learn instead of just preach.Enjoy

If a population changes so that it comprises two (or more) groups that cannot interbreed, how could that not be called speciation?

Cuz the term implies macroevolution and all that's really going on is normal variation within a species which is microevolution. It just happens to be occurring at a level of genetic reduction so that the usual changes are dramatic enough to make continued interbreeding impossible for one reason or another, either genetic mismatch or geographic isolation or sexual selection. The term "speciation" is a bogus tendentious word dictated by the ToE. My guess is that a study of the genetic situation would show a reduction in genetic diversity (toward increase homozygosity) in jthe new population as versus the parent population. Cdertainly that's obvious enough in the case of a split into two separate populations: each would have reduced genetic diversity comparied to the parent population. This is always denied but it has to be so and that should be demonstrable too..Edited by Faith, : No reason given.

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Cuz the term implies macroevolution and all that's really going on is normal variation within a species which is microevolution.

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That is incorrect, it is macroevolution - and if normal variation within a species causes mutual infertility I’d like to see some evidence. Also, simply refusing to admit that is speciation doesn’t change the fact that it is.

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It just happens to be occurring at a level of genetic reduction so that the usual changes are dramatic enough to make continued interbreeding impossible for one reason or another, either genetic mismatch or geographic isolation or sexual selection.

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Even ordinary within-species variation includes mutation as we know. And there is no reason to think genetic reduction causes infertility, certainly not as a general rule. Chromosomal variations seem to be important in some cases, like the incompatibility between horses and donkeys.

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The term "speciation" is a bogus tendentious word dictated by the ToE

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This is a complete falsehood. Your personal dislike does not make it bogus or even tendentious, and it is dictated by the definition of species - a concept which predates the theory of evolution.

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My guess is that a study of the genetic situation would show a reduction in genetic diversity (toward increase homozygosity) in jthe new population as versus the parent population. Cdertainly that's obvious enough in the case of a split into two separate populations: each would have reduced genetic diversity comparied to the parent population

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While it is likely that a population appreciably smaller than the original would have reduced genetic variation it is not true that the larger population will always be appreciably smaller than the original. Also both populations will include mutations that did not occur in the other (the larger population will have more, but they are more likely to be fixed - take over the population - in the smaller)

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This is always denied but it has to be so and that should be demonstrable too..

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It is certainly not always denied.

Severely genetically depleted animals cannot interbreed with others of the same species. Cheetah. Any very small portion of a population will have strongly reduced genetic diversity from the parent population. Even larger population splits will have some reduction in genetic diversity. When microevolution occurs through a series of population splits it progressively reduces genetic diversity in each new population. This is intuitively obvious. After enough such population splits that continue from one population to the next in reproductive isolation the genetic diversity could become as depleted as that of the cheetah. It's still the same species but won't be able to interpbreed because of genetic mismatch. Edited by Faith, : No reason given.

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Severely genetically depleted animals cannot interbreed with others of the same species. Cheetah.

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Can’t they? Cheetahs do breed, obviously. Besides, this severe genetic depletion is not a normal condition.(ABE) and let’s point out that the situation you are supposed to be addressing is where there are two populations each of which can breed perfectly well - but can’t interbreed. The cheetahs don’t address that at all.

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Any very small portion of a population will have strongly reduced genetic diversity from the parent population.

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I doubt that it will be that strong, unless it is a very tiny population that probably isn’t viable.

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Even larger population splits will have some reduction in genetic diversity.

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As I said, there is a relationship with population size, but it certainly isn’t linear.

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When microevolution occurs through a series of population splits it progressively reduces genetic diversity in each new population

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Only if the population continuously declines, which is a very unlikely case.

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After enough such population splits that continue from one population to the next in reproductive isolation the genetic diversity could become as depleted as that of the cheetah.

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Funny how there isn’t a single example of that happening. Or it would be if you weren’t making uninformed speculations.

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It's still the same species but won't be able to interpbreed because of genetic mismatch.

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I think that if cheetahs have fertility problems it will be due to genetic matches, not mismatches. Recessive genes, causing problems. But please if you have any actual evidence produce it. I say that genetic mismatches are far more likely the product of mutation causing the populations to become genetically different. And that is intuitively obvious.Edited by PaulK, : No reason given.

It is normal for mutations to accumulate in every generation. You are saying that you can take one step, but you can't repeat the same exact process to walk across the house or down to the store. That makes no sense.Do you agree that mutations happen in every generation?

it can't be mutations because at the rate you impute to them there would never be a stable population at all, it would always be mutating into something else, but we have lots of phenotypically stable populations, especially daughter populations after a series of splits. Like domestic breeds in many cases.

You don't need mutations to cause the populations to become genetically different. All that has to happen is that homozygous loci become more frequent in one population than the other. The new collection of gene frequencies in a daughter population can lead to that situation.Edited by Faith, : No reason given.

Not a problem, as long as the rate of change isn't enough to interfere with reproduction.

And in fact it is exactly what ALL of the evidence shows. We can identify individuals based on DNA because everyone's DNA has mutations.

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it can't be mutations because at the rate you impute to them there would never be a stable population at all, it would always be mutating into something else...

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Perhaps you can offer something more than an uninformed opinion. Like actual support for this claim.

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.... but we have lots of phenotypically stable populations, especially daughter populations after a series of splits.

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Species aren’t genetically - or phenotypically - homogeneous. Indeed, a mutations which introduced a degree of genetic incompatibility doesn’t need to have any visible effects on gross morphology - which is the only thing you are considering. So your objection is looking pretty weak. If there is variation at the level you do look at then variation you won’t even see can hardly undermine this stability.

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Like domestic breeds in many cases

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Which can only exist because the parent population had genetic and phenotypic variations. And are more the product of artificial selection - stronger than natural selection - than of population splits.

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You don't need mutations to cause the populations to become genetically different

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Reality is not dictated by what you think is needed. And when we are talking about variations appearing in the smaller population -or their descendants - that are not in the larger, mutations are the most likely way. And if the descendant populations do not interbreed for genetic reasons, that is by far the most likely way.

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All that has to happen is that homozygous loci become more frequent in one population than the other. The new collection of gene frequencies in a daughter population can lead to that situation.

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You assume it, but how likely is it? After all the parent population didn’t have any breeding problems. And the larger population and it’s descendants can’t be assumed to have changed much (we can’t assume that they will be changed by selection and drift will be slow, so long as the population is large). If the new species is completely unable to breed with the (original) parent population it doesn’t seem likely to be due to factors that were present before the split.