The End of Evolution By Means of Natural Selection

How many closely related species are different in only their allele frequencies? Squirrels? Finches? Cats? Any species at all?Say you have two members of the same species that are mutually unfertile because they each have one of a pair of antagonistic alleles. Now consider these same two individuals except they're in two closely related populations. Nothing has changed genetically, but in one case we consider them the same species and in the other we don't. You're going to explain fine distinctions like this to Faith?Another related issue is that Faith isn't looking at this at a genetic level. She sees isolation occurring due to physical differences caused by allele combinations that never occurred in the parent population.The objection to Faith's scenario isn't that it's impossible, because it isn't. The objection is that it's very rare, so rare that there are no known examples of it in the natural world. (I don't actually believe that, but since we've done the equivalent of the human genome project on very few other species I don't expect it can be contradicted at the current time. But even if it is it still must be very rare.) How could it be that we can find no examples of species produced by the process Faith thinks is the cause of all speciation?--Percy

I said it first, see Message 422.--Percy

In fact I said it in Message 46 and Message 111. But In this case I was raising a specific point about interfertility. If it is down to incompatible sets of alleles, and if we accept the standard YEC view that a pairs of an original species on the ark could give rise to a whole taxonomic family we do have to wonder how this could be plausible without seriously compromising the fertility of the original pair or their early offspring. Remember at the start, no alleles can be rare, since each must be represented at least once in half the population !

I'd be highly interested in this as well. The ability of speciation arising simply out of allele differences is a part of the train of thought I'm following on the other thread. Probably not the most important part, but one I'd like to be clear on.And if anyone sees me making any egregious errors in my train of thought over there, please let me know.Edited by ZenMonkey, : Clarity.

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I have no time for lies and fantasy, and neither should you. Enjoy or die.
-John LydonWhat's the difference between a conspiracy theorist and a new puppy? The puppy eventually grows up and quits whining.
-Steven Dutch

Okay, I concede, you have priority. --Percy

I see what you're saying. But I think you're wrong in assuming that large dogs and small dogs can't mate. Yes, it is a physical barrier for a large male dog to impregnate a small female dog. And it is a physical barrier for a small female dog to carry a large dog offspring to term. But if you flip the genders reproduction is easily possible. Other than the fact that the large female dog would have to be laying down, is there any reason why a small male dog physically could not impregnate her? Is there any reason why the large female could not carry a small offspring to term?My wife's old roommate had a rotweiller/dacshund mix. Rotweiller mother, dacshund father. The smaller father had minimal issues impregnating the larger mother and the larger mother had minimal issues carrying the pups to term. The dog grew to be larger than a dacshund but smaller than a rotweiller, a hybrid. A male dog from the litter could easily impregnate another female rotweiller or a female dachshund and then you would have fourth and fifth size variants.Unless there is a mechanism that would create barriers for a large mother/small father combination then I don't think size could be the lone cause of a speciation event.

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This is the definition Faith is using

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Sorry, I hadn't paid enough attention. At least she's made the argument easier!

Yeah, but WK didn't agree with me. I'm not persuaded that he's approaching it the right way by addressing her paradigm from within, but WK's views have to be given serious consideration.--Percy

Thank you for the acknowledgment of a possibility that fits with what I'm saying and a good example.

That's how I've always understood it. I don't insist on HOW reproductive isolation occurs, I'm trying to use the standard definitions of these things and this is one way species are considered to form.

I'm aware of this possibility which is why I try to remember to always specify that reproductive isolation is necessary for what I'm saying to occur. This is why I try to always say "barring gene flow" and that sort of thing. I'm trying to focus on what happens with isolated populations inbreeding on their own after a migration or series of migrations from the original population.

There were two or three such statements and I hope I can eventually find them to see if what you are saying applies or not, something to the effect that of course mutations are going to be compatible with the species, and I don't remember why it was said, apparently in answer to something I said.

This sounds to me perfectly compatible with my model and in fact good evidence for it. Such differences certainly suggest problems with interbreeding and also suggest that reduced genetic diversity plays a part in such a situation. WK very nicely showed how interbreeding problems could occur simply from allele loss without mutations and lead to speciation.I'm always saying that the smaller the daughter population the more apparent should be the effects, certainly the smaller the genetic diversity in the new population, certainly the emergence of a distinct new overall look from the new combination of a reduced number of traits available. I've also referred to the fairly equal splitting of an initial population as a probably less dramatic way the same events come about -- which is why I like the smaller-population example to make the point clearer.And I've also never said I expect speciation with the first or second migration though it COULD happen that interbreeding on a genetic basis could stop -- I'm including ALL the ways you can get reproductive isolation such as geographic barriers and behavioral barriers AND genetic barriers, because my point is all about what happens when you HAVE reproductive isolation, not how you get there.And again, I also am not making as big a point about speciation itself as some of you are. I started emphasizing it when people complained that where I was talking about evolution I seemed to mean speciation and I could see their point, although I also want to make the point that macroevolution depends on speciation, as some have acknowledged. I see speciation as the necessary end result of these processes if you're going to have macroevolution, but it's the trend up to and including that point that I'm trying to stay focused on -- the reduction in genetic diversity that allows the emergence of new phenotypes which become the basis of new varieties.

I wouldn't waste time and effort reconciling your different understandings at different times. Just keep working on improving your understanding, which is what all of us are doing here. Anyone who's understandings of everything are the same as even just a year ago isn't learning anything.Anyway, I commented on this back in Message 456: --Percy

I'm sure all of us just collectively threw up our hands in frustration.Faith, your position is that species are created through allele reduction. You deny mutation any significant role. Without mutations you cannot get differences in which genes and chromosomes each population has. In your model the genes and chromosomes between the two populations will remain forever the same.Mutations are the only way that changes in the character and number of genes and chromosomes can come about. You can't say that your model is "perfectly compatible" if it denies mutations any significant role. Without mutations your model isn't even a teensy tiny bit compatible.--Percy