What is the mechanism that prevents microevolution to become macroevolution?

Just saw mjfloresta's thread Hypermacroevolution? Hypermicroevolution, and I have a question for all those who make the micro/macro distinction:What mechanism prevents microevolution from becoming macroevolution?I mean, as far as I've seen, proponents of evolution argue macroevolution is simply an accumulation of the changes described by mjfloresta in 'microevolution'. If mjfloresta is right, then there must be some reason that this accumulation does not occur. What is it?Not sure if this belongs in the other thread. If not, Theological Creationism forum please.Edited by Ben, : No reason given.

Thread moved here from the Proposed New Topics forum.

We have our theories but no way to prove them. Mine has been based on the observation that all* the processes of evolution -- except mutation -- involve a reduction in genetic diversity, and that if these processes continue to split and diversify populations, the end result will be exremely decreased built in ability to evolve further because of the extremely limited allelic possibilities. Prime example is the cheetah with its single-allele situation at many loci. Just no other alleles possible. Reproduction can only pass on the one allele. Offspring have so little diversity they are virtually clones of the parents. This is an extreme but it illustrates the end result of the processes that lead to "speciation." Speciation is therefore not the genetically rich or open-ended thing you'd expect to find if evolution were true but in fact a stopping point. I started the thread "Natural Limitations to Evolutionary Processes" to explore this idea.I'm also intrigued by mjfloresta's discussions. He/she seems to argue from the observation that for all the multiple variations we see, say for example in dog breeding, we never see a variation that changes what he/she calls the basic "body plan." That is, a dog is always recognizable as a dog, as having the basic body plan of dogs. I intuitively appreciate this observation although I suspect it's going to be hard to defend. I look forward to the working out of this idea on her/his thread, and whatever she/he might say here.{EDIT on 9/4:
* When I say ALL the processes of evolution (except mutation) involve a reduction in genetic diversity, I'm overstating it as I often do. The idea is that the overall TREND of all the processes of evolution is reduction in genetic diversity (loss of alleles in the population). Of course many of these processes only shuffle the existing alleles and don't eliminate any, and in one case, hybridization, there is in fact an increase in alleles and therefore in genetic diversity, but this does not involve the addition of anything new; it is merely the reintroduction of alleles formerly lost between the populations. With this one exception, and keeping in mind that many of the processes merely shuffle and do not eliminate alleles, I'm saying that over time the general trend is nevertheless to reduction in genetic diversity through elimination of alleles. This is because those processes that do this are quite common and most populations eventually undergo them; that is, the processes that select, the processes that bring about a small new population and so on.This scenario is explained many times in the thread.And of course I'm arguing that mutation does not occur in enough numbers or to enough beneficial effect to make more than a negligible or destructive contribution to this whole scenario.}.Edited by Faith, : No reason given.Edited by Faith, : No reason given.Edited by Faith, : Edit noted in text

That is exacty right. That is why mutations is an essential part of the theory of evolution. Without mutations, the theory wold make no sense.

Funny how long it took to get that acknowledged, however. You do know that all those selective and recombination processes are labeled "evolutionary processes" although what in fact they do is reduce genetic possibilities.Yes, the entire theory of evolution rests on mutation as the driving force. Is it up to its role? Well, considering that MOST observed mutations (as opposed to those simply assumed by the theory to have brought all useful traits into existence) are deleterious or useless, this is debatable.Edited by Faith, : No reason given.

Research has proven genetic changes due to mutation. Research has proven that some genetic mutations enable an organism's survival in its environment. Research has shown that subsequent generations exhibit further genetic changes. There is no reason to doubt that changes accrue over time.Creationists deny that small genetic changes can accrue over time.Creationists are obligated to show what would prevent this, if they wish their ideas to be treated seriously as science.

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Archer

This makes for extremely high goalposts considering that evolution was considered science before anyone had a clue about DNA or what a mutation was.{EDIT: I wrote a better answer to this post in Message 146Edited by Faith, : No reason given.Edited by Faith, : No reason given.

Yes, the goalposts are high. Before Biblical Creationism or ID or YEC can be taken seriously they will have to produce models that explain ALL of the observations better than any current or reviesd models.

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Aslan is not a Tame Lion

I'm pretty sure it's been explained to you here that a bottleneck in the Cheetah population around 10,000 years ago is responsible for this lack of diversity, not a limit to speciation.I should know, given that I am an internet cheetah. ;-)Edited by RickJB, : No reason given.

A bottleneck is simply an extreme type of "evolutionary process" that drastically brought about what is normally a much more gradual kind of change over many more speciation events. One gets you there faster than the other, but both are going in the same direction.

A bottleneck is simply a dangerous reduction of population.Given enough outbreeding the Cheetah could regain diversity. It certainly hasn't hit any kind of "limit".

Isn't the greatest proposed bottleneck of all time the "flood bottleneck?" From one pair, through all that inbreeding, to the diversity of genetic failure we now observe?[cheapshot] Why are fundies so comfortable with inbreeding anyway?[/cheapshot]

Great point Faith.If the flood had happened, this is the kind of thing you should be able to point to as support for your model.If the flood happened we should see a genetic bottleneck in all living species where all of the indicators point to an event that happened about 4500 years ago. This would be great supporting evidence for there having been a flood (but of course no support for any theological implications). It would also be scale independent since as long as the same scale is used, every critter should show the same indicators at about the same period.If that isn't seen, then we can toss the idea of a flood on the trashheap of great ideas that just turned out to be wrong.If you ever want ID or YEC or Biblical Creationism to be considered as science you must be prepared to toss away your conclusions once they are shown to be wrong.You ready to do that Faith?

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Aslan is not a Tame Lion

I figure that whatever it is in the genome you expect to see as evidence of a bottleneck of the magnitude of the Flood is simply misinterpreted. I'd be looking at all that junk DNA myself.

That's fine Faith. If and when some ID or YEC or Biblical Creationist can show such evidence, it will be time to dust off the old flood and put it on the shelf. Once they also place the model on the table that explains the geological, radiometric, archeological, sociological data it might be worth even considering that such a flood might have happened.But three things to remember Faith.

1. The model must explain ALL the evidence better than any existing model or any revision of any esiting model or any competing model.
2. the model must be backed up by evidence which can be independantly confirmed.
3. Even if you could show that there was a world-wide flood and the resulting bottleneck, it provides NO support for the theological nature of the event.

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Aslan is not a Tame Lion