Wow, I see my attempts to post this last night did take after all, rather too many times, despite my getting the message many times that the site was down. Since then I corrected some things and added to it as well. Sorry, this will be a little different from the original(s), but not by much.
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Faith writes:
It's just a variation on the same theme. Subpopulations merely differ from one another because of having different frequencies of alleles from other populations of the same species/kind due to reproductive isolation from the other groups for one reason or another*. Why is this treated as something special? The accidents AND selectively determined incidents of reproductive separation predictably produce new phenotypes by shuffling the alleles at the very least, often reducing the genetic possibilities too. Nothing is necessarily added in order for this to occur. Same situation as in the OP really**, with somewhat different reasons for the variations.
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*"One reason or another" could be natural selection or geographical isolation or bottleneck or anything of that sort.
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Well, what is neat about it is the fact that it demonstrates speciation in action in a way that in a certain sense is frozen in time, so that any time one visits the place, one can see the living evidence.
But evidence of what? Of the fact that populations may vary quite a bit from one another under certain circumstances, sometimes to extremes? This is commonplace. The processes that bring it about are the subtractive processes under discussion, contradicting the idea that these very processes of variation and selection demonstrate evolution.
Wipe out that which connects the two extremes and they are no longer members of the same species -- but are they members of the same species while the bridge exists? Well, yes and no. Is cyan blue or is it green? At this point, we are asking the wrong question.
That's not a question I'm asking. While I'm sure it is possible to judge the limit of speciation from phenotypes somehow or other I'm not looking for it there. I expect to find the limit to speciation at the point where the subtractive processes that act on populations, known as Evolutionary Processes, put a stop to it naturally, which I would consider to be the genetic limit of a Kind.
Additionally, oftentimes those who deny the reality of macroevolution will do so at the level of species, claiming that one species cannot evolve into two. Or maybe they pick a somewhat higher level, such as denying that an autocatalytic RNA strand (essentially, a viroid with the ability to reproduce) could ever evolve into a human being. But once one admits speciation, the rest is largely just a matter of degree.
So goes the theory, but if the processes that bring about speciation simultaneously reduce the genetic diversity that evolution requires (beyond the commonplace variation on given genetic allotments), and mutation turns out not to be a sufficiently effective counter to this subtraction process, then this theory of an open-ended evolution is falsified.
As for the generation of "new information," this is something which occurs principally in terms of the populations. For example, a single nucleic polymorphism ("snip") will result in a new allele, one which didn't exist in the population before -- and that is the generation of new information, but simply noise until it passes through the filter of natural selection into the general population.
This is a side issue but presumably even a deleterious allele could be selected, because of its association with others, no? The perennial question of course is How often are these "new alleles" of any benefit? And, one I've asked before here that I don't believe has yet been answered, How do you KNOW a "new allele ... didn't exist in the population before?" How do you know it is not a rarely occurring event that has always been part of the genetic picture of this species?
However, the more interesting ways of generating new information consists of gene duplication, segmental duplication, chromosomal duplication, and polyploidy -- or the mutation of regulatory DNA which is responsible for determining when, where and how much a given gene gets expressed.
All these are bascially varieties of mutation, right? And the same questions apply. How many are of any real use to the species as opposed to a disease process? If they seem to confer some benefit or at least do no harm, how do you know they are unique to the species?
The duplications make possible sub-functionalization (which is responsible for the dichromatic vision of our ancestors becoming our own trichromatic vision) and neo-functionalization (which is responsible for an enzyme involved in digestion being co-opted for the coagulation of blood).
Again, what makes you so sure that these functions originated from novel events?
And the mutation of regulatory DNA? A great deal more, evidentally. 99% of our 25,000 genes are homologous to the 25,000 genes found in mice. 96% of those genes are in the same exact relative order. So it would seem that the majority of evolution does not occur as the result of mutations in the genes themselves but in terms of the DNA which regulates gene expression.
Such similarities are just as well explained by similarities of design as by descent. Probably at least 99% of all internal combustion-powered vehicles have parts with basically the same function despite vast differences in appearance and speed and so on. The same principle does just as well for living things, needing no appeal to genetic descent.
In any case, mutations take time. Natural selection will reduce the genetic diversity for a while when there exist strong selective pressures, but then new mutations will occur within the population, replentishing its genetic diversity.
So I've heard. But I haven't seen that this actually occurs, it is merely asserted to be the case. A lot is assumed here but not demonstrated.
Moreover, once the two populations have been separated (for whatever reason), the mutations which occur in one population will no longer be communicated to the other population. The two populations will diverge, then tend to adapt to different environments and different pressures.
Yes, again, so goes the theory. But even without mutation, with the portion of the given complement of alleles taken from the parent population, a great deal of divergent changes are not only likely but inevitable. The adaptations, the selection, all the processes work the same way without mutations being assumed. Again, how do you know that any beneficial mutations ARE mutations, that is, how do you know they are novel events rather than predictable events that occur normally and repeatedly in the population?
At some point, even if the two species come into contact with one-another, they will no longer be able to produce fertile offspring -- and they will continue to diverge. Quite simple, actually.
Yes, but the fact that they become unable to interbreed is simply a definitional point for evolutionists, supposedly marking a new "species," although it doesn't in itself demonstrate anything except that subpopulations of a species may vary to the point that interbreeding becomes difficult to impossible between them. (Creationist explanation: The Kinds were designed to vary enormously and the loss of the ability to interbreed would tend to preserve the varieties. In a fallen world unfortunately they tend to extinction at the extremes, but in the original Creation they would merely demonstrate its creative exuberance.)
Of course, if you are looking for really good smoking guns as far as demonstrating the reality of evolution, some of the best I am aware of are pseudogenes and endogenous retroviruses. Not exactly what you would call conclusive -- nothing is in empirical science. As Duhem's thesis shows, it is always possible for someone to choose a less reasonable interpretation of the empirical evidence over a more reasonable interpretation -- indeed, one can coherently maintain that the world is only five minutes or five seconds old without fear of self-contradiction. But for the good majority of people who understand what they are and how common they are, I suspect pseudogenes and ERVs would be enough. (Additionally, I am rather fond of the idea of having 30,000 retroviruses in every one of my haploid genomes -- quite a collection!, or the idea that nearly fifty percent of my genome appears to be retroviral in origin [e.g., consists of retroelements].)
I'm sure this would be a fertile subject for creationist investigation, but it is off topic, so maybe you could start a new thread for it.
This message has been edited by Faith, 12-07-2005 12:00 PM
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