Idris - Sorry root but I don’t recognize how Island Dwarfing in the natural world can assist the theory of evolution
Albeit Island dwarfing or Island giganticism, it is a species evolving over-time. Wether you choose to accept that this evolution is how Allah intended it to be or as a result of chance is for this thread neither here nor their. The point remains that a species that becomes isolated will go through a period of natural selection
sometimes with mutation, but mostly with genetic variation due to recombinant genes, etc. Keep in mind that this typically applies mostly to large warm-blooded species. Reptiles and small mammals often show the opposite trend, increasing in size, such as komodo dragons, giant geckos and tortoises, and giant island rats.
Steve - Ironic isn't it, that I -a theist- have to explain you -an evolutionist- how the theory of classical evolution works. But you don't have to take my -or wikipedia's- word for it. Ask any scientist in the field of evolution and he/she 'll tell you.
The difference in our two opinions based on the assumption of a large warm blooded mammal becoming isolated is that you seem to suggest that "mutational Change" will be the driving force where I am suggesting not, as genetic variation will already be in place natural selection will be the driving force, you don't seem to make a distinction between the processes and to all tense and purpose you see mutational change and natural selection as the same process. Unless I have misundertood you.
Change in genetic variation can be brought about be mutation, which generates new variation, and natural selection, which selects which of these variations shall propagate. The rate of change is able to happen much faster with natural selection. The rate of mutation is generally fairly stable. The rate at which natural selection can change the genetic variation in a population is highly variable, and there's essentially no limit to it. So under conditions which don't favour any individuals within the population, natural selection will have no effect and mutation will be the driving force of change in genetic variability. Under conditions that greatly favour the survival and reproduction of certain individuals natural selection will become the driving force.
It's also important to realize that size is governed by a lot of alleles, and is *highly* variable between individuals; it's one of the fastest things to respond to natural selection. So short and sweet, mutation and recombination create lots of genetic variation in size in all populations. If selection acts against large animals (or for them), then average animal size changes, often quite rapidly.