I can find nothing illogical in this idea whatsoever, it seems quite rational. but if anyone DOES see anything illogical about it, I would like to know what it is. Seems to me that if I have a large herd of any particular animal, then seperate a small part of them into a different cage, expose them over eons to much different stimulus and environment, as well as possible chemicals and radiation, and possible inbreeding due to isolation... enough mutation will take place to develop a new species seperate and unbreedable to the original species. Originally such mutations may be looked upon as birth defects.. but some birth defects, if the carrier of that gene breeds, become permanent changes in the DNA itself, and the first step to a new species.
2 problems.
1. The small pop. with the initial mutation is too small to have a sufficient number of mutations (per breeding individual) to get a second successful mutation to further differentiate the species.
2. The overwhelming percentage of mutations due to all causes are harmful or uselessly neutral.