(For those of you not interested in reading another post about the obvious unreasonableness of neo-Darwinism, I apologize. I'm pressed for time and need to get something posted, and so, well, it's just so easy to point out flaws in the Darwinian story.)
At least nine factors can be identified that affect the likelihood of a species’ either evolving or going extinct in the face of natural selection pressures. That is, assuming that evolution does work--that natural selection working on gene mutations can produce significant speciation--we can discuss natural history traits that are expected to constrain or allow such evolution. We can first carry out such discussion on a theoretical level; afterward, we can apply known mutation rates to the discussion and thereby estimate values for some of these parameters required for successful evolution (as opposed to extinction).
Nine factors necessary if, for a given species, evolution will be more likely than extinction are: large population size, short generation time, large reproductive output (many progeny per adult), low biocomplexity, small body size, generalized food supply, large available habitat, high ecological diversity, and little cultural advancement (or sociality). To look at these the other way, we would say that a species is likely to go extinct if any of these are true of it: small population size, long generation time, few progeny, high biocomplexity, large body size, specialized food supply, small amount of suitable habitat, low ecological diversity, and high cultural advancement.
In evolutionary textbooks, the two vertebrate groups that are lauded as the best evidence for Darwinian evolution are the whales and the horses. This is because we see in the fossil record that numerous different species of each of these types of animals have existed. Unfortunately (for the Darwinist), whales and horses are among the very worst candidates for evolving. For each group, every one of the nine ecological factors favors extinction rather than mutational advance. The life history traits of horses and whales make them among the least adaptable organisms one could name.
That whales and horses are--in spite of their inability to adapt or evolve--prominent and varied in the recent fossil record demonstrates that God likes whales and horses. When earlier forms of each were no longer able to exist in Earth’s changing conditions, God created new forms of each, with the result that, since their original creation, whales and horses seem to have been a nearly constant part of the biodiversity of Earth. Although the creation accounts of the Bible do not specifically mention numerous created life forms (insects and dinosaurs, e.g.), special mention is made of these two groups, and the Genesis 1 account refers to the creation of sea mammals (including whales) and long-legged, trainable creatures (including horses). God’s view of horses and whales is summarized in His statement following their creation--He pronounced what He had made “good.” Both whales and horses also have a special ability to interact with humans, and this interaction is likely another reason that the Creator continued to replace whales and horses as earlier species died out.
Using available data on the rates of genetic mutations, scientists have been able to estimate what the theoretical cut-off point is for some of these factors. These would include a generation time of 3 months and a population size of 1 quadrillion individuals. Application of such estimates to animals in general indicates that a very few species (of ants and termites, e.g.) may qualify as candidates for adaptive evolution. Whales and horses, obviously, do not come close.