Many people who argue against Intelligent Design’s position on transitional forms often don’t have any clue what it is that is actually being said. I’d like to take a moment to clear it up. If anyone disagrees with my commentary (especially ID’ers — I’d hate to misrepresent other’s opinions), please post below. My main point in writing is not so much a defence of the concept (though I do attempt that) but rather to show why it makes sense even in the absence of special creation, and why its use is not limitted to people who agree with special creation, but anyone who believes in a telic form of evolution.
What is a transitional form? If the generative force of evolution is atelic, then we should be able to detect many forms of organs and organisms on their way to being stable forms. If natural selection is acting on changes which are atelic, then we should see a gradual progression from one form to another in a gradual succession. Each individual change must be small (or else the search space would be too huge) and beneficial (or else it would be selected against). Likewise, it requires quite a bit of reproductive excess for this to occur, so there should be plenty of evidence in the fossil record of the dead animals required to make these changes. So, by transitional form, it is meant a midway point between organism X and organism Y.
Remember, ID is not an argument against evolution itself, but rather an argument for teleology as the prime mover in organismal form. This means that evolution may be coherent, but Darwinian evolution, where the substrate for change which is selected is atelic, is incoherent. It is fully within the bounds of ID for a basal organism to have pre-coded, fully-formed adaptations ready-to-go, and be able to assemble itself piece-wise at certain periods or in response to certain stressors.
What is found in the fossil record primarily is not transitional forms. What is found is transitional habitats and chimeras. A chimera should not be confused with a transitional form. A chimera is an organism which has fully-formed features put together in a unique way.
The fundamental question is how do novel body plans and tissue types arise? This is the fundamental question that needs answering. These things function in holistic ways in the present. What is the origin of such features? If the answer is Random Mutation + Natural Selection (RM+NS), then one has to figure out how such a process was able to find such remarkable, holistic structures. There are two possibilities as far as I can see — either all-at-once or a step-at-a-time. If it occurred a step-at-a-time, then where are the steps? We should see them massively in the fossil record, as each step requires reproductive excess to occur. If it was all-at-once, then how is that distinguishable from a miracle? And if it happens over and over again in the fossil record, can the generative mechanism really be random mutation?
Darwinists like to think that the fossil record shows random mutation + natural selection occurring. But there is no way to tell from a fossil what mechanism produced it. All you have are very discontinuous organisms at every step of the way. The question is, what best accounts for the pattern we see?
When a Darwinist claims a transitional fossil, the best questions to ask are, “what two specific species is this a transitional between?” and “in what ways are the features intermediate between them?” Most of the time, transitions are listed as between very large groups. But transitions can’t occur between large groups. They only occur between specific species. If something has “transitional features” between large groups, that isn’t saying much, given the large amount of variability among large groups. If something is claimed as a transitional between fish and amphibian, that is a huge range of features on both sides that someone could take from to claim intermediacy, despite the fact that for it to be evidence of Darwinian evolution it would have to be transitional between two specific species.
If multiple “transitionals” are found, with the lineages all mixed up in a chimeric way, this provides evidence against Darwinian evolution. How does descent work in a way in which would allow for crossing over of body parts? Instead, such is evident to me of either a preprogrammed set of features to diversify, an interventionist change, special creation for intermediate habitats, or hybridization.
There are a few examples of possible transitions. But the number of potential transitions is dwarfed by the number of humongously large gaps, which would be unexpected by a non-telic form of evolution.