OR,
I want someone to show me why it is that the scientific community does not believe that form follows function.
Of course form follows function. The form of a dolphin flipper is superbly in accord with its function as natural selection would drive it there.
With the apparent limitless number of forms available, why is it that so many unrelated water species have very similar appendages?
Now, don't tell me it is Natural Selection, because I fully understand that when a creature evolves to have a flipper instead of a hoof, it would most certainly be beneficial to it in the water environment, therefore will be selected for.
What I am after is before it is selected for.
Why do so many different animals that happen to live in or near the water have the such similar "random" mutations?
The only thing I can think of that makes sense (outside of direction, aim and intention of some sort being attributed to evolution) is that every life form's DNA is incessantly "trying" every possible combination of mutations and the ones that happen to be selected for in that species are the ones that are passed down.
In that situation, however, why do Polynesians not have webbed feet?
This is very difficult for me to clarify and I apologize if I am not making my point clearly enough.
I am not asking why flippers will "spread" throughout a species, I am asking how they get flippers in the first place.
Ok. Good question.
An animal (a Proto Dolphin, PD) lives comfortably on the margins of the sea, making its living off the animals (seals, penguins, otters, etc.) that come onto land to breed or whatever.
A new and better hunter/predator, NP, moves into the area due to climate change and begins seriously competing with PD.
NOTE: There is no guarantee that PD will not be driven to extinction by the more well adapted predator. If PD fails to find a new way to survive (not consciously of course), it will die out as have 99+% of all species that have ever existed. Extinction is the rule, adaptation the exception.
Now, PD had a penchant for swimming short distances once in a while for a snack. NP hates the water. Many PD's die in the water by predation from sea creatures and such. Some, however are much better swimmers, by virtue of having shorter forelimbs, bigger paw pads, shorter toes (all giving less drag and more power in the water).
Over many, many millenia, the PD's are driven nearly to extinction and have only survived due to luck and a large initial population with a liking for water. We now see though, a population of PD with greatly foreshortened front legs and toes and very large paw pads (the forelimb is almost all paw) which are almost useless for walking. It's more flipper now that paw. PD begins to make a comeback, living exclusively off of fish. Natural selection has bred for those PD with short forelegs and toes and large paw pads.
Do you see how this happens? There are so many creatures with similar flippers because of two things: 1) there were, by luck, structures that could form a general flipper shape, and 2) flippers have nearly ideal physics for the job they have to do. There are other creatures that pulsate, undulate, squirt, or bottom crawl for locomotion in the sea. It's luck, preexisting structures that can be modified, and the buffet of possibilities offered up by mutation. Most mutations kill the host, and most hosts go extinct given environmental changes. What we see (us included) are the amazingly lucky few with the preexisting structures that allowed them to be successful in a new environment.
Helpful?