AFJ, you should read up on Tiktaalik:http://en.wikipedia.org/wiki/Tiktaalik
FYI, lungs evolved before legs as an off-shoot from the intestine; in fact Corydoras catfish today can "breathe" through their intestinal lining as an adaptation to life in poorly-oxygenated water. Lungs were probably very common in early fish, and many acquatic fish today (such as gar) still have lungs while in other fish the lungs evolved into the swim bladder. As for limbs, the bone structure of lobe-finned fish is almost identical to that of terrestrial vertebrates, and thus a clear evolutionary ancestor. Add to this the existence of "missing links" in the fossil record (such as Tiktaalik and Ichthyostega), and we have a clear example of all necessary adaptations being in existence even before tetrapods began to evolve.
Hi, first, thank you for the link. Let me secondly say, I desire discourse and friendly debate. I do see intelligent design in things, but I do not disrespect evolutionary thinking. I can see why scientist could interpret things evolutionarily--resemblance, similarities in flora/fauna/genetic material etc., natural selection, speciation, mutation. These things are seen in a limited degree currently.
Okay, I read the link, and also researched more on lungfish. One thing I see is that lung fish stay in places where the water is still and hence a chance of low O2 content. I think we need to right off the bat say that evolution does not say that habitat causes adaptation (I'm not saying you say that either), but mutation first (independent of habitat), then speciation, and natural selection within habitats.
The hard part for me is what caused lungfish to mutate, evolve lungs, and at the same time mutate an instinct (information) to stay in potentially stagnate or low O2 areas? Somewhere in the genetics the instinct of habitat developed also through mutation FIRST--THEN speciation and natural selection. Why did it just so happen that these things developed in the GENETIC MATERIAL AT THE SAME RELATIVE PERIOD OF TIME? This is a MONUMENTAL COINCIDENCE, as many things are in the theory of evolution. Always there is the question of guiding force and mechanism in the genetics which caused so-called adaptation. What caused so many coincidences?
Again 1)Natural selection happens after mutation. 2)Habitat does not cause genetic mutation.
Therefore the development of lungs originated from mutation along with a mutation which caused an instinct (information) to stay in the lungfish habitat.
Intelligent design interprets this as evidence of design. The creation of lungs was necessary for their habitat.
A) Because it is harder for us to believe that so many coincidental upward mutations happened within the same relative periods of time.
B)Because of the complexity and the homeostasis of the organism
1)together with it's instinct (information) for habitat
2)together with how the organism works within the habitat
3)together with how it works in relation with other organisms within that habitat
This makes more than an organism but a finely tuned and well balanced ecological system. This points to designed purpose.