How did fish get onto land if they couldn breathe?
TD: Very early in their evolution, fishes had lungs while they were still aquatic, so the transition to breathing air was no problem. Many kinds of fish have primitive lungs and some actually are able to breathe air — we call it “air gulping.” Among the lobe-finned fish there was not a big problem with breathing air. They had developed lungs first for use in water. As they may have moved into these stream systems, perhaps lungs became more and more important, especially in waters that may have had a lot of decaying plant material and low oxygen content. Coming up to the surface and breathing air may have been no problem at all. One thought is that the development of limbs was to help push off the bottom to get your nostrils above the water surface and take in some air. Q: What are some of the scenarios that might have led from these fish with lobe fins to what we call tetrapods [fourlimbed creatures]? TD: The transition from fin to limb seems to have happened in a rather complex envir
