The Oxygen Super Highway II (Part 6)

After doing some reading I knew just about as much as I did before I began my brief investigation - not much about amphibian respiration. As in mammals and fish, amphibians require a moist surface for the exchange of oxygen and carbon dioxide. Some have lungs and some do not, but all of them have capillaries close to the surface of their skin which has special epithelial cells which function the same as the epithelial cells in the mammalian lung. One new thing I learned is that some frogs obtain up to 80% of their oxygen through their skin. It does leave us in the same place we left off in The Oxygen Super Highway I, though - still no possibility of evolution leading fish out of the sea. Gills would never develop into an amphibian form of respiration because the components are too different. How would internal organs ever lead to external organs through the process of natural selection? It becomes yet another example of evolution in reverse. How would it work the other way? Could external epithelial cells ever develop into gills? While I see tremendous benefit to having internal organs I simply can not imaging some sort of mutation that would lead to it! Let us take a look at some of the fruits of DNA mutations in humans - Down Syndrome, muscular dystrophy, chronic myelogenous leukemia and any number of others that lead to miscarriages.