[gallo]

Quote by: Fonceai Quote by: kubedawg You really don't think in the early stages of human life we didn't have fins and/or gills? Current embryonic development? No.

Aside from the grammatical confusion of the question caused by the double negative that injects considerable uncertainty of meaning, Fonceai is correct. If by "early stages of human life" kubedawg is referring to human embryos, then no we never had fins and/or gills. In fact, dolphins don't ever have gills either, and they have fins only in the broadest sense of the word.

Quote by: Fonceai Earlier forms of the mammal that would someday develop into humans? Maybe.

Nope. No mammal, embryonic or otherwise ever has fins or gills. As I explained to Hostile55 in post #3, "gill slits" and never become gills in mammals. They are folds caused by pharyngeal pouches that are characteristic of all embryonic chordates.

Quote by: Fonceai The ability of a fetus to breathe liquid is similar to gills, but only because that fluid is oxygen-enriched.

Nope. a foetus doesn't actually breathe liquid. The necessary oxygen for the foetus comes through the placenta from mother. CO2 is eliminated the same way. Early on, before the development of the placenta, the embryo is small enough that it can absorb oxygen and eliminate waste directly into the environment of the womb. But it can't actually be called "breathing."

Quote by: Fonceai The appearance of arms and legs being fins is closer evidence, as it demonstrates that the appendages develop into hands/arms and feet/legs later but had their basis in fins.

Except that as I recall from my embryology class, human embryos never do have fins. They have limb buds that are homologous to the fins of fish at about the same stage in development, but they don't even resemble fins. One must always remember that ontogeny does not recapitulate phylogeny.

Quote by: Fonceai Really though, because of the many many evolutionary leaps required to go from fish to land-fish to land creature to mammal that while reasonable to say that everything came from fish, dolphins and whales don't represent a lower step in the process. They represent a later step... the development of land mammals to water.

Exactly correct, as I also explained in post #3. A very interesting book on the topic is Zimmer, Carl. At The Water's Edge: Fish With Fingers, Whales With Legs and How Life Came Ashore but Then Went Back to Sea. 1998. Simon & Schuster. New York. 290 pages.

Even though the book isn't that old, there is one error in scientific thought that is apparent. Zimmer expresses earlier theory on the origin of whales as descended from mesonychids. Molecular biology indicates that that is not the case. They are more closely related to the artiodactyls (even-toed ungulates). Nevertheless, the book is very interesting.

Quote by: Fonceai Basically acquiring the advantages of land life and bringing them back to the sea.

Right, as long as you keep in mind that the first terrestrial vertebrates appeared about 400 million years ago, about 100 million years after land plants and about 350 million years before whales began to adapt to water.