[grey_whiskers]

It is often impractical and dopey to insist on taxonomical

But not in a discussion about evolution.

Time for another of my patented Bonehead^TM questions.

Apparently in the earlier days of evolution, many of the "family trees" etc. were created on the basis of taxonomic evidence.

But, as one of the earlier posts on the thread pointed out, the eye in the fruit fly, and in the octopus, have very different structures though a common purpose...they are both "eyes". Similarly, since whales came from land animals, the fins developed independently from those of fish.

So what methods or safeguards are put in place to prevent misclassification based upon structural similarities which may turn out to be of completely independent origin?

(Or is it a moot point since that type of thing happens so seldom...?)

Cheers!

[UndauntedR]

So what methods or safeguards are put in place to prevent misclassification based upon structural similarities which may turn out to be of completely independent origin?

Mis-classification has certainly happened before... in both directions.

Check out convergent evolution. Mimic species are populations of animals which have evolved to "mimic" morphologically those characteristics of a successfull species. IIRC, two species of a horned lizard were classified as the same for a good period of time (decades?) until someone found small DNA discrepancies that should be impossible on the sub-species scale. Further study showed they're were tiny, but reliable, differences in morphology (like leg and body length) as well but were so small (< 5%) they had been overlooked.

Interestingly, it can happen in the opposite direction as well. The female angler fish is the popular large, menacing deep sea fish with a huge mouth and a light bulb on it's head. The male kinda looks like a guppy. They were classified as two separate species for a time because morphologically they were so different and practically they were so hard to observe and study (we still don't have a complete, comprehensive taxonimic classification for this clade).

Scientists are not infallable and it can be quite exciting and surprising when an oops is uncovered. But by no means does this taint science or evolution as a whole. Evolutionary Theory itself felt no tremors when these (legitimate) mistakes were corrected because the theory is not dependent on the male Angler fish or "one" species of horned lizard.

[Virginia-American]

Apparently in the earlier days of evolution, many of the "family trees" etc. were created on the basis of taxonomic evidence.

Yes, of course they were. Linnaeus and later scientists used the morphologies, biodistribution, behavior, etc, to construct the classes, orders, families, and other taxa. Lamarck, Buffon, Comte, et al, and later Darwin and Wallace interpreted these taxonomies as phylogenetic trees.

But, as one of the earlier posts on the thread pointed out, the eye in the fruit fly, and in the octopus, have very different structures though a common purpose...they are both "eyes". Similarly, since whales came from land animals, the fins [nitpick - whales have flukes] developed independently from those of fish.

Eyes have developed independently many times, I've seen estimates as high as 40. Being able to tell light from dark, or to better resolve images, has obvious survival value in many different environments.

Whale flukes are a specialization of the tetrapod limb: one bone close to the body, two further out, then five groups. So are the flippers of ichthyosaurs, mesosaurs, pinnipeds, and sirenians.

So what methods or safeguards are put in place to prevent misclassification based upon structural similarities which may turn out to be of completely independent origin?

A good question. Convergent evolution is the fact that natural selection will tend to select the same features to adapt to the same niche. A famous case is the saber tooth "tiger" and its marsupial look-alike. Another one is the way fish, cetaceans, and ichthyosaurs have very similar fins (or flukes or whatever the right term is for the ichthyosaurs) and streamlining.

The answer is by studying the details of anatomy. The saber-toothed cat and the marsupial one are both extinct, so you can't just compare wombs and pouches. However, marsupial skeletons can be differentiated from placental ones, though you'll have to ask someone other than me about the details.

(Or is it a moot point since that type of thing happens so seldom...?)

It has happened, but not that often. Basilosaurus was given a reptilian name, even though it's a mammal. It's more of a problem, obviously, with fossils, but you still hear discussion as to how the giant panda, the red panda, bears, and raccoons should be classified. DNA analysis can provide conclusive answers.