The Definition and Description of a "Transitional"

Time for another orangutan to enter the fray! I think you need to be careful about defining a transitional this way. Nobody is saying that an animal retains all of the characteristics of it's ancestors. If a trait like climbing trees was not useful to one of our ancestors, why on earth would natural selection force human ancestors to keep it?On top of this, a loss of characteristic could also be viewed as useful like, for example, the loss of strong jaw muscles:The great apes, apart from ourselves all have very strong jaw muscles - very useful I'm sure you'll agree. Humans seem to have lost this aid to eating tough things (due to a mutation in a single gene), and a recent popular theory is that this removed a physiological barrier to developing larger brains. So not only was it not particuarly required to keep the muscles (due to a namby-pamby diet most likely), it was actually advantageous to lose them.

Hi,I never really understood how creationists can have a problem with convergent evolution without ignoring the principle of selection and overlooking the shared developmental pathways of organisms. I'm not quite as knowledgeable in this area as Mammuthus and Mark24, but let me try to put my case forward.

1. The power of a selective environment If two organisms are in the same environment, with the same selective pressures, then why shouldn't the same kind of structures be selected for? If a fin shape is advantageous for a shark, why not for a whale?
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2. Shared developmental pathways The underpinning principle of common descent is key when looking at convergent evolution. Evolution works with, and builds upon, what is already present . If two species share a common ancestor then they will undoubtably share some underlying developmental processses as well. Eyes are an excellent example of this: there are many different types of eye in the world, but it seems that they are all under the control of the same master control gene. Similary with your fishy example: why couldn't the same initial pharygeal 'arrangement' been co-opted from a shared ancestoral characteristic? I think there were once fish which had pharyngeal 'teeth' which are now extinct (I'll try and dig out the reference).

Taking that into account then (and trying to angle my argument vaguely towards the topic), discounting transitional fossils as simply abherrations of classification is not truly addressing the facts, and is misleading. It's all about looking at the whole picture, and looking at it carefully. Looking at the fins of whales and fish clearly shows that they are built differently, while there are similarities between whales and land mammals. Our eyes are fundamentally different to those of drosophila, but are similar to other mammals. Exactly how indentical are the "highly specialized mechanism[s]" of spiny teleosts and Cypriniformes? How fundamentally different are these structures from other teleost fish?