Why haven't we observed mutations of new body parts?

Since when is this an IDist (or creationist) postition?It seems to me that if there is a very powerful, intelligent designer then she/he/it could make the large changes that we can make in a human design. In fact, the idea of IC (irreducible complexity) is exactly this- that the designer can bring all the parts together at once and so make a large change.You are exactly 180 degrees from the actual case with the above. NJ, you have been here long enough by now to answer your "wonder" above. A modest understanding of evolutionary biology would stop anyone from making such a statment. Maybe it is a bit more than you can handle after all, eh?Since we do have a "littering" of examples the rest of your post is about as far off the mark as the quoted parts.

It doesn't matter to the ID movement what your position is. Their position is precisely that God micromanages at the biochemical level (e.g., blood clotting and bacterial flagellae). The majority (if not all) IDists also believe that an omnipotent god is the micromanager so I would take it as obvious that not only minor changes are possible but also something like a fully formed pair of feathered wings in addition to the other limbs of a quadraped (e.g., Pegasus and angels). To suggest otherwise is to belie what the Discovery Institute appears to be trying to say (not that they are clear or consistent). Of course, evolutionary processes work precisely because they don't require abundant beneficial mutations. The process is a hugely wasteful one (half of all things you call human thrown away over and over again) and slowly conserves and accumulates whatever beneficial mutations do appear. They don't need to be "abundant" at all. (of course, who knows what you mean by abundant).Your question concerning Pegasus has been answered already. You should be embarrassed for not being able to answer it yourself. That is better reaction than getting all upset about being condescended to when you have had the time and considerable effort made by others to help you understand. At this point in time my inclination is to not invest time but rather pat you on the head and send you to the vocational training class.

All one can say is "blink". :rolleyes"Sigh Nem, it is truly amazing. Here's a hint: The fishy thing HAD the traits selected for and maintained (though you are, yet again, wrong, the fishy thing has changed quite a bit). What you started off suggesting that something NOT present would appear BECAUSE it would be useful. They are very, muito, mucho different cases.Shall we step back to square one:
Changes (new traits) arise from thing like mutations. These are NOT directed; they aren't influenced by what would work nicely. Selection then acts on them and if what has been produced is a bit useful it is kept. If the trait doesn't happen to pop up then it can not be selected for.If you have questions on that try asking.

If IC is defined as something that won't function if a piece is taken away then there are lots of IC parts. However, that doesn't say anything about their evolution (as you point out).

I think you have it exactly right! That is the way the IDists have defined IC.However, it has pretty much nothing to do with the evolution of biological structures in the real world.