Down Syndrome itself is the duplication of all or part of chromosome 21, usually due to improper separation of chromosome pairs during meiosis. I kind of think

Down Syndrome itself is the duplication of all or part of chromosome 21, usually due to improper separation of chromosome pairs during meiosis. I kind of think of this like going around a factory and turning up every 23rd valve. Gene duplication seems less severe. I agree it is not known how to make wings on a giraffe by manipulating the environment so as to control or "benefit" from gene duplication. Your attempts to study this in nature might be frustrated by the difficulty in identifying paralogs vs orthologs, the fact that gene duplications are often not preserved between generations and the fact that many gene duplications are deleterious. It's also the case that it is not yet fully understood how gene expression regulates the development and structure of body layouts. New body parts like wings are complex biological structures and do not usually just appear due to a change in genes. At least when I last left the debate conditions in the womb, fetal orientation, rna from the mother, "junk" dna and many other things were being examined for their role in the development of body layouts. As you are probably aware, research has been done that shows duplication and deletion of body parts due to genetic abnormality. But this is usually not a good way to make an organism survive. How many people missing a leg or who have an extra arm do you know of who find life easier? Anyhow, my point regarding the giraffes was merely that it is going to take very many generations of giraffes before anything at all happens. You and your great grandchildren will be long dead before then. In that sense I don't think it can be held against science that we haven't been able to demonstrate evolution of wings on a giraffe. I personally don't hold out much hope for it either. The changes that must occur in a giraffe for it to support wings as a viable organism may be so great that it is no longer anything like a giraffe any more. So the entire concept of wings on a giraffe might just be a natural impossibility.