Microevolution or macroevolution?
Drosophila melanogaster was among the first organisms used for genetic analysis, and today it is one of the most widely used and genetically best-known of all eukaryotic organisms.
Perhaps, scientists speculated, evolution took place as genes were altered. DeVries claimed that if a gene changed - if it "mutated" - it would create a new species in a single jump. ... Morgan bred fruit flies by the thousands, and his team tried to create mutant flies with x-rays, acids, and other toxic substances. Finally, in one unaltered lineage of flies, the researchers found a surprise. Every single fly in that line had been born with red eyes, until one day a fly emerged from its pupa with white eyes. Something had spontaneously changed in the white-eyed fly. ... Here was a mutation, but one that didn't fit DeVries's definition. DeVries thought that mutations created new species, but the fly that had acquired the white-eyed mutation remained a member of the same species. It could still mate with other fruit flies, and its gene could be passed down to later generations in proper Mendelian fashion.
It is, of course, hardly to be expected that any random change in as complex a mechanism as an insect would improve the mechanism, and as a matter of fact it is doubtful whether any of the mutant types so far discovered are better adapted to those conditions to which a fly of this structure and habits is already adjusted. ... Evolution from this point of view has consisted largely in introducing new factors that influence characters already present in the animal or plant. ... In the breeding work with Drosophila we are dealing with artificial and unnatural conditions.
The four-winged fly
The importance of the four-winged fruit fly is that it demonstrated that a few mutations in a single gene were able to transform an entire structure.
The genetic mistake did not produce a new complex structure. It just made an existing complex structure appear in a place where it would not work. We want to see a Hox gene make functional legs or wings appear on a worm. Is that a "frustrating request" or "an unreasonable burden"? What makes it unreasonable? It is unreasonable because everybody knows it can't possibly happen. But, for the theory of evolution to be true, it has to happen often. Reptiles had to grow breasts to become mammals, didn't they? Every internal organ of every living creature is a complex structure that had to be produced by a genetic mistake, if the theory of evolution is true.
Scientists have bombarded fruit flies with X-rays to try to get them to mutate, and it works. They get mutant fruit flies without wings, fruit flies without eyes, and lots of fruit flies that die quickly. But they have never produced a dragonfly or a butterfly. All they get are fruit flies with birth defects.
It is a striking, but not much mentioned fact that, though geneticists have been breeding fruit-flies for sixty years or more in labs all around the world - flies which produce a new generation every eleven days - they have never yet seen the emergence of a new species or even a new enzyme.
If mutation were a variation of value to the species, then the evolution of the Drosophila should have proceeded with extreme rapidity. Yet the facts entirely contradict the validity of this theoretical deduction, for we have seen that the Drosophila type has been known since the beginning of the Tertiary period, that is for about 50 million years and it has not been modified in any way during that time. (p. 34)