The problem is that the source of novelty is so dammed elusive. Most genes don't change very much at all, even the body-plan genes seem to be very similar in the mouse and blue whale. Or, to compare even less similar creatures: a mouse gene essential for building the eye can be inserted into the fruit fly to produce a fly eye! This refutes a key prediction of Neo-Darwinism, Ernst's Mayr's statement that it would be futile to look for similar genes in different creatures. Neo-Darwinism predicted that random mutations would pile up until the genes of mice and men were as different as, say, the Finno-Ugric and the English languages.

i'm as far from an expert as physically possible, so feel free to extract the root of my opinion, but i don't see any problems with it. i think it wasn't neo-darwinism's prediction, more like ernst mayr's personal judgement, a fairly rushed one at that. he probably didn't consider the need of compatibility. if mice, humans, and flies share a common ancestor, that had a gene for developing some kind of "eyes", then it's entirely possible, that this ancestor's different offsprings will have different genes, that build their own functions on the function of it's original "gene for the eyes". the more genes build on it, the more unlikely, that the original gene can change without causing a disaster for its carrier.

the so-called "gene for the eyes" that, when transplanted from a mouse into a fly, creates a fly's eye, is probably just the "base-gene for the eyes", that needs other genes to use its effects. since these other genes are different in mice and flies, they develop different eyes.

could someone please correct me if i'm wrong?