If it is not to be believed, and with good and multiply reasons, that mutations are the raw material for evolution, then a necessary consequence is that old genetic material does not mutate so as to cease to be recognizable. It has recently been shown that dogs descended from wolves (Science 276, June 13, 1997). In the case of the dog breeds then, you would expect that since only recombinations of the material in the available genetic pool in the wolf population caused the new morphologies of the modern breeds, and not irreversible alterations of that genetic material by mutations, then the material that made up the wolf still exists in the dog populations. It might be reasonable then to reconstitute a wolf by breeding different dog morphologies together. This experiment has in fact been done already and successfully, not in wolves, but in pigeons, as observed by Charles Darwin. The common rock pigeon (C. Livia ) is characteristically blue with bar marks on the wings and tail as well as other characteristic marks. Darwin established that the fancy varieties of pigeons (Pouters, Fantails, Tumblers, etc.) are all descended from the rock pigeon, just as the breeds of dogs are descended from wolves. Breeding the derived varieties together, he discovered that offspring would often revert to show features characteristic of the rock pigeon. The facts hitherto given refer to the occasional appearance in pure races of blue birds with black wing bars, and likewise of blue and chequered birds; but it will now be seen that when two birds belonging to distinct races are crossed, neither of which have, not probably have had during many generations, a trace of blue in their plumage, or a trace of wing-bars and other characteristic marks, they very frequently produce mongrel offspring of a blue colour, sometimes chequered, with black wing bars, &c.; of if not of a blue colour, yet with the several characteristic marks more or less plainly developed. I was led to investigate this subject from MM. Boitard and Corbie having asserted that from crosses between certain breeds it is rare to get anything but bisets or dovecot pigeons, which, as we know, are blue birds with the usual characteristic marks. We shall hereafter see that this subject possesses, independently off our present object, considerable interest, so that I will give the results of my own trials in full. I selected for experiment races which, when pure, very seldom produce birds of a blue colour, or have wing bars on their wings and tail. Excerpt from Animals and Plants Under Domestication by Charles Darwin

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