They only recently marked the dog as a subspecies? I must have missed that news too.
Like I said, this news was apparently not considered newsworthy by the popular press.
I always thought that they were part of the same species because they could interbreed for any number of generations and still produce healthy, reproducing offspring.
That's not a valid criterion to use. We are also bird breeders and there are many bird species that can hybridize indefinitely. All of the species of Amazon parrots, all of the species of
Ara macaws, most of the species of conures (genus
Aratinga, outside North America they're usually mislabeled "parakeets") and many or most of the species of cockatoos have been hybridized in the pet trade for decades and the crossbreeds are now many generations deep. Even macaws, who take many years to reach sexual maturity, are into the fourth or fifth generation of hybridization. Seven parts Scarlet macaw with one part Blue and Gold macaw yields a Lavender macaw, which looks just like it sounds.
But worse than that, it's also been proven possible to crossbreed birds from different genera. The Blue and Gold macaw,
Ara arauna, can hybridize with the Hyacinthine macaw,
Anodorhynchus hyacinthus, and produce healthy offspring that have been named the Collson macaw after the breeder who did it. I'm not sure any of them have yet reached sexual maturity to try for a second generation.
The reason these discoveries are so recent is, of course, that hybridization is rare among wild animals because they often have courtship rituals that stimulate the hormones that generate the desire and/or ability to mate. Lions and tigers, for example, are genetically compatible, but tigers need to be clawed to stimulate their hormones and lions just hate that, so they can only be crossbred under controlled captive conditions or by artificial insemination.
With domesticated parrots it's quite a bit easier. Baby birds that grow up together from the moment their eyes open regard each other as the same species. The courtship rituals of macaw species tend to be rather similar, so they will often mate rather readily with a macaw of a different species that they've been socializing with for years.
I'm not exactly sure when they found genetic evidence linking the dog to having gray wolf ancestry, but it was recent you say?
I think the determination that dogs descended from wolves--as opposed to jackals, coyotes, or another
Canis species, goes back several decades. But the discovery that they are still the same species--not to mention pinpointing the location of that original wolf pack in China--is the result of gene mapping sometime in the last ten years. It has also been determined that the dingo is merely a dog, not a distinct species or subspecies. They only go back about 5,000 years.