One of the things I like about paleontology is the often creative hypotheses that get postulated in its literature. However, there are certain ideas that need better fleshing out with regard to molecular data, and sometimes, the tendency toward parallel evolution in certain clades is not adequately addressed in some of the morphological analyses that the discipline is force to use.
Among these would be the claim that arctic foxes evolved in the Himalayas. The paper that postulates a Tibetan origin for this polar species was well-publicized, as was the attendant out of Tibet hypothesis for arctic mammals. I must admit a certain amount of skepticism of the entire hypothesis, because it seems a bit of a stretch that evolution in high altitudes in the middle of a vast continent would create a lasting evolutionary lineage that could then colonize regions to the far north of that continent. It seems to me odd that you would get something like a polar bear started in the Himalayas, then have it colonize the arctic as a near marine organism.
The authors of the paper posit a Tibet origin for the arctic fox, based upon the remains of Vulpes qiuzhudingi, a Tibetan fox that lived over 5 million years ago. The dentition of this fox strongly resembles that of the modern arctic fox, and therefore, the authors think that the arctic fox must have derived from either this species or one that is close to it.
The authors also think that the next oldest arctic foxes were found in the arctic 3-4 million years ago, which is also interesting.
Both of these claims are interesting because the molecular data indicate that the closest relative of the arctic fox is the swift fox of North America, and what’s more, the arctic and swift foxes shared a recent common ancestor that lived about 900,000 years ago. The molecular data indicate that what we call an arctic fox today derived from the swift in the North American arctic.
So what the authors likely found with Vulpes qiuzhudingi is a parallel evolution of a more carnivorous fox in the high altitude of Tibet 5 million years ago. It might be the ancestor of “arctic foxes” found in the arctic 3-4 million years ago, but they are not the same thing that goes by Vulpes lagopus today. It is also possible that these arctic foxes that are older than 900,000 years old are another parallel evolution of more carnivorous foxes in cold climates.
This tendency toward parallel evolution matches so much of what we know about about canid evolution, and why virtually everything one reads about canid paleontology and systematic morphology needs to be confirmed with molecular data.
So yes, I do appreciated the creativity of paleontologists to describe the fauna of the world as it once was, but that darn ol’ DNA messes up the flight of fancy so many times.
Natural History 