The domestication of the dog has been a ripe area of evolutionary speculation for more than 150 years. A wolf ancestry and probable East Asian origin of domestication are now widely accepted. We offer a new allopatric hypothesis for the domestication of dogs that recognizes the importance of isolation in the speciation of the dog from the wolf. Although sympatric isolation during domestication of many other species would not have been problematic, it has always been difficult to keep dogs from breeding with wild canids. Furthermore, wild canids readily hybridize with one another. This would have made it very difficult for an early domestic dog lineage to diverge from the wolf and to evolve into the morphologically, developmentally, and behaviorally distinct species that we recognize today. Our allopatric model is consistent with two subhypotheses: isolation when tamer scavenger wolves followed humans south and away from hunting populations of wolves or isolation when climate forced humans and tamer scavenger wolves into isolated refugia. 1. Introduction and Background The importance of the domestic dog comes not only from the close relationship that humans share with it today, but also because it is the earliest known domesticate, predating any other plant or animal. This unique position as the first domesticate has inspired researchers to ask about the origins of the dog, and the process of its original domestication. The close relationship between the domestic dog (Canis familiaris) and the wolf (Canis lupus) has been recognized and discussed since at least Roman times [1]. Lamark [2] suggested the wolf as the ancestor to the domestic dog, although this hypothesis was dismissed later by Lyell [3]. Darwin [4] suggested multiple origins of domestic dogs from wild canid ancestors in contrast to Wallace’s contention of a single origin. Lorenz’s [5] assertion that there exist two distinct lineages of domestic dogs, descended from both wolves and jackals, has predominated during much of the last century. He based this dichotomy on physical characteristics including size and muzzle shape. Although dogs can successfully interbreed with both wolves and jackals, the dual origin model has been thoroughly discredited in recent years with new molecular phylogenies of the canids indicating wolf ancestry [6–10]. Lorenz’s [11] depiction of the domestication process has, however, persisted. Lorenz’s scenario is that domestication began with the adoption of a wild wolf pup as a pet for a child. We certainly have many examples of orphaned wild animals being reared by
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