Like the Australian dingo, it is argued that the New Guinea singing dog is a true wild dog, in that it is considered wild and not feral, even when raised in captivity and treated as a companion animal. Also like the Australian dingo, there is controversy around the classification — is it a primitive breed of domestic dog that found an ecological niche and returned to being wild, or a unique subspecies of wolf that evolved without human intervention, or somewhere in between? Currently it falls in line as canis lupus dingo along with the Australian dingo and the Thai dog (the finer points and history of this taxonomic classification is actually a whole story in and of itself). And finally, just as with the Australian dingo, the New Guinea singing dog in its pure form may be either very rare or possibly even extinct in the wild, as none have been spotted in Papua New Guinea since the 1970s. Those existing today are bred in captivity as part of a conservation effort to preserve the breed, which genetically seems to have stemmed from dogs brought with human travelers from China (the oldest remains of a New Guinea singing dog is a tooth dated to about 5,500 years ago). The dogs living in the lowland areas were more likely to reside with humans, and those were the first dogs to disappear as they interbred with dogs brought by Europeans. The pure members of the breed that persisted, and those which became part of the early captive breeding programs, were mainly those living in the highlands and less likely to live near human settlements.