Throughout recorded human history, the dog has been a loyal ally, while the wolf is a distrusted creature or even an enemy. There are few places in the world where these roles of wolf and dogs are more visible than in Greenland. Here the sled dog has been paramount for the success of Inuit cultures, and by contrast, the wolf is a competitor for resources and in folklore – a monster. However, contradicting their opposing relationship to humans the sled dogs and the wolves might have much in common in terms of bloodlines. Since the first European exploration of Greenland and the nearby Canadian Arctic, widespread admixture between sled dogs and wild wolves has been reported and today wolf blood in sled dogs is widely assumed. That this have never been genetically confirmed, shows how little actually is known about Greenland wolves and dogs, as all fundamental aspects of their evolution is completely unexplored by genomics. In addition, the last hundred years have brought great change to Greenland, where dog numbers have decreased due to alternative lifestyles of Greenlanders, warmer winters with less snow to sled on have given less use of dogs and introduction of snowmobiles give alternative means of transport. Further, canine distemper epidemics have wiped-out local dog populations, leading to dogs being imported from other areas. Put together these changes have almost certainly affected diversity and structure of sled dogs in Greenland. For the wolves in Greenland the last century has been devastating, with the 1930’s culminating in their extermination, meaning the potential loss of a distinct but uninvestigated wolf type. Since the 1970’s wolves have been returning to Greenland but the population context of these wolves is also uninvestigated. Therefore this PhD generates genome data of 113 (73 >1x) canids of mostly wolves and dogs, to explore and document the origin and genomic history of indigenous Greenland dogs and wolves. During data exploration, several findings were made, including many novel results in surprising parts of the data, overall making 6 structured datasets of focus. 1) When focusing on modern wolf population structure we find a distinct Polar wolf cluster, presently existing on Ellesmere Island and Greenland. 2) When focusing on the canid out groups, originally intended to be used in the investigation of Greenland wolves and dogs, we find massive gene flow among several members of the genus canis, testifying a complex speciation of most lineages including the ancestors of all wolves and dogs. 3) When focusing on an ancient Siberian dog genome we find that the sled dog genomic lineage was established in Siberia before 9.500 years ago and that these dogs were already used for sledging back then. 4) When focusing on ancient Siberian wolf genomes, we find that these belong to a extinct group of wolves, that carry coyote admixture, suggesting they originated in the Americas. Further, towards their extinction, these wolves receive gene flow from domestic before 18.000 years ago, testifying to an ancient origin and diversification of dogs. 5) When focusing on modern and historic dogs from Greenland, we find several historic populations, but when comparing these we find a large reduction in diversity and population replacements. Further, most surprisingly, we find no wolf gene flow in any sled dogs. 6) When focusing on Greenland wolves we find that the original exterminated wolves and the wolves that have re-colonised, are the same distinct Polar wolf population endemic to Axel Heibergs Land, Ellesmere Island and Greenland. The Polar wolves have very little gene flow with other wolf types and only a single historic individual have receive dog gene flow, testifying about strong genetic isolation of these wolves, likely as a consequence strong selection for unique local adaptations. Together these findings first of all bring extensive knowledge about the evolutionary history of Greenland dogs and wolves, but also extraordinary insight to dog domestication and the very complex nature of canid speciation and the origin of all wolves and dogs. With particular relevance to Greenland, it is concluded that the Polar wolves that inhabit Greenland have been there for centuries, and that this specific wolf type is genetically distinct from any other wolf in the Arctic. Regarding Greenland dogs, these results can be used to encourage conservation efforts of local dogs, by testifying how genetic diversity in Greenland dogs distinguishes them amongst the world’s dogs, most importantly by having their major pedigree to over 9.500 years old sled dog ancestors.