Dogs have lived with humans longer than any other animal, parasites excluded. We have changed them and they have changed us, and the sequencing of genomes from 27 ancient dogs tells us about the journeys human and canine teams have made together. Among the findings is that since dogs became domesticated, they have passed far more genes to wolves than have come back the other way.

The timing and location of canine domestication remain much debated, along with the question of whether this pivotal event occurred once or twice. A large collaboration led by Dr Anders Bergström of the Frances Crick Institute has provided the opportunity to learn much more by sequencing the genomes of dogs that lived up to 10,900 years ago. The specimens were scattered from modern-day Ireland to Israel and eastern Siberia, and represent a major expansion; only six dogs and wolves of similar age had been sequenced before this study.

All five major dog lineages existed at the start of the Holocene era 11,000 years ago, the team report in Science. No doubt many canine companions have sought a bit of rough with wolves since then, but the paper reports that “persistent gene flow into dogs has been so limited as to be undetectable at the current resolution of the data.”

Dogs, therefore, “derive from a single ancient, now-extinct wolf population, or possibly multiple closely related wolf populations,” well prior to the ending of the last glacial period and have evolved largely isolated from their nearest relatives.

The reverse isn't true, however, with almost all wolf populations, revealing the presence of gene variations that developed in dogs after the two originally split.

For all this time, the story of dogs is also our own, and Bergström and co-authors find this is the same on a more fine-grained scale. Clustering of canine genetics, with rare exceptions, match those already known in human populations suggesting that as ethnic groups migrated and intermingled, their companions usually did the same.

Yet sometimes similar canine genetics are found in association with very distinct human populations. Stranger still, East Asian dogs in the study had more in common with those in Europe than in the Middle East. The same was true for human populations at the time; the curious part is the human associations are thought to be the consequence of a divergence more than 45,000 years ago, long before dogs were domesticated.

“Dog population dynamics may have mimicked earlier processes in humans,” the paper notes, but how this happened is hard to explain. For all they learned, the authors were unable to shed light on the question of where the first domestication occurred.