North Americans are fanatical about dogs—there are more pet pooches on this continent than any other. The vast majority of these household pups are descended from dogs brought to the continent by European settlers within the last six centuries. But these animals were not the first dogs to roam North America.
As outlined in a comprehensive study published Thursday in Science, indigenous dogs migrated to North America at least 10,000 years ago, alongside their human companions—the ancestors of Native American peoples. When the European colonization of the Americas began in the 1400s, these original canines, or “PCDs” (precontact dogs) quickly vanished.
"This study demonstrates that the history of humans is mirrored in our domestic animals,” study senior author Greger Larson, director of the Palaeo-BARN at Oxford University, said in a statement. “People in Europe and the Americas were genetically distinct, and so were their dogs. And just as indigenous people in the Americas were displaced by European colonists, the same is true of their dogs."
Larson, along with a large international team of colleagues, shed light on this mysterious population of indigenous canines by sequencing 71 mitochondrial genomes from archeological canine remains, and comparing them to modern dogs.
Some ancient dog skeletons, like those excavated at the Koster Site in Illinois, died roughly 10,000 years ago. These pets were buried by their human companions alongside relatives, suggesting that the modern sentimental bond between dogs and people also existed in these early North American communities.
The genomic analysis of these dogs revealed that they descended from Siberian canine stock, not wild North American wolves, as previously speculated. Though they thrived on the continent, practically none of their DNA is present in modern North American dogs.
“Although greater degrees of PCD ancestry may remain in American dogs that have not yet been sampled, our results suggest that European dogs almost completely replaced native American dog lineages,” according to the study. “This near disappearance of PCDs likely resulted from the arrival of Europeans, which led to shifts in cultural preferences and the persecution of indigenous dogs. Introduced European dogs may also have brought infectious diseases to which PCDs were susceptible.”
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That said, these indigenous dogs did secure one genetic legacy—a sexually transmitted venereal tumor. Originating from American dogs that lived around 8,000 years ago, the cancer was passed on to the European dogs, who still carry it to this day.
"It's quite incredible to think that possibly the only survivor of a lost dog lineage is a tumour that can spread between dogs as an infection," said study co-first author Maire Ní Leathlobhair, a geneticist at the Department of Veterinary Medicine at the University of Cambridge, in a statement. "Although this cancer's DNA has mutated over the years, it is still essentially the DNA of that original founder dog from many thousands of years ago."
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