Origin of dog breeds revealed

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A toy xoloitzcuintlel, a dog breed that likely descended from dogs that crossed the Bering Land Bridge with the ancestors of Native Americans.
Credit: Penny Inan

The New World Dog, an ancient canine subspecies assumed to have died out centuries ago, has been discovered alive and well in many a pedigree kennel.

At least, parts of its genome have, thanks to the first-ever evolutionary tree for dogs, compiled from genetic sequences gathered from 161 modern breeds and published in the journal Cell Reports.

The gene map, created by a team of scientists led by Heidi Parker of the US National Institutes of Health, was created to tease out the complex relationship between breed development and human migration.

Among a number of surprising findings, the sequencing revealed significant differences between the genomes of certain American dogs – notably the Peruvian Hairless and the Xoloitzcuintle – and the bulk of familiar breeds developed in Europe and Asia.

Archaeologists long ago established that a type of dog, dubbed New World Dog, arrived in the Americas via the Bering Strait thousands of years ago with the ancestors of Native Americans. However, it was assumed that the breed eventually died out.

“We’ve been looking for some kind of signature of the New World Dog, and these dogs have New World Dogs hidden in their genome,” says Parker.

The new study is not fine-grained enough to sort precisely between New World and European-derived genes in, say, the Peruvian Hairless; doing so remains a target for future research.

The dog family tree also shows – perhaps not surprisingly – that another cohort of dogs, comprising pointers and gun dogs such as Golden Retrievers, share a very tight genetic grouping. These breeds, largely developed in Victorian England and optimised for use in gun-centred hunting, today display little genetic variation.

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The evolutionary tree showing the relationship between dog breeds.
Credit: NIH Dog Genome Project

In contrast, genomes from dogs bred for a specific purpose – herding – harbour considerable differences, indicating the animals were developed independently across a wide range of geographic locations and time periods.

“When we were looking at herding breeds, we saw much more diversity,” Parker says. “There was a particular group of herding breeds that seemed to come out of the United Kingdom, a particular group that came out of northern Europe, and a different group that came out of southern Europe.”

“This shows herding is not a recent thing. People were using dogs as workers thousands of years ago, not just hundreds of years ago.”

The scientists regard the canine family tree very much as a work in progress. About half of the world’s recognised breeds have still to be sampled.

The phylogeny, as it grows, will likely be useful for research in both canine and human health, because dogs and people share a number of diseases and neurological conditions.

Says study co-author Elaine Ostrander: “Using all this data, you can follow the migration of disease alleles and predict where they are likely to pop up next, and that’s just so empowering for our field because a dog is such a great model for many human diseases.”

“Every time there’s a disease gene found in dogs it turns out to be important in people too.”

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