Dog DNA study maps breeds across the world – Science News (blog)

Mapping the relationships between different dog breeds is rough (get it?), but ateam of scientists at the National Institutes of Health did just that using the DNA of 1,346 dogs from 161 breeds. Their analysis, which appears April 25 in Cell Reports, offers a lot to chew on.

Here are five key findings from the work:

As human lifestyles shifted from hunting and gathering to herding to agriculture and finally urbanization, humans bred dogs (Canis familiaris) accordingly.Then over the last 200 years, more and more breeds emerged within those categories. Humans crossed breeds to create hybrids based on appearance and temperament, and those hybrids eventually became new breeds.

Genetic backtracking indicates that, for example, mixing between bulldogs and terriers traces back to Ireland between 1860 and 1870. That timeframe and location coincides with historical records indicating a dog-fighting fad thats linked with crossing breeds to make better fighters.

While herderdog breeds showed a lot of genetic diversity, they fallinto two general groups from the rural United Kingdom and the Mediterranean on the breed family tree. When humans switched from hunting to farming, herding breeds may have emerged independently in different areas. Geography could also explain why these two groups use different herding tactics.

A genetic legacy of America's early canine inhabitants lives on in some of today's breeds. Dogs trekked to the Americas from Asia with peoplemore than 10,000 years ago, but when European groups started to colonize the Americas, they brought European dog breeds with them. Past studies suggestthat outside breeds largely replaced New World dogs, but the new dataset shows New World dog DNA actually does persist in a few modern New World breeds, such as Chihuahuas.

European mastiffs and Mediterranean sheepdogs dont share recent changes in their DNA, meaning their size traits arose separately and for different reasons. While both breed groups specialize in guarding things, mastiffs use their size to intimidate humans, while sheepdogs use their size to overpower animal predators. Larger size may have been one of the first traits that human breeders zeroed in on, the researchers suspect.

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