The first complete genome sequence of an ancient dog suggests that dogs were independently domesticated twice, in two different regions.

Researchers have debated whether domestic dogs originated in Asia or Europe about 15,000 to 12,500 years ago. Laurent Frantz of the University of Oxford, UK, and his team sequenced the mitochondrial DNA of 59 ancient dogs and the complete genome of a 4,800-year-old dog from Ireland. They also analysed DNA from hundreds of modern dogs and wolves, and found that populations of Western European and East Asian canines diverged several millennia after the first appearance of the animals.

Owing to a lack of archaeological evidence of ancient dogs between these regions, the authors propose that the animals were domesticated separately in Western Europe and East Asia from distinct wolf populations.

Science 352, 1228–1231 (2016)

For more on this research, see go.nature.com/1pzqqvr