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THE DOG EVOLVED from the wolf. It was man’s first domesticated animal, accomplished before humankind’s domestication of farm stock.
Details of canine domestication are still controversial. However, part of the puzzle may have been resolved by recent genomic evidence of a Bronze Age dog and DNA comparisons of it with modern breeds worldwide. It’s likely that dogs evolved from two separate wolf populations on either side of the Old World.
Results are given in “Genomic and Archaeological Evidence Suggests a Dual Origin of Domestic Dogs,” by Laurent A.F. Frantz et al, in the June 3, 2016, issue of Science, the weekly magazine of the American Association for the Advancement of Science. The research paper is an international effort: Frantz is at England’s University of Oxford, with colleagues from France, Germany, Greece, Hungary, Ireland, Northern Ireland, Romania, Russia, Sweden, Scotland and the U.S. In the same Science issue, there’s a summary, “Dogs May Have Been Domesticated More Than Once,” by David Grimm.
A key piece to unraveling the puzzle was an inner ear bone from an Irish dog dating to the time of Stonehenge construction, nearly 5000 years ago. The bone was part of the archaeological findings in Newgrange, a football-field-size mound of dirt and stone on the east coast of Ireland.
From this bone, these researchers completed an entire nuclear genome of the dog, the first from such an ancient canine. Then they compared this genomic data with DNA of 605 modern dogs from around the world.
A neighbor-joining tree is a bioinformatics means of comparing DNA or protein sequence data. It uses bootstrap values to assess the confidence of its neighborhood estimates: A value of 100 represents a certainty of closeness; one of 30, say, would be less compelling. The number of the study’s dogs of each breed is shown after the breed.
For instance, the Sarloos shown just above wolves are two modern offspring of captive wolves bred with German Shepherds. This breed was created in 1930 in the Netherlands and, as such, is separated from other dogs in the chart.
A second split of DNA evidence separates modern dogs of East Asia, the Shar Pei and Tibetan Mastiff, for example, from those of Western Eurasia, the Elkhound, Finnish Spitz and Qatar village dog, for example. Based on its genomic evidence, the ancient Newgrange dog resides firmly within this second group.
Researchers used color-coding, red for East Asian, yellow for Western Eurasian, as another graphical means of displaying the DNA splits.
Based on these DNA data, the researchers offer the following hypothesis: “Two genetically differentiated and potentially extinct wolf populations in Eastern and Western Eurasia may have been independently domesticated before the advent of settled agriculture.”
At some point between 6400 and 14,000 years ago, the eastern dogs accompanied their human pals into Western Europe, where they partially replaced an indigenous pre-agricultural dog population.
Though some animals may have undergone domestication only once, the researchers conclude that their combined archaeological and genetic results suggest that “dogs, like pigs, may have been domesticated twice.”
Pigs domesticated more than once? This sounds like another research project for another day. ds
© Dennis Simanaitis, SimanaitisSays.com, 2016