Among the other findings, Dr. Larson said he found it particularly intriguing that once dogs had become domesticated, and even while they were sometimes breeding with wolves, no new wolf DNA entered their genomes.
By contrast, pigs, for example, were brought to Europe by farmers from Anatolia. But the genes of those first domesticated pigs have been completely lost, replaced by the genes of wild European boars, even though the pigs stayed domesticated animals.
While dogs do interbreed, no new wolf genes survive over the years. One possibility, Dr. Larson said, is that “wolfiness” just doesn’t fit with an animal as close to people as a dog. Pigs can be a little wild but “if you’re a dog and you’ve got a little bit of wolf in you, that’s not a good thing and those things get knocked on the head very quickly or run away or disappear but they don’t get integrated into the dog population.”
Dr. Skoglund said another intriguing and unexplained finding from the genome data was how fast dogs spread around the globe, and diversified, so that by 11,000 years ago, not only were there five distinct lineages, but some fossil DNA also showed that those lineages had begun to recombine.
“How did that happen?” he said. “In ancient humans, we don’t really know of any human expansion that would have facilitated this, on the order of 15 to 30,000 years ago.”
In the past 11,000 years, he said, the dog genomes showed the evidence similar to that in human genomes of Anatolian farmers moving into Europe. But then there was the sudden loss of diversity in dogs starting around 4,000 years ago.
Also migrations from the steppes changed human genomes in Europe, but had almost no effect on dog genomes. Conversely, migrations from the steppes eastward left an imprint on dog genomic history, but not on humans.