The dog was born from the wolf - that's clear today. But where and when our ancestors began the domestication of Canis lupus, there are still conflicting hypotheses. According to one theory, this domestication first took place in Southeast Asia - DNA comparisons of the Y chromosome of dogs supported this assumption. Two years later, however, an analysis of mitochondrial DNA - a genome transmitted only through the maternal line - suggested a European origin of the domestic dog. This would also fit the fact that the oldest dog fossils were found on this continent. In 2016, another analysis caused confusion: comparing the mitochondrial DNA of 59 dog fossils revealed that the dog may have been domesticated twice independently of each other - once in East Asia and once in Europe. At the same time, the researchers found evidence that at the transition to the Neolithic so many Asian dogs came to Europe that they almost completely suppressed the native gene variants. Proof of this was a 5, 000-year-old dog fossil from Newgrange, Ireland.
Continuity instead of population exchange
To provide more clarity, Laura Botigue of Stony Brook University, New York, and her colleagues have once again conducted a comprehensive gene comparison of fossil and contemporary dogs. They analyzed both the complete nuclear DNA and the mitochondrial DNA of two dog fossils found in Germany. These originate from the time before 7000 and 4700 years ago, and thus exactly from the period in which the European dog population is said to have been almost replaced by the influx of Asian conspecifics. They compared this genome with the Newgrange dog, a 14, 700-year-old dog jaw from Bonn and 5, 649 modern canine and wolf varieties from all over Asia, North Africa and Europe.
The result: Both the Paleolithic dog and the three Neolithic animals are genetically very similar to each other and also to today's dogs. "This is against the hypothesis of a large exchange of European populations with dogs from East Asia, " say Botigue and her colleagues. "Instead, we find strong evidence of genetic continuity from the Paleolithic to the Neolithic, and even in moderation, to the present day." Most of today's dogs, therefore, are based on ancestors who lived in Europe more than ten thousand years ago. "So, if there was a major upheaval in the population, it must have happened long before the Neolithic, " the researchers said. According to their gene data, the genetic separation of European and East Asian dog lines is already 17, 500 to 23, 900 years back.
"As complex as the history of their people"
However, Botigue and her colleagues also found traces of Asian influences in the genome of the youngest fossil dog and some of today's breeds. "We suspect that this gene component comes from the dogs that came from the East to Europe in the late Neolithic and early Bronze Age with the steppe nomads, " the researchers said. At that time, the immigration of the Jamnaja and other members of steppe cultures brought new cultural impulses to Europe, which, among other things, created the band-ceramic culture. However, the apparently brought dogs were not so numerous and dominant that they completely repressed the European tribal lines, as the scientists emphasize. display
The gene data also help to narrow the time of the first domestication of the dog closer. "Our results provide benchmarks between 20, 000 and 40, 000 years ago today, " said Botique and her colleagues. However, where this crucial step from wolf to dog took place - whether in the Middle East, in Europe or anywhere in Asia, unfortunately their study can not conclusively clarify. "Our genetic data are neither old enough nor do they have a sufficiently broad geographic distribution to resolve this debate, " say the researchers. "Our findings, however, underline that the history of domesticated dogs is at least as complex as that of the people they once lived with."
- Laura Botigue (Stony Brook University, New York) et al., Nature Communications, doi: 10.1038 / ncomms16082