All of the dogs in the study descended from the same common ancestor, but this original dog population split into at least five branches as they grew in different directions. As groups of people split up, migrated, and met other groups, they brought their dogs with them. The dog’s DNA suggests that the history of their population mostly reflects the history of human populations.
“Understanding the history of dogs tells us not only their history, but our history as well,” Bergstrom of the Francis Crick Institute said in a statement.
We still don’t know who let the dogs out
We still don’t know exactly when or where the domestication of dogs first took place; it already had a rather complex history 11,000 years ago. But it seems like it only happened once. Ancient genomes suggest that dogs all share a common ancestor, which they do not share with modern wolves. According to Bergstrom and his colleagues, this likely means that the dogs are all descended from a group of wolves, and that group is now extinct.
Modern gray wolves don’t appear to be very closely related to any of the ancient or modern dogs in the study. This suggests that since domestication set them apart, wolves haven’t contributed much to the DNA of dog lines.
The oldest dog in the study lived with Mesolithic hunter-gatherers around 10,900 years ago in what is now Sweden. His DNA suggests that most of his ancestors came from an eastern branch of the dog family tree – the branch that gave birth to Siberian dogs, native North American dogs, and even New Guinea song dogs. and Australian dingoes.
But part of the dog’s ancestry also came from the branch that had followed humans to the Levant and Southwest Asia. These DNA fragments were probably picked up as keepsakes when the dog’s ancestors encountered dogs from another population. In other words, 11,000 years ago, dogs had time to become a species, divide into distinct populations as they went their separate ways, and then come together and exchange DNA. .
Have dogs, will travel
Bergstrom and his colleagues wanted to know how the history of the dog population aligned with that of humans. They compared the data from their ancient dogs to what ancient human DNA tells us about how groups of people have migrated and interacted over the past 12,000 years. Unsurprisingly, the timing of splits, mergers and moves mostly matched. This suggests that when groups of people migrated, they took their dogs with them, and dogs experienced much the same as humans when they encountered new neighbors.
Ancient human DNA tells us that the earliest farmers of what is now Turkey moved north and west to Europe around 8,000 years ago, and it only took a few centuries for them ‘they completely replace the hunter-gatherer populations that were already there.
“It is not known how these movements came about – whether through disease, or violence, or some kind of biased intermarriage process – but what genetics unambiguously shows is that these changes happened, and in a much more dramatic way than archaeologists thought, ”Reich said in 2018.
And the DNA of ancient European dogs tells us that very similar things were happening between the dogs of the Neolithic newcomers and those (like the 11,000-year-old Swedish dog mentioned above) that were already there. In general, dogs found in archaeological sites in northern and western Europe have more eastern ancestry and less Levantine ancestry than dogs found in southern and eastern Europe – and vice versa.
Some dogs were kept on a very long leash
The stories of dogs and humans match, at least in broad outline. But Bergstrom and his colleagues found a few points where the dog story seemed “decoupled” from ours. These differences are likely the result of illness, trade, preferences for particular types of dogs, or people moving to a new place without taking the dogs (which sounds awful, honestly). These “decoupled” population stories can tell us how dogs fit into ancient human societies.
A few thousand years after the Neolithic takeover of Europe, another group of people swept west from Central Asia. They probably brought dogs like the 3,800-year-old animal recovered from an archaeological site in the Russian Steppes.
But while Steppe breeders added their DNA to the mix that makes up modern European populations, their dogs didn’t seem to mix much with local dogs. Meanwhile, in China, the reverse has happened. The pastoralists of the steppes developed eastwards, but modern people in East Asia do not carry much of their DNA. However, modern East Asian dogs derive much of their ancestry from dogs like the 3,800-year-old Srubnaya dog.
“Maybe there is sometimes an element of chance in these processes as well, so if we could replay the human history tape multiple times, the outcome for the dogs might not always be the same,” Bergstrom told Ars.
Old dogs and new genomes
Part of the reason the early years of dog domestication are so fuzzy (not sorry) is that the ancient dog’s DNA was quite scarce. Until the recent study, scientists had only published six prehistoric genomes of dogs and wolves. In case you keep the score, we had sequenced more Neanderthal genomes than prehistoric dog genomes – until now, that is.
“Ancient DNA is still a young field, and for most animals there haven’t been a lot of whole genome studies yet,” Bergstrom told Ars. For him and his colleagues to add 27 ancient dog genomes to this list, it took an international effort on the part of archaeologists and museum curators. Collaborators found ancient dog remains in museum and university collections and on lists of materials excavated from archaeological sites.
Older dog genomes, along with additional archaeological evidence on how dogs fit into ancient cultures and economies, could help us understand the origin of dogs and parts of our shared history, Bergstrom says. that don’t seem to line up.
Perhaps one day we will even learn the answer to the most pressing question of all: “Who is a good dog?” ”
Science, 2020 DOI: 10.1126 / science.aba9572 (About DOIs).