As different as they may be from each other, all dogs belong to a single species ( Canis familiaris ) and are descended from a common ancestor: the gray wolf ( Canis lupus ). It is generally believed that the domestication of this animal took place in the Ice Age, at least 15,000 years ago. There is a second, more controversial hypothesis, which says that the wolf domestication process began more than 100,000 years ago.
What is not yet known is where the dog turned into a wolf and if it happened in one place or in several. A group of scientists has just published a study in which they conclude that domestic canids would come from, at least, two different populations of wolves.
Researchers have studied the ancient DNA of wolves , including some that have been preserved in permafrost for tens of thousands of years. “Thanks to this project, we have greatly increased the number of sequenced ancient wolf genomes, allowing us to create a detailed picture of wolf ancestry over time, even back to the time of the dog’s origins,” explains Dr. geneticist Anders Bergström, of the Francis Crick Institute in the United Kingdom. “In trying to fit the dog piece into this picture, we found that dogs derive their ancestry from at least two distinct wolf populations: an eastern source that contributed all dogs, and a more western source that contributed some dogs.”
Anders Bergström’s group of researchers included DNA from 32 dogs dating between 100 and 32,000 years ago in the study. They discovered that dogs had diversified 11,000 years ago, so domestication had to be earlier. It is generally accepted that domestication and diversification began sometime between 40,000 and 20,000 years ago, and probably more than once, in different parts of the world.
The new work is based on 72 ancient wolf genomes, 66 of which have been scanned for this analysis, dating back 100,000 years, spanning some 30,000 generations of wolves in Europe, Siberia and North America. These ancient wolf genomes were compared to 68 genomes from modern wolves, ancient and modern dogs, and other canid species, such as coyotes.
Among the exhibits were some famous recent finds, such as the almost perfectly preserved Dogor cub that spent 18,000 years in the Siberian permafrost, and the 32,000-year-old head of a wolf, also from the Siberian permafrost.
What the researchers found from the genomes is that both ancient and modern dogs are more closely related to the ancient wolves of Asia than to the wolves that lived in Europe. This suggests that domestication and diversification may have started in the East rather than the West.
However, there is something strange. The DNA of the earliest dogs in northeastern Europe, Siberia and the Americas is 100% derived from an eastern population of wolves. Early dogs from the Middle East, Africa, and southern Europe have a DNA contribution from wolves related to modern populations of southeastern Eurasia.
All this would support the idea that dogs were domesticated more than once and in different parts of the world. But it could also mean that dogs were first domesticated in the East and later mixed with a population of wild wolves. It is not yet clear which of these situations took place, since none of the genomes in the study match directly, so more information is needed.
The study has allowed scientists to learn more about ancient wolves and their evolution. They have tracked a genetic variant that went from being very rare to almost ubiquitous over about 10,000 years. This mutation affects a gene called IFT88 , which is involved in the development of the bones of the head and jaw, and is still present in almost all dogs and wolves today.
It is not known why the mutation became so common, but it could be due to natural selection and the types of prey available at the time making the changes brought about by the mutation especially beneficial. It is also possible that the gene did something that is unknown and that the mutation provided a benefit that we do not know about.
“This is the first time scientists have directly followed natural selection in a large animal over 100,000 years, watching evolution unfold in real time rather than trying to reconstruct it from current DNA,” said Dr. geneticist and lead author Pontus Skoglund, also of Crick. “We found several cases where the mutations spread throughout the wolf species, which was possible because the species was highly connected across great distances. This connectivity is perhaps one of the reasons wolves managed to survive the Ice Age while many other large carnivores disappeared.
Genome-wide studies that span a long time period, like this one with wolves and dogs, can give very detailed insights into how species move and change over time.
The next phase of research is to further narrow down which wolves were the ancestors of modern dogs. The team is expanding their research to areas of the world that they have not taken into account in this study.
Referencia: Bergström, A. et al. 2022. Grey wolf genomic history reveals a dual ancestry of dogs. Nature. DOI: 10.1038/s41586-022-04824-9
