Ancient Wolf DNA has been revealed. Dogs may have joined humans more than once

Ancient Wolf DNA has been revealed. Dogs may have joined humans more than once ...

The beloved pooch who is snorting on your couch or eating a snoot under your arm at dinner time came from a much wilder background. Under the guidance of domestication, dogs evolved to become the varied fuzzbutts that fill our homes and hearts with joy today.

The exact time and how this interaction occurred is a mystery. Now ancient DNA, including that of wolves preserved in permafrost for tens of thousands of years, is unraveling how wild wolves became some of our best non-human companions.

"Through this project, we have significantly increased the number of ancient wolf genomes, allowing us to reconstruct a detailed picture of wolf ancestry over time, including around the time of dog origins," said geneticist Anders Bergstrom of The Francis Crick Institute in the United Kingdom.

"We discovered that dogs derive ancestry from at least two separate wolf populations, an eastern source that contributed to all dogs, and a separate more westerly source that contributed to some dogs," says the author.

All domestic dogs today, from the teensiest chihuahua to the mightiest mastiff, belong to the same species, Canis familiaris. All are descended from wolf ancestry shared with today's gray wolf (Canis lupus). However, the timeline is unclear, and is hotly debated. Some scientists speculate that the process began more than 100,000 years ago.

Bergstrom and his colleagues examined the DNA of 32 dogs dating back between 100 and 32,000 years ago. They concluded that dogs had diversified by 11,000 years ago, so it had to have happened before then.

The new analysis is based on 72 ancient wolf genomes, 66 of which have been newly scanned for this analysis, that date back 100,000 years, covering roughly 30,000 generations of wolves across Europe, Siberia, and North America.

These were compared against 68 genomes from ancient and modern dogs, as well as from other canid animals, such as coyotes.

Among the samples were some well-known recent discoveries, such as the almost perfectly preserved cub Dogor, which had been locked for 18,000 years in the Siberian permafrost, and the 32,000-year-old head of a wolf, which was also collected by the Siberian permafrost.

'Dogor,' an 18,000-year-old wolf puppy from Yakutia, has been described as a "sergey Fedorov."

Both the ancient and the modern dogs were more closely related to ancient wolves in Asia than those that lived in Europe, suggesting that domestication and diversification may have begun in the East rather than the West.

Nonetheless, something was strange. Early dogs in Northeastern Europe, Siberia, and the Americas receive 100 percent of their DNA from an eastern population of wolves. Early dogs from the Middle East, Africa, and the South of Europe receive a DNA contribution from wolves similar to modern populations in Southeast Eurasia.

This might support previous theories that dogs were domesticated more than once in different parts of the world. However, it may also mean that dogs were domesticated first in the East and then mixed with a population of wild wolves.

It's unclear which of these events might have taken place; none of the genomes studied are a direct match, therefore more information is required.

The project also allowed the group to research ancient wolves, and their evolution. In particular, they traced a gene variation that went from being very rare to almost ubiquitous over a period of 10,000 years. This mutation affects a gene called IFT88, which is involved in the development of head and jaw bones and is still present in almost every dog and wolf today.

The team doesn't know why this mutation became so common, but it may be due to natural selection; perhaps the types of prey available made the changes wrought by the mutation particularly beneficial. It's also possible that the gene does something we've never known about, and the mutation provided an unknown benefit.

"This is the first time that scientists have directly monitored natural selection in a large animal over a time-scale of 100,000 years, seeing evolution play out in real time rather than trying to reconstruct it from DNA today," said geneticist and senior author Pontus Skoglund, also of Crick.

"We found several instances where mutations spread to the whole wolf species, which was probably due to the fact that the species was highly connected over long distances. This connectivity is perhaps the reason why wolves survived the Ice Age while many other large carnivores disappeared."

These findings suggest that such temporally broad whole-genome studies might provide much more detailed information about how species evolve and change over time.

The next phase of the research is to try to narrow down which wolves were the descendants of modern dogs. The team is expanding their investigation into other parts of the world that are not covered by this analysis.

The work has been published in Nature.

You may also like: