A new study unlocks secrets of dog domestication

There’s a good reason why so many people call dogs man’s best friend. Humans domesticated dogs more than 11,000 years ago, before we even invented farming. Today, dogs are popular as pets and “work” alongside humans in countless everyday jobs.

Yet despite our original connection to dogs, scientists do not fully understand the process by which modern dogs were domesticated and split off from their ancestral borders to wolves.

Now, a recent study published in the journal Nature has expanded our understanding of canine evolution. Among other things, the researchers, led by scientists from London’s Francis Crick Institute, found that modern domesticated dogs are overall more closely related to wolf ancestors from eastern Eurasia (i.e. modern Asia) than from western Eurasia (modern Europe). Remember that as recently as 10,000 years ago, wolves were among the most common predators on Earth, and wolves and their close canid relatives occupied every continent except Antarctica and Australia.

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“Our study makes important advances in addressing the question of the origins of dogs,” Anders Bergstrom, one of the report’s co-authors and a scientist at Crick’s Ancient Genomics Laboratory, told Salon via email. “By studying ancient wolves living at the time of dog domestication, we found that overall, dogs are more closely related to ancient wolves in Asia than to ancient wolves in Europe, suggesting a domestication process somewhere to the east.”

However, this does not mean that all modern domesticated dogs descended entirely from this East Eurasian domestication process.

“We find that some dogs, particularly in Africa and the Middle East, have an additional genetic contribution from a second wolf population related to wolves in the west,” Bergstrom noted.

Bergstrom concluded, “Thus, there appear to have been at least two separate wolf populations, leading to a dual lineage in dogs today.”

This makes dogs oddly similar to modern humans. The human genome contains about 2.5 percent Neanderthal DNA, meaning we are the modern hybrid of two hominids; Interestingly, however, not all humans have much of this DNA, and some human populations have almost none. Likewise, dogs appear to be the modern hybrid of two different “source wolves” of slightly different genetic make-up and from different regions – although like us, this second wolf contribution is not ubiquitous in dogs.

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To reach these conclusions, the scientists analyzed 72 ancient wolf genomes accumulated in Eurasia and North America, spanning the last 100,000 years of history. They then compared this data to existing information on the genetics of different dog breeds around the world.

“None of the old wolves included in our study closely match either source population, suggesting that the sources may have lived in parts of the world that we have not previously sampled,” the scientists mused.

“We found that wolf populations were strongly associated throughout the late Pleistocene, with levels of differentiation an order of magnitude lower than today,” the scientists write. “This population connectivity allowed us to detect natural selection across time series, including the rapid fixation of mutations in the gene IFT88 40,000-30,000 years ago.”

In addition, the scientists’ research helped them discover that modern dogs in Africa and the Middle East have at least half their ancestry descended from an entirely different wolf population related to modern southwest Eurasian wolves. This suggests “either an independent domestication process or an admixture of native wolves.”

“There are two scenarios that could explain the dual lineage we found in dogs,” Bergstrom explained. “First, there could have been two independent domestication processes, with the two populations then coming together and merging into one. Second, there could only have been a domestication process followed by gene flow from local wild wolves into dogs after the dogs arrived in B. the Middle East. We cannot currently distinguish these two scenarios, but hopefully future studies in early dogs will be able to distinguish them.

Bergstrom explained what types of future research are needed.

“None of the old wolves included in our study exactly match either source population, suggesting that the sources may have lived in parts of the world that we have not sampled yet,” the scientist mused. “Although our study shows that there would have been at least two source populations, the search for these sources continues. Hopefully future studies can more accurately narrow down where dogs come from by sampling older wolf genomes from other parts of the world.”

In recent years, scientists have made remarkable strides in learning more about the origins of domesticated dogs, and much of this work can be attributed to advances in genetic engineering. For example, a 2020 study published in the journal Science found that modern sled dogs are closely related to an ancient canine lineage dating back at least 9,500 years.

“Taken together, these results indicate significant long-distance travel and resource transport where dog sledding would have been very beneficial – if not necessary,” the authors write in their study. After reviewing the specific details of their analysis of a 9,500-year-old dog, they added that “our results imply that the combination of these dogs with the innovation of sled technology has facilitated human existence since the earliest Arctic Holocene.”

Read more salon articles about dogs: A new study unlocks secrets of dog domestication

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