Genetic Study Reveals Deep Link, Common History of Dogs and Humans

(CN) — Scientists announced Thursday they have now fully sequenced entire genomes of ancient dogs, yielding new comprehensive insight into the controversial early human relationships with dogs going back 11,000 years.

In a study published in the journal Science, Anders Bergström from The Francis Crick Institute in Great Britain and his colleagues analyzed ancient dog genomes from what is now Eurasia, and found 27 new whole-genome sequences, some as old as 11,000 years. 

They compared their findings with genomes from both ancient and modern dogs and found fascinating data highlighting the complex history of their friendship with humans.

"The dog is the oldest domesticated animal and has a very long relationship with humans. Therefore, understanding the history of dogs teaches us not just about their history, but also about our history," Bergström said in an accompanying video. 

Humans and dogs have a remarkably unbreakable bond. From service dogs to herding dogs to four-legged family members, they are undeniably an important part of everyday life. But little is known about when this relationship started or how it became what we know today and scientists struggle to agree on a time and place of this occurrence. 

While genetic evidence shows coexistence everywhere from southern China to Europe, archaeological evidence suggests domestication anywhere from 20,000 to 40,000 years ago.

The origin of modern dogs has been generally accepted as descendant from wolves, but as to how they morphed from ferocious hunters into our furry companions is the subject of many debates. 

Some experts believe it began from wolves scavenging food left behind by ancient humans, while others believe early hunter-gatherers worked to tame and breed them. Despite the confusion, dogs are accepted as the first domesticated animal and the only large carnivore to be tamed to this extent.

It’s unfortunately not an easy timeline to unravel and scientists remained puzzled. It is made further difficult due to the lack of available whole dog and whole wolf genomes to analyze for clues.

They found that all dogs are distinctly descended from modern wolves, and there has been little gene flow from wolves to dogs since their domestication. However, there has been a good amount of dog to wolf gene flow, indicating possible interbreeding.

Although it may forever be a mystery as to how exactly the partnership began, Bergström and his team have discovered that much of this genetic activity must have taken place in the Paleolithic era. During this time, they believe at least five different dog lineages had begun varying and distributing around the world.

During the Paleolithic, experts believe that dogs were then kept as pets, not just merely to serve a purpose such as hunting or guarding, but out of emotional attachment. In 2018, scientists found the oldest known instance of humans being buried together with their dog, a puppy who died at 19 weeks from canine distemper. 

In this instance, not only was the dog buried like a family member, with decorations surrounding the body, but it was likely taken care of for five to six weeks before its passing. Though they may have begun as a partnership based on their usefulness, they eventually became bonded on a deeper level.

After determining this, they compared data from their ancient dogs to that of ancient humans from around the same time, and found hints suggesting that they might have migrated alongside each other. On the other hand, they also found evidence that did not align with that hypothesis.

A similar study conducted in 2016 led by L.A. Frantz showed significant differences between dogs from Western Eurasia and East Asia. They conducted genetic analyses of 59 ancient dogs and one complete genome of a 5,000 year old Neolithic dog, and found such a great amount of splits between the two that they suspect ancient dogs to have been domesticated twice — once in Asia and once again in Europe.

Another study in 2018 led by M. Ni Leathhlobhair found that the first dogs who came to North America with humans were domesticated from ancient Siberian sled dogs, not wolves. When Europeans came to North America, the origin of the dogs already there was all but lost. 

This research team analyzed mitochondrial and nuclear genomes from North American and Siberian dogs from approximately 9,000 years ago when dogs first came to the continent. They then confirmed that instead of deriving from North American wolves, they likely originated in Siberia before settling down in America.

Despite the conflicting results and the ongoing disagreements, this research is evident of the long history dogs share with humans.

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