Dogs are humans’ oldest companions, DNA shows
“Dog is a man’s best friend” is the common saying. For thousands of years, dogs have been our companions for hunting, friendship, war, and many more. Dogs have managed to keep up with us humans and have now become ‘a mans best friend’. This could largely be down to a dog and their diet, which is why dog owners are quite particular when it comes to purchasing food for their companions. It’s become a regular activity for pet owners to get online and view recommended foods, such as pet food exposed, and others before choosing the right food for them! In modern times this has been largely reduced down to friendship and some may say our modern dogs lead a spoilt life of luxury, whether that is getting them decorative collars or procuring an orthopedic bed for dogs to help keep their joints healthy. There has been evidence that dogs have been kept as pets as far back as Ancient Egypt, with the finding of jeweled dog collars. But how far back exactly can the roots of our companionship with dogs be traced?
Science Magazine reports that evolutionary biologist Greger Larson of the University of Oxford, paleogenomicist Pontus Skoglund of the Francis Crick Institute, and their colleagues analyzed the genomes of more than 2,000 dogs who lived in Europe, Siberia, and the Near East as early as 11,000 years ago.
“This is a very interesting research,” notes the archaeogeneticist Wolfgang Haak at the Max Planck Institute for Human History Sciences. “We’re finally starting to see how the dog story and the human story match up.”
One of the main enigmas of domestication were dogs. Scientists still have not figured out when or where they appeared, much less how or why they emerged, after decades of studies.
A 2016 study concluded that dogs may have been domesticated twice, once in Asia and once in Europe or the Near East, but critics said there wasn’t enough evidence to be sure.
A few years later, researchers reported signs of dogs in the Americas as early as 10,000 years ago, yet those canines appear to have vanished without a genetic trace. Other studies have found evidence of ancient dogs in Siberia and elsewhere, but scientists don’t know how they got there or how they’re related.
To fill in some of the blanks, two big names in dog and human genetics teamed up: Greger Larson, an evolutionary biologist at the University of Oxford, and Pontus Skoglund, a paleogenomicist at the Francis Crick Institute. Larsen, Skoglund, and colleagues sifted through more than 2000 sets of ancient dog remain dating back nearly 11,000 years from Europe, Siberia, and the Near East. In the process, they added 27 ancient dog genomes to the five already on record. They then compared those with the genomes of 17 humans living in the same places and times as the dogs.
The dog DNA alone revealed some surprises. As early as 11,000 years ago, there were already five distinct dog lineages; these gave rise to canines in the Near East, northern Europe, Siberia, New Guinea, and the Americas, the team reports today in Science. Because dogs had already diversified so much by that time, “domestication had to occur long before then,” Skoglund says. That fits with archaeological evidence: The oldest definitive dog remains come from Germany about 15,000 to 16,000 years ago.
Remarkably, pieces of these ancient lineages are still present in today’s pooches. Chihuahuas can trace some of their ancestries to early American dogs, for example, whereas Huskies sport genetic signatures of ancient Siberian dogs, the team found. “If you see a bunch of different dogs in a dog park,” Skoglund says, “they may all have different ancestries that trace all the way back 11,000 years” (see figure below).
When the researchers compared their dog DNA with modern and ancient wolf DNA, they got another surprise. Most domesticated animals pick up genetic material from their wild relatives-even after domestication-because the two species often live in close proximity and can still mate (think pigs and wild boars). But dogs show no such “gene flow” from wolves. Instead, the wolves gained new DNA from the dogs-a one-way street.
Larson chalks this up to the intimate relationship between dogs and humans. If your pig or chicken becomes a bit wilder thanks to an infusion of feral DNA, it doesn’t matter, because you’re going to eat them anyway, he explains. But dogs that go native make bad guards, hunting companions, and friends. “If you’re a dog and you have a bit of wolf in you, that’s terrible,” Larson says. People will “get rid of the dog.”
The wolf-dog analysis also suggests dogs evolved only once, from a now-extinct wolf population. Still, Larson, who led the 2016 study on multiple domestication events, says more data are needed to seal the deal.
Then the scientists brought humans into the mix. They selected human DNA samples from the same places and eras for which they had ancient canine DNA and traced the genetic history of each. “It’s like you have an ancient text in two different languages, and you’re looking to see how both languages have changed over time,” Skoglund says.
In many places, the team found a strong overlap between human and dog genomes. For example, farmers and their pups in Sweden about 5,000 years ago both trace their ancestry to the Near East. This suggests early farmers took their dogs with them as agriculture spread throughout the continent. “Writ large, as humans moved, they moved with their dogs,” Larson says.
But sometimes the stories didn’t match up. Farmers in Germany about 7000 years ago also came from the Near East and also lived with dogs. But those animals seem more similar to hunter-gatherer pups, which came from Siberia and Europe.
That suggests many early migrants adopted local dogs that were better adapted to their new environment, Haak says. The benefits were many, adds Peter Savolainen, a geneticist at the Royal Institute of Technology and an expert on dog origins. “They were cute. You could use them. You could even eat them.”
Savolainen calls the study “very thorough,” and adds it’s “fantastic” that the researchers were able to bring together so many data. But he has long argued that dogs arose in Southeast Asia and says the work is incomplete without samples from that corner of the globe. “Without those, you could be missing an important part of the picture.”
For now, Larson says his team is analyzing “a ton” of wolf and dog genomes. He and his colleagues have also begun to look at ancient skull shape and genetic markers that could give clues to what early dogs looked like. Whatever he finds, he’s counting on being surprised. “We have to expect the unexpected,” he says, “because that’s all ancient DNA ever gives us.”