Around 9,000 years ago, farmers from the Near East, where agriculture first began, loaded up their domesticated sheep and pigs, collected some barley and lentils and began heading into Europe and Asia, spreading the new agrarian lifestyle to new parts of the world. George Dvorsky at Gizmodo reports they brought something else with them, too: their dogs. Over the course of several thousand years, those farm dogs eventually genetically replaced the dogs already living in Europe, according to a new study published in the journal Biology Letters.
The history of the bond between humankind and dogkind is surprisingly long and complex. Brian Handwerk as Smithsonian.com reports that dogs and modern wolves split from a common ancestor between 15,000 to 40,000 years ago. From there, the origin of dogs gets complicated. There is contradictory evidences suggesting dogs were domesticated just once, 20,000 to 40,000 years ago and other evidence showing they were domesticated independently in different geographic locations around the world. Researchers are looking for the ancient remains of dogs that they can genetically analyze to untangle this tale.
However the story shakes out, what we do know is that early farmers in the Near East, including in Iraq, Syria, Lebanon, Jordan, Israel and Egypt, lived with domesticated dogs and Neolithic hunter-gatherers in Europe also had domestic dogs. What we didn’t know is whether those farming groups brought their dogs with them when they set off into the wider world. To find out, researchers examined the remains of 99 sets of dog remains from 37 archaeological sites around Europe and the Near East, stretching from the Mesolithic to the Bronze Age.
Looking the mitochondrial DNA of the dogs, which can be used to track a common ancestor, the researchers found that all the dogs in Europe came from lineage called haplogroup C. But as that farming culture spread across Europe between 9,000 and 6,000 years ago, those C-group dogs were slowly replaced by dogs from haplogroup D, which originated in the Near East, until the C-group genetics more or less vanished.
“We have shown that dogs were an essential element of the Neolithic expansion in Europe. Much like sheep, goats, pigs, cattle and even cultivated plants (wheat, barley, peas, broadbeans and lentils), dogs travelled with farmers from the Near East during their multi-millennial migration across Europe,” say the study’s lead authors Anne Tresset and Morgane Ollivier of The National Center for Scientific Research (CNRS) in France in a statement. “The history of humans and dogs has been intimately linked for more than 15,000 years. It’s yet more evidence of our entwined story.”
It’s also not quite clear why the genetics of the farm dogs were more dominant than the indigenous dogs. It’s possible that they had some adaptations that made them more suited for living among human agrarianists.
“We don’t know yet but it’s a point to investigate,” Ollivier tells Dvorsky. “We would like to target mutations in the nuclear genome that are associated with metabolism, phenotype [i.e. physical attributes], and behavior. We would also like to investigate admixture [interbreeding] between these populations to better understand [potential] points of contact [between Mesolithic and Neolithic dogs].”
The story mirrors the tale of dogs indigenous to the Americas. Meilan Solly at Smithsonian.com reports that researchers also looked at the mitochondrial lineages of dogs that lived in North and South America prior to European contact and compared them to 5,000 modern dogs, finding almost no trace of the indigenous dogs. Researchers believe that the dogs were probably infected by diseases they had no resistance to, decimating their numbers.
Anyone who has lived with a dog should not be surprised that Fertile Crescent farmers brought their puppers with them as they journeyed into the unknown. While the dogs probably served a purpose like guarding livestock, it’s possible they were seen like dogs are today: as part of the family.
“We love our dogs, and we often use them to define ourselves,” study senior author Greger Larson, an archeologist at Oxford, says in the release. “So perhaps it’s not a surprise that hunter-gatherers in Europe had one kind of dog, and farmers from the Near East had a completely different sort.”