DNA extracted from the bodies of preserved ancient wolves has shown researchers the origin of humanity’s best bud, the domestic dog. Reporting their findings in the journal Nature today, their huge analysis shows that all modern dogs have a dual ancestry that can be traced to at least two populations of ancient wolves.

Despite our close relationship with canines, scientists are still not totally certain how dogs became domesticated. The current consensus says dogs were first domesticated from a now-extinct gray wolf population during the Neolithic period somewhere between 29,000 and 14,000 years ago, but many chapters of the story are missing. 

To help illuminate this history, a huge team of scientists led by the Francis Crick Institute analyzed 72 ancient wolf genomes, spanning the last 100,000 years, from across Eurasia and North America. 

This included DNA samples from labs across the world, including genetic material picked up from the physical remains of ancient Ice Age wolves that had been near-perfectly preserved in permafrost. Of all these ancient “mummified” wolves, the most impressive of which is the head of a Siberian wolf (pictured below) that lived 32,000 years ago. 

Another stunning specimen in the study is a beautiful preserved 18,000-year-old male wolf pup named “Dogor,” which means "Friend" in the Yakut language spoken in the area of Siberia where it was discovered. 

By looking at the 72 genomes, they found that almost 100 percent of the ancestry of early dogs in Siberia, the Americas, East Asia, and Europe can be directly linked to an eastern Eurasian-related species of wolf. 

Meanwhile, early dogs in the Near East and Africa developed up to half of their ancestry from the eastern Eurasian-related species and the remaining half from another population related to modern southwest Eurasian wolves. This may have occurred as the result of independent domestication in the Near East and Africa or due to dogs canoodling with local wolves.

Overall, dogs are more closely related to ancient wolves from eastern Eurasia than to those from western Eurasia, hinting that domestication may have occurred more prominently in the east.

“Through this project we have greatly increased the number of sequenced ancient wolf genomes, allowing us to create a detailed picture of wolf ancestry over time, including around the time of dog origins,” Anders Bergström, co-first study author and post-doctoral researcher in the Ancient Genomics lab at the Crick, said in a statement. 

“By trying to place the dog piece into this picture, we found 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."

The location of eastern Eurasia conveniently ties up with a study from last year that indicated dogs were domesticated in eastern stretches of Siberia approximately 23,000 years ago. However, the discovery of a dual ancestry suggests the story is slightly more complex than many imagined. 

For this latest research, it’s also clear that a gene variant known as IFT88 suddenly became extremely common in both wolves and dogs across the globe between 40,000 to 30,000 years ago. Once a rare variant, IFT88 is still found in all wolves and dogs today and continues to dictate the development of bones in the skull and jaw. The ubiquity of this variant, the researchers say, indicates that the global wolf population was highly connected over large distances in prehistoric times, which may have helped to give them the edge during the harsh times of the Ice Age.

"This connectivity is perhaps a reason why wolves managed to survive the Ice Age while many other large carnivores vanished,” added Pontus Skoglund, senior author and group leader of the Ancient Genomics lab at the Crick.

The origin of dogs is still hazy, but by tracking the evolution of the animals across 100,000 years, this new study provides one of the most comprehensive looks yet into their surprisingly murky history.