At a time when dogs were still wolves, an unlikely bond formed between them and our human ancestors - sometime before the last Ice Age ended, or at least 15,000 years ago.

In a new comprehensive comparison of ancient dog and human DNA, researchers are gaining new insights on where ancient humans and their "best friends" traveled together, as well as points in their history where they traveled apart.

Despite being among the most common pets and hunting partners for humans, the domestication of dogs still poses a lot of questions for the scientific community. A previous study published in 2016 suggested that canines might have been domesticated twice - one in Asia and another in Europe. However, critics of the study are not convinced with the conclusivility of the data presented.

DNA Sequencing Dogs Back to the Ice Age

To trace the possible start of this human-canine relationship, researchers sequenced ancient DNA from 27 dog specimens. Some of these dogs lived as far back as 11,000 years ago, shortly after the end of the last Ice Age, in Europe, Siberia, and the Near East. In the study published in the journal Science on October 29, researchers propose that after the Ice Age and before any known instances of domestication took place, there were at least five different kinds of dogs - each with their distinct genetic characteristics.

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"Dogs are our oldest and closest animal partner," said Greger Larson, Palaeogenomics and Bio-Archaeology Research Network director at the University of Oxford. He explains that by using the DNA from the ancient dogs, they were able to see the shared history of two species and hoping to understand how this relationship came to be.

Meanwhile, Pontus Skoglund, also an author in the study and the leader at the Crick's Ancient Genomics Laboratory, explains that some differences we now see between different dog breeds can actually be traced back to the Ice Age. "By the end of this period, dogs were already widespread across the northern hemisphere," Skoglund explains.

 

From Ice Age to the Modern Age

In studying ancient genomics, scientists have to extract DNA materials from preserved skeletons of the specimens. The sequence of these DNA materials are analyzed and compared to identify evolutionary divergence that happened over time.

Over the last 10,000 years, the ancient breeds of dogs mixed with each other, leading to the dogs of today. One instance, most European dogs today appear to originate from two very different populations - one related to the dogs in the Near East and the other to Siberian dogs.

RELATED: How Centuries of Domestication Have Changed Dog Breeds 

"If we look back more than four or five thousand years ago, we can see that Europe was a very diverse place when it came to dogs," said Anders Bergstrom, lead author of the study from the Crick Ancient Genomics Laboratory. He noted that genetically speaking, these dogs only come from a narrow subset of the formerly available diversity.

Check out more news and information on Dog Domestication in Science Times.