There has been considerable debate over when exactly dogs became ‘mans best friend’. Some evidence has suggested that the relationship began when humans were still hunter-gatherers, during the paleolithic era. Others hold that it was during the Neolithic era, after humans began to create more permanent settlements and take up farming.

At one point consensus seemed to be pointing to the Neolithic era. Recently, however, studies emerged of fossils found in Russia and Belgium of dog domestication in the late Paleolithic era.

In a new study, biologists Abby Grace Drake and Michael Coquerelle used a 3D scanning method to measure the Russian and Belgian canid skulls. The scans where then compared to modern and ancient canid skulls from Europe and North America. They found that the skulls which were labeled as late Paleolithic were in fact the skulls of wolves.

“Scientists have been eager to put a collar on the earliest domesticated dog. Unfortunately their analyses weren’t sensitive enough to accurately determine the identity of these fossils. The difference between a German shepherd skull and a wolf skull is subtle – you need to measure it in 3D to reliably tell which is which – and the same is true for these fossils,” said Drake in a statement.

The study includes interactive 3D images which help to show the differences between wolf and dog skulls.

“The difference between a wolf and a dog is largely about the angle of the orbits: in dogs the eyes are oriented forward, and a pronounced angle, called the stop, exists between the forehead and the muzzle. We could tell that the Paleolithic fossils do not have this feature and are clearly wolves,” said Coquerelle.

The researchers hold to the hypothesis proposed by Ray and Lorna Coppinger. It states that permanent settlements were necessary for the domestication of dogs.

“Dog domestication occurred during the Neolithic when wolves began to scavenge near human settlements… The establishment of permanent settlements in the Neolithic would have created an environment where sustained selection for tameness could exist for many generations thus setting the stage for dog domestication,” say the researchers.

The work of Drake and Coquerelle, published in the journal Scientific Reports, seems to agree with recent research on the history of dogs in North America as well.

That research, led by Kelsey Witt and Ripan Malhi of the University of Illinois showed that humans first arrived in North America about 15,000 years ago but dogs did not follow until later. According to their work, published in the Journal of Human Evolution, showed that dogs made their first appearance about 10,000 years ago.

If dog domestication had begun 30,000 years ago, it would seem unusual for the first North Americans to have arrived without dogs 15,000 years after that.

To date Drake has used 3D digitizers at the Smithsonian Institution to measure the skulls of 677 dogs representing 106 different breeds.

She notes that while domesticated dogs first appeared 15 thousand years ago, it is only in the last few hundred years that we began to name breeds and set breed standards.

“We have seen an explosion in dog diversity. People are inherently interested in dogs and we have influenced their evolution. They are such a part of our lives. Knowing when domestication of dogs took place in the course of human history is important to our story and to theirs,” said Drake