A team, led by the Royal Belgian Institute of Natural Sciences, claims that the brains of the paleolithic dogs were also removed after their death which could indicate a human's attempt to release the animals' spirits.
This is because the dog skulls show evidence that humans perforated them in order to remove the brains, and as better meat was available, it's unlikely that the brains served as food, the team says.
Mietje Germonpré, who led the team, said many northern indigenous peoples believed that the head contains the spirit or soul. "Some of these peoples made a hole in the braincase of the killed animal so that the spirit might be released," she added.
And, in the case of the third dog with a mammoth bone in its mouth, the palaeontologists believe that the bone may have been inserted in the animal's mouth by a human after it died, signifying a ritual burial, the 'Daily Mail' reported.
Germonpré said the mammoth bone could signify "that the dog was 'fed' to accompany the soul of the dead person on its journey'.
Another team member, Prof Rob Losey at the University of Alberta, said that the study shows that the dog domestication occurred much earlier than previously thought.
He said: "The distinctive treatment given some of the remains also is compelling, and this indicates to me that a special connection had developed between people and some canids quite early on -- long prior to any good evidence for dogs being buried."
The 'Journal of Archaeological Science', which has published the findings, reports the skulls discovered clearly showed signs of domestication as they're significantly shorter than those of fossil or modern wolves, have shorter snouts, and wider braincases and palates than wolves possess.
The dogs were described as large, with an estimated body weight of just over five stone and shoulder height at least 24 inches, resembling a larger and heavier Siberian husky.
The palaeontologists believe the animals were used for hauling meat, bones and tusks from mammoths and firewood.
The dogs are thought to have lived on a diet of mammoth tusks and meat, died when they were between four and eight years old, and suffered from numerous broken teeth during their lifetimes.
