London: Domestic dogs have “very good evolutionary reasons to enjoy chewing a bone,” say researchers.
According to them, social living drove dogs to evolve the “tools” for chewing bones.
Living and hunting in groups coincided with a shift in dogs’ diets, scientists analysing their ancestry found.
The animals adopted pack-living about eight million years ago in order to hunt larger prey, according to the team from the National University of Colombia.
The resulting evolution of their jaws gradually turned the ancestors of our domestic pets into “hypercarnivores”.
Dr Joao Munoz-Doran from the university and his colleagues have created a canine “family tree”, piecing together the relationships between each of the more than 300 dog species.
This map of canine evolution showed approximately when each species evolved, and it allowed the scientists to understand how an animal’s lifestyle and habitat was connected to the shape of its skull.
“We compared species that have very different diets. So we classified them as carnivores, hypercarnivores and omnivores [animals that eat meat and vegetation],” Dr Munoz-Doran explained.
Examining the hypercarnivores, which include the domestic dog’s closest relative, the grey wolf, showed that the animals’ strong jaw muscles and enlarged canine teeth started to develop when the animals first began hunting in groups.
“We found a common evolutionary history for these traits. Eight million years ago was when [less forested, more] open habitats were spreading through Asia, Europe and North America. And when there are open habitats, the big prey group together. So there will be more eyes watching for a predator,” Dr Munoz-Doran said.
The only way that dogs roaming the open plains could snatch very large prey from a herd was to work together.
“And after many generations of this grouping behaviour, there are new selective pressures on their [skull shape],” said the researcher.
This pressure meant that animals with larger teeth and stronger jaws were more likely to succeed in hunting, and to survive to pass on their large-toothed, strong-jawed genes to the next generation.
“They developed strength in their muscles - especially the muscles that close their mouth. And bones that are more resistant to bending, so they could support the mechanical strains of biting the prey,” said Dr Munoz-Doran.
“Over time, they became adapted to be ‘hypercarnivorous,’ the researcher stated.
“They have the tools to do that,” he told BBC Nature, “and they want to use their tools.”
Dr Munoz-Doran presented the findings from his study at the First Joint Congress for Evolutionary Biology in Ottawa, Canada.