12-million-year-old fossil Shows 'Bone-Crushing' Omnivorous Dogs in Ancient N. America

Studying the bones and jaws of an ancient bone crusher shows that dogs earlier were omnivores, not pure meat-eaters.

The canids were part of the Borophaginae, which lived in North America almost 10 million to 30 million years ago. They became extinct when they were not able to cope up with competition posed by ancestors of modern coyotes, wolves, and foxes.

Earlier, it was believed that Cynarctus wangi's diet was composed wholly of meat, mainly due to its powerful jaw. But deeper analysis revealed that the bone crusher earlier behaved like hyenas.

Insects and plants comprised about two-thirds of the animal's diet just like that of a mini-bear, said  Steven Jasinski of the University of Pennsylvania.

Many studies about the arguments relate to their anatomy, behavior, and diet. One study enabled scientists to explain that dogs are not completely carnivorous because their molars have flat surfaces that have been created to crush bones and grind fibrous plants.

Another school of thought says that modern day dogs do not have flat molar surfaces but huge and sharp teeth created for "shredding, ripping, shearing, and grabbing meat."

Dogs of today grew from carnivorous wolves about 15,000 years ago, which makes them carnivorous. The genetic make-up helped to form their teeth, jaws, gastrointestinal systems and also shaped their behavior.

Dogs also indicate omnivorous qualities, with the ability to digest almost all the carbohydrates in their diet. Their genes are important to metabolise fat and digest starch.Their anatomy is adapted for consuming meat.

Their high concentration of acids in their large stomachs can enable them to break down the proteins in their diet. Evolutionary history shows that they could also survive on vegetables and non-meat leftovers provided by humans.

President of Maybeck Animal Hospital and veterinarian Roger Welton supports the ingestion of healthy vegetables like broccoli, carrots, green beans, celery and spinach by dogs.

"It is also a good idea to integrate complex carbohydrate sources, such as brown rice and sweet potato, as well as some canine safe fruits like cantaloupe, apples, and pears," Welton wrote in his blog.