The feud between cats and dogs stretches as far back as ancient times. It was found that dogs prospered in North America, with over 30 species inhabiting the continent around 22 million years ago. But then the felines came. Researchers from the University of Gothenburg say that there are now only nine species of the dog family that reside in North America and all the other ones are gone, all thanks to the cat.

Researchers examined over 2,000 fossils to come to their conclusions, which was a surprise. Lead author of the study, Daniele Silvestro at the Department of Biological and Environmental Sciences, said in a press release:

"We usually expect climate changes to play an overwhelming role in the evolution of biodiversity. Instead, competition among different carnivore species proved to be even more important for canids.”

There seemed to be a direct cause and effect from the cat's arrival to North America from Asia. As competition became fierce between the native canines and newly introduced felines, researchers noticed the dogs of North America increased body size, becoming larger predators — some of them exceeded 66 pounds. While the ancient dogs dwindled and were forced to adapt, the cats of the time suffered little in their transition, indicating that they were more efficient predators.

It just goes to show you that little about cats have changed since 22 million years ago — they're still ruthless killing machines that wreak havoc on their environments.

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Photo Credit: China Photos / Stringer/ Getty