What happened to the Pre-contact dogs?

Remains of a pre-contact dog from 10,000 years ago. (Smithsonian Magazine)

Before the arrival of Europeans in the 15th century, there were dogs in the Americas that had been here for at least 10,000 years. They are called pre-contact dogs and are related to the arctic dogs that accompanied the human migration across the Bering Straights at the end of the last ice age. However, those dogs suddenly disappeared after Europeans and their dogs arrived. And no one knows why. One possibility is that the pre-contact dogs did not have immunity to the diseases brought by the European dogs. But it's a mystery . . .