It is said that miacids were the first primitive carnivores. They lived in the lower territory about 52 million years ago. Scientists believe that the dawn wolf was the first canid. Some believe canids originated in North America then spread to Asia and South America. Other believe that a small type of wolf crossed into Siberia from Alaska where they developed into the larger present-day wolf. Then they migrated into North America where it populated what is now Canada and the United States. Ancestors of wolves began to develop in the Paleocene Age about 60 million years ago. In one ancestor, Tomarctus , the fifth toe on the hing leg became vestigial and is seen today by dew claws on both wolves and dogs. The first grey wolf, Canis lupus, probably appeared in Eurasia in the early Pleistocene period about 1 million years ago. About 750,00 years ago they migrated to North America. The Dire wolf, Canis dirus, evolved earlier and the two co-existed in North America for about 400,00 years. As prey became extinct around 16,000 years ago, the Dire wolf gradually became extinct as well. Around 7,000 years ago, the grey wolf became the prime canine predator in North America.