Cladogram of American black bear
The black bear has a storied past that started 20 million years ago when the dog-like ancestors evolved and added triangular premolars to its teeth. The Ursavus was a genus split into 2 genera ( the ursavus and the protursus). The Ursavus genera is very dog-like and became extinct 7-8 million years ago when the northern hemisphere became much more drier. The Protursus genera was also very dog-like but made progress to the present-day bear by becoming larger and adding square molars. This genus was much more carnivorous than the Ursavus genera and very omnivorous. This genus is also very much extinct. The red panda is the only living representative. The next 2 species are together because it is controversial on which one was actually the ancestor of the American black bear. Ursus minimus was a very small bear that existed from 5.3 million years ago to 1.8 million years ago. This bear was much more plant-based than meat. They even had an adaptation that changed the length of their intestines in order to cope with their omnivorous diet. Their bodies became bigger to deal with the Ice Age/ colder temperatures. Ursus abustrus is widely accepted as being the first bear to be in North America according to fossil records. Many believe it was this bear that crossed the Bering Land Bridge (was between Russia and Alaska; now known as the Bering Strait) to North America from Asia. Over time, it eventually lead to the origination of the American black bear.