Why/how did black bears learn to climb trees?

To escape predators. A black bear cub instinctively knows how to climb before walking and will immediately climb a tree at the first hint of danger. read more

The second bear was able to climb the tree alnost to the first crotch, but fell and died on impact. The 3rd bear made it all the way up, and was able to procreate. It's genetic, fittest and most adaptable survive, climbing was a good gene to pass along. read more

All bears have the ability to climb trees. -- Many books will say that brown bears (grizzlys) can't climb trees. While they can climb if they have branches, the largest ones are too heavy to climb using just their claws, which are not as curved as a black bear claw is. read more

Black bears can, sure. However, the smaller bears of other species can climb trees to escape greater bears. Grizzly bears can't do it once they get older considering that they're method too tremendous. Polar bears are the same approach, and there are no trees within the artic. I believe there are a few asiatic bears that can climb trees. read more