What is the main conflict in City by Clifford D. Simak?

City, by Clifford D. Simak is about the possible evolution of life on Earth, the role of violence in our society and the effects of colonizing other planets. There are eight tales told from the perspective of dogs who take over humanity's place in the world. The tales are passed down by the Dogs through the generations to the point where humans are considered mythical creatures. Eventually, other Earth creatures evolve and the world is in danger of domination by ants.