Cats and Dogs (Elton Gahr's Short Stories)

Julio has lived in hiding his entire life because he is the descendent of a genetic experiment that gave them human levels of intelligence. But Julio has become restless and is convinced that, like his famous grandmother, he needs to go out into the world and change things.

But when he leaves, he discovers a world far different from what he had expected. The genetic experiments that had begun with his grandmother have continued and humans, fearing being left behind they have began to play with their own genetics creating both a wealthy class with huge genetic advantages but groups of poor people with far more unstable genetic changes to keep up.

Uncertain how to help, he is approached by a genetically altered cat who has an idea of how Julio might help.