There are already bacteria that eat (some) plastics. Plastics, unlike rocks, are basically just hydrocarbons, not that different from sugars and starches and qu

There are already bacteria that eat (some) plastics. Plastics, unlike rocks, are basically just hydrocarbons, not that different from sugars and starches and quite digestible if you have the right enzymes. Whether or not animals could evolve to do it is another story, though.