Modern Genetics Scientists now have a good enough understanding of genetics to know why evolution is limited. They know that physical characteristics are controlled by genes. The theory of evolution is based on the false notion that new genes can spontaneously form. For a bacteria to evolve into a pig, it requires many steps in which new genes appear that give the intermediate critter new characteristics. At least one reptile has to grow breasts and become the first mammal, which would have to evolve into a pig.
Mutations can t accidentally produce all the tissues and hormones necessary for functioning nipples.
So, it is just as impossible for a pig to evolve from a lower life form as it is for a pig to evolve wings and fly. If creatures have common ancestors, and have diversified because of small random changes in DNA, then the DNA of these related species should be very similar. For example, if you examine the DNA of a cocker spaniel and a collie, you would expect them to have very similar DNA because they are variations in the dog species. Creationists and evolutionists both agree that all the modern breeds of dog evolved from wild dogs. This is a classic example of microevolution.