Eugenics rests on some basic ideas. The first is that, in genetics, what is true of animals is also true of man. The characteristics of animals are passed on from one generation to the next in heredity, including mental characteristics. For example, the behaviour and mental characteristics of different breeds of dog differ, and all modern breeds are greatly changed from wolves. The breeding and genetics of farm animals show that if the parents of the next generation are chosen, then that affects what offspring are born. 