Mendel’s scientific fame rests on the pea-breeding experiments that he carried out in the years 1856 to 1864 (Fig. 16.2), in which he demonstrated the basic principles of transmission genetics. As we will see in Chapter 18, most genetic variation in populations is due to multiple genes interacting with one another and with the environment, while traits due to single genes, such as those that Mendel studied, tend to be rare. Nevertheless, Mendel’s experiments were so simple and presented with such clarity that they still serve as examples of the scientific method at its best (Chapter 1).