Long before anyone discovered DNA, chromosomes, or genes, humans had figured out something important about the world around us. When we turned from hunting and gathering our food to growing and raising it, we realized that we could breed plants and animals to bring out desirable traits. Wild grasses became wheat under human cultivation; we domesticated and bred cows, pigs, and sheep to produce food, leather, and wool. And we also noted similarities between parents and offspring without knowing what causes these similarities. The concept of heredity preceded the science of genetics, but it is genetics that explains why all living species carry inherited traits and qualities. This timeline lists some of the key advances in thinking about heredity and genetics.