The principal aim of archaeology is the reconstruction of history. How archaeology plays this part is usually not very clearly thought out, although Rouse has made a good attempt. In the reconstruction of history, we deal with human social units. These social units are composed of animals which reproduce their kind, inherit biological traits, mutate, evolve, take in food, give off waste products, react to their environment, die, and, in so doing, behave fundamentally like other animals. Moreover, the animals have a language, form part of a social pattern, have ideas of the supernatural and what we can call religion, and can manufacture certain objects in a certain way. These animals are grouped into families composed of mother, father, and children. They are further grouped into extended families, sibs, or clans made up of real or fancied relatives. A number of extended families under the leadership of one man or a group of men forms a political group.