4.2 Evolution. As time passes and people become isolated, differences in their accent, language, and other speech habits become greater. The pool of names they use for referring to each other changes as does the rest of their language. It may be argued that innovation with names tends to be more conservative than with other parts of the language. The process of temporal change is called evolution.

Figure 35 relates some of the languages as they have changed with y-axis corresponding roughly to distance back in time. Those languages connected by a line to another language above them are said to evolve from that earlier language. Languages whose names are in red are isolates, i.e., they are not known to be evolved from languages other than earlier versions of themselves.