Population density increases whenever a population grows more rapidly, or shrinks more slowly, than the area it inhabits; areal contraction therefore accelerates density increase. This consideration not only reinforces Dickson's (1987) suggestion that circumscription by anthropogenic environmental destruction contributed to the rise of some early states; it also implies that rate of density increase should be distinguished, as a motor of sociocultural evolution, from density itself. In light of this distinction the rise of the state in southwestern Iran, and occasional instances of high density among nonstate societies, are not necessarily inconsistent with population-pressure theories.