Based on published lexicostatistical dates, two intervals in the prehistory of southern Mesoamerica stand out as fertile periods in terms of the generation of new languages: the Terminal Preclassic/early Early Classic Periods, and the Early Postclassic Period. After comparing archaeological evidence with language distributions within the subregions of southern Mesoamerica during the first of these periods, we conclude that the cultural processes during both periods had the same potential for producing rapid rates of linguistic divergences. Just as rapid proliferation of linguistic divisions was symptomatic of the well-known collapse of Late Classic Maya civilization, so it can be taken as a sign of a collapse of Terminal Preclassic civilization. Both collapses were characterized by severe population reductions, site abandonments, an increasing balkanization in material culture, and disruption of interregional communication networks, conditions that were contributory to the kind of linguistic isolation that allows language divergences. Unlike in the Terminal Classic collapse episode, small refuge zones persisted in the Early Classic Period that served as sources of an evolving classicism; these refuge zones were exceptions, however, not the rule. Although the collapse of each site had its own proximate cause, we suggest that the enormous geographical range covered by these Early Classic Period site failures points to a single ultimate cause affecting the area as a whole, such as the onset of a prolonged and devastating climatic change.
