Kaminaljuyú has been an important focus of archaeological research since the 1930s, and the chronologies of various sites of the Southern Maya Area are linked directly to that of Kaminaljuyú. The implications of the currently prevalent chronology of Kaminaljuyú are that various social and political institutions developed significantly earlier in the Southern Maya Area than in the Maya Lowlands during the Preclassic period. Our evaluations of new and existing radiocarbon dates through the application ofBayesian statistics, as well as ceramic cross-dating, indicate that the Middle and Late Preclassic portions of the Kaminaljuyú sequence need to be shifted forward in time by roughly 300 years. Our chronological revisions have the following important implications: (1) many centers in the Southern Maya Area suffered political disruptions around 400 B.C., roughly at the same time as La Venta and the centers in the Grijalva region of Chiapas; and (2) highly centralized polities with divine rulers and their depictions on stelae developed roughly contemporaneously in the Southern Maya Area and in the Maya Lowlands after 100 B.C.

The probable E-Group assemblage was a primary focus of our investigation at the lowland Maya center of Ceibal. Tunnel excavation into Structure A-20 (the western structure of this complex) demonstrated that the Ceibal residents built the earliest version (Structure Ajaw) by carving natural marl around 950b.c.The earliest version of the eastern platform (Structure Xa'an) was also made at the same time out of the natural marl layer. Through a series of renovations, the western structure grew into a pyramidal shape, and later versions of the eastern platform were moved further to the east. In addition, excavations revealed numerous caches, many with greenstone axes, along the center line of the E-Group assemblage. These results show that a formal ceremonial complex was established at the beginning of occupation at Ceibal, and its construction and public events held there played an important role in the creation of a new community.