Our archaeological investigations at Ceibal, a lowland Maya site located in the Pasión region, documented that a formal ceremonial complex was built around 950 B.C. at the onset of the Middle Preclassic period, when ceramics began to be used in the Maya lowlands. Our refined chronology allowed us to trace the subsequent social changes in a resolution that had not been possible before. Many residents of Ceibal appear to have remained relatively mobile during the following centuries, living in ephemeral post-in-ground structures and frequently changing their residential localities. In other parts of the Pasión region, there may have existed more mobile populations who maintained the traditional lifestyle of the preceramic period. Although the emerging elite of Ceibal began to live in a substantial residential complex by 700 B.C., advanced sedentism with durable residences rebuilt in the same locations and burials placed under house floors was not adopted in most residential areas until 500 B.C., and did not become common until 300 B.C. or the Late Preclassic period. During the Middle Preclassic period, substantial formal ceremonial complexes appear to have been built only at a small number of important communities in the Maya lowlands, and groups with different levels of sedentism probably gathered for their constructions and for public rituals held in them. These collaborative activities likely played a central role in socially integrating diverse groups with different lifestyles and, eventually, in developing fully established sedentary communities.Mesoamerican archaeology | sedentism | Maya | public ceremony | subsistence R ecent archaeological investigations have shown that the development of agriculture and sedentism was more diverse than the simple model of agriculture leading to sedentism and then to social complexity. In Europe, for example, the farming lifestyle that originated in the Near East spread in complex ways, involving the coexistence of farmers and foragers in relatively small areas and differential adoptions of Neolithic cultural elements in different regions (1-3). Studies of early monuments, such as Göbekli Tepe in Turkey, Watson Brake in Louisiana, and Caral and earlier mounds in the Andes, show that large constructions involving significant collective labor could be built by preceramic people who were still foragers or were at the early stage of farming adaptation (4-7). These emerging understandings lead to important questions about how sedentary and mobile populations interacted and how their relations affected the process of social change. To address these questions, researchers need fine-grained chronological information and a broad spatial coverage, which are not easy to obtain in many cases. A uniquely rich dataset obtained from the Maya site of Ceibal (or Seibal) suggests the possibility that groups with different levels of mobility gathered and collaborated for constructions and public ceremonies, which contrasts with the common assumption that sedentary and mobile groups maintained...

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In eastern Hokkaido, 60 to 80 kilometers above a subducting oceanic plate, tidal mudflats changed into freshwater forests during the first decades after a 17th-century tsunami. The mudflats gradually rose by a meter, as judged from fossil diatom assemblages. Both the tsunami and the ensuing uplift exceeded any in the region's 200 years of written history, and both resulted from a shallow plate-boundary earthquake of unusually large size along the Kuril subduction zone. This earthquake probably induced more creep farther down the plate boundary than did any of the region's historical events.