Early Mayan Architects: Lowland Mayan civilizations began to construct dramatic pyramids beginning about 900 BCE. The cultural origins of these civilizations have been uncertain, particularly the connection to earlier Olmec cultures along the Gulf of Mexico. Inomata et al. (p. 467 ; see the cover; see the News story by Pringle ) describe excavations and extensive radiocarbon dating at the early Mayan city of Ceibal in Guatamala. The site shows incipient plaza and pyramid construction beginning before those seen in the lowlands or Olmec areas, suggesting a broader cultural exchange through to the Pacific Coast as Mayan cultures evolved.

Significance: The results of our research at the lowland Maya site of Ceibal add to the growing archaeological understanding that the transition to sedentism did not necessarily occur simultaneously across different social groups within a region and that monumental constructions did not always postdate fully established sedentism. Whereas sedentary and mobile populations are, in many cases, interpreted to have maintained separate communities, our study suggests that groups with different levels of mobility gathered and collaborated for constructions and public ceremonies. These data indicate that the development of sedentism was a complex process involving interactions among diverse groups, and that collaborative construction projects and communal gatherings played a critical role in this social transformation by facilitating social integration among different groups.

Significance: Tracing political change through refined chronologies is a critical step for the study of social dynamics. Whereas coarse chronologies can give an impression of gradual change, better temporal control may reveal multiple episodes of rapid disruption comprised in that span. Precise dating through radiocarbon determinations and ceramic studies is particularly important for the study of the Preclassic collapse, which lacks calendrical dates recorded in texts. The high-precision chronology of Ceibal revealed waves of decline over the course of the Preclassic and Classic collapses in a temporal resolution that was not possible before. The emerging understanding of similarities and differences in the two cases of collapse provides an important basis for evaluating the vulnerability and resilience of Maya political systems.

The successful analysis of LiDAR data for archaeological research requires an evaluation of effects of different vegetation types and the use of adequate visualization techniques for the identification of archaeological features. The Ceibal-Petexbatun Archaeological Project conducted a LiDAR survey of an area of 20 × 20 km around the Maya site of Ceibal, Guatemala, which comprises diverse vegetation classes, including rainforest, secondary vegetation, agricultural fields, and pastures. We developed a classification of vegetation through object-based image analysis (OBIA), primarily using LiDAR-derived datasets, and evaluated various visualization techniques of LiDAR data. We then compared probable archaeological features identified in the LiDAR data with the archaeological map produced by Harvard University in the 1960s and conducted ground-truthing in sample areas. This study demonstrates the effectiveness of the OBIA approach to vegetation classification in archaeological applications, and suggests that the Red Relief Image Map (RRIM) aids the efficient identification of subtle archaeological features. LiDAR functioned reasonably well for the thick rainforest in this high precipitation region, but the densest parts of foliage appear to create patches with no or few ground points, which make the identification of small structures problematic.

Although the application of LiDAR has made significant contributions to archaeology, LiDAR only provides a synchronic view of the current topography. An important challenge for researchers is to extract diachronic information over typically extensive LiDAR-surveyed areas in an efficient manner. By applying an architectural chronology obtained from intensive excavations at the site center and by complementing it with surface collection and test excavations in peripheral zones, we analyze LiDAR data over an area of 470 km² to trace social changes through time in the Ceibal region, Guatemala, of the Maya lowlands. We refine estimates of structure counts and populations by applying commission and omission error rates calculated from the results of ground-truthing. Although the results of our study need to be tested and refined with additional research in the future, they provide an initial understanding of social processes over a wide area. Ceibal appears to have served as the only ceremonial complex in the region during the transition to sedentism at the beginning of the Middle Preclassic period (c. 1000 BC). As a more sedentary way of life was accepted during the late part of the Middle Preclassic period and the initial Late Preclassic period (600–300 BC), more ceremonial assemblages were constructed outside the Ceibal center, possibly symbolizing the local groups’ claim to surrounding agricultural lands. From the middle Late Preclassic to the initial Early Classic period (300 BC-AD 300), a significant number of pyramidal complexes were probably built. Their high concentration in the Ceibal center probably reflects increasing political centralization. After a demographic decline during the rest of the Early Classic period, the population in the Ceibal region reached the highest level during the Late and Terminal Classic periods, when dynastic rule was well established (AD 600–950).