This paper examines the archaeological and biological evidence for shifts in human subsistence strategies during the transition from hunting and foraging to maize agriculture as posited in the Río Balsas, or lowland origin of maize, model and the Tehuacán, or highland origin of maize, model. These are two different interpretations of the genetic evidence for the ancestry of maize, the archaeological evidence for plant exploitation, and the ecological evidence for paleoenvironments and climate change in the two regions. In contrast to Panama, where there is good evidence for progressive intensification of human forest disturbance by 10,000 B.P., horticultural forest clearing by 8000 B.P., and slash-and-burn agriculture by 6000 B.P., the evidence for Mesoamerica, where maize agriculture originated, fits a different picture of biocultural evolution. The lowland regions of Mexico, Guatemala, Belize, and probably Honduras, were apparently undisturbed, semi-evergreen forests around 10,000 B.P. New findings from experimental maize genetics, combined with the comprehensive archaeological picture from Tehucán, Oaxaca, Tamaulipas, and the Valley of Mexico, support a highland Mesoamerican origin of maize.

Incised-engraved pottery and clays from the Malpaso Valley region of northwest Mexico are chemically characterized to investigate the nature of residential organization of the capital settlement, La Quemada, during the Epiclassic period, ca. A.D. 600-900. Scanning-electron microprobe analysis of 115 pottery and 10 clay samples from settlements in the valley, and from middens associated with the civic-ceremonial core of La Quemada and flanking residential terraces, identifies locations of pottery production and indicates patterns of pottery circulation. The distribution of pottery at La Quemada, manufactured in specific outlying settlements, suggests that the social composition of the polity was reproduced in microcosm at the site, and that activities in civic-ceremonial zones involved a greater degree of separation among social groups than those in flanking residential areas.

This investigation uses a bioarchaeological approach to test the existence of pre-Inka colonists within the Andean coastal valleys of Moquegua, Peru, and Azapa, Chile, as predicted by Murra's (1972) classic model of verticality. The archaeological evidence and biodistance results obtained using genetically controlled dental traits from 859 skeletal and mummified remains indicate that the Late Intermediate period (A.D. 1100-1476) coastal Chiribaya people of the Moquegua Valley, Peru, likely represent descendants of altiplano populations that migrated to the coastal region following the disintegration of the Middle Horizon (A.D. 750-1100) Tiwanaku colony located in the middle Moquegua Valley. In the neighboring Azapa Valley, Chile, genetic change among prehistoric populations was due to gradual in situ microevolution of local populations rather than colonization by altiplano people. Coastal populations of the Azapa Valley maintained biocultural continuity with the Archaic period Chinchorro coastal population. It is concluded that Murra's model of direct verticality should be evaluated using both biological and archaeological data on a case-by-case basis.

Round structures are considered a rarity in Maya architecture. Four late Middle Preclassic period (650-300 B.C.) round structures excavated at the Maya site of Cahal Pech demonstrate that this was a common architectural form for the Preclassic Maya of the upper Belize River Valley. These open platforms are described, and compared to similar forms in the Belize Valley and elsewhere. An interpretation of their significance is offered that uses information from artifacts, burials, and ethnohistory as well as analogy with round structures in other parts of the world. We suggest that these small round platforms were used for performance related to their role as burial or ancestor shrines.