Andean scholars have long debated the nature of the relationship between two Middle Horizon (ca. A. D. 750-1000) Andean states; many assumed Tiwanaku dominated Wari and preceded Wari in time. Recent research at the Wari administrative center of Cerro Baúl in the only known region occupied by both states (the Moquegua Valley of southern Peru) indicates that Tiwanaku may not predate Wari in Moquegua and that, contrary to previous assertions, both states occupied the valley for the last three centuries of the Middle Horizon. In support of this position, I review recent excavations at Cerro Baúl. Then I present eight new 14C dates and summarize the evidence for two major construction episodes at Cerro Baúl. I interpret the local Wari construction chronology based on the 12 14C dates now available from excavation contexts and I suggest that the new data, in comparison with 24 published 14C dates from other Wari centers, support a later date for Middle Horizon 1B Wari expansion than previously postulated.

An increasing number of publications supports the autonomous development of dense sedentary populations with advanced social organization throughout Amazonia in spite of abundant archaeological, ethnographic, physical, and biological evidence for environmental limitations to sustainable intensive exploitation of the varzea as well as the terra firme. Three articles in recent issues of Latin American Antiquity dispute the validity of the data collected during three decades of survey by participants of the Programa Nacional de Pesquisas Arqueológicas na Bacia Amazônica, which indicate that surviving indigenous groups perpetuate settlement and social behavior adopted at least 2,000 years ago, when the widespread use of pottery makes it detectable. Correction of the misunderstandings contributing to this "revisionist" assessment is essential because uncritical acceptance of the conclusions not only conflicts with ecological and archaeological evidence, but provides support for the unconstrained deforestation of the region.

Meggers's commentary does not effectively address our critique of the seriational argument that large Amazonian sites always represent occupational palimpsests. As a consequence, more general claims about the limitations that Amazonian environments posed for prehistoric cultural development based on this same argument remain unconvincing and fail to account for relevant variability in the archaeological record.

The origin of maize has been a topic of interest to both biologists and archaeologists. During the twentieth century, the view point that maize is a domesticated form of teosinte received convincing support from biological data and is now broadly accepted among biologists familiar with the issues and data. There is no support of any kind for an alternative view that maize is a hybrid of the grasses Zea diploperennis and Tripsacum.

MacNeish and Eubanks (2000) reject the AMS radiocarbon dates on maize from the Tehuacán Valley, claiming that the specimens were contaminated with a substance called Bedacryl. We do not believe that the dated fragments were contaminated, and we review the processes by which they were selected and analyzed. We also describe Bedacryl and conclude that, had it been present as a contaminant, the resulting 14C ages should have been older rather than younger than expected. Considered along with recent AMS dates on cultigens from Tamaulipas, it seems evident that post-depositional disturbances in rock-shelter sites sometimes caused mixing of older and younger objects. Direct AMS radiocarbon dating is currently the best and least destructive way to determine whether or not an individual plant specimen is the same age as seemingly associated wood charcoal.

Meggers's critique of views presented by DeBoer et al. (1996), Wüst and Barreto (1999), and Heckenberger et al. (1999) in Latin American Antiquity misrepresents these authors and others. Her criticisms, largely directed at the present authors, obfuscate fundamental points raised regarding the nature and variability of cultural formations and economic patterns in Amazonia. By conflating indigenous resource management systems, which we discuss, with mechanized development strategies of the modern world, she creates an unnecessarily polemical atmosphere for debate.

This paper addresses objections raised in an article by Bennetzen et al. (2000) in response to MacNeish and Eubanks (2000). Bennetzen et al. interpret the findings reported by MacNeish and Eubanks as opposition to the teosinte hypothesis for the origin of maize. However, by demonstrating a mutagenic mechanism that could have generated the genetic diversity essential for the transition from teosinte to maize, and the subsequent explosive evolution of maize in the archaeological record, the Tripsacum-diploperennis introgression derivatives confirm that teosinte is a progenitor of maize. Although Bennetzen et al. claim that the Tripsacum- diploperennis crosses are not credible, DNA fingerprinting verified that the hybrids contain genes from their teosinte and Tripsacum parents. Archaeobotanical remains of teosinte, Tripsacum, and hybrid specimens have been reported from Tamaulipas and Oaxaca. One of the "hybrid" specimens from Tamaulipas is virtually identical to an experimental Tripsacum-diploperennis segregate. The ability to experimentally reproduce forms that closely resemble archaeological specimens lends compelling support to the hypothesis that intergeneric hybridzation gave rise to the mutations that, through human selection, transformed teosinte into domesticated maize.

Long and Fritz argue that AMS dates on early maize were rejected because MacNeish suspected they were contaminated with bedacryl. In fact a letter from MacNeish to Long in 1988 addressed several possible explanations for the problems with the dates. The dates were rejected because they were inconsistent with well-established stratigraphic sequences and associated artifacts and ecofacts. The evidence is briefly summarized here, and the inconsistencies in the Arizona dates pointed out. It appears that the problem lies less with possible contamination with bedacryl, and more with the treatment of the samples by the Arizona laboratory.