Polity and Ecology in Formative Period Coastal Oaxaca

2. Paleoecological Evidence for Early Agriculture and Forest Clearance in Coastal Oaxaca

43 The intensive paleoecological analysis of lake and wetland sediments in Mesoamerica has provided important evidence of the origins and development of agriculture and the manipulation of the landscape by prehistoric groups (e.g., Deevey 1978; Jones and Voorhies 2004). This evidence not only complements the archaeological data but can temporally extend the record of human land use to periods of time for which no archaeological remains have been discovered for a region (e.g., Goman and Byrne 1998; Horn 2006; Jones 1994; Leyden 2002). The paleoecological record has also played an important role in the development and refinement of models of the geography and chronology of maize domestication and diffusion (e.g., Blake 2006; Dull 2006; Piperno 2006a). This chapter presents the first paleoecological evidence of early maize domestication in lowland Oaxaca and discusses changes in land use during the Late Archaic and Formative periods. Two rival theoretical models have evolved to explain the origins of maize domestication in Mesoamerica (MacNeish and Eubanks 2000; Piperno 2006b). The Highland or Tehuacán model posits that maize was domesticated in the highlands of Mexico resulting from the hybridization of two wild relatives of maize (Mangelsdorf et al. T w O paleoeCologICal evIdenCe For early agrICulture and Forest ClearanCe In Coastal oaxaCa Michelle GoMan, arthur a. Joyce, and rayMond G. Mueller DOI: 10.5876/9781607322023.c02 44 Michelle GoMan, arthur a. Joyce, and rayMond G. Mueller 1967). This hypothesis was supported by the findings of morphologically primitive corn cobs from the highland cave site of Coxcatlán in the Tehuacán Valley, Puebla (Smith 1967). In the alternate argument, known as the Lowland or Río Balsas model, a single genetic mutation of Zea mays subsp. parviglumis (Balsas teosinte) is thought to have occurred (Doebley 1990; Iltis 1983). Recent genetic evidence indicates that maize was indeed domesticated from a single event that arose in Balsas teosinte approximately 9,000 years ago (Benz 2006; Matsuoka et al. 2002; also see Pool, Chapter 10). This annual grass has a modern range that is limited to the Río Balsas drainage of Guerrero (Doebley 1984; 1990; Figure 2.1). The Río Balsas drainage region therefore offers a compelling location for the domestication of maize and the possible corroboration of the Lowland model; however, it is conceivable that paleodistributions of the grass at the beginning of the Holocene may have differed (Doebley 1990; Piperno et al. 2007). Accelerator mass spectrometry (AMS) age analysis and new phytolith data from Guilá Naquitz Cave in the highlands of Oaxaca (Piperno and Flannery 2001) shed further light on the issue of the location of maize domestication. Two primitive-looking maize cobs originally found during the 1966 excavations of Guilá Naquitz (Smith 1986) were directly dated by AMS and returned ages of approximately 4300 cal BC (3450 14 C yr BC; Piperno and Flannery 2001). Figure 2.1. Map of sites of earliest published claims for maize (Zea mays subsp. mays) macroand microfossils in Mexico mentioned in the text. 1, Tehuacán, Puebla; 2, Guilá Naquitz Cave, Oaxaca; 3, Xihuatoxtla, Guerrero; 4, Iguala Valley, Guerrero; 5, El Venancio, Guerrero; 6, Laguna Tetitlán, Guerrero; 7, San Andrés, Tabasco; 8, Laguna Catarina, Veracruz; 9, Laguna Pompal, Veracruz; 10, Pijijiapan, Chiapas. 45 PaleoecoloGical evidence for early aGriculture and forest clearance in coastal oaxaca This age places them as the oldest specimens of maize cobs found, to date, in Mesoamerica, significantly older than the cobs found in the Tehuacán Valley (Long et al. 1989). If the early Holocene range of the Balsas teosinte differed markedly from today, then it is possible that the highlands of Oaxaca might have been the locus of maize domestication. However, based on the detailed phytolith studies of soil samples from Guilá Naquitz, Piperno and Flannery (2001) suggest that this was not the case. while phytoliths of grasses and other plants were common, no phytoliths attributable to teosinte or maize were present in deposits that ranged between ca. 10,670–5840 cal BC (8700–5030 14 C yr BC; zones B through E), but maize phytoliths were present in the youngest zone (A), thought to date to ca. cal AD 690 (AD 620 14 C yr). These data indicate that maize was introduced to highland Oaxaca. Recent microbotanical evidence from the heart of the Balsas Valley appears to have put the long debate to rest as starch grain and phytolith evidence from the Archaic cave...