AMS Dates of New Maize Specimens Found in Rock Shelters of the Tehuacan Valley

Abstract

A large collection of maize macro-specimens has been gathered from archaeological sites across the American continent, but only a few have been directly dated by accelerator mass spectrometry (AMS). We recently conducted two new excavations in several rock shelters of Tehuacán valley (San Marcos, Coxcatlán, and Purrón) and uncovered 132 non-manipulated macro-specimens of maize suitable for morphological and paleogenomic analysis, including many complete cobs, stalks, internodes, and leaves. Direct AMS dates for 43 samples found in San Marcos or Coxcatlán confirm the previously reported chronologies for these sites. By contrast, a cob found in Purrón was dated to 3060±30 before present (3360–3180 cal BP) (2σ), demonstrating that maize was present at that site at least 1500 calendar years earlier than previously expected, and suggesting that other specimens of similar age are still likely to be found in the southeastern region of the Tehuacán valley. A global comparison of macro-specimen chronology across the continent shows that the current archaebotanical record does not yet reflect the chronology of dispersal from central Mexico to northern or southern regions, opening the possibility for finding the missing links in subsequent expeditions within Mexico and Central America.

Biophysical and Biocultural Upheavals in Mesoamerica, a Conservation Perspective: Mountains, Maize-Milpa, and Globalization

“…Maize cultivation in SMP has millennial roots: the eldest palaeoecological record stretches back to 6,250 BP in the Guilá-Naquitz Cave, Oaxaca (Benz, 2001;Piperno and Flannery, 2001). Also, ancient vestiges of maize cultivation have been detected throughout SMP: Panama (Piperno et al, 1985), Costa Rica and Nicaragua (Horn, 2016), Salvador (Dull, 2016), Honduras (Kennett et al, 2017), Guatemala (Castanet et al, 2022), Chiapas (Hammond, 2001;Rosenswig et al, 2015), and Puebla (Long and Fritz, 2001;Torres-Rodríguez et al, 2018). The presence of maize in palaeoecological records correlates with human genomic changes, sedentary lifestyle development, and farming techniques (Hünemeier et al, 2012).…”

Domestication and lowland adaptation of coastal preceramic maize from Paredones, Peru

“…1C and SI Appendix , Table S1). Par_N1 is older than any other maize macro-specimen found to date (36).…”

New AMS Radiocarbon Ages from the Preceramic Levels of Coxcatlan Cave, Puebla, Mexico: A Pleistocene Occupation of the Tehuacan Valley?

“…Importantly, this period saw the first introduction of domesticated maize ( Zea mays ) to the valley and to Coxcatlan Cave in particular. Although MacNeish and the TABP had originally suggested that maize arrived during the Coxcatlan phase, subsequent AMS dating demonstrated that the earliest samples dated to the Abejas phase (Crane and Griffin 1962; Long et al 1989; Torres-Rodríguez et al 2018). After the Abejas phase, Coxcatlan Cave experienced an occupational hiatus for up to 2,500 years, after which time it was reoccupied by people who made and used pottery (Fowler and MacNeish 1972:292).…”

“…The arid conditions of the valley have resulted in the exceptional preservation of organic materials within a series of dry caves, enabling the TABP to recover and document thousands of specimens of early domesticated plants, including chili peppers, avocados, squash, beans, and maize (Long et al 1989; MacNeish 1967b; Mangelsdorf et al 1967; Smith 1967, 2005). Although nearly 200 radiocarbon ages from archaeological settlements across the valley have been produced by the TABP and subsequent projects (Aiuvalasit et al 2010; Johnson and MacNeish 1972; Kaplan and Lynch 1999; Long et al 1989; Neely et al 2015; Smith 2005; Torres-Rodríguez et al 2018), the chronology for the Preceramic phases and the timing of the beginning of plant cultivation within the Tehuacan Valley have remained topics of scrutiny and debate (Fennell 2001; Flannery and MacNeish 1997; Hardy 1996, 1999; MacNeish 1997; Rosenswig 2015:123–125).…”