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Validity of Ams Dates on Maize from the Tehuacán Valley: A Comment on Macneish and Eubanks

Published online by Cambridge University Press:  20 January 2017

Austin Long  and
Gayle J. Fritz
Austin Long
Affiliation:
Department of Geosciences, University of Arizona, Tucson, AZ 85721
Gayle J. Fritz
Affiliation:
Department of Anthropology, Washington University in St. Louis, St. Louis, MO 63130
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Abstract

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.

Resumen

Resumen

MacNeish y Eubanks (2000) rechazen las fechas radiocarbónicas AMS sobre el maíz del Valle de Tehuacán, sosteniendo que las muestras fueron contaminadas con una substancia nombrada Bedacryl. No creemos que los fragmentos fechados fueron contaminados, y pasamos revista a los métodos por cuales fueron escogidos y analizados. También describimos Bedacryl y llegamos a la conclusión que, si hubiera sido presente como contaminación, las edades 14C resultados deberian sido más viejos en vez de más jovenes que se suponía. Considerados juntos con las fechas AMS recientes sobre plantas domesticadas de Tamaulipas, se parece evidente que disturbios en las cuevas algunas veces causaron la mescla de los objetos más viejos con los más jovenes. Hoy en día el fechado de radiocarbono AMS es el modo mejor y menos destructivo para determinar si o no una muestra individual de una planta es la misma edad como el carbón de madera aparentemente juntado.

Type
Comments
Information
Latin American Antiquity , Volume 12 , Issue 1 , March 2001 , pp. 87 - 90
Copyright
Copyright © Society for American Archaeology 2001

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