Introduction
The analysis of ceramics is a crucial feature of prehistoric and historical archaeology. Ceramics were possibly the earliest synthetic materials that humanity made. Indeed, broken ceramic fragments are “the most common artifacts found at archaeological sites around the globe” (Bishop, Rands and Holley 279). Therefore, ceramics comprise the most common materials that the archaeologists study. Apart from their wealth and sturdiness, ceramics have multiple microscopic and macroscopic characteristics of interest to scientists. Visual characteristics such as size, surface decoration and shape are ordinarily used as archaeological and cultural signs. Moreover, microscopic characteristics like the texture of the temper and clay compositions are used to analyze the preparation methods.
On the other hand, archaeologists use the chemical constituents of a ceramic to identify the origin of the ingredients used in its manufacture. The chemical composition of a ceramic also plays a significant role in determining the geographic displacement of the material. Further, archaeologists use the oxidation state of “iron-bearing ceramics to reconstruct firing conditions of the material” (Bishop, Rands and Holley 282). Through instrumental neutron activation analysis (INAA), archaeologists can come up with accurate information about a ceramic as well as the people that manufactured it. This paper will focus on instrumental neutron activation analysis as an archaeological method of analyzing ceramics. Besides, the paper will discuss how INAA is used to understand the past of the Olmec society.
Instrumental Neutron Activation Analysis
In spite of the numerous chemical methods that are used to analyze ceramics and clay, the instrumental neutron activation analysis is the most common technique. Other methods of analyzing ceramic materials include X-ray fluorescence (XRF), atomic absorption spectroscopy (AAS), inductively coupled plasma (ICP) and mass spectrometry (MS) among others. The instrumental neutron activation analysis has numerous advantages over the other techniques (Bishop and Blackman 605). First, INAA is highly accurate and sensitive to diverse elements. Thus, it enables the archaeologists to analyze all the constituents of a ceramic fragment. Second, it is easy to prepare and analyze small samples using the INAA technique. Third, instrumental neutron activation analysis prevents chemical reaction between the primary constituents of a ceramic. Last, it is easy to measure multiple constituents of a ceramic at the same time.
Instrumental neutron activation analysis mainly focuses on the characteristics of the nuclei of the constituents of a ceramic material. During collisions of a sample “with neutrons from a reactor, a fraction of the nuclei from each of the constituent elements are transformed into unstable isotopes that decay with characteristic half-lives” (Bishop and Blackman 607). In the course of the radioactive decay, the isotopes release many gamma rays that comprise different abundances and energies, which resemble the decaying isotope. The archaeologists measure the range of the released gamma rays to determine the number of constituent elements in a ceramic fragment.
Procedure of Ceramic Analysis through INAA
The study of ceramic materials through instrumental neutron activation analysis begins by extracting a small piece of the material. The archaeologists prepare the fragment for analysis and preserve a comparable piece for reference. At times, the surface of the piece may vary in composition from the original ceramic or paste used to make the earthenware due to numerous factors. The factors may include the contamination that might have arisen when the ceramic was under use. Besides, the difference may occur due to slipping or varnish available on the surface of the fragment or diagenesis (post-depositional processes) (Bishop and Blackman 609).
The inner and outer surfaces of the ceramic piece are extracted using a tungsten-carbide burring instrument. Once the burring process is over, the sample is polished using a toothbrush, cleaned using deionized water and left to dry for a couple of hours. Later, the archaeologists use a mortar and pestle to crush the fragment into powder. The powder is then placed in clean glass vials and heated for 24 hours (Glascock and Neff 21). The primary objective of heating the powder is to dry it. The different samples of the weighed powder are marked and put in distinct polyethylene ready for short and long irradiations.
After completing the irradiation process and collecting adequate data, archaeologists embark on an archaeological interpretation of the ceramic material. The archeologists focus on numerous things. First, they seek to identify the origin of the ceramic fragment. Second, they try to determine the materials used to make the ceramic. Third, the archeologists attempt to determine if the ceramic was made at the same location and duration as other samples (Glascock and Neff 25). In most cases, the data obtained through instrumental neutron activation analysis procedure comprise multiple elements. Therefore, the archaeologists rely on multivariate statistical analysis to determine and “quantify the similarities and differences between specimens and groups of specimens” (Bishop, Rands and Holley 294).
In some instances, the archeologists do the normalization of the chemical constituent contents. The goal of normalization is to cater for mineralogy and grain-size impacts on trace element concentrations. The normalization helps to minimize chances of wrong interpretation of the ceramic attribution. A standard approach “used in determining regional geochemical baselines is to normalize geochemical data using one element as grain-size and mineralogical proxy” (Glascock and Neff 31). Normalization in archeological ceramic analysis refers to a process that facilitates the reparation for the impacts of anthropogenic and natural processes. Therefore, the archeologists do not rely on statistical considerations when picking the normalizing element.
Case Study: Olmec-Style Ceramics
Over 3000 years ago, the early civilization in “ancient Mexico, the Olmec, coalesced along the Mexican Gulf Coast” (Blomster, Neff and Glascock 1068). Much of the New Mexico, together with Honduras, Belize, Guatemala, and El Salvador make up the cultural region referred to as Mesoamerica. Features of Olmec drawing techniques and related iconography were imprinted on tombstones in the Gulf Coast. Besides, it was possible to find characteristics of the Olmec drawing and painting techniques on moveable earthenware items that were found along the Gulf Coast in the entire Mesoamerica (Blomster, Neff and Glascock 1069). Archaeologists associated the presence of the iconography and drawing techniques with the propagation of the religious, political, and social institutions of the Olmec society.
The instrumental neutron activation analysis of the ceramic fragments collected along the Mexican Gulf Coast played a significant role in the interpretation of the growth and spread of a complex society in Mesoamerica. The presence of Olmec style in particular locations outside the Gulf Coast has been used to insinuate that it emerged in one region and later shipped to other areas. Some people argue that the Olmec-style ceramics reached other areas through interaction between the different regional chiefdoms (Blomster, Neff and Glascock 1071). The application of instrumental neutron activation analysis on archeologically collected ceramic materials helps to explain their origin as well as distribution during the Early Formative era.
The use of instrumental neutron activation analysis on ceramics obtained from the Gulf Coast helped the scientists to draw a clear picture of the Early Formative period. A recent study by archaeologists confirmed that the Olmecs had a superior sociopolitical level compared to other contemporaneous societies in Mesoamerica. The analysis concluded that “leaders, for example, at the emerging chiefdom of San Jose Mogote in the Valley of Oaxaca lived in somewhat better made wattle-and-daub huts than other villagers” (Costin 381). On the other hand, the leaders in San Lorenzo were quite advanced and dwelled in Red Palace. Moreover, the leaders used basalts to make step coverings, columns and drainage feeds for their houses. The analysis of ceramic fragments that bear Olmec art styles confirmed that the Olmecs had a composite degree of sociopolitical organization.
The archeologists use the absence of complete catalog of Olmec-style patterns at any single location to signify that every region had a hand in the development of the drawing and painting techniques. Besides, they support their argument by citing the evident regional disparities in the presentation of the Olmec style (Costin 384). Archaeologists have applied INAA technique to confirm that diverse communities used distinct, local assortments of Olmec-style signs. Some scientists claimed that the residents of the Valley of Oaxaca did not import ceramics from the Gulf Coast. Instead, the residents used Leandro Gray and Delfina Fine Gray to manufacture and export gray-ware ceramics to the entire Mesoamerica. To confirm this postulation, the archaeologists hollowed out Early Formative ceramics at an area known as Etlatongo (Pool 47).
The use of instrumental neutron activation analysis technique enabled the archaeologists to identify the nature of ceramic items that the Olmec produced. According to the analysis, the Olmec majored in the manufacture of luxury white wares like Xochiltepec White and Conejo Orange-on-White. The white wares were mainly made at San Lorenzo (Pool 48). The archaeologists concluded that a majority of the chiefdoms in Mesoamerica imported ceramic products from San Lorenzo. It underlines the reason Olmec-style ceramics were quite prevalent in most chiefdoms. The archaeologists found that some regions manufactured local alternatives of white wares. Nevertheless, the alternatives were only used locally. The archaeologists also found that the community that resided at San Lorenzo had the highest number of Olmec-style ceramics. The findings indicated that the Olmecs mainly lived at San Lorenzo (Pool 51).
The instrumental neutrons activation analysis offered numerous inferences for understanding the Olmec and their correlations with contemporaneous groups. The leaders of a majority of the chiefdoms in Early Formative Mesoamerica cherished the Olmec ceramics and signs related to Olmec. The rest of the regions did not contribute substantially to the developing of Olmec-style signs used outside each state (Pool 55). The Olmec never brought in ceramics bearing Olmec-style symbols from foreign states. Further, the analysis confirmed that neighboring regions never exchanged ceramics with one another. Some regions imported ceramics from distant locations. For instance, in spite of San Jose Mogote and Etlatongo being neighbors, the regions did not exchange ceramics. Instead, they opted to import them from distant regions like San Lorenzo.
The archaeologists argued that San Lorenzo Olmec contributed to the developing of unique styles and related iconography and distributing them across Mesoamerica. They theorized that the process of exchange of Olmec-style ceramics and signs differed based on the regions. According to the archaeologists, the Olmec did not impose their ceramics and signs on other regions (Pool 57). Instead, the regions embraced the ceramics, used, and later replicated them in varied ways.
The exchange of the ceramics and signs played a key role in negotiation and communication between societies at the interregional level. The analysis of the ceramics indicated that Olmec played a prominent role in social development in the larger part of Mesoamerica. The analysis showed that there was a significant interaction between the Olmec and other societies that consumed the ceramic products manufactured at San Lorenzo (Pool 63). The dynamic interaction between the Olmec and other communities explained the complex state of the Olmec associations during the Middle Formative era.
Conclusion
One of the greatest contributions of instrumental neutron activation analysis to archaeology is the identification of ceramic provenance. Archaeologists use INAA to determine the distribution of ceramics, influence of cultures, diffusion of communities, contacts between different regions as well as trading routes. Visual examination cannot enable archaeologists to identify different characteristics of archaeological artifacts. While visual examination may allow the archeologists to determine the style of decoration, color and shape of the ceramics, it may be hard for them to identify the constituent elements or provenance of the ceramic material. Therefore, archaeologists ought to study the chemical composition of the ceramic to understand its origin.
Besides, they need to use statistical methods to analyze the data corrected from ceramic fragments. The use of instrumental neutron activation analysis helped the archeologists to unearth the history of the Olmec society. The analysis did not only help the archaeologists to understand how Olmec-style ceramics and signs were distributed across Mesoamerica but also the correlations between Olmec and other communities. Most communities imported ceramics from San Lorenzo. Besides, they copied designs from the Olmec-style ceramics. The analysis confirmed that Olmec played a significant role in the sociopolitical development of Mesoamerica.
Works Cited
Bishop, Ronald, and James Blackman. “Instrumental Neutron Activation Analysis of Archaeological Ceramics: Scale and Interpretation.” Accounts of Chemical Research 35.8 (2002): 603-610. Print.
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Blomster, Jeffrey, Hector Neff, and Michael Glascock. “Olmec Pottery Production and Export in Ancient Mexico Determined through Elemental Analysis.” Science 307.5712 (2005): 1068-1072. Print.
Costin, Cathy. “The Use of Ethnoarchaeology for the Archaeological Study of Ceramic Production.” Journal of Archaeological Method and Theory 7.4 (2000): 377-403. Print.
Glascock, Michael, and Hector Neff. “Neutron Activation Analysis and Provenance Research in Archaeology.” Measurement Science and Technology 14.9 (2003): 19-37. Print.
Pool, Christopher. Olmec Archaeology and Early Mesoamerica, Cambridge: Cambridge World Archaeology, 2007. Print.