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The Elements of a Paleodiet: How Isotope Analysis Help Archaeologists in the Lab

The Elements of a Paleodiet: How Isotope Analysis Help Archaeologists in the Lab

by Esther Aguayo

Food is an important part of our lives, yet it is a difficult thing to see in the archaeological record. Usually archaeologists rummage through ancient trash piles to look for animal bones and residues in pots to find out what people ate. However, there is another tool that archaeologists use that can tell us more about what people and animals consumed called stable isotope analysis. This methodology helps archaeologists understand the chemical make-up of human and animal bones to reveal information regarding diet, social organization, and human-animal interactions. At the Archaeological Sciences Lab at George Mason University, I help prepare bones in order to extract that information.

All living organisms are comprised of molecules that they have absorbed or eaten throughout their lives. Bones, teeth, and even hair molecules can tell archaeologists a lot about an organism’s life history and environment. These molecules, referred to as stable isotopes, and their composition can vary depending on the environment of the organism. Factors such as temperature, altitude, nutrition, and humidity affect isotopic composition and will be reflected in the tissues we look at. There are several isotopes that can be analyzed such as carbon, oxygen, nitrogen, and strontium. 

Carbon is most familiar as the lead in our pencils and what we breathe out in carbon dioxide, but carbon also relates to the way plants obtain energy or photosynthesis. C3 and C4 cycles are the most common photosynthetic pathways a plant can use and can be determined from bones of an animal or person who ate plants. Since photosynthesis varies among plants, archaeologists can reconstruct what people and animals were eating, where they lived (based off where the plants grew), and how their diet changed over time. This is the information that can be deduced from carbon alone. It is important to collect the information stable isotope analysis provides. So, how do archaeologists conduct isotope analyses?

An archaeological deer bone with a piece removed for isotope analysis.

In the Archaeological Sciences Lab I help prepare the bones to extract the isotopic information we need. The bones from the Project Plaza of the Columns Complex (PPCC) are cleaned after excavation. Then, the bones are analyzed, identified to species, photographed, and documented for further reference. It is important to document the bones well because isotope analysis is a destructive process. First, I make sure the bones are cleaned completely. Using a hand rotary tool, I thoroughly clean off any excess dirt and build-up on and inside the bone. I also use the rotary tool to remove a part of the bone that will be used for the isotopic analysis. Then, I wash the bones in a sonic bath which uses high frequency sound waves to remove any remaining dirt that cannot be removed by hand.

Isotope samples ready to be soaked overnight.

After letting the bones dry overnight, I use an agate mortar and pestle to crush the bones into a fine powder. I weigh each sample and transfer them to tubes so they may soak overnight in a chemical solution to begin the removal of organic components. Then, the samples are rinsed in ultrapure water, and an acid solution is used to completely remove all organics in the sample. Once weighed a final time, the sample is ready for the mass spectrometer at the Smithsonian Museum Conservation Institute. The mass spectrometer is able to measure isotopic variations in a sample. It is through those variations that archaeologists can gain insight on the diet of the individual and the ecosystem they lived in.

Adding a chemical solution to remove organic material from the bone powder.

At first glance, isotope analysis is intimidating to someone with little experience with heavy machinery and chemicals. However, since working at the Archaeological Sciences Lab, I have greatly enjoyed my time learning about isotopes and the many questions about ancient life that can be answered through this process. Stable isotopes open a new window into ancient life that tell archaeologists about more than just food consumption. At the PPCC, isotope analysis has helped investigators find out more about animal management and how it had affected social structure in ancient Teotihuacan. The potential use of isotope analysis is quite vast, and archaeologists still have much more to discover using this fascinating methodology.

References:

  1. France, Christine A.M., Douglas W. Owsley, and Lee-Ann C. Hayek. “Stable Isotope Indicators of Provenance and Demographics in 18th and 19th Century North Americans.” Journal of Archaeological Science 42 (2014).
  2. Schwarcz, H.P, M.J. Schoeninger. “Stable Isotopes of Carbon and Nitrogen as Tracers for Paleo-diet Reconstruction.” In Handbook of Environmental Isotope Geochemistry, by M. Bakaran, 725-742.
  3. Sugiyama, Nawa, A.D. Somerville, M.J. Schoeninger. “Stable Isotopes and Zooarchaeology at Teotihuacan, Mexico Reveal Earliest Evidence of Wild Carnivore Management in Mesoamerica.” Plos One 10, no. 9 (2015).
  4. Sugiyama, Nawa, William L. Fash, and Christine A.M. France. “Jaguar and Puma Captivity and Trade among the Maya: Stable Isotope Data from Copan, Honduras.” Plos One 13, no. 9 (2018).
  5. White, Christine D. “Stable Isotope and the Human-Animal Interface in Maya Biosocial and Environmental Systems.” Archaeofauna 13 (2004). 183-198.
What can be learned through pottery analysis?

What can be learned through pottery analysis?

The case of candeleros

by Yolanda Peláez Castellanos

The potters who made the ceramic pieces recovered in archaeological excavations gave them different shapes depending on the function they would have (e.g., pots and bowls were used in the preparation and consumption of food). A very distinct form that corresponds almost exclusively to Teotihuacan can be seen in the figure below; these vessels have been found in various foreign sites, and each have been attributed to Teotihuacan presence or influence.

Candeleros from distinct phases (photograph by Fredy Álvarez)

These vessels are small and can have one (4x5x4cm) or two (5x8x5cm) cylindrical chambers, the latter usually having lateral perforations. In the Colony Period they were called candeleros (“candlesticks”) because the indigenous people reused them to support candles (Ceballos 1992: 205-206), but these did not exist when the city of Teotihuacan was inhabited.

The analysis of the candeleros gives us information about them (Peláez 2018):

PRODUCTION

– When examining the pieces, you can see the technique that was used to decorate them (e.g., punching, incision, fingerprints).

– More time was spent in the production of some pieces (e.g., it takes longer to manufacture a candelero with a polished lip like those of the Xolalpan phase than one with fingerprints like those of the Metepec phase).

– The method of making and decorating them has changed over time. Based on physical attributes, they were classified into three phases considering the parameters of an already established chronology (Rattray 2001). Accordingly, this indicated that the production of candeleros lasted for a period of approximately 400 years (250-650 AD). (See Ceramic Analysis, Relative Chronology)

USE

Some visible features give us clues about the use of the candeleros:

– The dark traces in the chambers indicate that something was burned inside them.

– Charred organic remains were found inside some of the tested chambers.

Candeleros with evidence of burning (photograph by Fredy Álvarez)

In order to determine the substances that these artifacts may have contained, their chemical residues were analyzed. These residues are stored in superficial pores where liquid or semi-liquid substances might have spilled. If this action (of use) was repeated or if a large amount of matter was deposited, some components present in these solutions can be identified (i.e., phosphates, carbonates, proteins, fatty acids, carbohydrates, and pH can also be measured) through tests called spot-tests (Barba et al. 2008: 721; Barba et al. 2014: 202-204). This type of methodology is also used for soil chemistry analysis (Barba et al. 1991).

Not all the candeleros demonstrated a discernible amount of residue, but the combination of components that were identified was interpreted as moderate combustion of cellulose, presence of substances of animal origin, and combustion of resins (Peláez 2018). This is consistent with the results of other investigations (Ortiz 2006).

DEPOSITION

The location where the materials were found in excavations sometimes corresponds to the place where they were discarded and not necessarily where they were used, although it is feasible that they were used in the vicinity and in various locations in Teotihuacan. In large part, the candeleros have been found associated with domestic spaces.

Most of the analyzed PPC candeleros (77%) came from Front C. It was originally hypothesized that this area was domestic, although so far only rooms have been found west of Mound 25Z and north of Structure 26A. The presence of candeleros supports the idea that this area could have been residential.

Excavation units with the presence of candeleros and percentage of sample present per front(Map data ©PPC, modified by Yolanda Peláez)

References

Barba, Luis, Roberto Rodríguez, y José Luis Córdova

1991      Manual de técnicas microquímicas de campo para la arqueología. Instituto de Investigaciones Antropológicas, Universidad Nacional Autónoma de México, México, D.F.

Barba, Luis

2008       Los residuos químicos en cerámica. Indicadores arqueológicos para entender el procesamiento de alimentos y el uso de recipientes. In Quaderni di Thule VIII. Atti del XXX Convegno Internazionale di Americanistica, pp. 721-728. Centro Studi Americanistici Circolo Amerindiano, Perugia.

Barba Luis, Agustín Ortiz y Alessandra Pecci

2014       Los residuos químicos. Indicadores arqueológicos para entender la producción, preparación, consumo y almacenamiento de alimentos en Mesoamérica. Anales de Antropología 48(1):201-239.

Ceballos Novelo, Roque

1922      Candeleros. En La población del valle de Teotihuacan, Vol. 1, edited by Manuel Gamio, pp. 205-212. Secretaría de Agricultura y Fomento, Dirección de Antropología, México, D.F.

Rattray, Evelyn

2001      Teotihuacan: cerámica, cronología y tendencias culturales. Instituto Nacional de Antropología e Historia and University of Pittsburgh, México D.F.

Ortiz, Nidia

2006      El candelero: estudio comparativo sobre su función en Teotihuacan durante el Clásico, Epiclásico y Posclásico Temprano. Tesis inédita de licenciatura en Arqueología, Escuela Nacional de Antropología e Historia, México, D.F.

Peláez Castellanos, Yolanda

2018       Los candeleros del Complejo Plaza de las Columnas, Teotihuacan. Tesis inédita de licenciatura en Arqueología, Universidad de las Américas, Puebla, Cholula, Puebla.

What type of information can be recovered from a sherd?

What type of information can be recovered from a sherd?

Ollas, jars, pots, and vases are just some examples of the incredible variety of pottery forms abundantly recovered in Teotihuacan. These sherds carry an astounding amount of information that archaeologists can recover through patient re-piecing of the data. Below we discuss other applications beyond relative chronology that are utilized in ceramic analyses.

Evolution of typology: Changes in ceramic style across time among the recovered pottery assemblage illustrate what the trends at Teotihuacan were in each phase and the rate of these changes. Such evolution of pottery types can be recorded by design type, decoration method, or material type used to manufacture ceramics across time periods.

The following image shows some of the changes in pottery types at Teotihuacan. For example, take the simpler Tzacualli Phase sherd compared to the more elaborate Metepec Phase sherd. The Metepec sherd presents a more elaborate design with painted stucco.

Ceramic from different phases. Source: Own creation, images of sherds modified from Rattray (2000a, b)
The evolution of ceramic phases over time. Source: Own creation, images of sherds modified from Rattray (2000a, b)

Context information: The distribution, frequency, and type of ceramics from different locations can be used to reconstruct what activities took place at a specific site. For example, a high density of utilitarian wares such as vases, plates, and jars can be an indication of an ancient kitchen. On the other hand, a large concentration of defective and unfinished ceramic assemblages can indicate the workshops where ceramics were manufactured.

Burials also contain ceramic objects used in mortuary rituals. Funerary contexts commonly contain pieces with very sophisticated designs with very little use ware, including some censers, miniatures, and Tlaloc vessels.

Commerce: Some sherds were clearly imported from other regions outside the Teotihuacan Valley. Foreign goods are identified by tracing where the raw materials (clays, tempers, paints, etc.) come from and by their distinct decorative and manufacturing techniques. Such data on the quantity and location of these imported ceramics have provided information on foreign relations between ancient Teotihuacan and immigrant groups from throughout Mesoamerica, as well as enclave settlements.

For example, archaeologists have identified large quantities of “Thin Orange” ware and granular ware that indicate foreign immigrants lived in Teotihuacan. These and many other imported ceramics from the Gulf of Mexico, West Mexico, Oaxaca, and the Maya region, among others, which indicate Teotihuacan was a metropolitan city composed of immigrants from disparate regions across Mesoamerica.


Literature consulted

Rattray, E. C. 2000a. Teotihuacan: Ceramics, Chronology, and Cultural Trends. University of Pittsburgh Memoirs in Latin American Archaeology, No. 13.

Rattray, E. C. 2000b. Teotihuacan: Ceramics, Chronology, and Cultural Trends–Color Illustrations. Latin American Archaeology Database, University of Pittsburgh. <URL: http://www.pitt.edu/~laad/rattray/>

Rattray, E. C. 2001. Teotihuacan: Ceramics, Chronology, and Cultural Trends. Serie Arqueología de Mexico, Instituto Nacional de Antropología e Historia / University of Pittsburgh. Mexico, D. F., pp. 617 + tables of frequencies of ceramic wares.

The Plant-based Diet and Plants

The Plant-based Diet and Plants

During field seasons, archaeologists unearth remains of ancient households, plazas, and other buildings made of stone and earth. These remains give us a snapshot of how these spaces looked like and how people used to live many years ago.

But archaeologists want to know more details and not just limited on where and how those people lived. They want to know about food and diet, of course!

Human diet is composed of two main food groups: animal- and plant-based. Among the materials recovered during excavation, there are a lot of animal bones. These bones let us know what kind of animals were consumed, but what about plants?

Unlike bones, plants, fruits, and seeds that were consumed during ancient times aren’t easily preserved. Nevertheless, we can find some valuable clues about their existence, use, and consumption. Burnt seeds are one example, but they are really small (just a few millimeters) and practically impossible to be seen during the digging process. And so, how can one recover them?

Seeds: the clues

When archaeologists are digging in an area where there´s a lot of cultural artifacts like sherds, worked stone, bones, etc., they collect several soil samples into 2-liter plastic bags to be analyzed later in a laboratory setting.

In the lab the sample is left to dry. The soil is then poured into a bucket of water where there is a gentle but constant flow and movement. This method allows for charred materials like wood and seeds to be separated from the soil and float to the surface so they can be easily recovered. For this reason, this process is called “flotation.”

By looking at these charred remains under the microscope, specialists can find and identify seeds, wood fragments, and even bones of small animal species.

Why charred?

Organic materials like seeds and plants usually disintegrate over time. However, the ones that were burnt have a better chance to be preserved over a long time and even one day, be found by archaeologists! On the other hand, roots and other non-charred organic material are often a result of modern, more recent intrusions into ancient deposits.

Charred seeds found at the Plaza of the Columns Complex (courtesy of Dr. Clarissa Cagnato, Plaza of the Columns 2018)


What seeds tell us about the Plaza of the Columns Complex

Research over charred organic materials recovered through the flotation process allows us to identify the many plants that were likely used or consumed by the inhabitants of the Plaza of the Columns Complex, including maize, beans, chili, squash, nopal (cactus), amaranth, Chenopodium, chia, and purslane.

One of our most exciting results thus far has been the discovery of guava seeds during our 2018 analysis. This is particularly interesting because the guava is not a local fruit from this region as it usually grows in areas of much lower altitudes. And so, this species was probably imported to the Valley of Teotihuacan during ancient times.

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