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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.
2018 Field Season

2018 Field Season

A Great Experience!

What a successful experience this summer has been with the closing of the 2018 field season of the Project Plaza of the Columns Complex. Beginning July 2nd, a small army came together to accomplish quite a bit: six archaeologists carried out excavations in five key areas of interest, another archaeologist resumed his extensive survey of the Teotihuacan Valley, and two international students along with 23 fieldworkers and 13 lab personnel have supported the team during these important activities. In addition, several research specialists have already arrived with more to come to study the plethora of collected archaeological materials and samples that will reveal even more interesting information about the past of this region.

Our goal is to increase and diffuse knowledge, and we only hope to continue sharing our experiences and valuable work with you after each season.

 

We are just about to close excavations, and all the project team members look forward to contributing more personalized experiences soon!

 

 

And behind the archaeologists… our fieldworkers

And behind the archaeologists… our fieldworkers

by Adriana Sánchez

It has been an intense week with the conclusion of the third field season (2017) of the PPCC. This includes putting the final touches on all pending fieldwork tasks: the last photo taken, the final line drawn, and the closing word of descriptions written in the notebook.

We have just three days left for filling in the last four open excavation areas. The first of them extends over an area of 12 meters long by 3 meters wide and reaches depths between 2 to 4 meters. The second area is not that wide but is certainly large and complex; it is a tunnel that runs over 10 meters long, 1 meter wide, and 1.5 meters high. The third one is located on one of the highest structures of the complex covering an area of approximately 9 meters long, 6 meters wide, and 3 meters deep. The last area revisits a tunnel previously excavated during the first fieldwork season in 2015 and continues to provide several interesting finds.

Upon finishing the last field details and closing out the season, the adrenaline runs high with a mixture of stress, anxiety, and emotions. All excavated areas must be cleaned and perfectly covered in backfill.

In order to accomplish these monumental tasks, we rely on local fieldworkers from neighboring communities near the “Zona de Monumentos Arqueológicos de Teotihuacan” (Teotihuacan Archaeological Monuments Area, ZMAT). These individuals are usually young men who recently turned 18 years old (legal working age in Mexico) and thus experience their first job with the project or, on the contrary, are mature men who each have more than 10 years of experience working for diverse archaeological research projects in the ZMAT.

These are the people who do all the hard and labor-intensive work: lifting heavy buckets filled with earth from excavation area to sifting station, carrying heavy stones out of excavation areas, finding out ways to protect excavations from rain by maneuvering a makeshift awning, among many others tasks. Although archaeologists lead the fieldwork and its activities, we acknowledge the hard and important labor our fieldworkers do to support us and the PPCC.

Often times, the fieldworkers have to endure when an archaeologist is in a bad mood during stressful situations due to lack of time particularly at the end of the field season. Despite this, they are supportive and encourage us to continue working on “that what we call archaeology.”

Not everyone can be a fieldworker in an archaeological project as this job demands a balance of finesse, precision, and strength. Finding the right combination and stamina may ultimately decide whether one returns for the next field season. However, we gladly welcome back most familiar faces who possess these characteristics and look forward to working together again out in the field, right until the inevitable stressful end of the season.

THANK YOU TO ALL who supported our PPCC team during this third field season! Muchas gracias!

2018 SAA Conference = A Success!

2018 SAA Conference = A Success!

Hello, everyone! We had an amazing turnout at the SAA’s 83rd Annual Meeting in Washington, DC, and had a wonderful time sharing with you just a snippet of our multidisciplinary work at the Plaza of the Columns Complex. On behalf of the PPCC team – past, present, and future – thank you so much for all the support! We resume excavations this summer and hope to continue exploring and sharing our findings straight to you.

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