The Chemistry of Archaeology: Summer Internship at the GVSU Stable Isotope Laboratory

Every student in the Applied Anthropology graduate program at MSU is required to complete an internship with an aim to provide students with practical experiences in an applied anthropology-based setting relative to their graduate studies. My thesis revolves around a quantitative zooarchaeological and stable isotopic analysis of the faunal remains recovered from the Khirbet Summeily excavations, co-directed and excavated by Dr. Jeff Blakely and my advisor, Dr. Jimmy Hardin. My goal was to find an internship that not only co-aligned with my interests, but also aided in my thesis research and future graduate studies. Amidst my searching, my outside committee member, Dr. Elizabeth Arnold, presented an opportunity to be a graduate research intern at the Stable Isotope Lab at Grand Valley State University. I immediately accepted the opportunity and began my incredible, chemistry-intensive, summer.

What are Stable Isotopes and How do they Relate to Archaeology?

Stable isotopes are elements with different atomic mass, based on the number of neutrons, and do not decay overtime. These isotopes include carbon, oxygen, nitrogen, hydrogen, and trace elements, such as strontium, barium, and lead. The extraction of these isotopes provides two lines of evidence for study; the isotopes ingested by a living organism reflects their surrounding environment and those isotopic values can vary regionally, providing spatial evidence. Stable isotope has typically been analyzed from preserved bone collagen, however, carbonate found in the biological apatite of bone mineral and tooth enamel has been shown to reflect the whole diet and has recently gained prominence as a tissue of study for carbon, oxygen, and strontium (and is the selected tissue for the GVSU Stable Isotope lab). Sampling of the tooth enamel can extract carbon and oxygen, as well as strontium (a trace element). Carbon isotope ratios can inform a researcher on past animal management practices and environments, based on the ingestion of C3 and C4 plant vegetation and oxygen isotopes in biological apatite are positively correlated to the isotopic composition of ingested environmental water. Strontium isotope values can indicate where the animal spent portions of its life, due to the animal intaking strontium in the vegetation from their geological environment, which would leave levels of strontium in the enamel apatite. The use of carbon, oxygen, and strontium isotopes allows archaeologists to reconstruct past environments, animal diet, past herding and exploitation practices, trade relations, as well understand how the mobility of the animals played a part in the socioeconomic structure of past societies.

The Job Description

The stable isotope lab at Grand Valley State University primarily focuses on isotopic research in the Levant region. This allowed me to work on material from multiple sites in Israel, including Ashkelon, Tell Yarmouth, Tell es-Safi, and Tell el-Hesi. My day consisted of arriving at the lab each day at 9:30am wearing appropriate lab attire (long pants, closed-toe shoes, and hair tied back) and my day concluded at 5pm. As a graduate research intern, my job included five major tasks: tooth selection, cleaning, cutting/sampling, processing, and running the samples (which concluded at the University of Illinois Urbana-Champaign). I had the opportunity to be involved and conduct each one of the following steps.

Step One: Tooth Selection

Most teeth collections came to the lab unsorted, so the optimal teeth for sampling needed to be selected. The “best” teeth were mandible molars than contained little to no cracks. Compared to maxilla molars, samples along a mandible molar can more accurately be identified to growth period. Cracks needed to be avoided for potential contamination and breakage during the cleaning and cutting process.

Pre-Cleaned Tooth.jpg

Step Two: Cleaning

Arguably the messiest, the cleaning process involved removing all the calculous, dentin, and cementum to expose the enamel with a dremel drill. Various dental drills were used to clean the enamel surface for sampling. Masks, goggles, and a lab coat were required pieces of attire for this step.

Post-Cleaned Tooth.jpg

Tooth Cleaning Day.jpg

Step Three: Cutting/Sampling

Using a diamond-tipped dental drill, bands of 1.0 mm width were drilled horizontally across the medial lobe of each molar tooth starting from the base of the enamel and working upwards. Depending on the size of the tooth, samples ranged from 10-25 lines. Each sample was collected in a microcentrifuge tube and weighed. All samples were recorded in the designated lab notebook.

Step Four: Processing

Processing days were the longest and most grueling days. The samples were treated with a bleach solution overnight to remove any organics. Then the samples were washed four times with distilled water and treated with acetic acid for four hours to remove diagenetic carbonates. The samples were additionally rinsed with distilled water another four times, entered a freezer for 30 minutes, then freeze dried overnight.

Step Five: Running the Samples

The final step required Dr. Arnold, Cece Roehm (the other student intern), and me to travel to the University of Illinois Urbana-Champaign to work in the Multi-collector Inductively Coupled Plasma Mass Spectrometer Lab (where samples for strontium were run) and the Stable Isotope Lab (where carbon and oxygen samples were run). The opportunity to work in these world-renowned labs along with other notable isotope researchers was incredible. I was even able to work in Dr. Stanley Ambrose’s isotope laboratory (one of the leading researchers in stable isotope studies). The entire process of running the samples required our team to be there a whole week, where we would run over 500 samples. Strontium had to be extracted through a series of acid washes before entering the mass spectrometer and carbon/oxygen had to be weighed out and placed in vessels before extraction could begin. Following testing, results were interpreted and graphed for each sampled individual.

Weighing for Carbon and Oxygen Samples at Illinois.jpg

The Trip to Israel

As a part of my internship, and through a summer research grant, I was awarded the opportunity to travel to Israel to collect and export additional teeth to submit for stable isotope sampling. During my two-week adventure I stayed in Kibbutz-Ruhama with Dr. Jimmy Hardin and Dr. Jeff Blakley and combed through box after box of recovered animal remains from the Hesi Regional Research Project to collect and bag teeth for export. Once all the teeth were collected, bagged, and recorded in an excel spreadsheet, I experienced the permitting process for exporting archaeological remains from Israel through the Israeli Antiquity Authority. Detailed photographs were shot of the 80 selected teeth for export, including photographs of how they were bagged and how they were going to be transported. A formal letter had to be written detailing where the remains were going, the sampling procedure, and the labs where the sampling would take place. After a few days, the Israeli Antiquities Authority issued me an export permit, and I was allowed to leave the country with the faunal teeth (the look on the TSA agent’s face when she pulled out a giant bag of teeth was priceless). While it was a field season, I still had time to visit a few archaeological sites, tour the Old City of Jerusalem with my advisor, and work on thesis research at the W. F. Albright Institute for Archaeological Research.

All Bagged Samples

The Big Picture

During my time as a graduate research intern I was able to work on a range of material ranging from the Early Bronze Age to the Iron Age in the Near Eastern region, gain hands-on stable isotope analysis experience from the leading experts in the field, and made necessary connections between understanding isotopic analysis and how they relate to archaeological questions and problems. Based on my summer as an intern, I will be involved in multiple publications based on the primary data recovered from the sampled. I will be presenting a paper on the Iron Age Hesi regional isotopes at the ASOR (American School of Oriental Research) conference this November in Denver, which will be turning into a book chapter for the upcoming Hesi Regional Research Project report. In addition, I will be a co-author in an upcoming paper on the Early Bronze Age isotope results from Tell el-Hesi and a co-author on a paper comparing the Early Bronze Age isotope results from the various sites we worked on this summer. This internship not only taught me the ins and outs of isotopic research that will be applied to my thesis and future endeavors, but it also provided me necessary skills to navigate the world of academia and research. It was a world-wind of a summer but I’m forever grateful for the experiences and knowledge that I gained through the experience. Thanks for reading!

By Kara Larson




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