Article
Magazine: Fall 2018
I was particularly intrigued by a gray tone that was frequently used in the paintings to color objects that were naturally blue or green, such as jade, quetzal plumes, or corn plants. Maya blue paint oxidizes black at high temperatures and could thus not be used as a slip; however, it was occasionally painted onto Maya vases after firing. Was the gray color we see today actually a faded blue-green, as some scholars had proposed? To explore this, we used X-ray fluorescence equipment to determine the elemental compositions of various slips on Maya vases in the collection. I shared the results with Satish [Myneni, professor of geosciences], who both confirmed our interpretation of the data‚—the color was never blue-green but always gray, produced by a mixture of white and black minerals‚—and noticed something else in the spectra that intrigued him: a high spike of arsenic.
Satish's own research includes the biogeochemistry of contaminants and their influence on the environment, primarily in contemporary contexts. To see significant levels of arsenic in an ancient object, especially a drinking cup, surprised and intrigued him and inspired research on which we have collaborated over the intervening years.
Our questions were many: How much arsenic would leach into the human body by eating and drinking out of ceramic vessels? How did the arsenic get in the clay? Were these high arsenic levels restricted in time and space, or widespread? In order to gain greater precision in our studies, we sought materials that had a specific archaeological context. With the help of Christina T. Halperin, a Maya archaeologist and then a Cotsen Fellow in the Princeton Society of Fellows in the Liberal Arts, and Ronald Bishop, a senior research archaeologist at the Smithsonian Institution, we were able to borrow ceramic sherds excavated at the famous Maya city of Tikal. Synchrotron mass spectroscopy was conducted on these sherds by Satish and Erika L. Smith, Class of 2013. It confirmed that arsenic was present in all pottery tested from the site, from all time periods throughout the city's history.
Understanding how the arsenic contaminated the clay and how it subsequently transferred into human bodies required analysis of additional archaeological materials. We have since studied human bones and teeth, as well as soil samples, excavated by University of Pennsylvania archaeologists at Tikal and loaned to us for our research by Penn's Museum of Archaeology and Anthropology with the assistance of Janet Monge and William Wierzbowski. Arsenic concentrations in bones and teeth of Maya remains are very high; moreover, as evidenced by cross-section analyses of teeth, people at Tikal were exposed to toxic levels of arsenic throughout their lives. Exposure to elevated levels of arsenic is known to cause cancer and ultimately death. Much of this most recent work was conducted by Catherine (Casey) Ivanovich, Class of 2017, for her junior paper and senior thesis, the latter of which was awarded the Edward Sampson, Class of 1914, Prize in Environmental Geosciences. Casey's thesis was the first study to provide a means of correlating arsenic levels in bone to quantifiable levels in ingested sources. As such, it provided a new method of studying an important aspect of human pathology, especially for ancient remains where soft tissues are not available for existing methods of analysis.
Satish's own research includes the biogeochemistry of contaminants and their influence on the environment, primarily in contemporary contexts. To see significant levels of arsenic in an ancient object, especially a drinking cup, surprised and intrigued him and inspired research on which we have collaborated over the intervening years.
Our questions were many: How much arsenic would leach into the human body by eating and drinking out of ceramic vessels? How did the arsenic get in the clay? Were these high arsenic levels restricted in time and space, or widespread? In order to gain greater precision in our studies, we sought materials that had a specific archaeological context. With the help of Christina T. Halperin, a Maya archaeologist and then a Cotsen Fellow in the Princeton Society of Fellows in the Liberal Arts, and Ronald Bishop, a senior research archaeologist at the Smithsonian Institution, we were able to borrow ceramic sherds excavated at the famous Maya city of Tikal. Synchrotron mass spectroscopy was conducted on these sherds by Satish and Erika L. Smith, Class of 2013. It confirmed that arsenic was present in all pottery tested from the site, from all time periods throughout the city's history.
Understanding how the arsenic contaminated the clay and how it subsequently transferred into human bodies required analysis of additional archaeological materials. We have since studied human bones and teeth, as well as soil samples, excavated by University of Pennsylvania archaeologists at Tikal and loaned to us for our research by Penn's Museum of Archaeology and Anthropology with the assistance of Janet Monge and William Wierzbowski. Arsenic concentrations in bones and teeth of Maya remains are very high; moreover, as evidenced by cross-section analyses of teeth, people at Tikal were exposed to toxic levels of arsenic throughout their lives. Exposure to elevated levels of arsenic is known to cause cancer and ultimately death. Much of this most recent work was conducted by Catherine (Casey) Ivanovich, Class of 2017, for her junior paper and senior thesis, the latter of which was awarded the Edward Sampson, Class of 1914, Prize in Environmental Geosciences. Casey's thesis was the first study to provide a means of correlating arsenic levels in bone to quantifiable levels in ingested sources. As such, it provided a new method of studying an important aspect of human pathology, especially for ancient remains where soft tissues are not available for existing methods of analysis.
