Everybody poops! This process of waste removal from the body is one of the most vital biological processes but is often forgotten about or dismissed within the larger archaeological community. Although its discovery at an archaeological site might not bring about the same initial excitement a shiny artifact might, preserved fecal matter can provide some of the most important archaeological insights. Archaeologists have increasingly turned towards preserved fecal matter as a means of investigating both the diet and living conditions of past societies.
The low preservation rate of poop proves it invaluable to archaeology research. To become fossilized, fecal remains must go through a mineralization process in which the organic material is preserved, turning them into coprolites. Because of its quick rate of decomposition, preservation can only occur in sedimentary environments, such as sand mud or ash, which protect the organic material from breaking down (Mani).
Fecal matter can also be analyzed through its preserved chemical compounds, or fecal stanols. The process of cholesterol nutrient breakdown within the gut results in a chemical called coprostanol, which has the ability to survive within soil for thousands of years. When congregating humans all poop in a concentrated area, the fecal matter washes into the surrounding bodies of water (White et. all.).
In Cahokia’s case, archaeologists have analyzed both the composition of persevered desecratory remains (coprolites) and the fecal chemical residues left behind (fecal stanols). Found within layers of sediment washed into Horseshoe Lake, fecal chemicals coprostanol and cholestenol can be analyzed in relation to one another. A higher ratio of these compounds found within the sediment layers correlates to a higher density of human waste—which can be directly related to Cahokia’s fluctuating population numbers (Smith). The higher the ratio, the higher the population and so forth. Following stratigraphic principals, the cores from Horseshoe lake are layered in a sequential manner. Through carbon dating of pollen and seed matter within these layers, archaeologists can correlate the fecal traces with a rough timeline of Cahokia (Taub).
Not only do the fecal stanol cores from Horseshoe Lake give rough population records in relation to time, but they also provide insight into the past Cahokian environmental conditions. When compared to other stanols from bacteria in the soil, the younger fecal stanols had increasingly heavy oxygen concentrations. This allowed archaeologists to conclude that water and lighter levels of oxygen evaporation was occurring at a greater rate—suggesting lesser levels of precipitation during the later years at Cahokia (White et all.). Not only were indicators of drought found, but the cores taken from the lake also provided evidence of flooding—leading archaeologists to hypothesize that changes in climate as well as other environmental factors contributed to the downfall of Cahokia (Taub). A society heavily reliant on maize production is vulnerable to the slightest fluctuation in climate, which could greatly explain the correlation of population decline through fecal matter traces and evidence of less rainfall.
Fossilized coprolites found in Cahokia and the surrounding area have provided archeologists with important dietary evidence. One of the more interesting fossilized feces analyzed was that of an ancient Cahokian dog. Close examination of the remains through the use of DNA, macroscopic, and isotopic analysis allowed archaeologists to conclude there was a significant overlap between human and dog diets (Witt et all). This discovery, in turn, provides a snapshot of the community diet as a whole.
K, Mani. “Coprolites – What Are They and How Are They Formed ?” Fossils – Window to the Past, Berkeley , https://ucmp.berkeley.edu/paleo/fossilsarchive/coprol.html.
Kiona N. Smith – Jan 29, 2020 11:27 pm UTC. “Ancient Poop Reveals What Happened after the Fall of Cahokia.” Ars Technica, 29 Jan. 2020, https://arstechnica.com/science/2020/01/ancient-poop-reveals-what-happened-after-the-fall-of-cahokia/.
Taub, Matthew. “What Poop Can Teach Us about an Ancient City’s Downfall.” Atlas Obscura, Atlas Obscura, 25 Feb. 2019, https://www.atlasobscura.com/articles/archaeology-of-cahokia-poop.
White, A.J., et al. “An Evaluation of Fecal Stanols as Indicators of Population Change at Cahokia, Illinois.” Journal of Archaeological Science, Academic Press, 31 Mar. 2018, https://www.sciencedirect.com/science/article/pii/S0305440318301006#fig4.
Witt, Kelsey E., et al. “Integrative Analysis of DNA, Macroscopic Remains and Stable Isotopes of Dog Coprolites to Reconstruct Community Diet.” Nature News, Nature Publishing Group, 4 Feb. 2021, https://www.nature.com/articles/s41598-021-82362-6.