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By analysing ancient human waste, scientists have found a way to track population changes in a region.
Palaeontologists are quite familiar with having to look at the droppings of dinosaurs to find out what the creatures might have eaten. Now, archaeologists are turning to human waste as a means to track something very different: population changes.
Existing methods to track population change have relied on census data and other information gathered from local areas but, aside from being limited to the past 200 years or so, they are also plagued with accuracy problems.
Census isn’t enough
So, a team from Binghamton University in the US has published a paper in the Journal of Archaeological Science detailing how faecal matter washed out to sea or a nearby lake has a biomarker capable of being tracked over hundreds of years.
While other human materials can be unreliable indicators of population prediction, faecal stanols are much more accurate.
To determine this, the team analysed sediment found in a lake next to the settlement of Cahokia near St Louis, Missouri, the site of one of the largest prehistoric populations in North America approximately between 600 and 1,500 years ago.
Schematic depicting the formation, deposition and degradation of human faecal stanols. Image: AJ White, Lora R Stevens, Varenka Lorenzi, Samuel E Munoz, Carl P Lipo and Sissel Schroede
Can be applied elsewhere
By analysing the abundance of faecal stanols found in a core sample from the lakebed, the team was able to show that population peaks for the site occured relatively early in its occupation and slowly declined.
This finding contradicts suggestions that Cahokia underwent a ‘collapse’ event or was victim to massive floods, which are known to have occurred.
While this work has been demonstrated in cold climates where faecal stanols are better preserved, this is one of the first archaeological cases where this method has been shown to work in a more temperate climate.
This latest discovery now means it can be applied to other sites as well, with the Binghamton team now looking to improve the technique for better accuracy.
“It has become relatively popular to think of the past as a series of periods in which cultures flourish and then catastrophically collapse,” said Carl Lipo, professor of anthropology at Binghamton University.
“Using empirical evidence available in the form of the faecal stanols, we can now see that the end of Cahokia was not so much a ‘collapse’ but a slow fading-away that took multiple centuries. Flooding events, for example, appeared to have had no effect on the relative population size.”
