CC by B Fouzy/@Rayabi

Biomarkers found in human poo are being used to track historical human presence in areas of Norway.

By observing changes in the levels of a compound called coprostanol in sediment cores taken from Lake Liland in the Lofoten Islands just north of the Arctic Circle Robert D'Anjou, a doctoral student at the University of Massachusetts was able to measure human presence in the vicinity.

Coprostanol is a biomarker formed when cholesterol is broken down during digestion. Faecal matter containing the marker washes into the lake and ends up as part of the sediment. Coprostanol can be found in a number of higher mammals but, as D'Anjou explains, "When you find these molecules at certain concentrations and in specific ratios, it provides an unmistakable indicator that people were living in the area."

By monitoring the coprostanol levels and combining the results with the presence of other markers and chemicals D'Anjou was able to build up a relatively detailed account of the human activity in the area.

According to the sediment composition, between 7,300-2,250 years ago no human activity was detected. After this point increased pyrolytic PAH (poly-aromatic hydrocarbons associated with wood burning) and human faecal material imply human presence in the area.

This burst of activity was followed by a 150-year lull and a steady 400-year rise. From this point rises and falls in the human population as recorded by the coprostanol in the sediment correlate well with summer temperature patterns -- logical given the relationship between summer temperature and successful crop growth.

In addition to linking human presence with changing climates and resources in an area, the technique could also be used to establish human presence in other fields.

According to Raymond Bradley, director of the Climate System Research Centre at the university and D'Anjou's advisor, "This approach opens the door to other studies, where the presence of humans is uncertain; we believe it has great potential for much wider applications in archaeology."


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