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In the wee hours of the morning in a lab in Amherst, Massachusetts, geoscience graduate student Rob D’Anjou sat looking over test results, a pot of coffee nearby. He’d been pulling long days to analyze two narrow columns of silt, mud, and other sediment cored from the bottom of Lake Liland in Arctic Norway, and, frustratingly, was seeing no sign of the molecules with which he’d been hoping to reconstruct the temperature and precipitation records during the lake’s last 7,000-odd years.

There were a number of other substances in the cores, though. And some of those other substances, he realized with a jolt, looked familiar. He turned to a cache of chemistry papers and, with their help, confirmed his suspicion: He was looking at human fecal sterols, the last chemical hurrah of poop. And these feces were decidedly ancient ones, manufactured, as it were, starting more than 2,000 years ago.

D’Anjou knew that the find, however unglamorous it might be, was an important one. Human fecal sterols are, by definition, indicators of the presence of human beings and may provide a way to track the migration of ancient peoples, as well as to help paleoclimatologists assess those populations’ effects on the environment. When he presented his data before the geosciences department at University of Massachusetts, Amherst, the scientists in the audience were quick to suggest colorful titles for his study. But D’Anjou and his colleagues spent the following couple years giving the samples a far more sober kind of consideration. Their work, published this week in the Proceedings of the National Academy of Sciences, marks the first time fecal sterols have been used this way, but it more than likely won’t be the last.