Coprolites and Their Analysis - Fossil Feces as a Scientific Study

The Archaeological Study of Human Fossil Feces called Coprolite

Coprolite from Paisley Cave (Oregon)
Human coprolite from Paisley Cave 5 radiocarbon dated to 12,300 BC. Image courtesy of Dennis LeRoy Jenkins

Coprolite (plural coprolites) is the technical term for preserved human (or animal) feces. Preserved fossil feces are a fascinating study in archaeology, in that they provide direct evidence of what an individual animal or human ate. An archaeologist can find dietary remains in storage pits, midden deposits, and within stone or ceramic vessels, but materials found within human fecal matter are clear and unrefutable evidence that a particular food was consumed.

Coprolites are a ubiquitous feature of human life, but they preserve best in dry caves and rock shelters and are occasionally discovered in sand dunes, dry soils, and swamp margins. They contain evidence of diet and subsistence, but they also can contain information about disease and pathogens, gender, and ancient DNA, evidence in a manner that is not readily available elsewhere.

Three Classes

In the study of human excrement, there are generally three classes of preserved fecal remains that are found archaeologically: sewage, coprolites, and intestinal contents.

  • Sewage or Cess, including privy pits or latrines, cess pits, sewers, and drains, contain largely mixed assemblages of human feces together with kitchen and other organic and inorganic wastes. When found well-preserved, particularly when water-logged, cess deposits provide valuable information on community or household diet and living conditions.
  • Coprolites are individual fossil or subfossil feces, preserved through charring, mineralization, or found as desiccated samples in caves and extremely arid places. Each sample provides evidence for foods eaten by an individual, and if found in a latrine area can also reveal community-wide diets.
  • Intestinal or Gut Contents refers to preserved human remains found within the intestines of well-preserved human or animal bodies. These are of the most value of the three for a study of an individual, because they are essentially uncontaminated remains which hold information on at most one or two meals, in fact, the last meal that the individual consumed. Gut contents are relatively rare discoveries, found only when whole humans are preserved, in the case of natural or (if not too extensive) cultural mummification, freezing or freeze-drying (for example, Otzi the Tyrolean Iceman), or waterlogging (such as European Iron Age bog bodies).

    Content

    A human or animal coprolite can contain a diverse range of biological and mineral materials. Plant remains found in fossil feces include partly digested seeds, fruits and fruit parts, pollen, starch grains, phytoliths, diatoms, burned organics (charcoal), and small plant fragments. Animal parts include tissue, bones, and hair.

    Other types of objects found in fecal matter include intestinal parasites or their eggs, insects, or mites. Mites, in particular, identify how the individual stored food; the presence of grit could be evidence of food processing techniques; and burned food and charcoal is evidence of cooking techniques.

    Studies on Steroids

    Coprolite studies are sometimes referred to as microhistology, but they include a wide range of topics: paleodiet, paleopharmacology (study of ancient medicines), paleoenvironment and seasonality; biochemistry, molecular analysis, palynology, paleobotany, paleozoology, and ancient DNA .

    Those studies require that the feces be rehydrated, using a liquid (typically a water solution of tri-sodium phosphate) to reconstitute the feces, unfortunately also including the odors. Then the reconstituted material is examined under detailed light and electron microscope analysis, as well as subjected to radiocarbon dating, DNA analysis, macro- and microfossil analyses and other studies of inorganic content.

    Coprolite studies have also included the investigations of chemical, immunological protein, steroids (which determine sex), and DNA studies, in addition to phytoliths, pollen, parasites, algae, and viruses.

    Classic Coprolite Studies

    Hinds Cave, a dry rock shelter in southwest Texas which had been used as a latrine for hunter-gatherers about six thousand years ago contained several deposits of feces, 100 samples of which were collected by archaeologist Glenna Williams-Dean in the late 1970s. The data Dean collected during her Ph.D. research have been studied and analyzed by generations of scholars since that time. Dean herself ran pioneer experimental archaeology studies using students to provide test fecal matter arising from documented dietary input, an unparalleled data set even today. Foodstuffs recognized in the Hinds Cave included agave, opuntia, and allium; seasonality studies indicated that the feces had been deposited between winter-early spring and summer.

    One of the earliest discovered pieces of credible evidence for pre-Clovis sites in North America was from coprolites discovered at Paisley 5 Mile Point Caves in Oregon state. The recovery of 14 coprolites was reported in 2008, the oldest individually radiocarbon dated to 12,300 RCYBP (14,000 calendar years ago). Unfortunately, all of them were contaminated by the excavators, but several included ancient DNA and other genetic markers for Paleoindian people. Most recently, biomarkers found in the earliest dated specimen suggest it was not human after all, although Sistiaga and colleagues had no explanation for the presence of Paleoindian mtDNA within it. Other credible pre-Clovis sites have been found since that time.

    History of the Study

    The most important proponent of research into coprolites was Eric O. Callen, a maverick Scottish botanist interested in plant pathologies. Callen, with a Ph.D. in botany from Edinburgh, worked as a plant pathologist at McGill University and in the early 1950s, one of his colleagues was T. Cameron, a member of the parasitology faculty.

    In 1951, archaeologist Junius Bird visited McGill. A few years prior to his visit, Bird had discovered coprolites at the site of Huaca Prieta de Chicama in Peru and collected a few fecal samples from the intestines of a mummy found at the site. Bird gave the samples to Cameron and asked him to search for evidence of human parasites. Callen learned of the samples and asked for a few samples of his own to study, to look for traces of fungi that infect and destroy maize. In their article recounting Callan's importance to the microhistology, American archaeologist Bryant and Dean point out how remarkable it is that this very first study of ancient human coprolites was conducted by two scholars with no formal training in anthropology.

    Callan's role in the pioneering study include the identification of a suitable rehydration process, still used today: a weak solution of trisodium phosphate used by zoologists in similar studies.

    His research was necessarily restricted to macroscopic studies of the remains, but the specimens did contain a wide variety of macrofossils that reflected the ancient diet. Callan, who died conducting research at Pikimachay, Peru in 1970, is credited with inventing techniques and promoting the study at a time when microhistology was disparaged as bizarre research.

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