I was a freshman in one of my first archeology classes when it hit me that archeology isn’t treasure hunting. Yes, archeologists find precious objects from time to time, but more often than not, archeologists study trash! People from the past used or took with them anything that was still good or useful. So what they left behind was either broken, lost or waste. Common archeological remains include table leftovers (fruit pits, charred bones), factory waste (a lot of empty glass bottles for instance), broken pottery, “débitage” (waste from stone tool manufacturing) and, the most glamorous of them all, human and animal waste.
“… Excuse me, what? How can poop fossilize? Why would I care? How do you know what it is? Why am I still holding it?!” is what I was thinking when my archeology professor placed a shapeless rock-looking object in my hands and informed me that it was a coprolite, also known as fossilized poop.
Fast-forward 7 years, I am now half way through my PhD and coprolites are one of my favorite things to find. Coprolites are just one example of all the animal byproducts that can become fossilized. Other byproducts include stomach contents and (although they are rarely found) urine, skin, muscle, hair, feathers, eggshells and nails. Coprolites and all these other byproducts can provide meaningful information on the lives of populations who lived hundreds, thousands, or even millions of years before us, all the way back to the time when Homo sapiens was not yet fully modern (and well before that too!). Actually, coprolites are by far the most common “byproducts” found at sites relevant to hominin evolution, because they tend to preserve the best in the fossil record. The most ancient identified hominin coprolite comes from the site of El Salt in Acoy, Spain and is attributed to a Neanderthal.
Scientists can link a coprolite to its maker based solely on its morphology (its shape, size and form), but doing so is rather difficult because coprolite shapes and sizes are highly variable. When possible, genetics and DNA can identify the maker much more accurately.
Coprolites contain genetic material from the animal that produced them, but some can also provide insights into diet, oral bacteria and intestinal microbiota. For paleoecology, the information that coprolites can provide about diet is most crucial because diets are frequently used to infer shifts in the environment.
Coprolite DNA is incredibly useful. It can provide us more information on poorly understood extinct animals, such as Oreamnos, a North American goat. It can help us understand ancient migration patterns: One study used coprolites produced by the “First Americans” from the site of Paisley, Oregon to reconstruct the peopling of America.
Fossilized feces can also contain other material relevant to DNA analyses, such as pollen and hair. The oldest hominin hairs (~250 thousand years ago), were found in fossilized hyena fecal remains at Gladysvale, South Africa. Although the specimen itself was too degraded to allow for DNA analyses, researchers have the technical ability to study ancient hairs, so say tuned for new discoveries!
Unfortunately, the study of coprolites has many obstacles. The fecal material is highly degraded so only short fragments of DNA can typically be sequenced. Similarly, a phenomenon called crosslinking often occurs between the DNA and proteins found in coprolites, which complicates the DNA sequencing procedures. A method called “next generation sequencing” helps address some of these obstacles, and was first successfully used on coprolites in 2008, in a study of the human microbiome on remains from Cueva de los Muertos, Mexico.
The study of hominin and animal coprolites from the Pleistocene has enormous potential. It could provide a wealth of information on our ancestors’ migration patterns, diet, environments, etc. Archeology really is treasure hunting. It’s just that sometimes, another hominin’s trash is actually our treasure.