Coprolites are fossilized feces that can be analytically examined to understand archaeological events. Fourteen coprolites were found by archaeologists at the lowest levels of the Paisley 5-mile point caves in south-central Oregon. The coprolites found it this site were morphologically human based on the size, shape, consistency, and color. Upon further analysis using multiplex polymerase chain reaction (PCR), all fourteen coprolites tested positive for human mitochondrial DNA (mtDNA). The next step for the archaeologists was to date the age of these coprolites.
The coprolites were dated using an accelerator mass spectrometry (AMS) system. This radiocarbon dating system found that the three oldest produced an age of 12,300 14C years B.P. To ensure the validity of these coprolites dates, the archaeologists sent the five coprolites from the deepest layers to be direct dated by AMS at two independent laboratories; Beta Analytic in Florida, USA and Oxford Radiocarbon Accelerator Unit at the University of Oxford, UK. These two labs used two different methodologies for analyzing the coprolites and could be cross examined for accuracy. From the five coprolites sent to both labs, four produced consistent dates ranging approximately 1300 to 12,300 14C years B.P. and three pre-dated 11,000 14C years B.P. This data confirms that humans were present in North America before the Clovis people.
The Clovis people are a group of prehistoric Native Americans commonly thought to be the first human inhabitants of North America. They are named after the town where their artifacts were found in Clovis, New Mexico and they inhabited the area around 11,000 14C years B.P. The latest coprolite studies from Oregon question the age of North American inhabitants. Many other pre-Clovis occupation sites have been recorded around North America but they remain controversial because of the lack of human artifacts to accurately date the sites. The coprolites found at the Paisley 5 mile point caves are so crucial because they undisputedly confirm pre-Clovis humans. The DNA in the coprolites not only dated the age of the humans who produced them, but they also gave us an insight to their diet.
Many of the coprolites contained canid 16S mitochondrial DNA that is similar to the red fox, coyote, domestic dog, or wolf. Among the coprolites the archaeologists also found a diverse amount of canid bones. The two most likely explanations for these findings are that the earliest humans in North America included canids in their diet or that canids inhabited the caves during nonhuman occupation and directly urinated on the human feces. Both theories give us insight to the past and the importance of coprolite analysis in resolving the historical record.
What AMS is and how it is works:
Analysis of Coprolites found in the Hidden Caves of western Nevada: