For a long time, archaeologists assumed that excrement degraded rapidly, especially when it’s humid. But maybe not. After all, if every person poops between 500 to 1,500 grams a day, excreta should be the most abundant organic findings at dig sites -- if you know what to look for. Now, researchers analyzing fossilized feces (or coprolites) show that not only do excreta keep, they can also be used to distinguish ancient cultures from each other based on gut microbiomes. Even preserved parasite loads are culturally distinct.
Over 3,000 ancient settlements have been discovered in Puerto Rico. Among them were the Saladoids and Huecoids, two horticulturalist societies believed to have co-existed on Vieques Island off the southeastern coast of Puerto Rico from 5 AD to 1170 AD. Originally from present-day Venezuela, the Saladoids migrated to Vieques by 160 BC and also to Puerto Rico’s main island by 430 BC. They maintained their ancestral heritage, exhibited by their signature white-and-red-painted pottery, and also incorporated different traits gradually learned from other cultures. Not much is known about the origins of the Huecoids, though they’re believed to be from the eastern Andes in present-day Bolivia and Peru, settling in Puerto Rico by at least 5 AD. They made delicate carvings of semiprecious stones and resisted incorporating cultural traits from others.
To see if these two populations, which co-existed for over a thousand years, had different microbiome compositions that reflected their diet and other cultural factors, a team led by Raul Cano from Cal Poly San Luis Obispo examined 34 coporolites that were from two Huecoid and Saladoid excavation sites. The fossils, dated from 180 AD to 600 AD, were screened for parasites, and DNA was extracted for microbiome analyses. The team focused on coprolites cores since these were less contaminated by microbes in the environment.
“By examining the DNA preserved in coprolites from two ancient indigenous cultures, our group was able to determine the bacterial and fungal populations present in each culture as well as their possible diets,” said study coauthor Jessica Rivera-Perez from University of Puerto Rico at the American Society for Microbiology meeting earlier this year. The work is detailed in PLoS One this month.
Saladoid coprolite samples harbored sequences from amoebic parasites associated with freshwater fish, suggesting that raw fish was a substantial component of their diet. Huecoid coprolites were characterized by maize and Ascomycetes and Basidiomycetes fungi sequences, and the presence of lung flukes implies they ate freshwater invertebrates or certain aquatic plants that were secondary hosts.
The team also found a greater parasite load in Saladoid coprolites, indicating a difference in living arrangements -- where the population was more likely to be exposed to fecal material and parasite transmission. They also had a wider variety of parasitic species, which may have something to do with how they handled their food and how close they were with their pet dogs.
The findings show that the two distinct cultures retained their technological and cultural differences even though they peacefully shared an extended period of close proximity. They likely formed the later-day Taínos, who were present when Christopher Columbus made contact.
Images: Center of Archaeological Research of the University of Puerto Rico, Rio Piedras (top), 2014 Cano et al., PLoS ONE (middle)