Parasitic worms that infect the human intestine lay eggs that are later excreted in feces. These parasites might spread from human to human, or they may be passed from intermediate animal hosts, such as pigs or fish, via meat consumption or contaminated soil. Could eggs laid by these parasites provide clues about what someone ate while they were alive?
While earlier research investigated past diets by using microscopy to identify parasite eggs in ancient waste, the advancement of DNA sequencing technology has recently given this field a boost. In a new PLOS ONE study, Martin Søe and colleagues from the University of Copenhagen used a novel approach to examine DNA in parasite eggs from ancient latrines in Bahrain, Jordan, Denmark, the Netherlands, and Lithuania, spanning a period from 500 B.C. to 1700 A.D.
To identify which parasite species were represented by the ancient eggs, the researchers first filtered and concentrated the eggs in their samples—a key step that had not been used in other studies of ancient parasite DNA. Then, they used a technique called shotgun sequencing for their DNA analysis.
Most of the egg DNA came from parasites known to spread from human to human, but much came from parasites that are transmitted via raw or undercooked fish and pork. The egg DNA also revealed which animals — domesticated or not — may have lived among humans, such as sheep, horses, dogs, pigs and rats.
To complement the egg analysis, the researchers also examined animal and plant DNA in the samples. Animal DNA reflected domestication as well as hunting and fishing practices; some of the Danish samples (1018 to 1400 A.D.) contained DNA from fin whales, roe deer and hares. Plant DNA reflected different areas’ diets, including an abundance of cabbages and buckwheat in Northern Europe.
“Ancient DNA from latrines was used to identify the remains of a broad range of human and animal parasites as well as animals and plants,” Søe says. “This allows novel and unique insights into parasitism, diet and subsistence patterns of past populations.”
Citation: Søe MJ, Nejsum P, Seersholm FV, Fredensborg BL, Habraken R, Haase K, et al. (2018) Ancient DNA from latrines in Northern Europe and the Middle East (500 BC–1700 AD) reveals past parasites and diet. PLoS ONE 13(4): e0195481. https://doi.org/10.1371/journal.pone.0195481
Image Credit: Søe et al (2018)