Last updated April 26, 2018 at 12:09 pm
Digging through old toilets builds a picture of past lifestyles in Northern Europe and the Middle East.
Researchers have long known that studying faeces from extinct species can reveal a lot – and now they’ve gone one step further by recovering DNA in parasite eggs from ancient toilets.
“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,” says Martin Søe, the main author of the study.
“This allows novel and unique insights into parasitism, diet and subsistence patterns of past populations.”
Parasite eggs were taken from ancient toilets in Bahrain, Jordan, Denmark, the Netherlands, and Lithuania. The samples spanned a period from 500 BCE (Bahrain) to 1700 CE (the Netherlands).
Why parasite eggs?
Parasites have two main ways of entering the human body: spread from human to human, or passed from animals, such as eating raw or undercooked meat.
They can also enter via contact with soil an animal or human has contaminated.
Once inside your gut, parasite worms lay eggs that are excreted in faeces.
The researchers used a novel approach in which the egg samples were filtered and concentrated.
Through shotgun sequencing – a technique for quickly sequencing large amounts of DNA and one not previously applied to studies of parasite eggs – they could match DNA sequences with parasite species represented by the eggs.
They could also detect parasites for which sheep, horse, dog, pig, and rodents serves as hosts, and so find the animals people had the closer contact with, presumably through domestication.
Although most of the egg DNA came from known parasites which spread from human to human, a number of parasites identified come from the consumption of raw or undercooked fish and pork.
Delving deeper with plant and animal DNA
So the study built a clearer picture than ever before of diet, animal domestication and hunting practices.
Some of the Danish samples (1018 to 1400 CE) contained DNA from fin whales, roe deer, and hares.
Meanwhile, plant DNA reflected different areas’ diets, including an abundance of cabbages and buckwheat in Northern Europe.
The genomic approach also allowed the reconstruction of mitochondrial parasite genomes which provide insights into the genetic diversity, how they spread, and biology of ancient and modern parasites.
The research is published in PLOS ONE.