Researchers studying modern-day disease have turned to medieval latrines for answers. Sifting through 14th and 15th century toilets, scientists have found that bacterial DNA from human excrement can last for centuries. The discovery has provided clues to how our gut contents have changed significantly since medieval times.
Analysis of two cesspits, one in Jerusalem and the other in the Latvian capital, Riga, could help scientists understand if changes to our microbiome – the genetic makeup of the bacteria, virus, fungi, parasites and other microbes living inside us – affect modern-day illnesses.
The variations may be linked to many of the diseases of the present-day world.
This includes inflammatory bowel disease, allergies, and obesity, according to the study published earlier this week in Philosophical Transactions of the Royal Society B.
Dr Kirsten Bos, a specialist in ancient bacterial DNA from the Max Planck Institute for the Science of Human History and co-leader of the study, told The Guardian of how the finding was the first of its kind.
She said: “At the outset, we weren’t sure if molecular signatures of gut contents would survive in the latrines over hundreds of years.
“Many of our successes in ancient bacterial retrieval thus far have come from calcified tissues like bones and dental calculus, which offer very different preservation conditions.”
They specifically chose latrines thought to have been used by large numbers of people.
This was intended to paint a vivid and wide-ranging insight into the intestinal flora of whole communities.
The study concluded that the microbial content of the medieval excrement was unique compared to modern humans and included those who lived hunter-gatherer lifestyles.
Dr Bos said: “It seems latrines are indeed valuable sources for both microscopic and molecular information.
“We’ll need many more studies at other archaeological sites and time periods to fully understand how the microbiome changed in human groups over time.
“However, we have taken a key step in showing that DNA recovery of ancient intestinal contents from past latrines can work.”
Piers Mitchell, a paleopathologist at Cambridge University who worked on the study, said ancient latrines could become a key source of biomolecular information and allow scientists to explain how modern lifestyles affect human health.
He explained: “If we are to determine what constitutes a healthy microbiome for modern people, we should start looking at the microbiomes of our ancestors who lived before antibiotic use, fast food, and the other trappings of industrialisation.”