Schistosoma mansoni’s Big Adventure

To most people, a bathroom is a purely practical thing. You go, you do your business, and you leave. It is not a place to be celebrated. But archaeologists aren’t most people. To them, discovering an old toilet buried in the earth is a window into the day-to-day life of a person who’s been dead for hundreds, if not thousands of years. Sure, that does mean digging through old poop, but the things that can be learned are so worth it.

Case in point, a study was recently published in Parasitology about a new discovery found in a 500-year-old latrine in Bruges, Belgium. Within that latrine, located inside what served as a meeting house and administrative seat for the Spanish merchant community in the city, the researchers found an egg belonging to Schistosoma mansoni, a parasitic flatworm.

S. mansoni is not typically the sort of houseguest one wants in their bathroom. In fact, as the parasite responsible for causing schistosomiasis, a disease that infects 200 million people worldwide and is the second-most deadly parasitic disease — only topped by malaria — it’s kind of the exact opposite of a welcome visitor. Particularly if you’re a Spanish merchant living several hundred years before the advent of a cure for the disease infecting your gut.

For the researchers, though, finding the egg in Belgium helped solve a mystery involving S. mansoni while also demonstrating the connectedness of the world, even in an age before planes, trains, and automobiles.

Today, S. mansoni is endemic throughout the tropics, but it is not native to much of its current range. A thousand years ago, the worm only lived in Africa. Somehow, it managed to find its way across an ocean to South America, and the discovery of the egg in the droppings of a Spanish trader demonstrates how. The Spanish merchants of Bruges were instrumental in the import of commodities from Africa such as gold and ivory, as well as the slave trade. And if this one hapless Spaniard could carry S. mansoni to Belgium, others like him could certainly carry it to all corners of the world.

Not only do the study findings demonstrate the complexity and interconnectedness of urban life, even in medieval times, Maxime Poulain, an archaeologist at Ghent University, said in a press release, it shows how Bruges, an international trade and cultural hub, “inevitably also facilitated the spread of diseases through its strong maritime trade networks.”

Hopefully, as our unfortunate merchant sat upon the toilet in Bruges so many years ago, the foresight that his plight would provide a group of scientists with a fascinating insight into city life and the movement of a nasty tropical disease was enough to provide comfort as the flatworm ransacked his body. Totally worth the debilitating disease.

Et tu, Plumbum? Then Fall, Caesar’s IQ!

Lead is a very, very bad thing to be exposed to. Children poisoned by lead suffer permanent negative health impacts, particularly with regards to development of the central nervous system, while lead exposure in adults can lead to high blood pressure, cardiovascular disease, and kidney damage. Leaded gasoline blighted an entire generation of children in the 1960s and 1970s, costing those born during those years an average 6 or 7 IQ points. Fortunately, with the banning of leaded gasoline in 1996, children now only have microplastics to stunt their intellectual development.

One might imagine that lead poisoning is a modern-day problem, a result of the Industrial Revolution and internal combustion engines. But that’s not the case. Despite physicians of the era recognizing lead as a poison and documenting cases of lead poisoning, it was very prevalent during the age of both the Roman Republic and Empire. A popular theory in the 1980s even posited that Rome’s fall could be directly linked to lead exposure.  

That hypothesis has been largely debunked, but ancient Romans were undeniably exposed to large amounts of lead, and a recent study published in PNAS has been able to quantify both how much lead the Roman civilization poured out and what the cognitive effects of so much lead pollution were. To do this, they analyzed cores of ice from places like Greenland and Antarctica, where atmospheric lead has settled among the slowly building glaciers. These cores, some as long as 11,000 feet, contain records of atmospheric anomalies stretching back eons. 

For a pre-industrial civilization, the Romans were exceptionally skilled at pouring lead over the course of their thousand-year history, mostly as a byproduct of large-scale silver mining all over the empire. Galena, the mineral the Romans pulled silver from, also contains lead, so much so that for every ounce of silver they extracted, a thousand ounces of lead were released into the atmosphere. 

While the atmospheric lead concentrations during Roman times were a fortieth of what was reached during the 1970s, the Romans still managed to release over 500 kilotons of lead into the atmosphere during the 200-year Pax Romana at the start of the first millennium AD. This was enough to raise childhood blood lead levels by 2.4 mcg/dL — today, 3.5 mcg/dL is enough to necessitate medical intervention — and reduce the average IQ of the European population at the time by 2-3 points. 

That “doesn't sound like much, but when you apply that to essentially the entire European population, it's kind of a big deal,” study coauthor Nathan Chellman of the Desert Research Institute in Nevada said in a press release. Indeed, with a bit less lead in the air, perhaps Caesar could have had the foresight to see that knife coming.

The Tooth, The Whole Tooth, And Nothing But The Tooth

When you hear or see the word "microbiome," there's one part of the body that immediately comes to mind: the gut. Those billions and billions of bacteria living in your gut are usually the star of the health show, but today, let's turn the spotlight someplace else. A different microbiome, underappreciated and unloved.

This is the story of our mouth microbiome. Or, more accurately, a history.

The new research asked a pretty simple question: How did our ancestors' mouths differ from those in the modern day? To answer this question, the researchers performed a genomic analysis of a pair of teeth taken from a man who lived in Ireland 4,000 years ago, during the Bronze Age.  

To no one's surprise, the consensus is that the man's dental microbiome at the time of death was not exactly healthy, and in fact he was at high risk for developing cavities. Hey, let's see you have a healthy mouth when you live in a society without toothpaste. It did exist at this time, but not in Ireland. 

While the poor shape of the man's mouth isn't a shock, the reason behind it is rather interesting, as the teeth were rich in Streptococcus mutans, a bacteria very well known as a major contributor to tooth decay. Now, this doesn't sound like it should be a surprise, considering the aforementioned lack of toothpaste, but other ancient mouth microbiomes do not show nearly as much S. mutans. It's actually very rare to see this bacteria in people living before 1500 AD. 

In our Irish friend's case, the S. mutans had done such a thorough job taking over his mouth that other, more beneficial streptococcal species were basically absent. That said, there were plenty of other bacteria species in the sample. So many, in fact, that the ancient microbiome was more biodiverse than modern-day mouth microbiomes. In a lot of ways, ancient teeth were healthier than ours, mostly down to the lack of sugar in their diets compared to ours.

So, if you think you could pluck a person out of ancient history and they'd have a smile like this, think again. All our Irish friend needed was ye olde dentist, which is something pretty much everyone over on the British Isles need. Yeah, we're ending with a "British people have bad teeth" joke. You knew it had to happen.