Unusual and interesting toilets from all around the world.

How to Discover Ancient Toilets through Biochemistry

Biochemistry Does The Job

How do you discover ancient toilets and sewers?

By finding human poop.

And how do you detect ancient human poop?


Scientists have used coprostanol for several decades now to detect human feces. It's similar to cholesterol, and it's produced in the human digestive system. Now a group has shown that bile acids are even more useful for detecting the specific makeup of human feces.

They demonstrated how well this works by analyzing sediment from a 1400-year-old sewer in the Agora in Athens. The distinctive chemicals are stable over these long time periods, and they clearly distinguish human feces from that of other mammals.

The Acropolis in Athens.

The Acropolis in Athens

The Discovery

In 2001 researchers reported that they had discovered a wastewater system over 1400 years old in the Agora at Athens. Its design and location had suggested that it was a sewer. The confirmation was the discovery of biomarkers, coprostanol and bile acids that are distinctive signs of human feces. The researchers were even able to tell that the sewer system had been suddenly abandoned, possibly when Slavic people invaded from the north in 582-583.

The restored Temple of Hephastus in the Agora in Athens.

The Agora in Athens as seen from the Areopagus rock. The restored Temple of Hephastus is at the left.

The restored Stoa of Attalus in the Agora in Athens.

The Agora in Athens as seen from the Areopagus rock. The restored Stoa of Attalus is at the right.

The Sewer in the Agora

The drain was a large one. It had a large U-shaped tile channel at the bottom, side walls made from tiles set into mortar, and a cover of curved terracotta tiles. It was dated to the Roman period based on its construction details and some coins that had been lost in it.

That's the problem with some togas — your fistful of drachmae are always falling out in the worst times and places.

Some small oil lamps had been thrown into the drain toward the end of its time of use, and they were found in the silt. Their style placed them in the late sixth to early seventh centuries AD, right around the time the Agora area was abandoned due to the AD 582-583 invasion of Slavic people from the north.

Romans, Greeks, Slavs, what was going on?

The End of Rome

By the late sixth century, "Rome" meant a Greek-speaking empire that had long since abandoned Rome. The city of Rome itself was now just an outpost of the empire based in Byzantium, by then called Constantinople.

The Ostrogothic Kingdom ruled the Italian peninsula from 493 to 553. A Germanic soldier named Flavius Odoacer had deposed Romulus Augustulus, the last Emperor of the Western Roman Empire, in 476. Then Theodoric the Great, the leader of the Ostrogoths, killed and replaced Odoacer in 493.


We call the Eastern Roman Empire the Byzantine Empire, but the people who inhabited it at the time never used that term. They said "Rome" to refer to the nation and its empire. The Western Empire had faded away, and the city of Rome had fallen to the barbarian tribes from the north. Since Constantine the Great's rule of the Eastern Empire in 324-337, the ancient city of Byzantium was renamed Κωνσταντινούπολις or Constantinople. Old Rome was gone, Constantinople was Νέα Ρώμη or New Rome. And eventually it would be renamed again, as İstanbul.

Haghia Sofia, the Ayasofya in İstanbul.

The Haghia Sophia in Constantinople, now the Ayasofya in İstanbul.

The Ostrogoths were a vassel state under the Byzantine Empire. Their leader was a subject of the Emperor in Constantinople and acted as his viceroy for Italy. Relations were always tense at best for both political and religious reasons. In 535 the Byzantine Empire invaded Italy.

Athens was sacked by the Slavs in 582. The Slavic people are mostly unknown before the 5th century, when they were described as living north of the Danube river. The Slavs began moving into the Balkans in the late 570s and early 580s. The Avars, a nomadic Turkic people, had moved in from the east and settled in Carpathia, subjugating the numerous small Slavic tribes. Meanwhile, the Byzantine Empire was involved in a series of wars with Sassanid Persia and unable to defend its northwestern frontiers. Large-scale Slavic settlement in the Balkans began during 581-584.

Interior of the Haghia Sofia, the Ayasofya in İstanbul.

Interior of the Haghia Sophia in what was known as Constantinople at the time, İstanbul now.

The Chemistry

The giveaway in the case of the Agora drain was a mixture of cholesterol derivatives and bile acids. Animals, including humans, excrete a variety of steroidal chemicals in their feces — various sterol and stanol molecules. The variety of these related molecules, and their relative proportions, depends on what the animal ingests, and more so on what their body synthesizes and how their specific gut flora transform that combination. The resulting profile of concentrations of various molecules tells us what animal produced that feces.

Coprostanol, from https://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Coprostanol.png/320px-Coprostanol.png


The researchers report that the neutral steroidal components were a mixture of Δ5 sterol and 5β- and 5α-stanols, dominated by coprostanol. The high percentage of coprostanol indicated fecal matter "of predominantly human origin". Coprostanol is also called 5β-cholestan-3β-ol. It is produced by intestinal bacteria acting on cholesterol ingested or biosynthesized by the host. This happens in the gut of most higher animals including mammals and birds.

Coprostanol is commonly used to detect sewage contamination of otherwise fresh water. Modern urban sewage systems contain about 1300 μg of coprostanol per liter.

A healthy human excretes from 0.2 to 0.6 grams of bile acids every day. The bile acids found in the Agora drain were mostly deoxycholic (or 3α,12α-dihydroxy-5β-cholanoic) and lithocholic (or 3α-hydroxy-5β-cholanoic) acid, with lower levels of other products of intestinal bacteria acting on human primary bile acids. The bile acid levels increased lower in the drain, as would be expected in a sewer carrying human waste.

Deoxycholic acid, from https://en.wikipedia.org/wiki/Deoxycholic_acid

Deoxycholic or or 3α,12α-dihydroxy-5β-cholanoic acid.

Lithocholic acid, from https://en.wikipedia.org/wiki/Lithocholic_acid

Lithocholic or 3α-hydroxy-5β-cholanoic acid.

Their conclusion was that the material filling the drain has the biochemical characteristics of a large volume of human feces. The bile acid mixture is like what you find in human feces. Low levels of other bile acids suggests that there were smaller amounts of feces from another source, possibly pigs or rats.

So, the work shows that the drain was a sewer. Perhaps more significantly, it shows how useful the bile acids are for detecting human feces after centuries to millennia.

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