Biochemistry Does The Job
How do you discover ancient toilets and sewers?
By finding human poop.
And how do you detect ancient human poop?
Biochemistry!
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 with the Acropolis beyond it.
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.
A drain in the Agora in Athens.
Late Roman-era drains in the Agora in Athens,
where the discovery was made.
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 the Roman Empire
By the late sixth century, "Rome" referred to
a Greek-speaking empire that had long since abandoned Rome.
The city of Rome was 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.
Visiting
İstanbul
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.
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.
Slavic people sacked Athens in 582.
The Slavs 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 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
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.
Scientific research projects searching for coprostanol include:
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 or
or 3α,12α-dihydroxy-5β-cholanoic 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.
Next article:
Panchagavya, an Ayurvedic elixir of dung and urine
