Kristina Killgrove
Kristina Killgrove

Teeth and Bones from Ancient Rome Hold Clues to Migration and Slavery

Kristina Killgrove
Kristina Killgrove

There’s an old saying that “all roads lead to Rome.” With good reason, too. Rome during the Empire was massive, with crowded neighborhoods boasting a population density comparable to New York, and with roads snaking throughout the Empire to help provision its capital. Along with goods came people; both immigrants looking for jobs or education and slaves brought to Rome to serve the upper classes. My new study, out today in PLOS One, uses teeth from Roman skeletons to start a conversation about migration to the capital during the Imperial period (1st–3rd century CE). 

We know from Roman history and from studies of ancient demography that the rate of migration to Rome had to be relatively high, and we know that many citizens could move freely around the Empire. But archaeologically speaking, migrants are practically invisible. Unless they were wealthy enough to leave monuments to their foreignness, these individuals are hard to see—especially among the lower classes and slaves who made the journey to Rome.

But Roman skeletons hold different information than historical records and archaeological remains like material culture. Bones and teeth can be analyzed by bioarchaeologists to reveal what someone ate, what diseases they had, and where they were born. So skeletal analysis is starting to provide new answers to longstanding questions about ancient Roman lives, including people’s origins. 

Using molars from two cemeteries in Rome that date to the 1st–3rd centuries CE, my colleague Janet Montgomery and I analyzed the isotope ratios of strontium in 105 people and of oxygen in 55 people who were likely among the lower class, judging by their simple burials with few grave goods (objects buried with them). The ratio between two isotopes, or variants of an element, reflects the environment where a person lived while their teeth were forming in childhood. By comparing the strontium and oxygen isotope ratios present in the skeletons with the ratios expected for people raised in Rome, we could identify individuals whose isotope ratios did not correspond with an origin there.

Since Imperial Rome was a very complex place—water was brought in via aqueducts from the east and wheat was brought in from as far away as North Africa—it is easiest to see immigrants whose isotopes are very far outside the norm for Rome. Out of more than 100 skeletons, we found four people—three adult males and one adolescent—who we are confident were from elsewhere. The adolescent's isotope ratios are consistent with an origin in Africa, and the males' are consistent with homelands in the Alps and Apennines.

The isotope ratios of another four people, including two older children and a male and a female teenager, are less clear-cut, but these individuals were probably also not from Rome. Isotope analysis isn't a biological GPS, though, so while we can't be sure exactly where they came from, it seems that people arrived from all compass points.

Given what we know from history, it is not surprising to find migrants among these skeletons, but it is a little surprising that we found so few. The scale of slavery and migration to Rome during the Empire means we should expect more people to be migrants. However, isotope analysis cannot distinguish among people who were born in Rome and people who were born in another, isotopically similar location. We may be missing some migrants who are hidden within the data.

The people who came to Rome as children and died in Rome as children are particularly interesting. Of the eight probable immigrants, there are three adults, three teenagers, and two older children. This number of juveniles was unexpected because both voluntary migrants and slaves mentioned in the historical records are usually men. Based on their isotope ratios, two of the juveniles came from somewhere with older geology, like northern Italy, while the other three came from someplace warmer and drier than Rome, like North Africa.

One adolescent in particular, whose eye orbit with an anemic condition is seen in the photo below, has a tooth with very different strontium, oxygen, and carbon isotope ratios compared to what we'd expect from Rome. His bones showed, though, that his carbon isotope ratio just prior to his death was in line with Rome. This indicates he changed his diet after migrating. While it makes sense that we'd see migrants adopting the diet of their new home at Rome, this is the first study to make that connection explicit through isotopes.

Based on skeletons alone, we've discovered that people of both sexes migrated, often as children, and we've demonstrated a change in diet following migration.

Why did they come to Rome? Some were motivated to migrate in antiquity for many of the reasons people are motivated today: to find a better job, to be educated, to make a better life. But many were forced to come. We know from historical records that the scale of slavery in the Roman Empire dwarfed the amount of voluntary migration. Still, slavery in ancient Rome was often a temporary legal status, and manumission of slaves was common.

There is nothing in the isotopes, the skeletons, or the graves that clearly identifies slaves or voluntary immigrants. This work, though, opens up a new way of looking at migration to Rome that may eventually yield new information on the history of slavery and the experiences of Roman slaves.

The work that I and many colleagues are doing in the bioarchaeology of ancient Rome demonstrates that physical remains can give us new information about a culture that people have been studying for millennia already. The bodies of people throughout the Empire are helping us flesh out the skeleton of Roman history with the experiences of the people whose stories have not yet been told.

My PLOS One article is freely downloadable here:

Killgrove K, Montgomery J (2016) All Roads Lead to Rome: Exploring Human Migration to the Eternal City through Biochemistry of Skeletons from Two Imperial-Era Cemeteries (1st-3rd c AD). PloS ONE 11(2): e0147585. doi: 10.1371/journal.pone.0147585.

All images courtesy of Kristina Killgrove

Penn Vet Working Dog Center
Stones, Bones, and Wrecks
New Program Trains Dogs to Sniff Out Art Smugglers
Penn Vet Working Dog Center
Penn Vet Working Dog Center

Soon, the dogs you see sniffing out contraband at airports may not be searching for drugs or smuggled Spanish ham. They might be looking for stolen treasures.

K-9 Artifact Finders, a new collaboration between New Hampshire-based cultural heritage law firm Red Arch and the University of Pennsylvania, is training dogs to root out stolen antiquities looted from archaeological sites and museums. The dogs would be stopping them at borders before the items can be sold elsewhere on the black market.

The illegal antiquities trade nets more than $3 billion per year around the world, and trafficking hits countries dealing with ongoing conflict, like Syria and Iraq today, particularly hard. By one estimate, around half a million artifacts were stolen from museums and archaeological sites throughout Iraq between 2003 and 2005 alone. (Famously, the craft-supply chain Hobby Lobby was fined $3 million in 2017 for buying thousands of ancient artifacts looted from Iraq.) In Syria, the Islamic State has been known to loot and sell ancient artifacts including statues, jewelry, and art to fund its operations.

But the problem spans across the world. Between 2007 and 2016, U.S. Customs and Border Control discovered more than 7800 cultural artifacts in the U.S. looted from 30 different countries.

A yellow Lab sniffs a metal cage designed to train dogs on scent detection.
Penn Vet Working Dog Center

K-9 Artifact Finders is the brainchild of Rick St. Hilaire, the executive director of Red Arch. His non-profit firm researches cultural heritage property law and preservation policy, including studying archaeological site looting and antiquities trafficking. Back in 2015, St. Hilaire was reading an article about a working dog trained to sniff out electronics that was able to find USB drives, SD cards, and other data storage devices. He wondered, if dogs could be trained to identify the scents of inorganic materials that make up electronics, could they be trained to sniff out ancient pottery?

To find out, St. Hilaire tells Mental Floss, he contacted the Penn Vet Working Dog Center, a research and training center for detection dogs. In December 2017, Red Arch, the Working Dog Center, and the Penn Museum (which is providing the artifacts to train the dogs) launched K-9 Artifact Finders, and in late January 2018, the five dogs selected for the project began their training, starting with learning the distinct smell of ancient pottery.

“Our theory is, it is a porous material that’s going to have a lot more odor than, say, a metal,” says Cindy Otto, the executive director of the Penn Vet Working Dog Center and the project’s principal investigator.

As you might imagine, museum curators may not be keen on exposing fragile ancient materials to four Labrador retrievers and a German shepherd, and the Working Dog Center didn’t want to take any risks with the Penn Museum’s priceless artifacts. So instead of letting the dogs have free rein to sniff the materials themselves, the project is using cotton balls. The researchers seal the artifacts (broken shards of Syrian pottery) in airtight bags with a cotton ball for 72 hours, then ask the dogs to find the cotton balls in the lab. They’re being trained to disregard the smell of the cotton ball itself, the smell of the bag it was stored in, and ideally, the smell of modern-day pottery, eventually being able to zero in on the smell that distinguishes ancient pottery specifically.

A dog looks out over the metal "pinhweel" training mechanism.
Penn Vet Working Dog Center

“The dogs are responding well,” Otto tells Mental Floss, explaining that the training program is at the stage of "exposing them to the odor and having them recognize it.”

The dogs involved in the project were chosen for their calm-but-curious demeanors and sensitive noses (one also works as a drug-detection dog when she’s not training on pottery). They had to be motivated enough to want to hunt down the cotton balls, but not aggressive or easily distracted.

Right now, the dogs train three days a week, and will continue to work on their pottery-detection skills for the first stage of the project, which the researchers expect will last for the next nine months. Depending on how the first phase of the training goes, the researchers hope to be able to then take the dogs out into the field to see if they can find the odor of ancient pottery in real-life situations, like in suitcases, rather than in a laboratory setting. Eventually, they also hope to train the dogs on other types of objects, and perhaps even pinpoint the chemical signatures that make artifacts smell distinct.

Pottery-sniffing dogs won’t be showing up at airport customs or on shipping docks soon, but one day, they could be as common as drug-sniffing canines. If dogs can detect low blood sugar or find a tiny USB drive hidden in a house, surely they can figure out if you’re smuggling a sculpture made thousands of years ago in your suitcase.

Big Questions
Why Don't Valentine Hearts Look Like Real Hearts?

Love is in the air this month, and images of two-lobed hearts are all over everything: candy, cards, decorations, you name it. That the heart is symbolic of love and passion isn't surprising—ancient Greek and Roman thinkers, including Aristotle, thought the organ was the center of all emotions. Why the heart symbol you see everywhere in February doesn't look anything like an actual human heart, though, is a little less clear.

The symbol goes at least as far back as the 1400s, when it appeared on European playing cards to mark one of the red suits, though it may even be older than that. The shape is pretty much a mystery, though. There are a few different hypotheses to explain it, but none of them have been confirmed.

One suggested origin for the symbol is that it comes from the ancient African city-state of Cyrene, whose merchants traded in the rare, and now extinct, plant silphium. The plant was used to season food, but doubled as a contraceptive. A silphium seedpod looks like a valentine's heart, so the shape became associated with sex, and then with love.

Another possibility is that the shape is a crude representation of a pubic mound, the vulva, a pair of breasts, buttocks, or a pair of testicles. It may even have come from a poor attempt at drawing an actual heart. A lousy artist, an inaccurate description of the subject, or a malformed model all could have led to that shape.

The Catholic church explains the symbol as coming from a vision that Saint Margaret Mary Alacoque had, where the "Sacred Heart of Jesus"—associated with love and devotion by Catholics—appeared in this shape surrounded by thorns. But Alacoque didn't have this vision until the late 1600s, well after the symbol was already documented. This makes it the unlikeliest of origin stories, but the church's frequent use of the shape was probably a driving factor in popularizing it as a symbol of love.

This story originally appeared in 2012.


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