Four Million Ancient Coins Reveal What Really Held the Roman Empire Together

Rome conquered with its legions, but nearly four million ancient coins reveal what truly held its vast territories together: money, markets, and trade. Researchers have reconstructed how money moved across the Roman world from 155 BCE to 2 CE, revealing an economy that became increasingly connected as Roman power spread. Their findings show how currency […].

Share Facebook Twitter LinkedIn Pinterest Telegram Email Reddit A denarius from Rome’s Republican period. Considering only the metal (silver), the coin is worth about USD 3, but taking into account the purchasing power of the time, its value could have ranged from as little as USD 20 to as much as USD 100. Their findings show how currency initially followed the legions into new territories but remained in circulation only after those regions developed permanent commercial, administrative, religious, and civic institutions.

The work demonstrates how data science is transforming the study of ancient history. Instead of relying only on written accounts, inscriptions, and individual artifacts, researchers can now combine millions of digitized archaeological records to uncover patterns that would otherwise remain invisible. Four Million Coins Reveal A Hidden Network The study was led by Eduardo Amaral Haddad, a professor at the University of São Paulo’s School of Economics, Business, and Accounting (FEA-USP), and Inácio Fernandes Araújo, now a professor at the Luiz de Queiroz College of Agriculture (ESALQ-USP).

Both are affiliated with the Regional and Urban Economics Lab at the University of São Paulo (NEREUS-USP) in Brazil. Their study, published in Humanities and Social Sciences Communications, combined regional economics, spatial analysis, geographic information systems, and international archaeological databases. Its goal was not simply to map where coins appeared, but to use their movement as evidence of how the Roman economy developed.

“Each coin preserved by archaeology provides three key pieces of information: where it was minted, when it was produced, and where it was found some 2,000 years later. Taken in isolation, that information reveals little.

When millions of records are analyzed together, they can reveal the paths taken by money, the intensity of economic exchanges, the integration between different regions, and even the institutional evolution of one of the largest economies of antiquity,” says Haddad. FAPESP supported the research through two projects ( 14/25030-2 and 19/00057-9).

A Side Interest Becomes A Major Study The project began in 2014 during Haddad’s sabbatical at Princeton University in the United States. Although he was there to conduct economics research, an interest in ancient history drew him to weekly seminars organized by the Department of Classical Studies.

“At one of those meetings, I attended a presentation of a study that used shipwreck remains and pottery shards to reconstruct trade networks in the ancient Mediterranean. That idea stuck with me.

Shortly thereafter, while exploring the university library, I found a catalog of Roman coins that contained the information I needed: the date of minting, the location where each coin was produced, and the site where it was found during archaeological excavations. I photocopied the catalog, thinking it would be possible to analyze those networks using tools from regional and urban economics,” he recalls.

What began as a personal interest grew into a long-term research effort. Haddad later enrolled in a distance-learning graduate program on the ancient Mediterranean at the University of Leicester in the United Kingdom.

A paper he completed during that program eventually became the basis of a published article. The broader project became possible because archaeology itself was changing.

Roman coin records that had long been dispersed among museums, libraries, private collections, and researchers’ archives were being digitized and standardized. Institutions such as the American Numismatic Society helped develop shared systems for recording finds, allowing once-isolated collections to be studied together.

Building A Digital Map Of Roman Money The principal source was Coin Hoards of the Roman Republic Online ( CHRR), which records groups of coins from the Republican period. The researchers also used ORBIS, developed by Stanford University, to estimate the time and cost of traveling along ancient roads, rivers, and sea routes.

Additional geographical information came from the Pleiades gazetteer and the Roman Road Network databases. Together, these resources supplied location data for settlements, roads, and ports throughout the ancient Mediterranean.