New surprise from Rome's Metro excavations

Planks from ancient villa in Rome started life in eastern France

       

The construction of Rome’s new Metro line continues to unearth clues and artifacts from the ancient past. This example from articles in The Economist, on Dec 5, 2019, and Science Daily, is one of the latest fascinating additions to the story. 

Oak planks, once part of the portico of a property just outside Imperial Rome, travelled a long way before the builders got their hands on them. The science of dating trees by looking at their growth rings is now so good that Mauro Bernabei of Italy’s National Research Council and his colleagues were able to say, in a paper just published in PLOS One, where the trees that provided the planks had grown, and when they were cut. Rings’ thicknesses are affected by the local climate. Comparison with samples of known origin showed that the trees grew in what is now eastern France, and were felled between 40 and 60 AD. That speaks of a sophisticated timber trade, which floated the logs down the Saône and Rhône to the Mediterranean, and thence to the Eternal City.

Map showing important roads across Europe 2,000 years ago. The red dot shows where the trees have been traced to. The numbered areas represent important regions at the time. Bernabei at al., 2019

The timber requirements of ancient Rome were immense and complex, with different types of trees from various locations around the Roman Empire and beyond used for many purposes, including construction, shipbuilding and firewood. Unfortunately, the timber trade in ancient Rome is poorly understood, as little wood has been found in a state adequate for analysis. In this study, Bernabei et al successfully date and determine the origin and chronology of unusually well-preserved ancient Roman timber samples.

The twenty-four oak timber planks (Quercus species) analyzed in this study were excavated during Metro construction in Rome during 2014-2016. They formed part of a Roman portico in the gardens of via Sannio (belonging to what was once a lavishly decorated and rich property). The authors measured the tree-ring widths for each plank and ran statistical tests to determine average chronology, successfully dating thirteen of the planks.
By comparing their dated planks to Mediterranean and central European oak reference chronologies, the authors found that the oaks used for the Roman portico planks were taken from the Jura mountains in eastern France, over 1700km away. Based on the sapwood present in 8 of the thirteen samples, the authors were able to narrow the date these oaks were felled to between 40 and 60 AD and determined that the planks all came from neighboring trees. Given the timber's dimensions and the vast distance it traveled, the authors suggest that ancient Romans (or their traders) likely floated the timber down the Saône and Rhône rivers in present-day France before transporting it over the Mediterranean Sea and then up the river Tiber to Rome, though this cannot be confirmed.
The authors note that the difficulty of obtaining these planks -- which were not specially sourced for an aesthetic function but used in the portico's foundations -- suggests that the logistical organization of ancient Rome was considerable, and that their trade network was highly advanced.

"We were extremely excited...when we discovered the origin of the timber. [We were] very, very surprised. This long transportation [of timber] was not known," Bernabei said. He added that the wood would have had to be moved over land by animals, then across both the Saone and Rhone rivers, then transported across the Mediterranean Sea until reaching the Tiber River and arriving in the center of Rome.

Finding that timber used to build a villa in Rome came from so far away shows the huge logistical and administrative efforts that would have been made to get high-quality construction products for buildings in the capital. "Considering the distances, calculated to be over 1700 km [1056 miles], the timber's dimensions, road transport with all the possible obstacles along the way, floating the timber down rivers and finally shipping it across the sea, the logistic organization of the Romans must have been formidable," they said.

Considering the planks were used in the foundations of the portico, rather than being transported for aesthetic purposes, the researchers say the effort is even more surprising.

Journal Reference:

1. Mauro Bernabei, Jarno Bontadi, Rossella Rea, Ulf Büntgen, Willy Tegel. Dendrochronological evidence for long-distance timber trading in the Roman Empire. PLOS ONE, 2019; 14 (12): e0224077 DOI: 10.1371/journal.pone.0224077