Archaeologists and AI have figured out what the Romans played at Coriovallum

In the Netherlands, scientists have figured out what kind of strange stone was kept in a museum for decades and kept researchers busy. It's a smooth slab of limestone with carved straight and diagonal lines found in Heerlen, the site of the Roman-era city of Corjovallum. The team now believes it is the playing field for a Roman-era board game, and the likely rules were helped to be reconstructed by artificial intelligence.

How they realised it was a game

Archaeologist Walter Christ (Leiden University) noticed signs of wear and tear on the cut lines - in places where chips might have been regularly moved across the surface. High-precision 3D scans showed that some of the grooves were literally a fraction of a millimetre deeper than others, meaning they were used more often.

Where is the AI and what did it do?

Next, specialists from Maastricht University got involved with the Ludii system - it knows how to select rules for games based on the shape of the field. It was "trained" on the rules of about a hundred old European games from a close cultural region. Then the algorithm produced dozens of variants of rules, "played" with itself a lot of games and left a few options that look logical and interesting to humans.

After that, the possible rules were checked against the actual wear marks on the stone: which moves should have been repeated more often to leave just such scuffs.

What the rules suggest (and why it's not 100% true)

According to the authors' conclusion, the wear marks correspond most to the so-called "blocking" game - a strategy where the goal is to prevent the opponent from moving and eventually "lock up" his pieces. Such games in Europe are usually confidently recorded in sources only from the Middle Ages, and here it turns out that such games could be played already in Roman times.

At the same time, the researchers emphasise the limitation of the method: if you give Ludii a pattern of lines, the program will almost always be able to suggest some rules - so the exact version of how the Romans played cannot be guaranteed.