How Scientists Solved the Mystery of a 2,000-Year-Old Shipwreck

In 1965, a diver searching for sponges off the coast of Cyprus discovered the remains of a ship on the bottom of the Mediterranean Sea. When archaeologists brought a Greek ship from the Hellenistic period to the surface, they realized it was carrying a cargo of wine and almonds.

Now, six decades later, those almonds have helped researchers piece together the chronology of the disaster. Analysis of the nutritious nuts, along with wood samples taken from the ship’s beams, suggests it sank between 286 and 272 B.C., according to a study published last week in the journal PLOS One.

Scientists have been studying the 46-foot wreck of the Kyrenia for years. They know it had a crew of four, was built of wood with lead sheathing and had a single mast with a square sail.

“The contents of a shipwreck can tell us what specific items were traded or exchanged, where and how people traveled by sea, which groups of people maintained contact with each other and how these early social and economic networks affected them,” study co-author Brita Lorentzen, an anthropologist at the University of Georgia, told Reuters’ Will Dunham.

Although researchers managed to gather a lot of information about the wreck, its age remained a mystery.

They had previously tried to date the ship by analyzing some of the items found on board, including coins and pottery. Those analyses suggested the ship sank in the late 300s BC, according to the researchers. They later estimated that the ship actually sank between 294 and 290 BC, but they were still unsure.

Scientists wanted more conclusive evidence, so they turned to radiocarbon dating and dendrochronology, a dating technique that involves examining tree rings.

But first they had to overcome a major obstacle. When the shipwreck was pulled from the water in the 1960s, conservators applied a petroleum-based compound called polyethylene glycol (PEG) to the wood to slow its decomposition.

“The addition of PEG prevents the ship wood from drying out, shrinking and turning into dust when it’s taken out of the water,” Lorentzen told Reuters. “But it also contains crude oil with a lot of carbon from long-dead organic remains.” As a result, any samples treated with PEG could skew carbon dating results.

Scientists have developed a new method for removing PEG from wood, which they tested on Roman wood samples that have already been dated using the dendrochronological method, according to Popular ScienceLaura Baisas. Their technique worked, so they tried it on a sample from the wreck of the Kyrenia; they also found a rough piece of wood from the wreck that was sitting in the museum.

Their analysis indicates that the wood for the ship came from trees that grew in the second half of the 4th century BCE. The trees were probably cut down sometime between 355 and 291 BCE.

They also examined some of the fresh green almonds that went down with the ship, as well as a piece of sheep or goat bone. Using statistical modeling, they were able to determine that the ship likely sank between 286 and 272 B.C.

In the process, they discovered and corrected discrepancies in the scientific standards researchers use to analyze old wood, so their work has broader implications for research on other ancient shipwrecks.

Why were researchers able to date the ship when others failed? “(Carbon) dating and dendrochronology have been evolving and developing and refining their results over many decades,” Mark Lawall, a classical scholar at the University of Manitoba in Canada who was not involved in the study, tells CNN’s Taylor Nicioli.

“Learning—whether hard or soft—is developed over time through hard work in the trenches,” he adds. “It takes time and time.”