Professor Sturt Manning of Cornell University is very clear: Shipwrecks, he says, are “time capsules” that open a window into history from the bottom of the oceans. But sometimes the view they leave us is a bit blurry. It’s not always easy to clarify the origin of a wreck. Don’t date it either. A good example is the Kyrenia, a 14m-long Hellenistic merchant ship found off the northern coast of Cyprus in the 1960s. Although it was discovered almost sixty years ago, archaeologists have devoted themselves to studying it. I still haven’t been able to answer one important question: When did the ship sink?

Now Manning and his teammates have solved the mystery.

And it was made possible, in large part, thanks to some nuts.

A ship named Kyrenia. Although we now understand its history better, the Kyrenia is a ship that archaeologists are well acquainted with. It was discovered in November 1965 on the northern coast of Cyprus, near the port city from which it takes its name, and between 1867 and 1969 archaeologists devoted themselves to excavating the remains of the wreck. As they progressed through the field, they came across an ancient Greek trading ship, 14m long, filled with hundreds of ceramic vessels.

The discovery of Kyrenia was not so important because of the wreck itself or its cargo, but because of its significance for archaeology: it was the first large Greek ship of the Hellenistic period, recalls Cornell University, with a hull that was “almost intact”. In fact, its good condition allowed the wreck to be excavated and the pieces to be reassembled outside for later analysis.

“It was a historic moment”This is a statement made by Manning, who agrees that the discovery of Kyrenia was a turning point in archaeology and the understanding of shipwrecks. “Kyrenia was one of the first times it was realised that this kind of evidence from the classical world could be found practically intact on the seabed after more than 2,000 years,” he says. “Shipwrecks are unique time capsules and their preservation is incredible.”

From the timber that made up Kyrenia, experts have been able to draw valuable conclusions about the maritime technology of the time, how ships were built or maritime trade. The wreck is so important to scientists that at least three replicas have been made and released since the 1960s. By studying them, experts have been able to better understand the performance of Greek ships.

Surprising… and mysterious. Considering that they remained under the sea for thousands of years, the fact that they are more or less well preserved does not mean that shipwrecks like Kyrenia make the job of archaeologists easier. In his case, a mystery remains. It is also very important to understand the history of the ship. It was known that the merchant ship dates back to the Hellenistic period (IV-I BC), but… Was it possible to date it more precisely? Can scientists go one step further?

Cornell University admits: “The chronology of the Kyrenia’s origins and the precise date of its sinking have always been uncertain at best.” To rule out doubt, researchers first examined artifacts recovered from the wreck, such as ceramics and a small group of coins found on the ship. They concluded that the merchant ship sank in the late 4th century B.C.

PEG, the big enemyThat initial guess wasn’t easy to verify or even to go beyond with reasonable certainty. And that was largely due to polyethylene glycol (PEG), a petroleum-based compound that 20th-century conservators applied to wood to prevent it from decomposing. In addition to keeping the wood away from water, PEG contaminated it, making radiocarbon dating impossible, Manning says.

To overcome this obstacle, he and his team teamed up with researchers from the University of Gronongen to develop a method that removes 99.9% of PEG from wood. Their efforts paid off. Using their method and a small piece of wood salvaged from Kyrenia that had not been included in the reconstruction process, Manning and his colleagues estimated that the original trees were likely cut down sometime between 355 and 291 BCE.

Solving the mysteryNow researchers have gone a step further and have been able to present a “most probable chronology” for the sinking of the Kyrenia. With the support of the Cornell Tree-Ring Laboratory, they calculate that the merchant ship sank between 296 and 271 BC. Furthermore, they believe that the fatal event is most likely to have occurred between 286 and 272 BC.

“The model determined that the most likely date range for the last voyage was between 305 and 271 BC (95.4%) and most likely between 286 and 272 BC (68.3%), several years later than current estimates.”

But… How did they do it? That’s the key. Scientists used wood from the wreck, but they also found an unlikely ally: thousands of almonds stored in jars that once lay in the remains of the shipwreck. “That, combined with clean wood samples and the team’s expertise in modeling and dating, led the Cornell Tree-Ring Lab to determine the probable chronology of the collapse,” he recalls.

The team examined pottery and coins, but “focused” on organic material, including thousands of green almonds found in large amphorae and the remains of an astragalus, a bone extracted from the leg of a sheep or goat, used to perform divination rituals. “These ‘temporary’ sample materials helped determine the date of the final journey.”

Clearing the way. This work is not only interesting because it sheds light on a mystery that archaeologists have been struggling with for decades. The team boasts that it has paved the way for other future dates. Why? During their investigation, the researchers noticed that the dates they obtained did not match the international radiocarbon calibration curve used to convert measurements to specific dates in the northern hemisphere.

After a detailed analysis of the cause of this disparity, Manning discovered a lack of data for the period between 350 and 250 BC, which allowed him and his team to “recalibrate” the curve for almost the entire period. “The new findings will not only clarify the chronology of Kyrenia and its cargo, but will also help researchers for very different projects,” he said.

Their work was published in an academic journal PLoS One.

Images | Cornell University and Wikipedia

In Xataka | We finally know what sailors ate on the high seas in the 16th century. Thanks to CSIC and the sunken galleon