Decoding the Heavens
Page 6
Early on, it was the statues from the ship’s cargo that got most of the attention. They were clearly recognisable as Greek and were dated to various periods between the fifth and the first centuries BC. Sparks flew in the debate about their exact age, but generally the bronzes were judged to be earlier and of higher quality than the marbles, which looked like later copies of classical originals.
The ancient Greeks are considered to have reached the height of artistic excellence in the fourth and fifth centuries BC. In the subsequent Hellenistic period (which runs from the death of Alexander the Great in 323 BC until the Romans took over in the first and second centuries BC), things went rather downhill. There was still much going on from an artistic point of view, but there wasn’t the same innovation, the same magical inspiration. Sculptors and other artists, although of great technical skill, tended to look back rather than forwards and to copy the styles of the classical masters. In fact, despite apparent aberrations such as Archimedes and Hero, it has been assumed that the search for knowledge idled too. The great thinkers of ancient Greece still tend to be seen as those from earlier classical times, such as Socrates, Plato and Aristotle.
The other notable feature of the Hellenistic period is that the prominence of city states on the Greek mainland, such as the great old rivals Athens and Sparta, faded. They were rather too close for comfort to the growing shadow of Rome in the west. Young and ambitious Greeks headed steadily east into the huge and exciting empire that Alexander’s conquests had opened up, particularly to Alexandria and Antioch, capitals of Egypt and Syria, which became the new centres of Hellenistic culture.
Valerios Staïs, director of the Athens National Archaeological Museum when the fragments were discovered, plumped for the Hellenistic period, specifically the second century BC, as the most likely time when the Antikythera ship sank. As well as the statues, the sponge divers had brought up a collection of terracotta jars, called amphoras, which would have carried a range of supplies including the crew’s food. Clams and oysters clung to them, but one of the sailors on the Syros managed to prise off some of the encrustations with his pocket knife and found both Greek and Latin letters denoting the jars’ capacity. Staïs pointed out that it was during Hellenistic times, while the Romans were taking over but before they completely dominated, that Greek and Latin characters were used interchangably in this way.
However, this would have made impossible coin expert John Svoronos’s dating of the inscriptions on the Antikythera mechanism to the third century AD and, sure enough, he had a different theory. Convinced that such a prestigious cargo of statues would not have gone unrecorded in ancient texts, he scoured the records of city after city for information. Eventually, from Argos on the Greek mainland, he found a document from the fourth century AD referring to artworks that he matched to those found in the Antikythera wreck. The mystery was solved, he announced proudly, in the newspapers and to anyone who would listen. The precious cargo had originated in Argos during the 300s, and was perhaps being taken east to Constantinople – by that time the capital of the Romans’ eastern empire.
Svoronos’s unorthodox methods aside, however, the statues couldn’t reveal a precise date for the shipwreck. These classical works of art might have been preserved and displayed for centuries, just as the Mona Lisa or the Antikythera Youth himself are still admired today, so the pieces on the ship could have been hundreds of years old by the time it went down. But they did provide a crucial clue to the identity of the ship: the bronzes still had traces on their feet of the lead that had once attached them to their bases. These were not newly crafted figures being shipped for trade. They had already been on display for some time, before being wrenched from their pedestals in a hurry. In other words, the statues were stolen.
There was one obvious culprit: the Romans. From the middle of the second century BC onwards, their all-powerful armies spread out from Rome and gradually took control of the whole Mediterranean region. As they did so, they milked the conquered territories of their assets: slaves, food, gold – and art. The Romans loved foreign culture when they saw it and took as much of it as they could home with them to decorate Rome. A steady stream of statues, paintings, furniture, precious bronzes and silverware – both old classics and newly created works – arrived across the sea, filling the villas and palaces of emperors, officials and art collectors with masterpieces from Egypt, Asia and especially Greece.
Even Greek buildings weren’t safe. Carved marble blocks and friezes were shipped back too; and used to decorate public buildings such as theatres and temples. The shipwreck at Mahdia in Tunisia, for example, which sank in around 100 BC on its way to Rome from Athens, was carrying a load of 70 giant marble columns.
From circumstantial evidence, then, one thing that Staïs and Svoronos could agree on was that the ship bearing the Antikythera mechanism was probably a Roman vessel, loaded with artworks and other treasures looted from Greek cities.
There the matter rested until many decades and two world wars later, when a new generation of archaeologists and divers became interested in the Antikythera wreck. In 1953 the diving pioneers Jacques Cousteau and Frédéric Dumas were travelling around the Mediterranean in their steamship Calypso, still looking for adventures that would challenge their recently developed scuba equipment. After hearing about Antikythera, and no doubt tantalised by the risks of the site, they decided to go and see if the sponge divers had left any treasures behind.
Dumas describes the expedition in his 1972 book, 30 Centuries under the Sea. After being forced by one of the area’s ubiquitous gales to shelter for a while at Kythera, the divers arrived at Antikythera’s tiny port Potamos, where Kontos and his men had first hidden from the storm half a century before. This time Dumas was first in the water, which was so transparent he felt as if he might fall right down to the bottom. There was no sign of the wreck or its contents, but there was a dark, raised platform from which flowed the long green ribbons of posidonia plants. After exploring the area, Dumas was convinced that much of the ship was still there, buried in the seabed.
When a ship first sinks, its organic material becomes a veritable feast for sea creatures. Teredo worms (really a kind of mollusc), bacteria and other organisms eat their way mercilessly through the wooden hull, until it collapses under the weight of its contents. Eventually, any exposed wood disappears, leaving just a pile of cargo to mark the spot – like the heap of statues that had so stunned Elias Stadiatis on his first dive at Antikythera. But the entire hull doesn’t necessarily disappear. As these creatures live and eat and die they produce particles of debris, which over time filter down to bury the lower parts of the wreck. This protects it by keeping out the dinner guests. As the centuries tick by the sediment gradually hardens from the bottom up, entombing the preserved remains within a case of limestone.
Subsequent dives, during which the divers dug with their hands like rabbits, turned up a few fragments of pottery, but not much else. Many stories had been told of riches that had rolled over the cliff below the wreck site, out of the sponge divers’ reach – like the giant statues that the crew of the Syros had shifted in the belief that they were boulders – so one still evening Dumas ventured into the deeper water, guided down by Calypso’s anchor chain. The cliff dropped off to nearly 90 metres, at which point sand, punctuated by large blue gorgonian corals, stretched as far as he could see. Dumas didn’t immediately find any remains from the wreck. But he couldn’t risk stopping so deep down and his brain was thick with narcosis, so he worked his way back up the chain to the surface. He paid for his brief exploration over the cliff with only the second decompression injury of his long diving career – a shoulder so sore it felt as if he had fractured it.
Cousteau was unimpressed by the lack of pickings at the site. He spent the next few days exploring another ancient wreck that the party discovered just 300 metres away, with no statues but hundreds of amphoras – it must have been a trading ship, carrying staple supplies. But Dumas insisted on returni
ng to Antikythera for one last dive before they moved on. He poked around with a crude suction device that he had made out of a metal pipe, powered by the air compressor in the boat above, and found various fragments of pottery as he pushed the pipe into the sand. Then, on his last attempt, he hit something hard:
At the bottom of my last funnel, about two yards from the rocks, the pipe ran right into the hull of the sunken ship, which was perfectly preserved under a foot and a half of sand. If only I had more time!
He could even see traces of paint on the 2,000-year-old wood. The lower parts of the ship, along with any cargo buried as the sediment settled, were surely still fresh and intact under the sand . . . Bound by the laws of nitrogen, Dumas had to surface. But as Calypso sailed the next day towards other adventures, his head was full of plans to return and dig further. He had no idea that it would be more than 20 years before those plans came to fruition.
The next advance towards understanding the origins of the wreck came in Athens. As Dumas and Cousteau sailed from Antikythera, an American archaeologist called Virginia Grace was working with a young Greek graduate, Maria Savvatianou, on a project to catalogue 25,000 broken amphora handles that had been found at sites across the Mediterranean, but were now lying uncatalogued at the National Archaeological Museum.
Savvatianou was searching for clues to help identify where the different amphoras had come from, and in 1954 she came across Svoronos’s publication from 1903, in which he described the finds from Antikythera. It included a black-and-white photo showing some of the salvaged amphoras in a terracotta line-up against the wall. An excited Savvatianou showed it to Grace. Using the photo as a guide, it might be possible to identify the Antikythera amphoras from the unlabelled piles at the museum.
When the jars were first salvaged, they had been of limited interest to archaeologists. Back then there were no other wrecks around, and although ancient Greek and Roman artefacts had been found at various land sites around the Mediterranean, few had been accurately dated. All scholars could do was give a rough estimate of the century from which an object might have come. But archaeology had changed a lot since 1900. By the 1950s hundreds of wrecks had been discovered (the discoveries have continued – there are now well over a thousand sunken ships from before 1500 AD known in the Mediterranean alone). And the study of land sites across the region had become a much more precise art, with the squashed layers of ancient remains peeled apart and correlated to particular historical events.
If Grace could find the Antikythera amphoras, she had a good chance of dating them and therefore the wrecked ship. But as she looked at the rest of the photos in Svoronos’ paper, she realised that other uncatalogued artefacts, including pottery and glassware, should be identifiable too. So Grace enrolled some friends and colleagues from the intimate community of American archaeologists working in Athens, with the intent of finding out when the ship sank and where it sailed from. Henry Robinson was the kindly director of the American School of Classical Studies at Athens (ASCSA) and an expert in early Roman pottery, while his friend Roger Edwards, who was based at the University of Pennsylvania in Philadelphia, was a specialist in Greek Hellenistic pottery and a frequent visitor to Athens’s ancient marketplace. Gladys Weinberg of the University of Missouri would check out the glassware, and the journalist and archaeologist Peter Throckmorton would study the shrivelled fragments of wood from the boat itself.
Getting access to the museum storerooms was a master-class in cajolery – the Greek staff were touchy to say the least about allowing a team of foreign experts access to the museum stores. And even once the team was in, their task was far from straightforward. Like the amphoras, most of the objects from the wreck had never been properly catalogued or labelled, and the chaos caused by the Second World War, as well as changes in the museum’s management, meant that a significant proportion of the finds described in 1903 had been lost altogether. Working out which of the dusty items in the stores came from Antikythera meant comparing them against the few that had been drawn or photographed at the time, then looking around to see what else seemed to be part of the same batch.
Throckmorton was an experienced diver who had worked with sponge divers to explore several ancient wreck sites in the Mediterranean. Grace knew him well, because she had often helped him to identify the amphoras he recovered from wrecks. One of his expeditions was the ingot-filled galley at Cape Gelidonya, off the sunbaked coast of Turkey, which he had excavated with a team that included Frédéric Dumas. The Frenchman didn’t like the wealthy American much, complaining that he was more interested in collecting pricey souvenirs for himself than in the scientific value of the wrecks he explored. At Cape Gelidonya, Dumas says that Throckmorton ‘started chipping algae off the first raised block to expose the ingots before we even got it to the beach. I had to ask him to stop and follow scientific protocol’.
Nevertheless, Throckmorton’s work in the Mediterranean was hugely influential at a time when marine archaeology was just starting to become a scientific subject (it was always a few steps behind its terrestrial cousin). And few people knew more than he did about the art of ancient shipbuilding.
In the museum stores Throckmorton found a dozen pieces of dessicated planking lying in a crate, shrunk to a fraction of their original size as the water that had propped up the cells in the wood for so long dried out. The wood was elm, from central Italy, indicating that the ship had indeed been built by the Romans (the Greeks tended to use pine, from Samos or Aleppo). And the strange construction that had so intrigued the archaeologists in 1901 was now instantly recognisable to Throckmorton as a ‘mortise-and-tenon’ or ‘shell-first’ construction.
Modern wooden ships tend to be built frame first, the planks forming the sides being fitted after the skeleton frame has set the shape of the hull. But the ancients built their boats the other way around. The planks were tightly slotted together using wooden tongues called tenons, in a precise manner that Cousteau once described as ‘more akin to cabinet-making than ship carpentry’. Only after the planks had been fixed together to form a smooth, watertight hull were the ribs of the frame attached inside.
This method of construction lasted for more than 3,000 years, from the Egyptians to the Romans, despite being incredibly labour intensive. It’s not clear why it took so long for shipwrights to switch to the much cheaper and easier frame-first method; maybe because mortis-and-tenon ships were so well built that they literally lasted for centuries.
Throckmorton was frustrated that the museum staff wouldn’t allow him to remove any of the wood from Athens for further study. But one tiny fragment was eventually sent away for a test that would have been unimaginable for Svoronos and Staïs: carbon dating.
All carbon atoms have a nucleus that contains six protons – that’s what defines them as carbon. The number of neutrons in the nucleus can vary, so you can get carbon-12 (which has six neutrons) or carbon-13 (seven neutrons). Both are stable, and will stick around in the atmosphere for as long as you like. But you can also get tiny amounts – just one part per trillion of the carbon on the Earth – of carbon-14 (eight neutrons). It is made when energetic particles from space called cosmic rays strike atoms in the upper atmosphere, causing them to spit out neutrons. If one of those neutrons hits a nitrogen-14 atom (seven protons, seven neutrons), it jumps into the nucleus and kicks out a proton for good measure, resulting in carbon-14. This form of carbon is unstable, however, and it undergoes very slow radioactive decay back into nitrogen-14.
This carbon-14 filters down into the air around us and as we breathe, we constantly take in tiny amounts of it, and incorporate it into the molecules of protein, carbohydrate and fat that make up our bodies. It gradually reverts to nitrogen, but as long as we stay alive we keep breathing in more of it, so the level of carbon-14 stays roughly the same as that in the atmosphere. Once we die, however, that process stops. The amount of carbon-14 in a dead body then falls very slowly as the individual atoms decay, halving for every 6,000 years or so
that passes. The same holds true for any living organism, from a sailor on a ship, to the ship worm eating holes in the wooden hull beneath him, to the trees that first made the hull’s timbers.
By measuring the amount of carbon-14 in a piece of wood and comparing it to the amount of carbon-12 and carbon-13, which stays constant, it’s possible to work out roughly how long it has been since the tree was cut down. The test could give the first scientific indication of the date of the Antikythera wreck.
The fragments were sent to Elizabeth Ralph, one of the only scientists in the world with the expertise to carry out the new-fangled technique. She had worked with its inventor, Willard ‘Wild Bill’ Libby at the University of Chicago, but since 1951 she had been working at the University of Pennsylvania, where she set up the country’s second carbon-dating lab in the basement of the physics building.
Ralph’s results soon came back: she concluded that the wood dated from between 260 and 180 BC. That gave 260 BC as the earliest possible limit for the wreck. But the ship could have sailed a fair bit more recently than 180 BC, she pointed out cautiously. Although the cells in our bodies are recycled throughout their lives, trees work differently. Once the rings in a tree trunk form, they are effectively dead – the life and growth of the tree happens around the edges as the trunk thickens, and at the tips of its branches and the ends of its roots. If the bit of wood that was tested came from the middle of the trunk of a very large elm it would have been laid down when the tree was a young sapling. The mature tree wouldn’t have been cut down until many decades later. The wood itself could also have been quite old when the ship was built, and the ship could have been quite old when it sank.
Still, the result was consistent with Staïs’s idea that the ship sank in the second century BC, and effectively ruled out Svoronos’s theory that it sailed from Argos some 500 years later.