Amphorae were the workaday containers of the ancient world, used to ship everything from aromatic wine to smelly fish sauce around the Mediterranean and beyond. Thousands have been found, in shipwrecks and in fragments at their destinations.

Over the years, certain assumptions have grown up as to what was shipped in particular forms of amphorae and from specific source areas, and the remains of pottery containers have stood proxy for their presumed contents’ significance in ancient economies. In most cases no direct evidence of those contents could be obtained: long burial in the ground or on the seabed had, it was thought, washed away any evidence.

A new study now shows that traces of ancient DNA can survive more than two millennia underwater. These can be multiplied using the polymerase chain reaction (PCR) established in forensic analysis to yield evidence of what the amphorae contained: sometimes the results are surprising.

Writing in the Journal of Archaeological Science, Maria Hansson and Brendan Foley report such an overturning of assumptions. Two complete 2,400-year-old amphorae found in a shipwreck off the Greek island of Chios, just off the Turkish coast, were examined.

“The first (A-1) is a 4th century BC style from Chios typically interpreted as a wine container, the second (A-2) might be from the Eurasian mainland or Chios itself”, the investigators say. DNA was extracted from organic matter soaked into the vessel walls, cloned by PCR and their structures analysed using an automatic sequencer.

These were then matched with the genetic sequences of plants. The first amphora yielded evidence of olive and oregano, the second a plant of the Pistacia genus. Neither vessel yielded the expected evidence of wine.

“Archaeologists and historians have assumed for several reasons that amphoras of this particular A-1 style from Chios usually contained wine,” Drs Hansson and Foley noted. “Chios was renowned in antiquity for its fine and distinctive vintages and Chian coins depicted grapes dangling above an amphora very similar in style. The contents of the second amphora could have been either mastic or terebinth, both used for flavouring and preserving wine; if the vessel had been used for wine, the absence of its DNA could have been due to degradation or its greater solubility. It is also possible that the resinous material could have been used to seal the porous walls, keeping the wine from direct contact.”

“Our method enables isolation and identification of genetic fragments trapped for thousands of years and will provide fresh insights into the contents of ancient Mediterranean shipwreck cargoes and the functioning of protohistorical economic networks,” the investigators conclude.

Journal of Archaeological Science 35: 1169-1176.