Where did the rare tin used to make bronze come from? Isotope analyzes of metal ingots from the Uluburun shipwreck, which is more than 3000 years old, show that the Mediterranean region was supplied with tin at the time, some of which even came from remote ore deposits in Central Asia. The scientists say that this reveals an extremely complex long-distance trade in the late Bronze Age, which apparently included small communities of raw material suppliers and the great powers of the era.
It is an alloy that gave its name to an era: In the 2nd millennium BC. BC, bronze formed the basis of mankind's high technology. In the early advanced cultures of Asia and the eastern Mediterranean area, weapons and many everyday objects were made from this material. In order to form the alloy, two metals had to be mixed: the main component, copper, was relatively easy to access - there were numerous deposits in the area of the old advanced civilizations. But that wasn't the case for tin: it rarely occurs in a degradable form.
Metallurgical fingerprints provide clues
Although tin was one of the most important raw materials in Eurasia for over 2000 years, the exact sources of the metal have remained largely speculative, with few exceptions. Above all, it is unclear where it came from in the later Bronze Age and how it reached consumers in the Mediterranean region. In order to get new information, the researchers led by Wayne Powell from Brooklyn College in New York have now used a modern metallurgical process. It is based on the comparison of isotopic signatures in constituents of metal finds with those of ores from known deposits. Findings of tin ingots from the famous Uluburun shipwreck served as research materials for the team. It is the remains of a merchant ship that sailed around 1320 BC. BC off the southwest coast of present-day Turkey.
“The Uluburun shipwreck is iconic. It is described in every study or analysis of ancient trade in the Mediterranean and is fundamental to our understanding of the large-scale trade in goods between the great Bronze Age kingdoms, including Egypt, Mycenae and the Hittites of Anatolia,” says Powell. In the wreck discovered in 1982, underwater archaeologists found, among other things, large amounts of raw metal in the form of bars: ten tons of copper and about one ton of tin. This charge could have produced enough bronze to equip a force of nearly 5,000 soldiers with swords, the researchers write. When it comes to the origin of the copper, they assume the nearby island of Cyprus. But where the tin from the cargo of the ship that crashed came from has remained unclear.
Tin from Central Asia
For their study, the scientists recorded the patterns of isotopes of the elements tin and lead as well as trace elements in 105 tin bars from the Uluburun shipwreck. They were then able to compare the results with the signatures of the ores from known tin deposits in Eurasia. It turned out that two-thirds of the bars have an isotope pattern that corresponds to a source in the nearby Taurus Mountains in Turkey. This region was under the control of the Hittite Empire during the Late Bronze Age, the researchers explain. For the remaining third, however, the focus is on distant Central Asia: the results show that their metallurgical fingerprint matches ore deposits in present-day Tajikistan and Uzbekistan. You are therefore more than 3000 kilometers east of where the merchant ship was found. Apparently the tin had been transported over a surprisingly long distance.
According to the researchers, it is also noteworthy that the region of origin of Central Asian tin is an area that was then only characterized by small villages and mobile shepherds who were probably outside the control of the great powers. Nevertheless, according to the results, tin was mined there in the Bronze Age, which then flowed into the large international trade networks. “It was nomads and communities with different adaptations that shaped the market. The idea that tin found this long way to the Mediterranean and was then smelted into ingots is amazing. It turns out that there was extensive trade in goods thousands of years before modern times," says co-author Michael Frachetti from Brooklyn College in New York, explaining the significance of the study results.
Source: Washington University in St. Louis, Juniata College, professional article: Science Advances, doi: 10.1126/sciadv.abq3766