A set of composite bonds may have appeared more than 3,000 years ago

Long-term supply chains, torn apart by tumultuous wars and rampant disease, may form a millennium before anyone gasps at today’s gas prices or enjoys empty shelves of supply.

About 3,650 to 3,200 years ago, the shepherds and villagers who supported the lead mines found new interest in the supply chain that transported the metal from Central Asia and southern Turkey to the merchant ships surrounding the Mediterranean.

Remote communities near rare tin deposits placed in intense demand among ancient urban civilizations for the metal, which, along with copper, was needed to produce copper, researchers report on Dec. 2. Journal of Sciences.

Lead access transformed shepherds and part-time farmers into powerful city partners and rulers in the Late Bronze Age, say archaeometallurgist Wayne Powell of Brooklyn College in New York and colleagues. Until now it has been difficult to demonstrate such an ancient, long-distance lake supply chain or geographical origins.

Powell’s group builds their argument on earlier archaeological evidence that mobile groups in Central Asia spread crop cultivation throughout much of Asia more than 4,000 years ago (SN: 4/2/14) and pioneered popular clothing innovations for 3,000 years (SN: 2/18/22). An overland route from those Central Asian groups connected the pond’s sources to the Mediterranean Sea, the researchers say.

Evidence of ancient tin pipelines stretching more than 3,000 kilometers from mining sites in present-day Tajikistan and Uzbekistan to merchant ships carrying tin in the eastern Mediterranean is highly visible, says anthropologist Michael Frachetti at Washington University in St. Louis.

“That network of lead was the first version of today’s supply chains of commodities like gas and oil,” says Frachetti.

Writing on clay tablets from the Bronze Age sites in what is now Turkey and Iraq indicates that tin arrived from the far east as early as about 3,900 years ago. But the accurate sources of the eastern pond proved to be misleading.

An ancient shipwreck discovered in 1982 off the coast of Turkey has sparked new research. Known as the Uluburun shipwreck, the vessel is around 3,300 years old and is one of the oldest known shipwrecks. The price is one metric ton of tin. Metal cast into portable, distinctly shaped pieces called ingots.

Powell’s group documents the chemical fingerprints of 105 coins, almost all of which were found in the Uluburun wreck. Ingot IDs are based on the distinct combinations of different forms, or isotopes, of tin, lead and trace elements in the ingots. Data on the isotopic profiles of tin deposits in different parts of Eurasia have become available in recent years, allowing researchers to obtain tin deposits, Powell says.

Powell, Frachetti and colleagues traced the origins of the Uluburun tin to about one-third of the os deposits in Tajikistan and several others in neighboring Uzbekistan. Previous excavations indicate that groups of stone hammers were used to hammer iron out of the rocks in those areas.

Most of the remaining shipwrecks were attached to a small tin deposit on Mount Tauri in southern Turkey. According to Frachetti (SN: 5/1/18). Until now, many researchers have assumed that Turkish sources of lead were exhausted by the late Bronze Age.

Despite the new evidence, the geographic origins of the Uluburun stands remain obscure, says archaeometallurgist Daniel Berger of the Curt-Engelhorn-Centre for Archaeometry in Mannheim, Germany. Berger, who was studying Bronze Age sources with another research group, was not involved in the new study.

Lead mines are typically flat-bearing, but wrecks show high-grade tools. Lead was probably added, either intentionally or through accidental contamination, to suggest that the pond was somewhere near the Mediterranean Sea. If so, that could potentially hamper Powell’s group’s efforts to synthesize tin and lead isotopes to identify the sources of the tin.

The isotopic signatures of lead in the same ore deposits vary greatly, and another exists between different deposits, Berger says. Therefore, tin isotopes by themselves cannot definitively identify the sources of the Uluburun ingots.

“Retrieving the sources of the Bronze Age is and remains one of the most difficult problems in archaeology,” says Berger. Efforts to identify the chemical and molecular properties of the different Eurasian tin deposits are still in their early stages.

In February, Berger and colleagues reported that tin evidence from a Late Bronze Age shipwreck found off the coast of Israel shows an isotopic link to tin deposits in southwest England. Further research is needed to confirm that finding, he says.