Merchants of the Bronze Age faced the same problem as merchants from London to Lisbon today: how to know you’re getting what you pay for in a transaction. It usually takes a ruling authority, like a king, pharaoh, or perhaps the European Union, to establish standard weights, which amount to a unit of value in the age before coins and bills.
A new study suggests merchants in Bronze Age Europe were an exception: Through informal networks, Mesopotamian merchants established a standardized system of weights that later spread across Europe, enabling trade across the continent. The advance effectively formed the first known common Eurasian market more than 3000 years ago.
“This is quite a blow to the idea that elites or a central authority is running the show,” says Leiden University archaeologist Maikel Kuijpers, who was not involved with the work. “The [researchers] make a really good case.”
Standard weights—used by merchants to trade goods of equivalent value—were invented in Egypt or Mesopotamia 5000 years ago. By 3000 years ago, they had spread across Europe, where some graves included pouches or boxes containing bone balance beams, tweezers for picking up scraps of gold or silver, and stone weights.
For more than 100 years, historians have assumed that weight standards were handed down from on high, first created by a king or religious authority to collect taxes or tribute, then later adopted by merchants. The first artifacts to clearly be weights, for example, were found in the highly stratified civilizations of ancient Mesopotamia and Egypt. But Bronze Age Europe boasted few such states when weights proliferated.
To find out whether standardization without centralization was possible, Georg August University of Göttingen archaeologists Lorenz Rahmstorf and Nicola Ialongo spent nearly 10 years visiting museum collections and weighing stones and other objects they thought might have been used for commerce. They analyzed weights from previously excavated sites spanning nearly 3000 years in Europe, Anatolia, and Mesopotamia.
To their surprise, more than 2000 such objects crafted over the course of 2000 years and an area spanning nearly 5000 kilometers weighed nearly the same amount—between 8 and 10.5 grams from Great Britain to Mesopotamia. Over the time spans involved, the consistency was remarkable, they report today in the Proceedings of the National Academy of Sciences. “It is like we were still using the Roman systems of measurement [today], with just some minor variations,” Ialongo says.
In Mesopotamia, that unit was referred to as a shekel. “Weight systems in Europe were only slightly different from weight systems in Anatolia, which were only slightly different than in Mesopotamia,” Ialongo says.
The researchers suggest that in all these areas it was merchants who kept the weights standard, because it was in their interest to do so. Each time traders met, the archaeologists write, they would bring out their own scales and weights and compare them—or introduce them to new traders. With enough time and contacts, a standard system emerged—laying the groundwork for the equivalent of an integrated market from Great Britain to Babylon. “The weight units were regulated by the market,” Ialongo says.
To test its model, the team came up with a unique experiment. Using replica Bronze Age bone balance scales, co-author and Göttingen archaeologist Raphael Hermann carved 100 weights out of stone. Each new weight was modeled randomly from the weights already produced: Weight two was based on weight one, but weight three could be modeled on either weight one or weight two, weight 10 could be modeled from any of the previous nine, and so on.
Human error, combined with the slight imprecision of the ancient balance, led to deviations up to 25 grams from the original 153-gram weight. But the drift tended to stay within 5%, still within a range that would have been acceptable in an ancient marketplace, Rahmstorf says. In a system where all the weights were copied from a central standard under palace supervision, the deviations would have been much smaller.
When the researchers plotted their own weights on a graph, the pattern matched the distribution of the ancient samples they had found.
The research helps explain how far-flung Bronze Age societies traded across long distances, says Johannes Gutenberg University of Mainz archaeologist Christopher Pare, who was not involved in the research. “Complex systems are perpetuated by convention and exchange, rather than a central authority. … It’s fascinating.”
In a related study, published last month in the Journal of Archaeological Science, Ialongo and colleagues found nearly 3000 bronze fragments from the same time period in hoards in central Germany and Italy that were all multiples of the same 10-gram weight. That suggests people in both regions were using hacked-up bronze in standard amounts as an early form of currency, Ialongo says.
However, Pare and others caution that it’s tricky to apply modern economic concepts to the distant past. Pare notes that when 19th century archaeologists applied their concepts of how societies were organized to the question of weights, they concluded a king must be in charge. The idea of the market standardizing itself “fits a little too well into our modern neoliberal discourse,” he says. “Should we really be using these terms to talk about societies which are so foreign to us?”