Was coinage in ancient India invented independently or acquired from the Persian Empire by diffusion? The Persians adopted the concept of coinage from the Lydians and Greeks in western Asia and it is argued that punch-marked silver bars were circulated in the satrapy of Gandhara after the Persian conquest for use as coins and were later copied and diffused into northern India. The Gandharan punch-marked bars, however, differ from die-struck coins in the Persian Empire based on the Ionian model. Why were different coins circulated in Gandhara? Is it possible that punch-marked silver coins already existed in the region and the Persian authorities issued their bars because their Indian subjects would find them familiar? The paucity of archaeological evidence from controlled excavations and hoards makes it difficult to test this hypothesis and speculation based on visual similarities and unprovenienced finds can easily lead to circular reasoning.
The concept of a coin as a small piece of metal marked by an authority guaranteeing its weight and purity is, properly speaking, a meme. Once invented, a meme spreads widely, especially if it is a simple one. Archaeologists call this spreading diffusion and there are two relevant types here, cultural and stimulus diffusion, both requiring the movement of concepts and techniques but not movements of people or direct contact between cultures. Diffusion is tricky to study archaeologically because it can be confused with independent invention. Memes may be invented independently and coins in different cultures may appear similar but the similarities may be superficial. The similar appearances of the coins may result from the operation of Alexander Goldenweisser’s Principle of Limited Possibilities which holds that there are only so many ways that something can be made and thus similar outcomes will invariably result in convergent forms. The similarities are due to the materials used and the purpose of the artifact: a coin must be small, of standardized weight, made from a material that is both rare and resistant to decay, and marked in some way that is recognizable as authorized currency. These requirements will result in convergent solutions such as using copper, silver, gold, and stamping the metal pieces with marks of some kind. Throughout western Asia unmarked metal, particularly silver, circulated as currency as early as the fourth millennium BC if not long before. The use of silver as a medium of exchange and store of value was part of interaction spheres that involved trade in lapis lazuli, turquoise, gems, shells, spices, wood, pottery, glass, slaves and much else by land and sea. Theoretically, the coin meme was independently invented more than once as the need for a currency was felt and convergence led to similar forms.
We are familiar with simultaneous discoveries and independent inventions, for example the discovery by Alfred Russell Wallace and Charles Darwin of the principle of natural selection in biological evolution in the 1850s. In that case, however, both men lived in the same society and read the same literature and it is unsurprising that they reached similar conclusions. Bronze metallurgy based on a copper-tin alloy was invented at least twice on two continents and at different times: once by the Tiwanaku in Andean South America and again among the Early Bronze Age cultures of SW Asia. Bronze metallurgy was an independent solution to serve similar needs. Such examples suggest that the coin meme may have arisen independently in different parts of Asia. It is a relatively simple concept and cultural convergence is easy to imagine. This point can be illustrated with an artifact like a garden spade. Since the beginning of agriculture a tool with a long handle and an attached cutting edge has been needed for tilling fields and spades have been invented and diffused multiple times. The spade is found today in almost every culture in the world and if you look in garden-tool catalogues you will see that there are many different shapes, designs, and manufacturing techniques for spades. Independent invention is the most parsimonious explanation for this variety because the concept (meme) of the spade is simple and the sequences of manufacture leading to different forms are learned behaviors specific to each culture.
Archaeologists have developed a method to distinguish between diffusion and independent invention. The method involves the examination of artifacts for evidence of their manufacture to determine whether they were made in the same way as in another culture (implying diffusion) or made in a culturally specific manner (implying independent invention). In my archaeological specialty of lithic analysis (the study of flaked stone tools) the specific form of this method is called chaîne opératoire and consists of the identification of the sequence of individual steps and mental concepts that can be deduced from the characteristics of the artifact being studied. We compare different types of stone tools, for example, as they progressed from the extraction of raw materials to the acquisition of their final form necessary for use. An example might be the iconic Palaeolithic stone handaxe from Africa which is a large ovate core tool that has been flaked into a shape with two sharp cutting edges converging to a distal point. Handaxes were used for one and a half million years throughout Africa and some parts of Europe and Asia. Handaxes in Africa and India, however, may appear to be similar, but when analyzed by the chaîne opératoire we may find (this is a hypothetical example just to make the point) that they were made following completely different sequences of manufacturing steps that were presumably learned by toolmakers in each culture.
The chaîne opératoire works well for determining if similar stone tool technologies in different cultures are due to diffusion. Can it be applied to the question of the origins of Indian coinage? Below I propose 13 steps for the production of coins in the two cultures, Persia and India, based on my own observation of the coins as archaeological artifacts analogous to stone tools. Based on the resulting sequences of manufacturing steps, the culturally-learned concepts behind these steps appear to be different. Viewed from the perspective of archaeological artifact analysis, I conclude that the Persian and Indian coinages were independently invented. Confirming evidence would require the discovery of Indian punch-marked coins in controlled archaeological excavations or in datable hoards that predate the Persian presence in Gandhara in 515 BC. If coins are found in secure contexts dating to before ca. 600 BC, independent invention would become the preferred hypothesis.
Persian Indian
Metal purified Metal not purified
Metal refined (depletion etc.) Metal unrefined
Hot dump or cut bar flans Sheets of cold-hammered metal flans
Obverse/reverse images Imagery on one face only
Striking with two intaglio dies Positive punches, usually 3 or more
Weight predetermined for flan Flan clipped to adjust weight
Filed or polished flan edges Clipped edges of flans
Representational animal imagery Abstract imagery
Humans portrayed No humans portrayed
Metal hot when struck Metal cold when punched
Irregular to discoidal flans Irregular to square flans
Inscriptions No inscriptions
Monograms as control marks No monograms or control marks