Communication in Middle East and Abroad

The East-to-West process of diffusion picked up pace subsequent to the Islamic conquests, when the Islamic world acquired (in the words of Joseph Needham) "a focal character in the process of diffusion." The innovations diffused included a package of Indian crops and the irrigation technologies needed to grow them in arid or semiarid environments that the Arabs recognized as comprising a distinctively Indian style of agriculture, which they called filaha hindiyya (Indian agriculture). The package included the noria (an animal-powered water-lifting wheel), and a whole roster of crops including sugar cane, rice, citrus trees, and the watermelon. From Persia came the qanat or filtration gallery (a way of tapping water for irrigation that became attached to the Indian package), perhaps the windmill, the artichoke, and the eggplant. China was the most fecund source of technological innovation (paper, block printing with a press, the compass, gunpowder, to name only the most salient). The agents of diffusion were varied, mostly merchants and soldiers fulfilling their characteristic historical role as bearers of new ideas, but agricultural innovations were typically borne by folk migrations of tribal segments or clans, such as those who left Arabia in the seventh century and whose children and grandchildren settled in Islamic Spain, where they introduced Indian-style agriculture.

The Silk Road was an overland caravan system (with a number of auxiliary sea routes via India) that brought silk from China to Mesopotamia or the Roman frontier around the first century C.E., and to Baghdad after the Arab conquests. Not much merchandise besides silk was carried because there was little demand in China for Western products, with some exceptions such as Roman glassware. However, once established, the route became a conduit for the spread of ideas and techniques. Medieval Arab and European travelers (for example, ibn Battuta [1304–1365] and Marco Polo [1254–1324]) used it, as did merchants, and some specific Chinese techniques, such as textile machinery, are known to have reached Europe via the Silk Road. Chess is thought to have been a diversion perfected by Muslim Silk Road merchants. Persian merchants bore ideas to and from China to Persia from the fifth through the tenth centuries.

Richard Bulliet describes a reciprocal relationship between the decline of Roman roads and the introduction of the camel. Camels do not need paved roads. The Muslim conquest represented, in its early centuries, the dominance of nomads over settled areas, made possible by the adoption of the North Arabian camel saddle. Once the dominance was established, a decisive cost factor (20 percent) over shipping by wagon quickly led to the disappearance of wheeled vehicles in most areas of the Islamic world. Roman roads were already in decline and the caravan routes that replaced them were shortened long-distance overland trade routes because wheeled vehicles required fairly gentle gradients (following the crest lines of ridges rather than heading straight across valleys). With respect to trade, caravan routes were linked to overseas trading networks, forming a great web for the transportation of goods that knit together the "world economy" of the Islamic Empire. Trade over long distances led to the invention in the Islamic world of methods of business organization and credit that later were adopted, first in Italian commercial ventures, then those of other European countries: the partnership among merchants, called commenda in medieval Europe, was known in the Arab world of Muhammad (Arabic, shirka, "partnership") and the European bill of exchange was modeled on the Arabic suftaya, the check on Arabic sakk (both conceptually and etymologically). The Muslim world economy functioned as a kind of free-trade zone (propitious as well for the transfer of ideas and techniques), powered by the gold dinar and the silver dirham.