My recently retired colleagues at the University of Minnesota, Carla and Wim Phillips, have asserted, “By the late fifteenth century, the ocean had ceased to be a barrier and had instead become a highway or bridge to what lay beyond.” That may pertain to Europe and the voyage of Columbus, about whom they were writing, but in Asia, way before the late fifteenth century, water created a trading network — at the very least a proto-world system. In fact, as early as the third millennium BCE we have evidence for trade by sea, and a flourishing trade network is documented by the first century BCE.

Around 2500 BCE, when we first can document cross-cultural sea trade, civilizations with access to the ocean could enhance local economies through trade, providing not only a means of selling locally produced goods to a vastly expanded market, but also providing a means of importing luxury goods and expanding the repertoire of products locally available. Sea trade created a system linking a huge area extending from East Africa to Arabia and on to China, bridging a region that transcended cultures and kingdoms and regions of distinct sovereignty. What is the advantage to the sea? Imagine taking goods overland, even on well-established routes. Traders would have needed many pack animals, a very large herd of them, to take the same weight or volume of goods that can be carried on a single boat; a single ship's cargo of 500 tons would have been enough to provide every inhabitant of Rome with one pound of pepper per year, probably an exaggeration but nonetheless a useful figure in visualizing the impact of sea trade. A mule can carry about 100 kilograms and travel only about 25 kilometres in a day, so it would take about 4,500 pack animals to carry the amount that could be loaded on one ship. Michael Pearson puts the contrast even more powerfully, noting that a dhow can travel the same distance as a camel caravan in one-third of the time and that a boat can carry the equivalent of 1,000 camel loads.