In the realm of land transportation, caravans played a key role in moving goods and people over great distances. This was especially true in the vast stretches of Central Asia, North Africa, and parts of the Middle East. Unlike much of Europe and parts of China, these regions did not possess numerous navigable rivers or a canal network, which facilitated easier overland trade and transport. Beasts of burden such as donkeys, mules, and horses could not only provide the muscle power to haul trade goods, but they proved better suited for traversing rugged terrain that was not amenable to the use of carts or wagons. It is the camel, however, that is most closely identified with the idea of caravan transport.         We have evidence from southern Arabia that single-humped dromedaries were being domesticated as early as 3000 BCE. With the invention of the "north Arabian saddle," between 500 BCE and 200 CE, camels became even more highly valued beasts of burden. With such saddling and equipment a single camel could now carry loads of somewhere between 136 and 227 kg. Like horses, mules, and donkeys, camels could travel more rapidly than carts and they did not need specially constructed roads or bridges, so long as the terrain was not totally impassable or streams completely unfordable. Between 300 and 500 CE, camel breeding was widespread in Arabia and much of Mesopotamia, the Levant, and Egypt. As such, camels effectively displaced a great deal of wheeled transport in these areas. Regions that were further from the Arabian breeding centres had to import camels, so the animals did not entirely dominate the transport networks of Asia Minor or northern India, where oxcarts were still widely used. Meanwhile, in Central Asia, the two-humped Bactrian variety of camel appears to have been first domesticated by the inhabitants of Turkestan. While these camels, like their Arabian-bred counterparts, played a similar role in transport, they did not entirely replace the use of wheeled vehicles in Central Asia, China, or the rest of the Far East. In fact, in the grassy Central Asian steppes, horses and mules were used more so than camels because fodder abounded in these regions. Why were camels more highly prized as transport animals in arid regions? Simply because they could travel farther and longer with little food or water than any other pack animal. A camel could last from four to nine days without water and could survive much longer without food, as it was able to get energy from the reserve of fat stored in its hump. In areas where some forage was available, part of the day would be devoted to grazing the beasts for the next day’s march. At the end of a journey through arid wastes, when a camel was forced to go for days without water and even longer without food, the animal would usually have to rest for about a month with plenty of fodder and water in order to build up its fat reserves again. Because of the camel’s prodigious powers of endurance, formerly impenetrable regions, such as the Sahara or the "Empty Quarter" of Arabia, could now be traversed. The rapid spread of Islam owed much to the ability of camel caravans to travel great distances. In a caravan, one attendant could usually manage about six camels. There were often strings of twelve camels tied head to tail, with one attendant stationed at the front of the string and a second at the rear. Large caravans made up of a number of such strings were less common and required adequate supplies of food and water along the way, along with heavier security. The only real infrastructure that caravans needed were the "caravanserais," which provided safe places to deposit transported goods while both animals and attendants rested and ate. During the period from 300 to 1300 CE, caravans could, on average, carry goods more cheaply, more quickly, and with less chance of seasonal interruption than other forms of land transport. Production at this time was not yet geared for trade in bulk items such as grain, cotton, or wood on a mass scale. Trade in such staples, therefore, tended to be local. It was luxury goods that moved hundreds and even thousands of kilometres. Although ships had greater carrying capacities than caravans, shipping at this time depended on seasonal conditions and was prone to various dangers such as shipwreck and piracy. The movement of lower-bulk luxury goods did not necessitate the use of spacious ship holds anyway. Hence, for more than a thousand years caravans were able to compete successfully with shipping in the trade of luxury goods between China, India, the Middle East, and Eastern Europe. Western Europe would, in turn, receive such goods through Byzantine, Islamic, or East European entrepots. After 1300, things began to change. Improvements in navigation and ship design allowed vessels to travel at almost any time of the year. The superior cargo capacity of the ship could now be more fully exploited by merchants. After 1500, when European ships plied the oceans of the world, caravan transport steadily declined in importance down to the present day. Of course, within the arid regions of the Old World, camels and caravans would still remain vital for transportation until the advent of modern petroleum-powered vehicles in the 20th century.