he first major period of Silk Roads trade occurred between c. 50 BCE and 250 CE, when exchanges took place between the Chinese, Indian, Kushan, Iranian, steppe-nomadic, and Mediterranean cultures. A second significant Silk Roads era operated from about 700 to 1200 CE, connecting China, India, Southeast Asia, the Islamic realm, and the Mediterranean into a vast web based on busy overland and maritime trade. The primary function of the Silk Roads during both periods was to facilitate commercial trade, but intellectual, social, and artistic ideas were also exchanged. Historians believe that it is these nonmaterial exchanges that have been of greatest significance to world history.
Large-scale exchanges became possible only after the small early agrarian civilizations were consolidated into huge and powerful empires. By the time of the first Silk Roads era just four ruling dynasties — those of the Roman, Parthian, Kushan, and Han empires — controlled much of the Eurasian landmass, from the China Sea to the Atlantic Ocean. Order and stability was established over a vast geopolitical environment, great road networks were constructed, advances were made in metallurgy and transport technology, agricultural production was intensified, and coinage appeared for the first time. By 50 BCE, conditions in Afro-Eurasia were much different than they had been before the consolidation of empires.
