The Road That Was Not a Road

The phrase "the Silk Road" was invented in 1877 by a German geographer named Ferdinand von Richthofen, writing about potential railway routes. No merchant who ever crossed Central Asia would have recognised it.

There was no road. There were shifting networks of tracks between oases, mountain passes that opened and closed with the politics of the season, river crossings, and caravanserais spaced a day apart. And silk was one commodity among many: horses moving east to west and west to east, glass from Syria, paper from China, furs from the north, spices, medicines, slaves, and above all silver.

The correction matters because the name encourages a picture of a single artery with China at one end and Rome at the other, and almost nobody made that journey. The trade worked in relays. A merchant carried goods from one node to the next, sold to another merchant, and went home. The goods travelled further than any of the people carrying them.

Which explains the prices. Every relay is a sale, and every sale has a margin, so a bolt of silk that left Chang'an cheap arrived in Rome at a multiple that Roman writers found scandalous. Pliny complained that a hundred million sesterces a year drained east. The number is unreliable. The complaint is not, and it points at something structural: Han China and India wanted very little the Mediterranean produced. The exchange was unbalanced, and unbalanced trade settles in bullion.

That pattern recurs. Fifteen hundred years later, Europe still had little China wanted, and what bought tea and porcelain was silver from American mines. Trade deficits settled in precious metal are among the oldest stories in economic history.

The cities along these routes deserve more attention than they get. Samarkand, Merv, Bukhara, Kashgar, Turfan: places that produced almost none of the goods that made them rich, and were rich enough to fund observatories, libraries and some of the finest architecture of the medieval world.

Their wealth came from a geographical monopoly. A desert route is not an open plain you can cross wherever you like; it is a chain of places with water, and the gaps between them dictate the whole geography. A city on a spring or an irrigated delta is the only viable stopping point for a hundred miles, which means it controls rest, fodder, provisioning, credit, translation and information. It can tax everything that passes because there is no route that does not pass.

It also means that when the route moves, the city dies. A great deal of Central Asian archaeology is the study of extremely wealthy places that are now sand.

Now the part that gets left out of the commodity list. These routes carried religions, and they carried them very efficiently.

Buddhism travelled from India into China along the Tarim Basin oases over several centuries, with monasteries serving as waystations, warehouses, moneylenders and translation centres as well as places of worship. Nestorian Christianity reached Chang'an by the seventh century and left a stele to prove it. Manichaeism became the state religion of the Uyghur khaganate. Islam moved along the same corridors later and more completely.

The reason merchants are such effective missionaries is worth stating plainly, because it is not piety. A trader operating far from home, with no legal recourse against a foreign partner, needs some basis for trusting a stranger, and shared religion supplies exactly that: a common law, a community that can apply pressure, a network of coreligionists in every city who will house you, lend to you and vouch for you. Religion spread along trade routes because it was commercially useful, and this is true of every faith that travelled on them.

There is one more cargo, and nobody wanted it.

A connected world is a single epidemiological unit. Pathogens move on the same routes as goods, with none of the transport costs and none of the tariffs. The Justinianic plague of the 540s and the Black Death of the 1340s both travelled established trade networks, and the second reached Europe through Genoese ports connected to the Black Sea, from a Central Asian reservoir, along corridors made unusually safe by Mongol rule.

That is the trade-off in its starkest form. The same integration that makes a bolt of silk in Rome possible makes an outbreak in one region into a pandemic across three continents, and no amount of prosperity buys you out of it. We have not solved this. We have only made the journey faster.