Empires expanded into trade networks other people had built

The age of empires arrives at the same moment as a widening of trade: more kinds of goods, longer routes, more places connected. The two are joined in a particular way. Empires generally expanded into regions where complex trade relations already existed. The Neo-Assyrians took the Levant, which was already the crossroads of Middle Eastern commerce. Rome took the whole rim of the Mediterranean, the sea along which everything moved. Aksum went the other way and took producing country, seizing the sources of frankincense, myrrh, gold and ivory. In each case an army was used to capture revenue that trade was already generating, to hold the choke points, or to own the supply. Africa was central to this. It furnished the gold, ivory and aromatics the ancient world wanted, and it produced states whose rulers understood as clearly as any in Rome or Nineveh that whoever controls commerce can pay for an army.

Around 1000 BCE Ortoiroid communities completed a long movement up the Lesser Antilles and reached Puerto Rico. Their arrival brought them within reach of a different world. Hispaniola, immediately west across the Mona Passage, was held by Casimiroid peoples who had entered the islands from another direction entirely and had been there for thousands of years. The two now shared a frontier. Rouse reads the archaeology of the following centuries as a flow of technique running northwest to southeast, from the Casimiroid side into the Ortoiroid one, carrying ways of flaking and grinding stone. That direction is the interesting part. The newcomers coming up the chain were the ones learning. Whatever the older population of Hispaniola had worked out about local stone over several millennia of residence was worth adopting, and it moved across the passage into Puerto Rico. The Mona Passage has been a channel of exchange for three thousand years, and Haiti sits on the western side of it.

A Greek commercial handbook of about 340 BC, later wrongly credited to Skylax, placed the island of Cerne twelve days' sail from the Straits of Gibraltar and said no ship could get past it for shallows, mud and weed. Phoenician merchants moored there, pitched tents on the island and ferried goods to the mainland in small boats. They took away hides of deer, lion, leopard and cattle, and the hides and tusks of elephants. The people they dealt with used ivory ornaments and cups, put ivory anklets on their women and ivory decoration on their horses, drove chariots, and made a great deal of wine from vines, which the merchants also carried off. In return came perfume, Egyptian stone, Attic pottery and jars. The tents suggest that the permanent colony Hanno had planted on Cerne was already abandoned. Cerne has never been located.

Herodotus wrote down what Carthaginians told Greek listeners about a coast beyond the Straits of Gibraltar. The ships would land, the crews would set their wares out in a row along the shore and raise smoke. People living there came down when they saw it, left gold beside the goods and withdrew. The Carthaginians came ashore and looked. If the gold matched the value they took it and sailed; if it did not they went back aboard and waited while more was added. Neither side touched what the other had put down until the exchange was settled. The same silent barter appears in much later accounts of the gold trade in the West African interior. The metal most likely came from the alluvial fields of Galam and Bambuk on the upper Niger and Senegal. This is among the earliest written notices of West African gold reaching the outside world.