Sheep and goats crossing into the eastern Sahara open the exchange age

The earliest exchange anyone can date is the movement of sheep and goats out of the Levant and south into the eastern Sahara, to peoples speaking Cushitic and Nilo-Saharan languages, under way shortly before 6000 BCE. It opens a long stretch of history with no clean start and no clean finish, conventionally bracketed at 6000 to 3000 BCE. What changed in this period is that the independently invented farming systems of the world began to meet. Thirteen separate centres had each worked out their own crops and their own domestic animals. Those packages now started to circulate, and every system that took something in became more productive for it. The herders of the eastern Sahara were already keeping African cattle when Levantine sheep and goats arrived, and they added the newcomers to a pastoral economy of their own making. Traffic in the other direction, out of Africa and into Eurasia, would prove at least as consequential.

The Levisa rock shelter in Cuba holds a Lithic age deposit dated to 4190 BCE. It is among the earliest confirmed human occupations anywhere in the Caribbean islands. The people who left it worked stone, took what they needed from the rivers and the high ground behind them, and moved with the seasons rather than settling in one place. They were foragers, and the way they lived has to be kept separate from the Taino societies that European ships met almost six thousand years later. Those were farmers with villages, chiefs and ball courts, and they came out of a different tradition. This matters for how the region gets narrated. A Caribbean history that opens in 1492 treats the islands as empty until Europe arrives. A rock shelter in Cuba dated to 4190 BCE says the islands had been occupied for something like six thousand years by then, which makes the usual starting point a decision somebody took.

Crops domesticated in West Africa had taken root in southern Arabia by 3000 BCE. Once they were established in Yemen and Oman they went aboard ship, and before the third millennium was out they were growing on the Indian subcontinent. The archaeologist Dorian Fuller and his colleagues assembled the evidence: a sphere of intercontinental contact more than four thousand years old, running from Africa through southern Arabia into South Asia. The usual account of ancient long-distance trade opens with Mesopotamia and the Indus valley and gives Africa a line in the notes. Fuller's material puts African plant breeding at the head of the chain, with West African crops travelling thousands of kilometres through Arabian hands and changing what Indian farmers grew. Ehret's own summary is that historians have nearly everything still to learn here. A whole sphere of ancient exchange sat unexamined because the discipline had already settled that Africa contributed nothing to the connected world.

Hor-Aha, first or second king of the First Dynasty, sent his forces south and destroyed what remained of the Qustul state. The southern frontier of the Old Kingdom was fixed by that campaign and held for centuries afterwards. He did it wearing the White Crown that a Qustul ruler had worn before him, attended by the Horus falcon that had attended a Nubian king, carrying an idea of sacred kingship developed upriver in the country he was burning. The Old Kingdom that followed went on displaying its inheritance in plain sight. Its political institutions and its ritual observances kept the marks of the wider Middle Nile world they came out of, in the ceremonies around the king, in the handling of royal death, and in the claim that a ruler holds divine authority. Conquest ended the kingdom. It left the kingdom intact inside the conqueror's own practice, where it is still legible.