The donkey may have taught Eurasia to ride the horse and the camel

The donkey was the first animal anywhere to carry trade goods over distance and to pull a vehicle, which made it a working model for others. Ehret argues it supplied both the example and the push for domesticating the camel in southwestern Asia, an animal then used for riding and for hauling over short and long stages. He goes further and suggests that word of the donkey reaching the Pontic steppes during the fourth millennium BCE may have prompted the early Indo-Europeans to stop treating the horse as a meat source and start loading it with people and goods. Follow that chain out. Mounted warfare, cavalry empires, the nomadic movements that redrew the map of Eurasia, the chariots of the Hittites, the bowmen of the Scythians and the Mongols: some part of that genealogy may run back to a herder in the Horn of Africa who first put a load on the back of a wild ass.

Sites in Haiti have produced lithic workshops given over to making large flaked-stone blades, with concentrations in the Casimira and Las Alejandrinas areas. The output is specialised. These are a standard product turned out in numbers at a place chosen for its stone, rather than general-purpose flakes struck as the need arose. Marcio Veloz Maggiolo and Jose Cruxent were among the first to document the complexes, and the size and frequency of the blades became the main indicator archaeologists use when dating preceramic sites in the region. Making blades in bulk at a quarry implies mobility, since the people using them lived elsewhere and moved between the source and the coast. It also puts Haiti near the centre of the question of how human beings first spread into the Greater Antilles, because these workshops are among the best evidence for how that expansion was supplied. Around 3000 BCE this island was producing tools for a wider region.

Around the thirty-fourth century BCE the climate of the eastern Sahara turned sharply drier and stayed that way. Steppe and semidesert grassland that had carried herds for millennia became the desert it is now, though patches held on well enough to support marginal livestock raising as late as about 2000 BCE. The pastoralists living out there had to go somewhere. They moved out of the emerging desert and settled among the communities already living along the Nile. That is the event that produced the Egypt of the textbooks, the thin green ribbon dependent on an annual flood. Before it, this was open country with mobile herders and a river running through it. After it, thousands of people and their cattle were compressed onto a floodplain a few kilometres wide. The competition for land and the density of population that followed drove polities to grow and swallow one another until the whole valley was unified around 3100 BCE.

Where social and economic stratification rose in several parts of Africa, it did not carry female subordination with it. The list is long. The authority of the Kandake at Meroe. Economically independent women running major commerce in West Africa down to recent centuries. Queen mothers holding power in West and Central African kingdoms, alongside other institutions through which women acted on the state. Women holding chiefships in the kingdoms of the southern savanna belt. And in Matamba a queen who was the customary monarch. In the matrilineal savanna societies a suitor needed the consent of the bride's mother and her sisters, worked bride service under their direction for months or years, and deferred to his mother in law for the rest of her life. Those customs turn up in societies whose Bantu languages sit on different deep branches, which puts them in place by the proto-Savanna Bantu period of the early second millennium BCE. Patriarchy is not the entry fee for complex society.