Sirius and Orion were being watched at Nabta before any pharaoh

The five megalithic alignments at Nabta Playa point at specific things. One is set on the position where Sirius rises just ahead of the sun. A second is set on the belt of Orion. The remaining three appear to mark the rising point of Arcturus as it shifted across the middle fifth, the late fifth and the early fourth millennia BCE, which is a record of the slow wobble of the earth kept in stone by people watching one star over centuries. The first two choices are the striking ones. In pharaonic Egypt the appearance of Sirius before dawn was the event that set the year and announced the coming Nile flood. Orion's belt became the celestial address of Osiris, god of death and resurrection and of the return of the flood. Both anchors of Egyptian sky religion were already fixed in a desert monument southwest of Aswan while Upper Egypt had built nothing monumental at all.

Barrera-Mordan, in the Dominican Republic, is one of the sites that forced archaeologists to move the date of human arrival in the northern Caribbean. The material there is a stone-working complex built on flaked tools struck from cores, and it dates to around 4000 BCE. The people who made it belong to what is labelled the Lithic age. They had no pottery, and they should not be confused with the ceramic-producing groups who reached the islands thousands of years afterwards and are far better known. What the assemblage records is a specialised adaptation, worked out for a set of islands with particular stone, particular coastlines and particular food. Sites like this are how the initial migration routes from the surrounding mainland get mapped, because the tool types are the trail. Hispaniola, the island Haiti shares, was inhabited about six thousand years ago by people who knew exactly what they were doing with rock.

Copper was in use before anyone learned to smelt it. It occurs here and there as native copper, relatively pure pieces sitting inside the ore, and those can be hammered cold into shape. People did this in several parts of Africa and Eurasia, and the makers of the Old Copper Complex around the North American Great Lakes were doing it six thousand years ago. Getting metal out of ore is a different problem. It needs sustained high temperature under control, and in every region where it happened, smelting arrived only after ceramic technology was already known there. The kiln comes first and the furnace follows. That dependency has a consequence worth stating plainly. Ceramics were invented independently in Africa, among the oldest anywhere, by communities in the Sahara. The technology that made a fired pot possible is the technology that eventually made a smelter possible. Bronze and iron both rest on a foundation laid by potters.

Three hundred kilometres southwest of Aswan, in country that is now open desert, there was a lake that filled in the rains. By the middle of the fifth millennium BCE the people who watered cattle there had turned the place into a ritual centre. They erected megalithic arrays, including a circle of stones that works as a calendar and five separate alignments, each pointed at the rising position of a particular star. Every material indication at Nabta Playa and across the wider region says the builders were Nilo-Saharan speakers, the same livestock-raising communities whose pottery and burial customs were moving north down the Nile. The date is the point. The Great Pyramid at Giza went up a full thousand years after these stones were set. The astronomy that later gets described as an achievement of the Egyptian priesthood was already being practised by African pastoralists in the desert, who read the sky closely enough to fix its motions in stone.