A flint workshop in western Puerto Rico works through the change

At Cerrillo, in the west of Puerto Rico, there is a place where people went to work flint. It reads as a workshop rather than a village, since the ground holds the waste of tool manufacture, the flakes and rejected pieces that come off shaping a nodule into something usable. Cerrillo was busiest during the changeover into the Ceramic age, when pottery was being adopted and settlement was reorganising, and the flint had been quarried there before that. The evidence indicates people were taking nodules out of the same deposit back in the Archaic age. That continuity is the interesting part. A source of good stone gets found once and then used for as long as anyone needs stone, across changes in pottery, diet and social arrangement that archaeologists treat as boundaries between cultures. The people at the flint outcrop in the seventh century were going to a place their predecessors had gone to for centuries, for the same reason.

The first Muslims in Africa landed on the Eritrean coast, and the first mosque on the continent stood at Massawa, possibly built in the 620s or 630s by members of the Prophet's own family. By the tenth century Islam was spreading inland from the Somali coast through the country that is now Somalia, Djibouti, Ethiopia and Eritrea. The usual telling makes the following twelve centuries a straight fight between cross and crescent. Trade reports something quieter. Muslim merchants worked the Christian highlands in numbers and formed a recognised class there known as jiberti, growing wealthy as Red Sea traffic expanded. The Ethiopian state meanwhile cultivated the image of a Christian kingdom besieged in its mountains, a second Israel with the Bible at the centre of its self understanding. The Oromo made Harar a Muslim city of consequence, and its sultanate rose on links to the Funj in Sudan. Sufi orders did the spreading, the Qadiriyya out of Harar into Somalia and Eritrea, the Salihiyya and Ahmadiyya among the Somali.

At the Canas site in Puerto Rico the Saladoid and Ostiones layers sit one above the other with a clean line between them, and the early conclusion drawn from that line was that two separate cultures had occupied the site in turn. The difficulty with that reading is that nobody could find anywhere for the second culture to have come from. No source region, no migration route. So the material was examined again, and the current view is that Ostionoid pottery grew out of the Saladoid tradition in the islands themselves, with recent argument pointing to the eastern Dominican Republic and the exchanges taking place there. Other evidence supports continuity. Stone toolmaking runs straight through the transition with no equivalent break. What changed was the pottery, and pottery is the loudest thing in an excavation. The change marks the beginning of a period in which the Greater Antilles broke into regions, each developing a look of its own.