a1 British Institute in Eastern Africa
Mrs Barbara Ottaway has proposed that the interquartile range of the radiocarbon dates available for a given industry will provide an estimate of the floruit of that industry. The present paper examines some four hundred radiocarbon dates which have so far been processed from Iron Age sites in Bantu Africa, and concludes that the intersextile range provides a more accurate approximation for the floruit of individual industries than does the interquartile range. This approach permits the presentation of a more precise inter-regional synthesis of Iron Age chronology than has previously been attempted. It is demonstrated that the earliest manifestations of the Early Iron Age Industrial Complex are in East Africa. Further to the south, two distinct streams of the Early Iron Age are recognized: that in the eastern part of the sub-continent had penetrated as far to the south as the Transvaal some centuries before the western stream spread into what is now Zambia. The inception of the later Iron Age, around the eleventh century A.D., is shown to have been at least as rapid as was that of the Early Iron Age.
In view of the greater precision which the above methodology imparts to the radiocarbon-based chronology, a brief discussion is presented of the calibrations which dendrochronological studies provide between radiocarbon ages and calendar ages. It is concluded that, for the period of the sub-Saharan African Iron Age, the corrections which are called for are minor in comparison with the standard errors of individual radiocarbon dates; and the application of such calibrations to Iron Age dates is not recommended.