A Prehistoric Source of the Nile

Abstract

concerning the Nile valley has continued unabated up to the present, and the range of disciplines contributing to this knowledge has diversified. Geomorphological investigations of the evidence for environmental changes have often been made in association with archaeological work, for example, studies in Nubia by Butzer and Hansen (1968) and Wendorf and Schild (1976), and work in the Central Sudan and Blue Nile valley by Arkell and Ucko (1965), Adamson et al. (1974), and Williams and Clark (1976). Recent major works concerning the history of the Nile include those by Rzoska (1976) and Williams and Faure (1980). The basin of Lake Turkana, formerly Lake Rudolf, has been the scene of much archaeological and other scientific investigation in recent years. This is the result mainly of the discovery of early hominid remains in the lower Omo valley, particularly by French and American expeditions of the late 1960s, and discoveries on the east shore of the lake by Richard Leakey, the results of which are discussed by Coppens et al. (1976). As a result of their work, we have an unusually detailed record of environmental changes in the Turkana basin over the last two to three million years, especially for the northern and eastern margins of the lake. It is against this background of interest and research in the Turkana basin that the British Institute in Eastern Africa has been conducting archaeological exploration in the adjacent areas of the Southern Sudan since 1978. Early in 1980, as part of the commemoration of its 150th Anniversary, the Royal Geographical Society, jointly with the British Institute, sponsored an expedition to the area north-west of Lake Turkana. As members of this expedition, our project was to investigate evidence for changes in the level of Lake Turkana, which resulted from climatic changes, and to explore an ancient overflow channel which lies in the south-east corner of the Sudan. The results of our work are outlined here. Shortly before the expedition left for Africa, an important paper dealing with the history of Lake Turkana was published by Karl Butzer (1980), outlining fluctuations in the lake level during the Holocene. These fluctuations have been reconstructed on the basis of radiocarbon dates for raised beach features. There are 67 dates available for Turkana from sites in all parts of the basin. Figure 1 shows a lake level fluctuation curve based on radiocarbon and historical dates. Using 21 dates on shells from lacustrine deposits in the lower Omo valley, Butzer (1971) suggested that from its present level of