The first step in a behavioural ecological study of stone-tool-using hominids involves the description of the character of lithic discard and the context within which the discard occurred. We examine and put into paleogeographic context the known archaeological traces in the Turkana Basin at three successive time intervals: 2.3 million years ago (Ma), 1.9-1.8 Ma, and 1.7-1.5 Ma. At 2.3 Ma, hominid use of stone appears restricted to small areas on the landscape where many resources such as water, shade, and stone are juxtaposed. In contrast, archaeological traces at 1.6 Ma are found in a variety of settings, which may; in part be explained by the paleogeographic changes taking place at that time. This change coincides with the emergence of Homo erectus. The hominid fossil and archaeological records are shown to complement each other in the generation of ecological hypotheses of H. erectus behaviour.