A Preliminary Report of some Late Stone Age occurences in the Lake Ziway area of the Central Ethiopian Rift Valley
Authors: Humphreys Gerald K. 
Published: September 2009

The cultural occurrences on Macho and Waso indicate that man made use of the hills as living sites as early as 10,000 years ago at Eth-73-3-III and that occupation has continued to as late as 230 years ago. Waso hill was used as a burial ground as late as World War II according to our workmen, who identified some stone cairns near area A and the brow of the hill. It was more than 10,000 years ago that the area became available for occupation as the once extensive lake receded and the Jiills were exposed and became accessible from the southeastern end of Gademotta ridge: The desirability of these hills probably became less and less as the lake shore became more remote from them and it was not until rather recently that they were again occupied by Neolithic stockherders who had the necessary ceramic technology to maintain a water supply at some distance from the lake. The three excavated occurrences represent a subsistence technology based on tools made predominantly from blades "punched" from cores. It is impossible to place an end date on this tradition based on information from the sites but it did occur before or with the ash fall event some 1450 years ago. It is likely, considering the dates obtained by Clark from the Lake Bekasa area, that it ended many years before the ash fall or at least the technological system had undergone a considerable transformation by that point in time. The youngest excavated horizon is likely that found on Waso hill, Eth-73-3-1, but this cannot be argued conclusively, even though it lies immediately below the pumice cap. It is not known, since there is no means to independently date the occurrence, if the site has not lain on the surface for millennia or was not once buried within a now truncated soil profile that at one time had a yellow-brown zone corresponding to that occurring at Macho hill. It is unquestioned that Eth-73-1 represents the most intensive occupation of the three excavated. Site Eth-73-3-I likely dates between the other two buried occurrences. At least it is seemingly strati- graphically above Eth-73-3-III in reference to the base of the pumice cap. But the sites are horizontally displaced some 75 M. and the stratigraphie zones in which they are located are not sedimentary but pedological. Thus their positions within these soil zones may have more to do with the topography of the hill as the soil developed on a stabilized surface just prior to the ash fall than they do with the topography of the hill when it was occupied. They may even be contemporaneous. Only Eth-73-3-III is dated with a technically reliable date to 10,330 B.P. The surface feature, Eth-73-3-II, is definitely a late event and evidently represents the very specific activity of hide working, very similar to that observed by Gallagher (1971) among the Gurage, the Arussi-Galla, and the Sidamo. These scrapers, based on the date reported by Clark (1974), may have been an item in the tool kits used in the area for some 3500 years and occupations such as Eth-73-3-II offer unique situations where the characteristics of prehistoric activity areas may be determined using ethnographically generated hypotheses. Once some characteristics are known, it may be possible to more reliable identify and spatially delimit activity areas in archaeological sites of the more remote past. Comparative typological studies with other assemblages of similar technology from East Africa will be reported when completed. A study of use-wear markings on the tools from the excavated occurrences is also in progress. It has been found that these obsidian tools, when microscopically observed under the appropriate lighting conditions, show striations (scratch marks) that suggest how the tools were used. Using the assumption that morphologically similar tools exhibiting the same patterned use-wear marks were used for the same task, it is feasible to extend the completed morphological tool typology to a functional typology. Such use- wear studies will not reveal the function, either physical or cultural, of the tools but they can tell something about the motions involved in the specific task for which the tool was used. It is theorized that such studies may eventually, when significant and sufficient numbers are completed, help the prehistorian identify more precisely the activity areas occurring at a site. This in turn should become an additional source of information for generating and testing ecological models of man's cultural use of past environments.