A Library of Ancient Technologies
Near the northeastern shore of Lake Eyasi, a large outcrop of metamorphic gneiss forms the Mumba Rock Shelter. The floor of this shelter contains one of the most complete records of human occupation in East Africa, with sediment deposits nearly 11 meters (36 feet) deep. These layers document a history stretching back at least 130,000 years. The shelter's location was advantageous, offering protection from the elements and proximity to the lake, which provided water and attracted animals.
Archaeologists have identified several distinct layers, or beds, which contain different sets of stone tool technologies, called industries. The oldest layers, dating from roughly 131,000 to 73,000 years ago, contain the Sanzako Industry, a typical Middle Stone Age (MSA) toolkit. Above this is the Kisele Industry. The shift occurs around 63,000 years ago with the appearance of the Mumba Industry. This toolset shows a clear transition from the larger, more generalized tools of the Middle Stone Age to the smaller, more refined microlithic tools of the Later Stone Age (LSA). This transition is constrained by optically stimulated luminescence (OSL) dating, which places the end of the Kisele industry at 63,400 years ago and the start of the Mumba industry at 56,900 years ago.