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.
The Technological Leap
The shift from the Middle Stone Age to the Later Stone Age changed how early humans thought about and made tools. MSA technology often involved creating larger flakes and points. The LSA is characterized by the production of microliths—small, standardized stone blades and points designed to be hafted onto shafts to create composite tools like spears and arrows. The Mumba Industry, found in Bed V of the shelter, contains these advanced LSA technologies.
Along with the change in stone tools, other indicators of complex new behaviors appear in the same layers. Archaeologists have found numerous ostrich eggshell beads, suggesting the creation of personal ornaments and symbolic communication. They have also recovered pieces of ochre and grinders, likely used to process pigments for body paint or other forms of art. The faunal remains show that the inhabitants hunted a variety of animals, including buffalo, zebra, and warthog. Later layers at the site continue the sequence, documenting subsequent LSA industries, the arrival of pastoralism, and the Iron Age, and the shelter is a continuous record of technological and cultural change.