From Acheulean to Middle Stone Age in the Kapthurin Formation, Kenya

The Acheulean to Middle Stone Age (MSA) transition is examined from an evolutionary perspective. The replacement of Acheulean handaxes by MSA points represents a shift from hand-held to hafted technology, but the timing and nature of this process are poorly understood due to the rarity of sites from the early MSA (EMSA), here defined as the portion of the MSA predating 130,000 years ago. The well-calibrated sequence in the Kapthurin Formation, Kenya, spans the transition, and shows that MSA technology was present before 285,000 years ago. This date coincides with the age of known African fossils that most likely represent the earliest members of the Homo sapiens lineage. Occurrences with characteristic Acheulean and EMSA artifacts are interstratified in the Kapthurin Formation, demonstrating that the transition was not a simple, unidirectional process. A variety of flake production techniques is present at both Acheulean and MSA sites in the formation. The Levallois tradition begins before 285,000 BP in an Acheulean context; Levallois production methods diversify in the MSA. The precocious appearance of blades, grindstones, and pigment in the Kapthurin Formation before 285,000 BP shows that the array of sophisticated behaviors known in the later MSA (LMSA) began at the Acheulean to MSA transition, and it is suggested that such technological changes are among the causes or consequences of the origin of our species.