Undated Acheulean (ESA) artefacts are well documented across West Africa. The emerging chronometric record of the Middle Stone Age (MSA) indicates that core and flake technologies have been present in West Africa since at least the Middle Pleistocene (~780–126 thousand years ago or ka) in northern, open Sahelian zones, and that they persisted until the Terminal Pleistocene/Holocene boundary (~12ka) in both northern and southern zones of West Africa. This makes them the youngest examples of such MSA technology anywhere in Africa. The presence of MSA populations in forests remains an open question; however technological differences may correlate with various ecological zones. Later Stone Age (LSA) populations evidence significant technological diversification, including both microlithic and macrolithic traditions.