Paper short abstract:

The paper studies presence and continuity of several important hominin behaviors across the Acheulean / MSA technological boundary and throughout the period of modern human evolution in East Africa, with particular reference to the Kapthurin Formation.

Paper long abstract:

The Middle Pleistocene (780–130 ka) of equatorial East Africa is an important time and place for modern human evolution. This period records the continuing existence of Early Stone Age Acheulean technologies as well as the development of new types of tools (i.e. hafted points) and techniques for producing them, often collectively referred to as Middle Stone Age (MSA) technologies. Equally significant as the events of modern human evolution in East Africa is our ability to accurately date and reconstruct these events in the region. Volcanic ashes (tephras) in East Africa provide the ability to precisely date archaeological sites, and volcanic glass (obsidian) artifacts from the region are used to determine distances hominins transported raw materials. Recent correlation and dating of tephras found at Kapthurin Formation archaeological sites show Levallois recurrent and blade methods of core preparation were present along with Acheulean tools by 465–396 ka, over 100,000 years older than previously demonstrated in the region. Recent geochemical sourcing of obsidian artifacts shows long-distance raw material transport (>150 km) was a feature of human behavior by ~200 ka, over 150,000 years older than previously demonstrated. New obsidian-sourcing data further show that by 465-396 ka hominins making Acheulean tools transported obsidian raw materials, from multiple sources, distances of 55–120 km. Thus, in East Africa, both diverse prepared core technologies and long-distance raw material transport appear in the Middle Pleistocene in association with Acheulean tools and persist into the Late Pleistocene (130–10 ka) where these behaviors are found alongside MSA tools. This indicates continuity of several important hominin behaviors across the Acheulean / MSA technological boundary and throughout the period of modern human evolution in East Africa. These behaviors are not tethered to defined typological categories such as Early or Middle Stone Age, nor to a single particular hominin species. Further, by pre-dating technological features of the MSA and biological features of Homo sapiens anatomy by ~100,000 years in East Africa, diverse lithic technologies and long-distance raw material transport were likely important selective pressures on the evolution and dispersals of modern humans.