Middle Pleistocene archaeology and paleohabitats of the lacustrine facies, Kapthurin Formation, Kenya

The taxonomy of Middle Pleistocene hominins remains unresolved, and little is known regarding their behavior and ranging patterns. The Middle Pleistocene is of particular importance because it is the time period immediately preceding the appearance of modern Homo sapiens. The Kapthurin Formation, Kenya, which spans most of the Middle Pleistocene, provides the ideal location to address these issues. The time interval under investigation spans roughly 40,000 years and is tightly constrained by two 40Ar/ 39Ar dates of 509 ± 9 ka and 545 ± 3 Ka. This target interval contains abundant archaeological remains as well as hominin fossils now attributed to Homo rhodesiensis, the most likely precursor of modern H. sapiens. The archaeological and fossil deposits are found in varied paleohabitats, including a saline/alkaline lake, a fresh water spring and a fluviolacustrine floodplain crosscut by small ephemeral streams.^ This project focuses on the paleoenviornmental investigation the lacustrine and spring facies of the Kapthurin Formation and the excavation of three archaeological localities. Although this target interval dates to a time period during which Acheulian technology is ubiquitous in East Africa, excavations at GnJh 42, GnJh 50 and GnJh 23 unearthed a simple flake and core lithic industry that lacks formal tools such as handaxes, the fossiles directeurs of the Acheulian. Consequently, these assemblages would fit comfortably within either Acheulian or Middle Stone Age technological repertoires. However, blade cores and refitting blades, most commonly found in MSA and LSA industries, were recovered from GnJh 42. This represents the earliest known occurrence of blade technology worldwide. Blade production is known from the time interval ∼285-510 ka in the Kapthurin Formation, and the new finds establish the existence of a longstanding tradition for the production of laminar industries in this part of East Africa. Although the manufacture of blades may not indicate any cognitive leap per se, the presence of well executed blade cores does indicate a diversification in the conception of the lithic manufacturing process that long precedes the Middle Stone Age and highlights the inadequacy of the three stage system to describe the behavioral variability present in the Middle Pleistocene.