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Well-documented Pliocene archaeological sites are exceptional. At present they are known only in East Africa, in the Hadar and Shungura formations of Ethiopia and in the Nachukui formation of Kenya. Intensive archeological survey and a series of test excavations conducted in the Nachukui formation since 1987 have led to the discovery of more than 25 archaeological sites whose ages range from 2.34 to 0.7 million years before present (Myr), and to the extensive excavation of two 2.34-Myr sites, Lokalalei 1 in 1991 and Lokalalei 2C in 1997. Lokalalei 2C yielded nearly 3,000 archaeological finds from a context of such good preservation that it was possible to reconstitute more than 60 sets of complementary matching stone artefacts. These refits, predating the Koobi Fora refits by 500 Kyr, are the oldest ever studied. Here we describe a technological analysis of the core reduction sequences, based on these refits, which allows unprecedented accuracy in the understanding of flake production processes. We can thus demonstrate greater cognitive capacity and motor skill than previously assumed for early hominids, and highlight the diversity of Pliocene technical behaviour.

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The classification of archaeological assemblages in the Middle Stone Age of South Africa in terms of diversity and temporal continuity has significant implications with respect to recent cultural evolutionary models which propose either gradual accumulation or discontinuous, episodic processes for the emergence and diffusion of cultural traits. We present the results of a systematic technological and typological analysis of the Still Bay assemblages from Sibudu and Blombos. A similar approach is used in the analysis of the Howiesons Poort (HP) assemblages from Sibudu seen in comparison with broadly contemporaneous assemblages from Rose Cottage and Klasies River Cave 1A. Using our own and published data from other sites we report on the diversity between stone artifact assemblages and discuss to what extent they can be grouped into homogeneous lithic sets. The gradual evolution of debitage techniques within the Howiesons Poort sequence with a progressive abandonment of the HP technological style argues against the saltational model for its disappearance while the technological differences between the Sibudu and Blombos Still Bay artifacts considerably weaken an interpretation of similarities between the assemblages and their grouping into the same cultural unit. Limited sampling of a fragmented record may explain why simple models of cultural evolution do not seem to apply to a complex reality.

The recovery at Shi'bat Dihya 1 (SD1) of a dense Middle Paleolithic human occupation dated to 55 ka BP sheds new light on the role of the Arabian Peninsula at the time of the alleged expansion of modern humans out of Africa. SD1 is part of a complex of Middle Paleolithic sites cut by the Wadi Surdud and interstratified within an alluvial sedimentary basin in the foothills that connect the Yemeni highlands with the Tihama coastal plain. A number of environmental proxies indicate arid conditions throughout a sequence that extends between 63 and 42 ka BP. The lithic industry is geared toward the production of a variety of end products: blades, pointed blades, pointed flakes and Levallois-like flakes with long unmodified cutting edges, made from locally available rhyolite. The occasional exploitation of other local raw materials, that fulfill distinct complementary needs, highlights the multi-functional nature of the occupation. The slightly younger Shi'bat Dihya 2 (SD2) site is characterized by a less elaborate production of flakes, together with some elements (blades and pointed flakes) similar to those found at SD1, and may indicate a cultural continuity between the two sites. The technological behaviors of the SD1 toolmakers present similarities with those documented from a number of nearly contemporaneous assemblages from southern Arabia, the Levant, the Horn of Africa and North Africa. However, they do not directly conform to any of the techno-complexes typical of the late Middle Paleolithic or late Middle Stone Age from these regions. This period would have witnessed the development of local Middle Paleolithic traditions in the Arabian Peninsula, which suggests more complex settlement dynamics and possible population interactions than commonly inferred by the current models of modern human expansion out of Africa.

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