Rebeca Barba

Unraveling hominin behavior at another anthropogenic site from Olduvai Gorge (Tanzania): new archaeological and taphonomic research at BK, Upper Bed II.

New archaeological excavations and research at BK, Upper Bed II (Olduvai Gorge, Tanzania) have yielded a rich and unbiased collection of fossil bones. These new excavations show that BK is a stratified deposit formed in a riverine setting close to an alluvial plain. The present taphonomic study reveals the second-largest collection of hominin-modified bones from Olduvai, with abundant cut marks found on most of the anatomical areas preserved. Meat and marrow exploitation is reconstructed using the taphonomic signatures left on the bones by hominins. Highly cut-marked long limb shafts, especially those of upper limb bones, suggest that hominins at BK were actively engaged in acquiring small and middle-sized animals using strategies other than passive scavenging. The exploitation of large-sized game (Pelorovis) by Lower Pleistocene hominins, as suggested by previous researchers, is supported by the present study.

The Middle to Later Stone Age Technological Transition in East Africa. New Data from Mumba Rockshelter Bed V (Tanzania) and their Implications for the Origin of Modern Human Behavior

Recent re-excavation of Mumba Rockshelter unearthed an unbiased lithic sample from Bed V. Technological analysis has permitted a reinterpretation of the so-called Mumba Industry, a transitional industry between Middle and Later Stone Ages originally defined by Mehlman (1989). Our data confirm Mehlman’s observation that the “evolutionary” markers in Mumba Bed V are basically typological. However, our study differs from his in that we classify all of Bed V as LSA based on the combined analyses of typology and technology in our excavated assemblage. From a technological perspective, no changes have been observed throughout the sequence, and continuity is the main technological characteristic of the series. The only transitional marker from Lower through Upper Bed V is the appearance of the geometric crescent in the latter, taking into account that microliths exist throughout the sequence. This evidence casts some doubts on previous interpretations and underscores the need to recover a larger sample using modern excavation techniques. It also stresses the need to define the MSA/LSA transition in better terms, combining techno-typological criteria.

New Excavations at Mumba Rockshelter, Tanzania

Mumba Rockshelter in northern Tanzania presents one of the richest and most complete archaeological sequences in East Africa for the Middle Stone Age through the Iron Age. Past excavations of the shelter revealed an extremely rich lithic and faunal assemblage, but were problematic, either because of poor excavation and recording methods (in the 1930s), or because the materials were never fully studied (in the 1979/1981 excavations). In both cases, excavators had concluded that the shelter contained a deposit without visible separation between archaeological levels. Re-excavation of Mumba, using modern techniques for recording spatial data, show that the previous geological and archaeological sub-divisions of the shelter deposits need much revision. The results of the excavation have implications for the interpretation of the “transitional” Mumba Industry in the Pleistocene levels and for the co-occurrence of ceramic traditions in the Holocene levels.

The archaeology of the Middle Pleistocene deposits of Lake Eyasi, Tanzania

Ongoing archaeological research at North Lake Eyasi has produced a wealth of information, including a new hominid fossil and several archaeological sites dating to the end of the Middle Pleistocene. One of the sites (WB9) has been excavated and has produced evidence of multiple processes in its formation, including evidence of functional associations of stone tools and faunal remains which are scarce for this time period. The stone tool industry is based on a core and flake industry, which is not very diagnostic and attributed to MSA. Earlier heavy-duty tools classified as Sangoan may derive from the underlying Eyasi Beds. The stratigraphic provenience of previous fossil hominids is unknown. Surface collections from the Eyasi lake, thus, comprise two different sets of stone tools and fossils, which can only be clearly differentiated in the field. This advises against the use of previously curated collections as a homogeneous sample. Earlier definitions of the Njarasa industry should be revised. This work presents results on the paleoecology of the area and of its paleontological and archaeological information, with special reference to the excavation of WB9, the most complete site discovered in the area so far. This contributes to the limited information available about site functionality and hominid subsistential behaviour in East Africa during the end of the Middle Pleistocene. A technological study from WB9 also shows the variability of stone tool traditions at this time.

Geological and paleoecological overview of Olduvai Gorge

The Plio-Pleistocene of Africa (and elsewhere) is marked by a general trend towards cooler and drier climatic regimes. This is superimposed on what has been summarized as “a succession of wet-dry cycles with a longterm shift toward drier conditions, punctuated by step-like shifts in characteristic periodicity and amplitude” (deMenocal, 2004: 8). These punctuations, which have been found to coincide with the onset and amplification of high latitude glacial cycles (Shackleton, 1995; deMenocal, 1995, 2004), occurred at 3.0–2.6 Ma, 1.8–1.6 Ma, and 1.2–0.8 Ma. Profound changes in vegetation structure accompanied these large-scale environmental patterns. Especially significant is the rise and expansion of grasslands and savannas in Africa beginning in the Mio-Pliocene and continuing into the Plio-Pleistocene (Cerling, 1992; Cerling et al., 1993, 1997). Importantly, the establishment of savannas probably signals more-or-less modern patterns of seasonality and rainfall because such C4 ecosystems (i.e., with tropical grasses and sedges and woody species that do not form continuous cover [Bender, 1971]) are more tolerant of arid, seasonal environments (Jacobs et al., 1999). However, modern levels of C4 dominance do not develop in East Africa until the Middle Pleistocene (Cerling, 1992), which suggests that Plio-Pleistocene savannas were generally wetter and more closed than today. This theme is confirmed by isotopic data from other studies in the Baringo (Kingston et al., 1994) and Turkana (Cerling et al., 1988; Wynn, 2004) basins of Kenya, and at Gona, Ethiopia (Levin et al., 2004), although subtle variation in the timing and pattern of savanna expansion in these regions is documented as well. These environmental changes are also reflected in patterns of faunal turnover. In the Omo-Turkana Basin, for example, high turnover rates began occurring among bovids, equids, suids, and primates by 2.5 Ma and peaked after 1.8 Ma, reflecting the gradual expansion of grasslands (Behrensmeyer et al., 1997; Bobe et al., 2002; Bobe and Behrensmeyer, 2004). Increased climatic variability is also indicated in the Omo-Turkana Basin as rapid fluctuations in faunal composition between 2.5 Ma and 1.8 Ma have been documented. Broadly contemporaneous faunal turnover at Olduvai Gorge at about 1.7 Ma (Gentry and Gentry, 1978a, 1978b) and at Konso, Ethiopia between 1.7–1.4 Ma (Suwa et al., 2003) also show a shift towards openadapted taxa. Overall, broad-scale analyses suggest three punctuated, step-wise shifts in aridification in Africa during the Plio-Pleistocene. The concomitant expansion of C4-dominated savannas occurred at slightly different rates in different regions. It is also important to realize that “the record does not support unidirectional shifts to permanently drier conditions” (deMenocal, 2004: 18). Rather, the general trend toward aridification progressed in the context of increased environmental variability. That is, relative to earlier periods, Plio-Pleistocene 33