P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

African Archaeological Review, Vol. 19, No. 4, December 2002 (C 2002)

Stone Age of the Songwe River Valley, Lake Rukwa Basin, Southwestern Tanzania

Pamela R. Willoughby1,2 and Charmaine G. Sipe1

This paper reports on results from survey and preliminary test excavations at MSA and LSA sites along the Songwe River in the Lake Rukwa Rift Valley of southwestern Tanzania. At IdIu22, a continuous, extensive archaeological deposit was revealed which may have both and components. The lithic material here shows a gradual transformation from a flake based LSA assemblage to one employing microburin techniques. Cet article discute la recherche prehistorique´ aux environs de la riviere` Songwe, dans le vallee´ rift de Lac Rukwa en la sud-ouest de Tanzanie. Au gisement IdIu22, un sequence de l’ageˆ de la pierre finale (LSA) a et´ ed´ ecouverte´ avec possible niveaux du Pleistocene et Holocene.` Les assemblages lithiques changent graduellement des` un LSA avec outils sur les eclats,´ vers un LSA employant la technique´ microburin. KEY WORDS: Middle ; Later Stone Age; Mbeya region; Tanzania; modern origins.

INTRODUCTION

Geneticists studying mitochondrial and nuclear DNA in living people have proposed that Africa was the continent in which anatomically modern Homo sapi- ens developed, sometime between 100,000 and 200,000 years ago (Cann et al., 1987; Wilson and Cann, 1992). This “mitochondrial Eve,” replacement, or “Out of Africa 2” model (Stringer and Andrews, 1988) suggests that descendants of this founder African population migrated out of the continent sometime before 40,000 years ago, with little (Br¨auer, 1992) or no interbreeding with hominid groups elsewhere. A number of African sites contain fossils which could be clas- sified as anatomically modern Homo sapiens, but the earliest are all associated

1Department of Anthropology, University of Alberta, Edmonton, Alberta, Canada. 2To whom correspondence should be addressed at Department of Anthropology, University of Alberta, Edmonton, Alberta, Canada T6G 2H4; e-mail: [email protected].

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with artifacts belonging to the Middle Palaeolithic in North Africa and the co- eval (MSA) south of the Sahara (Br¨auer, 1992; Clark, 1988; Goodwin, 1928; Rightmire, 1989), between 30,000 and 200,000 years ago. Similar human fossils are found in two Middle Eastern sites, the Mugharet es-Skhul and Jebel Qafzeh, approximately 100,000 years ago (Akazawa et al., 1998; Kaufman, 1999). But there is no sign of modern Homo sapiens anywhere else in the Old World until the onset of the Later Stone Age (LSA) and/or Upper Palaeolithic, between 30,000 and 40,000 years ago. African MSA assemblages are composed of retouched such as scrap- ers and points produced from flakes removed from discoidal or radial cores, but without classic bifaces (Goodwin, 1928). The of standardization of cores for the production of finished flake tools is present in variable amounts. Once established, such MSA, Middle Palaeolithic, or mode 3 (Clark, 1977) assemblages are believed to be quite static until around 30,000– 40,000 years ago, when geometric , backed pieces, blades and bladelets (Figs. 1 and 2) appear for the first time, or increase in number and importance in assemblages where they already existed. In Sub-Saharan Africa, this is character- istic of the LSA or mode 5 (Clark, 1977) and is believed by many researchers, such as Richard Klein (1992, 1999, 2000), to be the archaeological sign of the beginning of fully modern symbolically-based cultural behavior. In Western Europe, modern seem to have replaced the indigenous neandertals (Homo sapiens neandertalensis or Homo neandertalensis) by 30,000 bp (Stringer and Andrews, 1988). In Europe this replacement is also marked by the archaeological transition from mode 3 Middle Palaeolithic industries to mode 4 Upper Palaeolithic ones (Clark, 1977) based on long, parallel sided blades struck off from prismatic, single platform, cores (Klein, 1992). Mode 5 industries similar to LSA ones appear in Europe towards the end of the Upper Palaeolithic, and are generally referred to as or (Price, 1987). Many prehis- torians believe that the variation within and between Middle Palaeolithic/MSA assemblages reflects functional constraints, rather than culture-historical or stylis- tic ones, since they were manufactured by people without culture, archaic hominids who were not capable of investing stone tools with symbolic, ethnic, or cultural meaning (Binford, 1989; Chase and Dibble, 1987; Hayden, 1993; Stringer and Gamble, 1993; for an alternative, see McBrearty and Brooks, 2000; Willoughby, 2000, 2001). In Africa, however, modern human anatomy developed well before modern (meaning “Upper Palaeolithic”) culture and . Since the African MSA and LSA are both associated with the same species of humans, Homo sapiens, is the transition between them only a technological or a behavioral one? The major difficulty in answering these questions is the ab- sence of unbroken archaeological sequences which include the transition. The period is associated with the Last Glacial Maximum, and this seems to have had drastic effects on human settlement throughout the continent (Brooks and Robertshaw, 1990; Parkington, 1990). North Africa may have been completely P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

Stone Age Prehistory of Southwestern Tanzania 205

Fig. 1. Scrapers from IdIu22 test pit 4. a–b, concave scrapers; c–d, concavities; e, convergent ; f, convex end scraper; g, circular scraper (drawn by Katalin Nagy).

abandoned from 30,000 to 18,000 bp; only one site, Haua Fteah in Libya, seems to have an early Upper Palaeolithic occupation (Close, 1986; Close and Wendorf, 1990). In South Africa, the rich coastal MSA sites like Klasies River Mouth either lack any LSA component, or were reoccupied within the last two mil- lenia (Deacon, 2001; Singer and Wymer, 1982). It is only in East Africa that unbroken sequences might exist: at Nasera and Mumba-H¨ohle near Lake Eyasi in northern Tanzania (Mehlman, 1989, 1991) as well as at Enkapune ya Muto and perhaps other Kenyan sites (Ambrose, 1998, 2001; Klein, 1999, p. 492). Here LSA types are present in the MSA, and gradually become more fre- quent over time. At no time is there a sudden change which would be of P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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Fig. 2. Backed tools from IdIu22 test pit 4. a–d, crescents; e–f, triangles; g–k, trapezes; l–o, curved backed pieces; p–w, microburins (drawn by Katalin Nagy).

similar magnitude to the European Middle/Upper Palaeolithic transition. In or- der to investigate the MSA–LSA transition, it is imperative to discover places where continuous sequences might be found. Only in this way will we be able to test current models of modern human behavioral origins and subsequent dispersals. P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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THE STONE AGE PREHISTORY OF THE SONGWE RIVER, LAKE RUKWA RIFT VALLEY

It was with these questions in mind that a project was developed to study the pattern of cultural and behavioral evolution during the MSA and LSA in south- western Tanzania. An archaeological survey conducted in 1990 along the Songwe River Valley in the Rukwa Rift Valley (Figs. 3 and 4) resulted in the discovery or rediscovery of numerous prehistoric sites (Miller, 1993; Willoughby, 1990, 1992, 1993, 1996a,b). The valley had been briefly visited a number of times be- fore this and showed substantial research potential (Clark, 1970, 1988; Haynes, 1970; McBrearty et al., 1982, 1984; Wynn and Chadderdon, 1982). Classification

Fig. 3. Map of southern Tanzania showing location of stone age sites. P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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Fig. 4. Archaeological sites along the Songwe River Valley, Lake Rukwa drainage.

of types and comparative data is provided by Mehlman’s (1989, 1991; Mabulla, 1996) research on Pleistocene and Holocene archaeological sites near Lake Eyasi in northern Tanzania (Fig. 3). The Songwe River Valley contains a number of environmental regions, most of which contain prehistoric, protohistoric, and historic cultural remains. At the north end, near the village of Galula, are extensive lacustrine deposits, formed by a greatly expanded Lake Rukwa, which were later exposed and cut through by the Songwe and other rivers (Clark, 1970, 1988; Haynes, 1970; Spurr, 1953). These date to the Pliocene and later and represent various high water stands, most recently in the early Holocene (Delvaux et al., 1998; Morley et al., 1992; Wescott et al., 1991). Artifacts associated with these deposits are found near the surface and are all relatively recent (LSA and Iron Age); the most likely conclusion is P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

Stone Age Prehistory of Southwestern Tanzania 209

that the lake occupied much of this area when earlier human populations were present. About 15 km south of Galula, the lacustrine deposits end and the valley is composed primarily of terraces formed by the Songwe during the Pleistocene. It is on one or more of these terraces that many of the MSA and LSA occurrences are found. Many (for example, IcIu4-MSA and IcIu5-LSA) are associated with distinctive stratigraphic horizons which can be traced laterally over a few kilome- ters. Some fossil mammal bones were collected; the only identifiable ones were bovids indicative of open savanna conditions. All sites were given SASES registration numbers (Nelson, 1971) and were assigned to cultural periods on typological criteria. MSA sites contain scrapers, points, and bifacially modified pieces, made from flakes detached from radial, “peripheral,” or discoidal cores. LSA sites are dominated by backed tools, mi- croburins, and geometric microliths (crescents or segments, triangles, and trapezes). LSA cores tend to be single platform prismatic or bipolar, and blades or bladelets are present for the first time. Iron Age sites are defined by the presence of ceramics, grindstones, domesticates and/or evidence of metal production (iron tools, slag or furnaces). Representative MSA sites, where artifacts were surface collected, in- clude IcIu4, where three small test pits were excavated in 1990, as well as IdIu19, a quarry site. IcIu4 (8430S, 3370E) is a dense lithic scatter on a river terrace at the farm of Mama Beatrice Seme. At an elevation of 1000 m at the south end of Mjele village, Mbeya District, this is the terrace on which the road to Galula was constructed. A total of 742 stone artifacts were collected from the surface, including a range of tools, cores, and (Table I). Most of the tools were scrapers; others included bifacially worked pieces and becs, small flakes with a unifacially retouched projection like an awl (Table II). Some heavy duty or core tools were also collected (1 core scraper, 2 bifaces, and 3 choppers). Raw materials were mainly cryptocrystalline silica and quartz (Table III). Three small test pits were excavated here, the deepest to 40 cm below datum. These produced a number of artifacts, many of which were quartz and more reminiscent of the LSA than the surface finds. IdIu19 (8460S, 33110E) is a quarry site located 7 km north of Njelenje village in Mbeya District. Artifacts are present within a quartz pebble deposit capping fine grained lacustrine deposits; this deposit also contains fossils, concretions, and a few potsherds. The site covers an estimated area of 5000 m2, and extends for about 1 km north–south. In 1990, 312 stone artifacts and 2 potsherds were collected from the surface, along with some raw material samples (Table I). Of the 55 tools, over half were scrapers. Some bifacially modified and heavy duty pieces were also collected (Table II), of the same types as at IcIu4. About half were quartz, with cryptocrystalline silica and volcanic rocks well represented (Table III). Quartz ar- tifacts were manufactured on the local pebbles while cryptocrystalline silica ones were manufactured on tabular slabs about 3 cm thick. A distinctive, red wine col- ored, volcanic rock is present here and also in northern Songwe MSA sites (IcIu2, IcIu3, and IcIu4), indicating transport of cores and/or flakes over a few kilometers. P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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Table I. Artifact Categories From Selected MSA and LSA Sites No.(%) Test pit Retouched tools Cores Debitage Total

IcIu4 MSA 199 (26.8) 93 (12.5) 450 (60.6) 0 (-) 742 IdIu19 MSA 55 (17.6) 58 (18.6) 199 (63.8) 0 (-) 312 IcIu5 LSA 11 (6.7) 7 (4.2) 147 (89.1) 0 (-) 165 IdIu22-97 LSA 175 (10.8) 80 (4.9) 1364 (84.6) 0 (-) 1619 IdIu22tp1 LSA 408 (2.6) 267 (1.7) 14,783 (95.6) 3 (-) 15,461 IdIu22tp2 LSA 2820 (22.9) 596 (4.8) 8891 (72.2) 4 (-) 12,311 IdIu22tp3 LSA 3170 (24.5) 568 (4.4) 9192 (71.1) 4 (-) 12,934 IdIu22tp4 LSA 1978 (9.3) 551 (2.6) 18,818 (88.1) 11 (-) 21,358 IdIu22tp5 LSA 763 (27.6) 134 (4.8) 1866 (67.5) 2 (-) 2765 IdIu22tp6 LSA 678 (23.4) 125 (4.3) 2098 (72.3) 0 (-) 2901

Songwe LSA sites include IcIu5 and IdIu22, where six test pits were excavated in 1995 and 1997. IcIu5 (8430S, 3370E) is a surface site in fine grained gravels and volcanic ash at the south end of Mjele village. It is stratified above the level containing the IcIu4 MSA. A total of 165 artifacts were recovered from the surface in 1990, including a few tools (Tables I and II). The raw material is predominantly white quartz, and most pieces are microlithic (Table III). Northeast of Njelenje village, there is a series of hills immediately west of the Mbeya highlands, locally known as Mapogoro or Mapogoro Kampi (camp). These hills are unique as they are associated with numerous volcanic kopje or boulder rockshelters, many of which have surface indications of prehistoric settlement. One of these, IdIu17 (8460S, 33120E), along with a former (now collapsed) rockshelter (which became IdIu22) located just south of it, were test excavated during a brief field season in 1995. One hundred and fifty-six stone artifacts and 11 potsherds were collected from the surface of IdIu17. Most were quartz (71.2%) or cryptocrystalline silica (25.6%). Eleven tools were collected, including 7 scrapers, 2 backed pieces (1 crescent, 1 curved backed piece), and 2 outils ecaill´ es´ . Two test pits (IdIu17tp1 and IdIu17tp2) were excavated in 10 cm arbitrary levels behind the shelter’s dripline, both to a depth of between 70 and 80 cm below datum. Excavated stone artifacts were rare, but generally similar to those on the surface. Organic preservation was quite good, and shell, charcoal, ash lenses, and bone fragments were observed. Potsherds are only found in the top 30 cm of each test pit; these were generally undecorated. The first test pit revealed the presence of an intrusive pit in the southwest corner. Below 40–50 cm, this was the only area which could still be excavated (what was thought to be roof fall or bedrock covered the remainder of the surface). The reason for this pit became clear as the lower part of a human burial (composed of a fragmentary tibia and fibula, distal femur fragments, and one patella) was discovered between 70 and 80 cm below datum. Excavation was suspended at this point. A radiocarbon date of 1810 50 bp (TO-5670) was obtained by Isotrace P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

Stone Age Prehistory of Southwestern Tanzania 211 es Heavy duty Others Total ecaill´ No.(%) Retouched Tool Types From Selected MSA and LSA Sites Table II. Tool type Scrapers Backed Points Burins Bifacial Becs Composite Outils ´ IcIu4 MSAIdIu19 MSAIcIu5 LSAIdIu22-97 LSA 158IdIu22tp1 (79.4) LSA 32IdIu22tp2 (58.2) LSA 56IdIu22tp3 (32.0) LSA 126 4 (30.9) (2.0)IdIu22tp4 8 LSA (72.7) 3645 100 (5.5)(22.9) (57.1)IdIu22tp5 LSA 225 (55.1)569 (18.0) 1 1989 (0.5)IdIu22tp6 (70.5) LSA 0 487 (-) 0 1 (24.6) 2323 (-) (9.1) 3(73.3) (0.7) 144 2 8 (18.9) (1.0) (0.3)1312 (66.3) 26 30(0.8) 133 (7.4) (19.6) 0 35 8 (-) (1.2) (4.6) 538 2 38(70.5) (3.6) 5 (1.2) 8 (0.3) (4.0) 447 (65.9) 311 70 130 (0.7)(1.4) (2.5)63 (4.1) (3.2) 3 0 (1.7) 9 15 (-) (16.4) (7.5) 13 6 (1.7) (0.9) 12 63 (2.9)65 25 (2.2) (2.1) (1.3) 0 14 4 (-) (2.1) 4 (2.3) 13 (2.0) (1.7) 3 71 0 4 (0.7)3 (3.6) (-) (0.1) (0.1) 20 (2.9) 38 1 (5.0) (0.6) 0 (-) 5 (0.3) 46 (6.8) 0 (-) 1 1 (9.1)(0.1) 12 0 (0.4) 0 (-) (-) 2 0 (0.3) (-) 0 (-) 2 (0.1) 0 (-) 3 6 (0.1) 5 (3.0) (0.7) 5 6 (1.2) (0.2) 9 (1.3) 3 8 (1.7) 0 (0.4) (-) 1 (0.5) 0 0 (-) 1 (-) 0 7 (0.2) (-) (12.7) 199 0 3169 0 1 (-) (-) (0.1) 408 2 2820 (3.6) 0 (-) 1978 1 0 175 (9.1) (-) 55 763 0 (-) 678 11 P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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Table III. Raw Material Distribution From Selected MSA and LSA Sites No.(%) Raw material Quartz Quartzite CCSa Volcanic Other Mb Other Sc Total

IcIu4 MSA 239 (32.2) 40 (5.4) 317 (42.4) 65 (8.7) 38 (5.1) 43 (5.8) 742 IdIu19 MSA 157 (0.3) 10 (3.2) 92 (29.5) 50 (16.0) 2 (0.6) 1 (0.3) 312 IcIu5 LSA 155 (93.9) 1 (0.6) 6 (3.6) 1 (0.6) 0 (-) 2 (1.2) 165 IdIu22-97 LSA 1121 (69.2) 171 (10.6) 306 (18.9) 21 (1.3) 0 (-) 0 (-) 1619 IdIu22tp1 LSA 8456 (80) 115 (1.1) 1711 (16.2) 280 (2.6) 6 (-) 2 (-) 10,570 IdIu22tp2 LSA 6417 (52.1) 3987 (32.4) 1721 (14.0) 175 (1.4) 4 (-) 7 (-) 12,311 IdIu22tp3 LSA 8718 (67.4) 2380 (18.4) 1712 (13.2) 114 (0.9) 4 (-) 6 (-) 12,934 IdIu22tp4 LSA 10,179 (7.7) 8410 (39.4) 2426 (11.4) 330 (1.5) 6 (-) 7 (-) 21,358 IdIu22tp5 LSA 2206 (79.8) 191 (6.9) 337 (12.2) 27 (0.9) 0 (-) 4 (0.1) 2765 IdIu22tp6 LSA 2202 (75.9) 244 (8.4) 432 (14.9) 22 (0.8) 1 (-) 0 (-) 2901

a Cryptocrystalline silica. bOther metamorphic rocks. cOther sedimentary rocks.

on charcoal from a depth of 20–30 cm, but another of 380 50 bp (TO-5671) at was obtained at 50–60 cm. A sample of human bone was submitted for dating (TO-5673), but no collagen could be extracted. A second test pit was excavated in order to determine the orientation of the burial. The individual is lying on its left side or stomach facing southeast, towards the modern city of Mbeya. Local informants told us that this is the traditional burial practice of the Wasafwa people who occupy this area at present. A date of 1920 50 bp (TO-5672) was obtained for charcoal from test pit 2 at a depth of 50–60 cm. Given that the majority of the skeleton is buried under what was initially thought to be bedrock, it is more likely that this represents large stones or slabs associated with the inhumation. No further excavation was attempted due to the need to consult local officials about attitudes towards the excavation of human remains. A large volcanic boulder, likely the back wall of a collapsed rockshelter which existed here in stone age times, divides IdIu17 and IdIu22. Six 1 m2 test pits were excavated at IdIu22: test pit 1 in 1995, and the rest (test pits 2–6) in 1997. Test pit 1 was excavated next to the boulder which separates the two sites. Test pits 2 and 3 were excavated about7mdownhill south of test pit 1. The 1 m2 baulk between them became test pit 4, and was excavated to bedrock. Test pit 6 was located a few meters south of test pits 2 through 4, and test pit 5 was laid out west of the main site, in what may have been a separate chamber. All yielded LSA artifacts, except test pit 5, which contained a number of Iron Age ceramics. There is no evidence of disturbance below a depth of about 20 cm in any of the pits. Only two stratigraphic units can be detected: a black surface plough zone which was produced during farming activities, and a brown archaeological fill beneath it. Dating this deposit has been problematic due to the lack of charcoal. Two bone fragment samples from test pit 1 were submitted to Isotrace for accelerator radiocarbon dating. One (TO-5674), from a depth of 50 to 60 cm below datum, had a small amount of P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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collagen, and yielded a date of 7540 280 bp. The other (TO-5675), from 60 to 70 cm below datum, contained no collagen. Since the artifacts from this test pit are undoubtedly LSA, produced through microburin technique, a Holocene date seems reasonable. IdIu22-97 refers to artifacts collected from the surface of the site in 1997, prior to the test excavations. It is included here to demonstrate that surface collections provide a representative sample of what is buried at specific sites One notable thing about all test pits at IdIu22 is the high density of stone artifacts recovered (about 15,000 per m3). The number of retouched tools varies, with a minimum of 2.6% in test pit 1 to a maximum of 27.6% in test pit 5 (Table I). Cores are rare, but whole flakes and flake platform fragments, as well as chips and chunks, are abundant, suggesting that the cores were reduced to unidentifiable fragments. In test pit 4, 6337 whole flakes were recovered, making up 29.6% of all artifacts (n = 21,358). Only 169 whole blades, or, more accurately, bladelets, were found (0.8% of total artifacts), while proximal fragments are four times as frequent (n = 534 or 2.5% of all artifacts at test pit 4). Either the raw material used here does not lend itself well to technology, or the occupants of IdIu22 might be repairing composite tools, and discarding the broken haft ends. IdIu22tp4 was excavated to 145 cm. At this point, a solid rock barrier ap- peared, possibly the bottom of the rockshelter. Alternatively, this could have been a large piece of roof fall, but this could only be established by more extensive ex- cavation. A total of 21,358 artifacts and 8 potsherds were recovered (Sipe, 2000). Of these, 9.3% were retouched tools (Table I); predominantly backed pieces or small scrapers (Table II). Quartz is the most common raw material, but it is less abundant here than in the other test pits (Table III). Sample sizes vary with level at test pit 4, but there is no real change in percentage of tools, cores or debitage with depth (Fig. 5). Raw material, however, shows an unusual pattern. Quartz is most abundant in the top and bottom levels, and quartzite in the middle (Fig. 6). The percentage of cryptocrystalline silica decreases with depth, as was also seen in test pits 1–3. The switch in preference from quartz to quartzite in test pit 4 was surprising. It is possible that quartzite was preferred for certain blanks, such as bladelets, as it preferentially flakes in parallel pieces. But why this should only be seen at test pit 4 is unclear. The switch in raw materials is reminiscent of the numerous MSA sites in South Africa such as Klasies River Mouth (Singer and Wymer, 1982), where Howieson’s Poort assemblages with higher percentages of silcrete are interstratified with flake-blade MSA quartzite ones. The percentage of tool types does not really change with depth, as small scrapers and backed pieces are abundant in all levels (Fig. 7). The same scraper types are present: circular, convex end, concave, concavity, and convergent. Many are notched or denticulated, something also characteristic of Songwe MSA tools. When microburins are frequent, as in the top levels of test pit 4, geometric microliths are numerous (Fig. 8). Microburins and geometric microliths vary inversely with oblique and orthagonal truncations, and with curved and straight backed tools. Test pit 4 has the smallest frequency of microburins of any excavated P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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Fig. 5. Change in artifact types by depth for IdIu22 test pit 4.

unit at IdIu22, and their numbers and percentage frequency decrease with depth. Some researchers (Ambrose, personal communication) believe that microburin technology was a Holocene invention, only in use after 10,000 years ago. So the decrease of microburins with depth may point to the presence of a late Pleistocene/ last glacial component here. The presence of many unretouched flakes and flake fragments at IdIu22 also shows that tool making was a major activity at this site. Many proximal ends of flakes and blades (“talon fragments”) are present, sug- gesting that repairing and retooling was also taking place. The small number of whole blades/bladelets can be explained in a number of ways. Possibly these were highly desired, so they were taken away for use elsewhere. Alternatively, the re- liance on small quartz and quartzite pebbles for artifact manufacture may mean that production of blades or bladelets was almost impossible.

COMPARISION OF MSA AND LSA ASSEMBLAGES IN THE SONGWE

In general, Songwe MSA surface sites contain scrapers, points, becs, burins, heavy duty tools such as choppers and core scrapers, and some bifacial flake P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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Fig. 6. Change in raw material frequencies by depth for IdIu22 test pit 4.

tools (discoids, point blanks). They are manufactured on a variety of fine grained raw materials, including a milky quartz, quartzite, cryptocrystalline silica, and volcanics. By contrast, LSA artifacts were manufactured on small quartz pebbles, and secondarily on cryptocrystalline silica. Retouched tools include small scrapers, backed pieces, microlithic elements, microburins and outils ecaill´ es´ , or scalar pieces. Bipolar reduction of pebbles seems to be preferred, but some pyramidal bladelet cores point to more standardized blank reduction methods. Bipolar flaking is also reflected in the presence of outils ecaill´ es´ , as well as in the abundance of flakes with cortical platforms but no cortex on the dorsal surface, Toth’s (1982) reduction stage III. However, late stage (V and VI) debitage with no cortex on the striking platform and little or no dorsal cortex is still the most frequent in all assemblages of both periods. The key to understanding technological changes that took place between the MSA and LSA in this region would be the excavation of a site with both periods in a stratified context. It was hoped that IdIu22 would be such a site, but to date it has only produced LSA materials. However, at this stage of the research project, it is still possible to compare results obtained from sites of each period, in order to isolate general temporal and spatial patterns. Surface MSA sites, such as IcIu4 and P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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Fig. 7. Change in retouched tool type frequencies by depth for IdIu22 test pit 4.

IdIu19, contain many retouched tools and cores, and only about 60% debitage. All LSA sites, whether surface or excavated, are dominated by debitage (over 80%; Table I). The IdIu22 test pits vary greatly in tool frequency, and few cores are recovered from any LSA site. Since many flakes were removed using bipolar methods, cores may have been reduced to unrecognizable chunks before discard. MSA tools are predominantly scrapers. At IcIu4, the most common scraper types are convex end and side scrapers, as well as circular ones. Circular refers to the presence of retouch all around the edge of a flake of any shape. A few becs, bifacially modified pieces (including point blanks or preforms), and heavy duty tools (1 core scraper, 2 bifaces, and 3 choppers) were also collected. Similar types were observed at IdIu19. Cores are predominantly peripheral, worked around their equator; this category includes discoidal, radial and occasional Levallois types. The most common are Mehlman’s (1989) part peripheral cores: a pebble, proba- bly broken in half, then worked radially on one face. The other face is left untouched (cortical). LSA tools were manufactured on flakes or blades struck from prismatic single platform cores or from bipolar ones. The tools recovered from IdIu22 are backed pieces (geometric microliths, microburins, other backed pieces) and scrap- ers. The same kinds of scrapers are present in the surface collections (IdIu22-97) P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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Fig. 8. Change in backed tool frequencies by depth for IdIu22 test pit 4.

and excavations. Of Mehlman’s (1989) 23 scraper types, six are most common here: convex end, convex side, circular, convergent, concavity, and concave scrap- ers. Many are denticulated, so both scraper type and final form is similar to that in the MSA collections. This is perhaps a stylistic or isochrestic (Sackett, 1982) signature, hinting at continuity between MSA and LSA technology in this region. The main difference between the two periods is in the high frequency of backed pieces in the former, and in the technology of artifact production. Backed pieces are the hallmark of the Songwe LSA, both geometric microliths (crescents, triangles and trapezes), as well as truncations and other backed types (defined by the shape of the backed edge). Microburins are included in this category, and are always the most common backed element. But test pit 4 at IdIu22 hints that this is not always the case. While tool types do not change in frequency with depth (Fig. 7), the percentages of backed types do (Fig. 8). Microburins and tools produced through microburin technique are only abundant in the top layers, while truncations and other backed elements are more common in deeper deposits. In addition, raw ma- terial frequencies fluctuate between quartz and quartzite, with cryptocrystalline silica only important in the top layers (Fig. 6). This is a bit unexpected, as surface P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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collections and other test excavations at IdIu22 are always dominated by white quartz (including rock crystal), and secondarily, more siliceous raw materials. All test pits show at least 25% cryptocrystalline silica in the top layers; much of which was obtained right at the site, as tiny amygdules were extracted from vesicles in the volcanic rock of the shelter. This may hint to increasing use of locally avail- able rock from the site itself, but continued pressure to obtain the best quality, regardless of size. Earlier sources, such as IdIu19, may have become unavailable for some reason, or were incorporated into other people’s territories, where the IdIu22 people could no longer go. MSA sites have a wider range of raw materials, with quartz and cryptocrys- talline silica being the most common. Volcanic materials are present, but are more usual in southern Songwe sites (e.g., IdIu20, IdIu21), which are closer to the vol- canic highlands that form the southern boundary of this region. No obsidian sources have been discovered, and obsidian artifacts are exceedingly rare in assemblages from both periods. On the other hand, a distinctive red wine colored volcanic rock from IdIu19 is found in all northern Songwe MSA sites, hinting at larger territo- ries or high mobility at this time. Researchers like Kusimba (1999) suggest that there was increased mobility from the Pleistocene LSA to its Holocene equiva- lent around Lukenya Hill in southern Kenya. This is measured in frequency of exotic raw materials, and distance to their sources. But IdIu22 shows the opposite situation. It is clear that the Songwe area, including the Mapogoro rockshelters, pre- serves stratified archaeological sequences from the MSA, LSA, and Iron Age. MSA sites are found predominantly in open air occurrences on river terraces. MSA arti- facts were discovered in association with rockshelters north of Mapogoro in 1997, and this, along with a renewed effort to determine chronometric ages for sites and landscape features, will be the focus of the next field season. LSA assemblages, dominated by microlithic quartz pieces, are found in both open air contexts and at the Mapogoro rockshelters. Organic preservation is only good when archaeo- logical deposits are buried under rock overhangs, so dating of any of these sites remains a challenge. But with continued study of the archaeological occurrences, it will eventually be possible to create a culture historical sequence for the Songwe, to reconstruct patterns of mobility and settlement within and between the MSA and LSA, and to test hypotheses about the onset of modern human technology and behavior.

ACKNOWLEDGMENTS

The field research described here was conducted under permits from the De- partment of Antiquities, Government of Tanzania (most recently, permit 1/97/98), as well as the Tanzania Commission on Science and Technology (most recently, permit 97-132-ER-90-47). I appreciate the continuing support of both agencies. P1: IXP African Archaeological Review [aar] pp689-aarr-456252 November 19, 2002 16:8 Style file version June 4th, 2002

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Thanks to the previous director of the Department of Antiquities, Dr S. A. C. Waane, and to those Antiquities officers who have participated in this research over the years (O. S. Kileo, Eliwasa Maro, Peter Abwalo, and Digna Tillya). Thanks to Jarrod Goldsmith for help with data analysis, and to Katalin Nagy for providing the artifact illustrations used in Figs. 1 and 2. Field and laboratory anal- ysis has been supported by the Social Sciences and Humanities Research Council of Canada (grants #410-90-0408 and 410-96-0240, Canada Research Fellowship #455-87-0163). Support for the 1995 field season also came from a Gordon and Jean Southam Fellowship from the Association of Commonwealth Universities. Continuing assistance from the Support for the Advancement of Scholarship Fund, Faculty of Arts, and from the Social Science Research Fund, both at the University of Alberta, is also gratefully acknowledged.

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