A Late Stone Age Sequence from West Ethiopia: The

Title: A Late Stone Age Sequence from West Ethiopia: The sites of K'aaba and Bel K'urk'umu (Assosa, Benishangul-Gumuz Regional State) Authors: Víctor M. Fernández, Ignacio de la Torre, Luis Luque, Alfredo González-Ruibal & José Antonio López-Sáez Issued in: Journal of African Archaeology, Vol. 5 (1) 2007, pages 91-126 DOI: 10.3213/1612-1651-10087 Copyright: Africa Magna Verlag, Frankfurt a. M. (Germany)

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A LATE STONE AGE SEQUENCE FROM WEST ETHIOPIA: THE SITES OF K'AABA AND BEL K'URK'UMU (ASSOSA, BENISHANGUL-GUMUZ REGIONAL STATE) Víctor M. Fernández, Ignacio de la Torre, Luis Luque, Alfredo González-Ruibal & José Antonio López-Sáez

Abstract

Résumé

In this paper, the results of the test excavations in two rock shelters in the Central Ethiopian escarpment near the Sudanese border are presented. A continuous sequence of quartz lithic industry, from the lowest levels of K’aaba (with an archaic MSA-like industry of side-scrapers, Levallois-discoid cores and unifacial points) to the upper levels of Bel K’urk’umu (with a LSA industry, characterised by elongated flakes and end-scrapers, that still displays many archaic features such as centripetal flakes and cores) may be inferred. The escarpment’s mountainous and forested areas may have acted as a refuge zone from the end of the Pleistocene, when hyper-arid conditions deterred human occupation of the Sudanese plains nearby, and may also have been a cause for the cultural archaism of the late MSA groups, a case similar to others recorded in the African continent (South Africa, Zimbabwe, Nile Valley). The arrival of Sudanese pottery in the mid-Holocene period may be explained by the onset of arid conditions that drove “aqualithic” groups and early herders towards more humid areas. The conservative character of the late prehistoric cultural sequence derived from both sites is consistent with the resilient traditional nature of the NiloSaharan groups that currently settle the Ethio-Sudanese borderlands.

Cet article présente les résultats des sondages dans deux abris-sous-roche proches de l’escarpement central éthiopien, près de la frontière du Soudan. Une évolution continue de l’industrie lithique en quartz peut y être observée, des niveaux les plus bas de K’aaba (une industrie archaïque du type MSA avec des racloirs, des nucleus Levallois-discoïdes et des pointes unifaciales) aux niveaux supérieurs de Bel K’urk’umu (une industrie LSA définie par des éclats allongés et des grattoirs qui montre toujours des caractéristiques archaïques telles que des éclats et des nucleus centripètes). Les secteurs montagneux et boisés de l’escarpement ont pu servir de zone de refuge depuis la fin du Pléistocène, quand les conditions hyperarides ont empêché l’occupation humaine des plaines soudanaises proches, et ont peut-être été l’une des causes du conservatisme culturel des derniers groupes de MSA, un fait déjà observé dans d’autres parties du continent africain (Afrique du Sud, Zimbabwe, vallée du Nil). L’arrivée de la poterie soudanaise au cours de l’Holocène moyen peut être expliquée par les conditions arides qui poussèrent les «aqualithiques» et premiers bergers vers des secteurs plus humides. L’archaïsme de la culture LSA découverte dans les deux sites rappelle celle des groupes Nilo-Sahariens qui habitent actuellement la frontière éthio-soudanaise.

Keywords: Middle Stone Age, Later Stone Age, Western Ethiopia, lithic technology, Mesolithic-Neolithic pottery Víctor M. Fernández (corresponding author)/ Alfredo González-Ruibal Departamento de Prehistoria Universidad Complutense 28040 Madrid Spain E-mail: [email protected] [email protected]

Ignacio de la Torre Institute of Archaeology University College London 31-34 Gordon Square London WC1H 0PY U.K. E-mail: [email protected]

Luis Luque Fundación Conjunto Paleontológico de Teruel 44002 Teruel Spain E-mail: [email protected]

José Antonio López-Sáez Departamento de Prehistoria Instituto de Historia, C.S.I.C. 28014 Madrid Spain E-mail: [email protected]

DOI 10.3213/1612-1651-10087 © Africa Magna Verlag, Frankfurt M. 2006 Journal of African Archaeology Vol. 5 (1), 2007, pp. 91-126

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V.M. Fernández, I. de la Torre, L. Luque, A. González-Ruibal & J.A. López-Sáez

Introduction: The cultural and geological context The K’aaba and Bel K’urk’umu rock shelters are located in the upper edge of the Ethiopian escarpment 30 km to the east of the Sudanese border and 100 km southwest of the Blue Nile river. They are, respectively, one and three kilometers from the capital of Benishangul-Gumuz Regional State, Assosa, and their altitude is 1530 and 1520 meters (Figs. 1 and 2). The whole region was completely unknown from an archaeological point of view before our first survey and test excavations in January 2001. Even though the area is a difficult one for archaeological work due to its predominantly rugged and densely forested landscape, a general outline of the regional cultural sequence has been unravelled after four field campaigns (2001– 2003, 2005). This paper presents an overview of the excavations conducted in 2001 and 2002 at the two oldest sites discovered so far, whose archaeological sequence extends from approximately the end of the Pleistocene, before 10,000 bp, to the end of the Later Stone Age after 2000 bp.

many considered the region a “no-man’s land” (BRYAN 1945; TRIULZI 1981). Its mosaic of little known and supposedly ‘archaic’ peoples were known until recently in the anthropological literature as “pre-Nilotes” (Berta, Gumuz, Komo, etc.), their features being considered the survival of a stage previous to the present Nilotic cultures of southern Sudan (GROTTANELLI 1948; MURDOCK 1959: 170–180). Not less intriguing has been the problem of the historical origins of those Nilo-Saharan peoples and their relationship with their neighbours to the west

The excavations have provided information on the Middle and Later Stone Age in the area, which partially fills the enormous gap in our knowledge of this period, not only here but throughout West Ethiopia. Extensive palaeontological research in the Rift Valley, fostered by remarkable public interest, has strongly prevailed in the country to the point that “Pleistocene and Holocene developments have received alarmingly little attention” (BARNETT 1999: 95). Recently published maps of known MSA and LSA sites in Ethiopia and the Horn not only show their very low number but also reveal the empty space stretching through the whole western fringe of the country (e.g. BRANDT 1986: fig. 1; BARNETT 1999: figs. 5.1 and 5.8; KUSIMBA 1999: fig. 1; PLEURDEAU 2003: fig. 1). Furthermore, sites like K’aaba, yielding both MSA and LSA levels, are extremely rare in Ethiopia, where most of the allegedly ‘transitional’ deposits have proved to be mixed or secondary contexts (BRANDT 1986: 62). Data from the excavations are also relevant to the many issues still unaddressed with regard to the recent history of the area. Linguistically and culturally, the border areas between Ethiopia and Sudan north and south of the Blue Nile puzzled observers in the past and Fig. 1. Location and geology of the research area. Places mentioned in the text: 1) Assosa (sites of K’aaba, Bel K’urk’umu, Bul K’aito), 2) Bambasi (K’unda Damo), 3) Menge (Bela Sharafu), 4) Gizen (Section after Geological Survey of Ethiopia. 1997, sheet Kurmuk and Asosa, NC 36-7, NC 36-8).

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Journal of African Archaeology Vol. 5 (1), 2007

A Late Stone Age Sequence from West Ethiopia

Gojjam and Wollega on both sides of the Blue Nile, until they were pushed west, back to the lower, unhealthy areas where they live today, by the expansion of Amhara and Oromo peoples during the last centuries (e.g. CORFIELD 1938: 157–158; GROTTANELLI 1948: 322–324). Recent research, however, has cast considerable doubt on this idea, suggesting instead that most Nilo-Saharans were originally confined to the lower zones (e.g. for the Gumuz in Wollega, see UNSETH 1985: 93; JAMES 1986: 130).

Fig. 2. Geomorphologic map of the Assosa area, based on aerial photographs taken in 1985; archaeological sites are indicated in some of the rocky outcrops (in black).

(Sahelian Arabs and southern Nilotes in Sudan) and east (semitic Amhara, cushitic Oromo and Agaw, and Omotic Shinasha in Ethiopia). Worsening ecological conditions attested throughout the savannah/Sahel belt after the mid-Holocene have been identified as the main cause for a demographic displacement of the Sudanic groups towards the Ethiopian Highlands. These displaced populations have been credited with introducing agriculture to the indigenous populations of the Ethiopian Plateau (CLARK 1976: 80–81), although archaeological proof of this hypothesis is still lacking. The actual extent of the initial Nilo-Saharan occupation of the Highlands has been also much debated. Conventional wisdom until a few decades ago had it that Nilo-Saharan populations occupied large areas, i.e. a considerable part of the modern provinces of

The area explored is part of the western margin of the Ethiopian plateau and is mainly composed of metamorphic proterozoic and palaeozoic rocks of the AfroArab shield. During and after the orogenic deformation that elevated the present plateau, the zone was intensively eroded, so that most of the sediments deposited in the previous periods, Mesozoic and Tertiary, were washed away. During the Oligocene and Miocene, several fissure volcanic episodes had covered the deeper areas of the palaeo-landscape with erupting lavas. The volcano-sedimentary units in the Assosa area belong to the Birbir Group and are formed of green schists, phyllites, quartzites and metamorphized volcanoclastic rocks. The older rocks are granitic and granodioritic plutons from the early Palaeozoic. The Tertiary lavas that cover the crystalline basement are the Makonnen Basalts deposited during the Oligocene to the Miocene (MENGESHA TEFERA et al. 1966; DAVIDSON 1983).

In this area most archaeological sites are located in rock shelters of outcrops that form a characteristic boulder landscape. Lithologically they are classified as granites, granodiorites, tonalites, diorites, hornblendes, gabbro and ultramaphic rocks, all very abundant in the region, which they cover in about two thirds of its Precambrian basement. On the margins of the Makonnen Basalts (35–20 ma) that cover most of the Assosa area, some of these intrusive materials protrude to the surface (granites and granodiorites). Their shape is generally elongated following the N-S direction that is also that of the tectonic and lithological contacts. Petrologically, the rock grain size is medium to large, although a few are fine-grained. The diorites sometimes have inclusions of xenolith. The rock structure is massive, but is frequently fissured. The big intrusive rocks that initially


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Fig. 3. A view of the K’aaba rocky outcrop from the southeast, showing the place between the two big rocks where the excavated shelter is situated.

protruded to form a single block were later cracked and finally broken through the lines of fissures (joints) to form a rectangular grid. This eventually creates the final shape of the mostly rectangular blocks. The surface in the Assosa area is smooth with shallow valleys. At about 1500 m average elevation, it is defined both to the north and to the south by two mountain ranges, Gangan to the north and Shida to the south. The intrusive rocks in the form of the previously mentioned inselbergs or kopjes stand out very clearly in some parts of the landscape. The largest is the Inzi mountain near Assosa, which could not be examined because of the presence of a military post, but according to our informants has no appreciable archaeological remains. Inselbergs and boulder outcrops are also very common in the escarpment area, where valleys, with about 500–600 m depth in average, cut the final part of the Highlands, very often following the dominant N-S direction. Just along the escarpment border, an area several kilometers long to the west of Assosa with granodiorite outcrops can be seen. It was created by extensive fault lines that underwent differential weathering to produce inselbergs, whose erosion resulted in a large variety of morphologies such as boulders, overhangs and sheltered cavities (Fig. 2). These shelters acted as sediment traps and have preserved concentrated prehistoric remains, i.e. archaeological sites that, except for scattered lithics and some recent settlements, seem to be very rare elsewhere in the region. Of the 16 shelters test excavated, nine yielded significant archaeological remains. Four of the shelters are situated near Assosa: K’aaba, Bel K’urk’umu and Bul K’aito A and B (alternative name: Ts’alenger). Since the cultural material

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found in Bul K’aito A and B belongs mostly to the more recent periods, only the first two sites will be presented in this paper. The acidic nature of the soils in most of the shelters resulted in bone and macrobotanical remains not having been preserved; this being observed both with the naked eye and through the microscopic analysis of a substantial number of soil samples. The site of K’aaba The name of K’aaba is given by local Berta people to the largest granodiorite outcrop in the Assosa district, located 1 km southwest of the town by the prison road (Fig. 3). The name is probably related to the Berta verb “k’ába”, “to hunt” (BENDER 1993: 285). The boulders are situated between two small streams and the place is used by local people as a picnic spot. They are located at about 1530 m above sea level, the UTM coordinates of the central area being E 0667730 / N 1111040. There are several sheltering places under the rocks yet only the biggest one, under two big stones leaning against each other, yielded significant archaeological remains; it was labelled K’aaba-1 (Fig. 4). The covered area in the shelter is approximately 6 x 3 m, i.e. about 20 square meters. In February 2001, one 1 m2 square was excavated in the central part of the cavity to test the archaeological value of the site (Fig. 4, square A). The deposit was excavated in arbitrary units of ca 10 cm each, down to the beginning of the crumbling granite (lehm) above the bedrock, at 70 cm depth. Units 1 and 2 were deposited during the recent occupation of the whole outcrop area by a Berta community, whose only noticeable remains are some recent mortar stones in the wide open areas between the rocks. A thin whitish layer of compacted clay in Unit 2 corresponds to the floor of a Berta dwelling. Units 3 and



Fig. 5. K’aaba rock shelter during the excavation in 2002

exploration of other nearby cavities was undertaken. At one of them, immediately east of K’aaba-1, a test pit of 1 m2 was excavated down to 120 cm deep. Some lithics and pottery sherds of Sudanese type (decorated with packed rocker impression) were discovered. The sediment was particularly homogeneous, maybe as a result of termite activity — a termite mound was still visible on the surface (MCBREARTY 1990). Two other small shelters were also tested, without significant results.

Fig. 4. K’aaba site plan and section, showing the excavated squares.

4 were interpreted as belonging to the Later Stone Age due to the presence of some blades and end-scrapers, whereas Units 5 and 6 were preliminarily assigned to the Middle Stone Age because of the abundance of larger flakes and two retouched points; some of the flakes had been knapped from discoid and Levallois-like cores. In February 2002, excavations in the outcrop were resumed. Before starting in the biggest shelter, a short

The excavation of another 2 m2 was undertaken immediately next to the test pit excavated in 2001 towards the shelter entrance (Fig. 4, squares B–C). After reaching the Later Stone Age levels, only one square meter was continued (square B). Its deposits were dug in arbitrary spits of about 2 cm wide, from Unit 1 at -30 cm until the base deposits of Unit 34 at -105 cm. All artefacts recovered from those units were three-dimensionally plotted (Fig. 5). The excavated sediments were sieved through a 2 mm mesh. Special care was taken to not mix the artefacts coming from the different sediment levels. A sediment classification of the deposits follows (Figs. 6 and 7): Level A (0–0.1 m), fine brown-grey sands, with small granite and granodiorite blocks and pebbles.


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Level B (0.1–0.15 m), loose grey muddy sands with a great deal of organic matter and charcoal particles. Level C (0.15–0.25 m), compact grey-brown muddy sands with pottery sherds, millimetric granodiorite pebbles and centimetric charcoal fragments. Level D (0.25–0.5 m), fine dark grey muddy sands with more gravels, rich in organic matter with centimetric granodiorite pebbles and some concentrations of small pottery sherds. Level E (0.5–0.6 m), brown sands with gravels and centimetric granodiorite blocks, especially in the southern half; quartz flakes and haematitic rock fragments are abundant. Level F (0.6–0.75 m), loose sands with light brown mud and many quartz flakes; its base is a gradual transition to the following level.

Fig. 6. Stratigraphic cross sections of the excavated squares at the K’aaba rock shelter.

Fig. 7. Soil texture data from samples at different depths (m) from the K’aaba rock shelter.

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Level G (0.75–1.1 m), light brown muddy sands with gravels, size increasing with depth; in some areas the level is sandier and less muddy; some sand agglomerates coated with mud are found with more organic matter, probably as a result of marshy conditions; there are also big granodiorite pebbles, especially near the crumbling rocks at the base.

The gravel fraction is mainly composed of granodiorite fragments with charcoal and mud-wall fragments in the upper levels. An increase in granodiorite blockpebbles and quartz flakes is observed between -0.6 and -0.65 m. Sands are composed of angular feldspar and quartz grains, together with mica (biotite) in the smaller sizes. The finer fraction is largely of quartz with less mica. Neither carbonates, nor manganese nodules were found. This can be interpreted as an indication of the acidic nature of the soils, resulting in the complete absence of bone remains at the site. Several plant seeds were collected between the surface and -40 cm, all of them of seemingly recent date according to their examination by Dr. Anwar Abdelmagid Osman (Bergen University). A change of sedimentary conditions is apparent between Levels E and D. The upper part has a higher organic component, with the presence of mud-wall and pottery fragments. Processes of chemical soil formation are evident, suggesting slower edaphic



processes. The lower part, on the contrary, suggests higher deposition energy, or the greater abundance of large materials. Alternative explanations could be a period of greater temperature variation, an increase in humidity, or human action. Charcoal samples for radiocarbon dating were taken at -0.25 m (Level C) and -0.64 m (Level E), and sediment samples for Optically Stimulated Luminescence dating (OSL) were obtained at -0.4/0.45, -0.75/0.8 and -0.95/1.0 m, hammering light-proof PVC-sealed tubes horizontally into the freshly cleaned exposures of the northern vertical wall of the excavation. The lowest organic sample (Level E) was radiocarbon-dated by the AMS method at the Uppsala University laboratory (Ua-19925) with no result as the sample was more recent than 1950. We were also unlucky with the OSL sediment samples, which were analysed by Dr. Norbert Mercier of the Laboratoire des Sciences du Climat et de l’Environnement (UMR CEA – CNRS) in Gif-surYvette, France. The two lower samples presented an OSL signal undistinguishable from saturation levels, that is to say, they appear saturated and thus of “infinite” age. This condition might be explained by the high content of radioactive elements in the sediment, something to be expected in granite rocks having more Uranium than most other rock types. For the upper sample, estimating the radiation dose from a fraction of the sediment collected, a date of 2600 bp was obtained. The soil of this sample was extracted from the middle of Level D, i.e., the dating corresponds with the Later Stone Age and, although more recent than expected, it basically agrees with the LSA dates from the Bel K’urk’umu site that will be discussed later in this paper. If we assume that the same dose measurements from the upper sample apply to the lower sediments, extracted from Levels F and G, whose technology displays features typical of the Middle Stone Age, the inference can be made that they are more than 10,000 years old, which is the time needed for saturation of OSL signals in quartz at the assumed dose rate (N. Mercier, personal communication, June 2004). The same procedure of using saturated luminescence samples to estimate minimum ages has been applied to other Middle Palaeolithic sites (e.g. RINK et al. 2000: 169). The uppermost Levels A–C were deposited in recent times during the occupation of the shelter by local Berta people. They are characterised by thick pottery sherds of coarse material with vegetal temper and polished black outer surface. A few sherds found with thinner walls, mineral temper and decorated with cord-impressions contrast with the former type and could be of slightly earlier date (Fig. 28: 15). Only a small portion of the compacted mud floor recorded in square A was preserved in square B. A small number of quartz artefacts were found

in the three upper levels, most probably coming from the lower deposits through the effect of post-depositional processes. The base of Level C, devoid of artefacts, had a higher content of crumbling granodiorite blocks, which probably corresponds to a period of human abandonment of the site. From Level D downwards Berta pottery disappears and abundant stone tools increasingly appear. On the basis of their lithic industry, Levels D and E may be tentatively ascribed to the Later Stone Age, while Levels F and G yield a technology typical of the Middle Stone Age. Lithics General characteristics A total of 5,280 lithic pieces amounting to 26,429 grams in weight were recovered in the 2002 excavation. The predominant raw material is medium-quality quartz (96.6 %) and high quality quartz (2.1 %) with some pieces of chert (1 %) and quartzite (0.4 %). The following lithic categories were distinguished: fragments less than 2 cm in size (59.7 %), 2–5 cm (23.6 %), bigger than 5 cm (0.6 %), complete flakes (13.2 %), blades (0.1 %), cores (1.5 %) and retouched tools (0.5 %). The distribution of raw material and flaking types in the four Stone Age levels is shown in Tables 1 and 2. Due to the high number of lithic pieces and their fragmentation, neither in K’aaba nor in Bel K’urk’umu was refitting of lithics accomplished. As a way of testing the technological-typological variation at the site, a representation was made of the absolute lithic frequencies in the various arbitrary units (Fig. 8). A clear distinction can be seen between the upper levels, D–E, with a far larger number of stone artefacts, and the lower ones, F–G, which produced much less material. The difference may be explained by more intensive occupation of the site in later times, but a taphonomic cause cannot be ruled out. Differences in raw material also occur, as high quality quartz and chert are more abundant in the lower than in the upper levels (Tab. 1). The fact that small débitage and chips are more frequent in the upper levels (59–64.6%) than in the lower (39.2–42.1%) suggests that hydraulic or depositional processes could have operated more intensively when the site was first occupied, or that early stages of the reduction sequence were carried out elsewhere. In order to minimize the distortion produced by taphonomic alterations, the percentages of technological types were re-calculated excluding the fragmented material (Tab. 3). The table shows that there are no noticeable differences between the levels in terms of the distribution of technological categories, with quite similar percentages of flakes, blades, cores and retouched tools throughout the whole sequence.


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Raw material Medium quartz High quality quartz Quartzite Chert

Category

Cores Retouched pieces Hammerstones Flakes Blades Frags. > 50 mm Frags. 20–50 mm Frags. < 20 mm TOTAL

Category Cores Retouched pieces Hammerstones Flakes Blades

Level D n % 1769 4 9 24

98.0 0.2 0.5 1.3

Level E n %

n

2741 97.6 43 1.5 7 0.2 18 0.6

Level F %

153 18 1 4

Level G n %

86.9 10.2 0.6 2.3

436 44 4 5

Level D

Level E

Level F

n

n

n

29 11 1 195 17 6 481 1065 1805

% 1.6 0.6 0.1 10.8 0.9 0.3 26.6 59.0

27 3 1 326 19 23 594 1814 2807

% 1.0 0.1 0.1 11.6 0.7 0.8 21.1 64.6

Level D

Level E

Level F

Level G

11.5% 4.3% 0.4% 83.4% 0.4%

7.2% 0.8% 0.3% 90.5% 1.1%

7.1% 3.4% 84.3% -

10.9% 5.4% 82.3% 1.4%

5 6 0 59 3 0 37 69 179

89.2 9.0 0.8 1.0

Tab. 1. Frequency distribution of the different raw material types in the K’aaba Stone Age levels.

Level G

%

n

%

2.8 3.4 33.0 1.7 21.0 39.2

16 8 0 115 8 0 136 206 489

3.3 1.6 23.7 1.6 27.8 42.1

Tab. 2. Frequency and percentage distribution of lithic categories in the K’aaba Stone Age levels.

Tab. 3. Percentage distribution of different categories in the K’aaba levels, excluding fragmented pieces and chips.

Fig. 8. Frequencies of lithic pieces in the arbitrary units excavated at K’aaba rock shelter, showing the archaeological levels: Level D: units 1–10; level E; units 11–18; level F: units 19–22; level G: units 23–34.

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Level

G F E D

Number of Length Weight flakes and (mm) (g) blades n Average Std. Dev. Average Std. Dev. 83 54 194 203

32.3 29.5 28.1 25.1

10.8 9.8 8.4 8.6

13.3 11.0 8.0 6.7

17.4 9.7 8.2 9.6

Tab. 4. Average length, weight and standard deviation of flakes and blades from Level G to D.

Fig. 9. Size scatter diagram (length and width, in mm) of flakes (left) and blades (right) from the K’aaba rock shelter, showing the lower (circles) and upper (triangles) levels.

Débitage We evaluated 742 flakes and blades, constituting 14 % of the total lithics; in only 534 cases were complete dimensions available. A gradual decrease in size is noticeable in the sequence from the lower to the upper levels. Average length and standard deviation in mm from Level G to D are presented in Table 4. Differences of the means can be seen, especially between the upper Level D and the other three levels. Accordingly, the average flake weight also diminished during the occupation time period (see Tab. 4). Sample variation in every level, however, is quite large and there is a considerable overlap between the four groups (Fig. 9, left). For the blades and bladelets the model of reduction from the lower to the upper levels can be seen more clearly in Figure 9, right. Throughout the sequence, the bulk of the flakes has no cortex on their dorsal faces (92.2 %). The majority of the striking platforms (81.8 %) are flat, other types such as faceted and cortical being far less abundant (6.2 % each). There is a significant difference between the lower levels, G–F, where faceted butts are 14.4 % and 12.5 % respectively, and the upper ones, E–D, where they amount to only 4.5 % and 3.1 %,

a fact that suggests a more sophisticated technology when the site was first occupied. Further evidence for a more thorough and systematic knapping practice in the lower levels is provided by comparing the number of previous scars (Fig. 10). Flakes with 5 or more scars are more abundant in Levels G (5 %) and F (6.5 %) than in the Levels E (3.4 %) and D (0.6 %). On the contrary, flakes with 1-2 scars are on the whole less frequent in the lower levels G – D – E (33.8 – 43.5 – 36.3 %) than in the upper level D (53.9%). Observing the direction of previous scars on the dorsal faces of the flakes also provides evidence of the change in flaking techniques. Due to the irregular mechanical properties of quartz, it is often difficult to recognize those directions, and in fact, this could only be analysed in 158 flakes (21.6 %). Unidirectional models prevail throughout the sequence (75.3 %), followed by centripetal (16.5 %) and multidirectional (8.2 %) patterns. Whereas in the upper Levels D–E the flakes are mainly irregular, displaying a less complex technique and smaller size, in the lower Levels F–G and a part of


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butts and centripetal knapping of the cores, some of these being actually of Levallois type (Fig. 12). Even though the model is not at all clear, some evidence can be seen of a change from centripetal to unidirectional flaking, the latter being more frequent in Level E than in Levels G and F. A curious and unique find must also be noted, an elongated blade in mudstone from Level D in square A (Fig. 15: 13), which is reminiscent of the mudstone “long-blades” recorded in the Aksum area (FINNERAN 2000: 29–31).

Fig. 10. Frequency of flakes with diverse number of previous scars in the four levels of the K’aaba site.

Cores A total of 78 cores were collected, their size tending to be similar in all the levels, with a mean length of 36.4 mm and a mean weight of 39.2 g. The predominant raw material is quartz, although there are a few pieces made of chert (2.6 %) and quartzite (5.2 %). Most of them came from tabular quartz blocks (70.1 %), river cobbles (10.4 %) and even a few flakes were used as core blanks (5.2 %); the original blank was unknown in some cases (14.2 %). According to their technical features, they may be classified in seven types as follows (Figs. 13 and 14). Core type 1: the simplest, with a few isolated flake scars without any programmed knapping structure. Type 2: unidirectional cores, some with cortical platforms and others with prepared ones, producing mostly elongated flakes. Type 3: cores with two or three independent striking platforms. Type 4: unifacial, centripetal cores, where only one horizontal plane following a radial pattern is exploited (Fig. 14: 5).

Fig. 11. Elongated flakes from level E (a–e) and G (f) of K’aaba rock shelter. All in quartz except (e), in chert. Item (f) is a pseudo-Levallois point with a shape very similar to the retouched points of Figure 16 and was probably used for the same purpose. Scale in cm.

Level E, which shows some transitional features, the flakes are larger and more skilfully prepared on a better- quality stone. In the earlier phase of the site two flaking patterns prevail, one of long flakes and blades, 40–50 mm in length and thin sections (Fig. 11), and a second one of wide and short flakes with prepared

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Type 5: bifacial cores, with several types ranging from those with a bifacial edge without any preparation to those better structured such as the discoid and Levallois types (sensu BOËDA 1993) (Fig. 14: 1–4). Type 6: multifacial cores, with more than 3 unrelated striking platforms. Type 7: blade cores, with very few examples even though some blades and flake-blades were collected during the excavation; two examples from Level D in square A are of bipolar type (Fig. 14: 6–7).



apparently random variation, although those types producing elongated flakes and blades (types 2 and 7) appear more frequently or exclusively in the upper levels.

Fig. 12. Centripetal and Levallois flakes from levels E (a–c), F (d–f) and G (g–i). All in quartz. Scale in cm.

Retouched tools With regard to the retouched tools (Figs. 15 and 16, Tab. 6), a total of 28 pieces were recorded, made on flake fragments (64.3 %) and complete flakes (35.7 %). High-quality quartz was consciously chosen for the tools, since it represents 17.9 % of the retouched pieces, compared to a mere 2.1 % of the whole lithic assemblage. Also bigger blanks were selected, as suggested by the mean size of the tools being 31.9 mm and the mean weight 13.2 g, whereas the mean for the collection as a whole is only 27.2 mm and 8.6 g. An uneven decrease in size is perceptible from the lower levels (mean of 40.8 mm and 23.5 g) to the upper ones (24.7 mm and 6.7 g). Throughout the stratigraphic sequence there is no significant variation of the absolute frequencies of retouched lithics. With respect to the typology (Fig. 15), they are mostly side-scrapers (75 %), with a small proportion of end-scrapers (17.8 %) and denticulates (7.2 %). The end-scrapers are very homogeneous and most of them can be classified as ‘typical’. There are two main groups of side-scrapers, one characterised by a straight retouched side, transversal or lateral (35.7 %), and the other with one or two convex retouched sides, i.e. simple or double (39.3 %). Morphologically, those in the second group can be defined as retouched unifacial points, since the knapper’s intention was most probably to produce a pointed tip at their ends (Fig. 15: 1–6; Fig. 16). All of them are unifacially flaked using normal, direct retouch.

The distribution of types in the four archaeological levels (Tab. 6) fits into the chronological frame, since end-scrapers appear concentrated in the upper level while the frequency of retouched points decreases steadily from the bottom to the top. As the end-scraper is typical of the Later Stone Age in many parts of Africa, whereas retouched points have repeatedly been proposed as the “guide-fossil” of Middle Stone Age in most Eastern and Southern Africa, a straightforward conclusion would be to consider the lower levels of the site, F and G, as MSA-like, and the upper levels, D and E, as LSA-like.

Fig. 13. Diacritic schemes of the core types of the K’aaba rock shelter.

The frequencies of each type at the site can be seen in Table 5. Unifacial centripetal and bifacial are the most common types, as would be expected by the abundance of centripetal and Levallois flakes (Fig. 12). Unidirectional and multifacial core types are also represented according to the number of elongated (Fig. 11) and amorphous flakes recorded at the site. As to the representation of core types at the different levels (Tab. 5), most of them show an irregular model with


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Fig. 14. Cores from the K’aaba rock shelter: Levallois (1–4), unifacial centripetal (5) and bipolar (6–7), from levels D (2, 3, 6, 7), E (4, 5) and G (1). All in quartz.

LEVEL Core Type

D

Type 1 (irregular) Type 2 (unidirectional) Type 3 (independant platforms) Type 4 (unifacial centripetal) Type 5 (bifacial) Type 6 (multifacial) Type 7 (blade cores) Total

3 3 5 5 9 7 2 34

Total

E

8.8% 8.8% 14.7% 14.7% 26.5% 20.6% 5.9%

1 5 1 8 6 1 1 23

F

4.3% 21.7% 4.3% 34.8% 26.1% 4.3% 4.3%

1 1 0 1 1 1 0 5

G

20% 20% 0 20% 20% 20% 0

3 0 0 7 4 2 0 16

18.7% 0 0 43.7% 25.0% 12.5% 0

8 9 6 21 20 11 3 78

10.2% 11.5% 7.7% 26.9% 25.6% 14.1% 3.8%

Tab. 5. Frequencies and percentages of the core types in the levels of the K’aaba site.

LEVEL D RETOUCHED TOOL TYPE

Total

Denticulates Endscrapers Unifacial points Sidescrapers

0 0 5 45.4% 1 9.1% 5 45.4% 11

Total

E 1 0 2 0 3

33.3% 0 66.6% 0

F 1 0 3 2 6

16.7% 0 50.0% 33.3%

G 0 0 5 3 8

0 0 62.5% 37.5%

Tab. 6. Frequency and percentage distribution of retouched tools in the archaeological levels of K’aaba site.

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2 5 11 10 28


Fig. 15. Retouched tools and blade from the K’aaba rock shelter: unifacial points (1–6), side scrapers (7–10), denticulate (11), end-scraper (12), blade in mudstone (13). From level D (12, 13), E (5, 11), F (1, 9, 10) and G (2–4, 6–8). All in quartz except no. 13 in mudstone.

Fig. 16. Four unifacial points in quartz from the K’aaba rock shelter. From level E (1), F (2) and G (3–4). Scale in cm.


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The site of Bel K’urk’umu In February 2002, an excavation was carried out in this rock shelter, situated under a large granodiorite boulder (UTM E 0666103 / N 1110392). Two interpretations of the name were given by local Berta people: “Black rock” or “Rock of the pigeon”. Six 1x1 m squares were excavated in its central area down to the granodiorite bedrock (squares A–F) and the upper levels only of two others (G and H) were excavated in order to increase the sample of pottery decoration types from the site (Figs. 17 and 18). The rock shelter follows a line approximately N-S of about 20 m, facing west. Although today it is covered by bamboo that hides the entrance, from the shelter one can glimpse the small lateral valley with a seasonal stream that joins other tributaries, which about 15 km further on join the river Yabus at the current political frontier with Sudan. The escarpment is not very steep here, this being one of the places where the ascent is easier. The shelter is located at 1520 m above sea level, and the valley bottom at approximately 850 m.

Fig. 17. The Bel K’urk’umu rock shelter during excavation works.

Fig. 18. Bel K’urk’umu site plan and section, showing the excavated squares.

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Fig. 19. Bel K’urk’umu: Western stratigraphic cross section of the excavation. The big hole in levels C and D is a den.

Level B (0.05–0.15 m), sandy level of grey to dark brown colour; organic material and pottery sherds are abundant. Level C (0.15–0.2 m), sandy grey level with granodiorite fragments and fewer muddy components; mud wall fragments and charcoal are scarce here. Level D (0.2–0.55 m), brown sands and gravels in a muddy matrix, grain size decreasing downwards; at -0.35 there is a layer richer in gravels; seeds, organic matter and charcoal diminish throughout the level.

Fig. 20. Soil texture data from samples at different depths at the Bel K’urk’umu rock shelter.

The deposits were formed as a sedimentary colluvium coming from an opening between the two big rocks above it, and occupy an area of approximately 50 m2. The sediments are predominately sandy and their characteristics (grain size, organic components, etc.) allow the deposits to be separated into several levels (Figs. 19 and 20): Level A (0–0.05 m), superficial level, of brown sandy mud with parts of a mud wall (probably from the construction of a recent grave above it), charcoal remains and many plant roots and well-preserved seeds of recent origin.

Level E (0.55–0.7 m), sands and gravels in a mud matrix with alternating proportions of fine and coarse grain sizes and some patches composed almost exclusively of quartz flakes and chunks resulting from human activity (Artificial Units 8 to 17). Charcoal is abundant from the top to -0.60 m. Level F (0.7–1.1 m), gravels with sand in a fine muddy matrix; crumbling granodiorite in different sizes ranging from light to dark brown colour; blocks and pebbles are increasingly abundant near the small boulders of the basement rock (Fig. 21). Levels A and B correspond to Artificial Unit 1, Level C to Unit 2, Level D to Units 3–7, Level E to Units 8–11, and Level F to Units 12–18. Mineralogical composition is fairly homogeneous. Gravels (>2 mm) are mostly of granodiorite, diorite and quartz from the bedrock, together with allogenic materials such as rolling quartzite pebbles and anthropic elements. Sands (2–0.063 mm) are composed


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Fig. 21. The site of Bel K’urk’umu at the end of the excavation.

Radiocarbon sample

Depth

Unit

Ua-19921 Ua-19922 Ua-19923 Ua-19924

30 cm 50 cm 60 cm 70 cm

2 7 10 12

Level

Horizon

C (base) D (base) E F

Upper Upper Lower Lower

Date (bp) 875 + 40 2020 + 45 4965 + 55 4470 + 55

Date (calibrated) 1040 – 1220 AD 90 BC – 60 AD 3660 – 3800 BC 3030 – 3340 BC

Tab. 7. Radiocarbon dates from the Bel K’urk’umu rock shelter (calibration by program OxCal version 3.9, date ranges with probability of 68.2%).

of angular grains of vein quartz and feldspar-plagioclases, tiny flakes of hollocrystalline quartz and small mica laminae. Mud-silt fraction ( 50 mm Flakes Blades/bladelets Retouched pieces Cores Manuports Hammerstones

n

%

17987 6679 198 711 44 26 157 19 1

69.7 25.9 0.8 2.8 0.2 0.1 0.6 0.1 0.0

Tab. 8. Frequencies and percentage distribution of the different lithic categories in the Bel K’urk’umu site.

boulders, although some cobbles had been picked up in the nearby streams, as was also the case with a few fluvial quartzite cores (0.1 %). Some pieces were found of finer quartz (rock crystal, 0.4 %) and a few of a high-quality chert (0.2 %) that had been transported from distant sources (there seems to be high-quality chert in the area near the Blue Nile, e.g. at Gizen). Two-thirds of the stone fragments (69.6 %) are less than 20 mm in size and can be considered flaking by-products, which is indicative of the importance and intensity of these activities at the site. Moreover, the high number of small pieces suggests that hydraulic depositional processes were unimportant in the shelter. The fragments of medium size (20–50 mm) are also very abundant, amounting to 26 % of the assemblage. Many of them are fractured flakes, their abundance probably due to the rough material and the expeditive technology applied. The poor quality of most of the quartzes was without doubt an important determining factor when exploiting the stone material and had a decisive effect on the enormous fragmentation of the blocks and the poor patterning of the flaking techniques. The density of artefacts increases towards the bottom of the deposit (Fig. 22), reaching a maximum in Artificial Units 9–13 (Level E and beginning of F) and decreasing again towards the bedrock. The percentages of flaking categories do not vary appreciably throughout the sequence (Tab. 9), yet since there are some lithological differences between the upper (C–D) and lower levels (E–F) as well as a likely chronological distinction too (see Tab. 7), a comparison between the two members seems advisable. The lower horizon is composed of more mineral and less organic components, and is dated to ca 4500–5000 years bp, whereas the upper horizon

Fig. 22. Distribution of lithic artefact weight in grams throughout the artificial units of the excavation of Bel K’urk’umu site (compare with Fig. 29).


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Total

Level

Flakes

Blades

A-B C D D D D D E E E E F F F F F F F

17 42 35 19 27 34 55 36 78 91 7 63 72 43 71 12 6 3 711

0 2 1 0 0 3 6 2 2 9 0 3 5 3 5 1 1 1 44

Frag. 20-50 Frag. >50 Frag. 80 %). Poaceae (ca 35 %) and Chenopodiaceae-Amaranthaceae (20–25 %) make the major contribution to the herb histogramme. Xerophytic elements (Artemisia, Capparidaceae) or weed taxa such as Boraginaceae, Asteraceae liguliflorae and Asteraceae tubuliflorae also increases in this level. Taxa from dry montane forests as aforementioned are now at very low percentages, especially Podocarpus (< 5%), while hydro-hygrophytic elements have disappeared. The floral composition of both spectra indicates that the environment was very open, extended open grasslands (savanna-like) especially dominated by grasses and with only a few trees or shrubs (Acacia 10 %, Combretaceae, Commiphora). High percentages for xerophytic and weed taxa and low for trees and shrubs, as well as the disappearance of the hydro-hygrophytic flore, allow us to consider the existence of very arid climatic conditions at the time of first human impact into the landscape. The identification of Sordaria type (ca 10–20%), corresponding to the coprophilous ascospores of some Sordariaceae species that normally live in anthropic areas where domestic cattle exist (LÓPEZ SÁEZ et al. 1998), in both pollen spectra KAB-5 and 4 could testify to pastoral activities in the surroundings of the K’aaba site during the final LSA times (Level D is dated by OSL to ca 2600 bp, vid. supra). Pollen samples from Level E (BKU-4 and 5) of the Bel K’urk’umu site, radiocarbon dated to ca 5000–4500 bp, show pollen spectra completely similar to Level D of the K’aaba site: herb pollen percentage > 80 %, high values for Poaceae (ca 40 %), Chenopodiaceae/ Amaranthaceae and Artemisia, very low values of hydro-hygrophytic elements, and finally, relatively high percentage for Sordaria type (15–25 %) (Fig. 32). Fire events have been evidenced in the BKU-4 pollen sample by the presence of carbonicolous fungi ascospores (Chaetomium sp.) (LÓPEZ SÁEZ et al. 1998). Unfortunately one pollen sample from the lower Level F (BKU-6) of Bel K’urk’umu was sterile of pollen content, possibly due to its sedimentological nature. In conclusion, the results of our palynological analysis at the sites of K’aaba and Bel K’urk’umu, during the LSA period, indicate that the vegetation of the area surrounding the sites was a very open savanna grassland with very arid climatic conditions in the

second half of the Holocene. The low cover of arboreal vegetation and the identification of some evidence of human impact could indicate the first development of felling processes of anthropic origin, which in the case of BKU-4 could have also implied the use of fire. These results at the Benishangul-Gumuz Regional State (Ethiopia) are similar to those obtained from the Blue Nile area (Central Sudan) in the Middle Holocene (LÓPEZ SÁEZ & LÓPEZ GARCÍA 2003), including pastoral activities near the archaeological sites, or from the Tigray region (Northern Ethiopia) in the Middle and Late Holocene (BARD et al. 2000). Additionally, numerous palynological studies carried out in Africa demonstrate a regression of the arboreal cover starting from 5000 bp, which cannot be interpreted as a result only of the anthropic activity but also of the climatic change towards conditions of extreme aridity (BONNEFILLE 1993). Pollen spectra from the uppermost levels of both sites are very similar (Figs. 31 and 32). In K’aaba, KAB-3 Level C, KAB-2 Level B and KAB-1 Level A were deposited in recent times and correspond to an abandoned Berta settlement. In Bel K’urk’umu, BKU-3 Level D and BKU-2 Level C were radiocarbon dated to 2020 and 875 bp respectively (see Tab. 7). The spectra are characterised by the extreme abundance of herbaceous taxa, in which Poaceae is dominant (> 50 %). Very high percentages of Poaceae in the uppermost level at each site could indicate the dense cover of bamboo hiding the entrances to the rock shelters today. Other important herbaceous taxa identified are Chenopodiaceae/Amaranthaceae, both Asteraceae liguliflorae and tubuliflorae, and finally Artemisia. Shrubby elements from the savanna vegetation (Acacia) have also been identified but in smaller percentages than in the LSA levels. The hydro-hygrophytic elements are also not very common. Sordaria type and Chaetomium sp have been also identified. Cereal pollen has been identified in both uppermost KAB-1 and BKU-1 and BKU-2 (Figs. 31 and 32), indicating some type of agriculture. It is remarkable that drier conditions have also been postulated from 1800 to 950 bp in the Dela Sala swamp in the Arsi mountain range in Arussi province of southeastern Ethiopia (BONNEFILLE & MOHAMMED 1994), although this pollen record lacks evidence of direct anthropogenic indicators. We suggest that the vegetation in the vicinity of both archaeological sites from the Benishangul-Gumuz Regional State (K’aaba and Bel K’urk’umu), during the last 2000 years, represents an anthropogenic ecosystem, with the presence of grazing and agriculture and the possible recurrence of controlled fires, but we cannot discard that very arid climatic conditions can also be responsible for the scarce arboreal covering that is detected in the pollen diagrams.


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Discussion A case of technological archaism in the Holocene Both in K’aaba and Bel K’urk’umu there appears to be a distinct change in the lithic technology, from techniques that are known elsewhere to be of earlier age to others usually considered of more recent chronology. The human groups that lived in the two rock shelters were most probably related, since the two industries have a great deal in common. K’aaba rock shelter was the first to be occupied and Bel K’urkumu later, but not long after the abandonment of the former or, more probably, while K’aaba was still inhabited. A connection between K’aaba upper Level D and Bel K’urk’umu lower member, Levels F–E, appears reasonable since the retouched tool types are the same in both contexts, i.e. side and end scrapers. Percentages of core types show a moderately gradual increase within each site and from one site to the other, the centripetal unifacial and bifacial varieties (Types 4–5), including discoid and Levallois cores, being progressively replaced by unidirectional and multidirectional cores (Types 2–3) (Fig. 33). This trend corresponds to the replacement of wide centripetal flakes, including some Levallois products, by narrow elongated flakes and blades that is clearly observed in K’aaba (Figs. 11 and 12) and less obvious in Bel K’urk’umu. A small yet steady decrease in flake dimensions is also evidenced throughout the whole sequence at the two sites (Fig. 34). On the other hand, the length-width ratio does not display any systematic variation in the same sequence. Even though the available radiometric dates for Upper K’aaba (2600 bp) and Lower K’urk’umu (5000–4500 bp) do not totally agree, the disparity could be due to the different methods applied (OSL and radiocarbon), and in any case both ranges belong to the same general period, the second half of the Holocene. The possibility that both sites were inhabited during the last four millennia BC by the same groups of hunter-gatherers but with different economic functions seems highly probable. The two shelters also differ in that pottery is recorded only in Bel K’urk’umu, being absent in the upper K’aaba levels. Could this be explained by the location of K’urk’umu at the edge of the escarpment, nearer than K’aaba to the influences and exchanges from the Sudanese plains? For a long time, the existence of “transitional industries” between the Middle and Later Stone Age has been proposed for the Horn of Africa. The best known case is the Magosian of southern Somalia which is allegedly composed of MSA unifacial and bifacial points, Levallois cores, side and end scrapers, blade cores and microliths, and which stratigraphically overlies the 118

Fig. 33. The variation of percentages for several core types in the levels of the two sites (KAB: K’aaba, BK: Bel K’urk’umu).

typical MSA or “Stillbay” deposits (CLARK 1954). Most of the Somali sites, though, have proved to be culturally mixed assemblages, and the same may be said of the ‘Magosian’ deposits in Ethiopia such as some levels of Porc-Epic and Aladi Springs (BRANDT 1986: 59, 62). The cave site of Midhishi-2 in north-eastern Somalia has been excavated more recently and its transitional features seem more reliable: a combination of Levallois-disc cores and blade cores, the replacement of points by end scrapers and microliths, and a general decrease in the size of most artefacts. Except for the absence of microliths, the K’aaba features are fairly comparable with the Midhishi model, which was dated to 18,790 + 340 bp (BRANDT & GRESHAM 1989: 473). Though a significant blade element is present in many African MSA assemblages from the very beginning (MCBREARTY & BROOKS 2000, 494–496; for Ethiopia, see PLEURDEAU 2003), its increase towards the end of the period seems to characterise its final, “evolved” or “transitional” stages in some sites of Eastern and Southern Africa (CLARK 1988: 296; MEHLMAN 1989: 87; ROBBINS et al. 2000: 1103–1104). The lack of microliths and other backed elements in Upper K’aaba, as well as their very limited presence in Bel K’urkumu, is difficult to explain. A technical limitation due to the poor quality of the prevalent raw material, quartz, does not seem likely, since occupiers of both sites were aware of and had access to better, although also more scarce, raw materials such as chert. Furthermore, as mentioned above, there is a noticeable worsening of the quality of flaked quartz from K’aaba’s lower to its upper levels.


Flake length (mm)


Bel K’urk’umu

K’aaba

Fig. 34. Boxplots summarizing the flake lengths in the levels of K’aaba and Bel K’urkumu

This is even more apparent at the Bel K’urk’umu site, a trend reminiscent of similar evidence recorded at the White Paintings site in Botswana (ROBBINS et al. 2000: 1105). The anomalously recent date of the lower K’aaba deposits, the minimum age of which has been approximately put at 10,000 bp, could be a product of the radiometric analysis, but it seems quite reasonable bearing in mind the shallow stratigraphic levels of the deposits at the site, a mere 50 cm between the lowest findings and Level E. It also agrees with the much repeated statement that MSA forms may have persisted in some areas long after the beginning of the LSA transition (CLARK 1982; SMITH 1982; BRANDT 1986: 59; THACKERAY 1992: 402). Even though recent data support an increasingly early date for the beginning of this cultural shift, around 50–40,000 years bp (MCBREARTY & BROOKS 2000: 490–491), previous examples of “backward” MSA occurrences have not been refuted. MSA-like traits seem to remain in the Tshangula industry of Zimbabwe until 13,000 bp (LARSSON 1996), and in South Africa there are also MSA deposits dated after 20,000 bp, although they are generally disregarded because the radiocarbon dating was done when the method had only recently been introduced (THACKERAY 1992: 399, fig. 7). Also in Northern Africa there are known cases of Levallois or “prepared-core” technologies that survived possibly until after 20,000 bp in the Maghreb and Sahara (SMITH 1982: 349), and even until 12,000 bp in the Egyptian and Nubian Nile Valley, where the Sebilian industry, based on continuous centripetal flaking of discoid cores, has been dated to ca 15,000–12,000 bp, even if doubts

have intermittently been cast on its chronology (VERMEERSCH 1992: 139–141). In most cases, advanced and retarded, and though some hiatuses have been detected here and there (e.g. at some sites of South Africa), there is fairly widespread agreement that, contrary to the European record, there are no abrupt interruptions in the African MSA-LSA transition. South African evidence also indicates that the MSA may have persisted longer in the more mountainous areas than in coastal and better connected areas (THACKERAY 1992: 402). The Benishangul region is situated on the border of the elevated regions that preserved the grassland and savannah conditions during the extremely arid period of the Last Glacial Maximum beginning ca 18,000 bp (CLARK 1988: fig. 3). The palynological results presented in this paper, with a much higher representation of tree and shrub pollen in the lower levels of K’aaba than in the upper levels of the site and the whole sequence of Bel K’urk’umu, also point to the same fact. Probably because of this condition, the region could have attracted the human groups from the adjacent, lower Sudanese areas where Late Acheulean and MSA industries have been recorded near Khartoum and around Singa on the Blue Nile river (ARKELL 1949b; ZIEGERT 1981). The isolation of the “refuge area”, created by the mountainous conditions, was very likely the main cause of the conservative technical resources of those populations in an atypically recent period, as discussed in the foregoing paragraphs. A terminological problem is posed here: can the earliest K’aaba deposits be ascribed to the MSA proper, or should they be seen, as J.D. CLARK (1982: 315) put


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it referring to the Tsangulan of Zimbabwe, rather as “a local tropical complex that has continued to use a prepared core technology”? The same general aspect of technological conservatism persists in the LSA levels of the Upper K’aaba and the Bel K’urk’umu site. Centripetal unifacial and bifacial cores continued to be used until the end of the latter site’s occupation, and though elongated unidirectional flakes are prevalent in the upper levels, blade cores and blade elements are always statistically insignificant. The archaism perceived is also apparent in the scarce lithic industry recorded at the subsequent ceramicbearing sites excavated by our team in the region (Bul K’aito, K’unda Damo, Bela Sharafu), dated to the first and second millennium AD. This evidence contrasts sharply with what is known from the vast majority of LSA Ethiopian sites, most of which had blade-microlith industries (BRANDT 1986: 67–70; BARNETT 1999: 98–100). Could raw material or function be the determinant of these typological differences? We have already mentioned the role that the prevailing raw material, medium and poor-quality quartz, could have played, though a similar rock type was appropriately used for microlithic industries in many African areas (e.g. in the forested central region, cf. CORNELISSEN 2003). In other African regions a dual model has been detected, such as at Lukenya Hill in southern Kenya where there are microlith-based and scraper-based sites, the first group based on the use of chert and obsidian and the second having greater amounts of quartz. Quartz-scraper sites seem to correspond to human groups with small home ranges and longer occupation of rock shelters, and the opposite applies to the microlithic sites (KUSIMBA 1999). Experimental data and observations from other parts of the continent also suggest that high proportions of scrapers are typical of areas where hide clothing is ethnographically attested (DEACON 1984: 305). A very different industry was recorded during our most recent survey season north of the Ethiopian Blue Nile in the Metekkel region (June 2005), with small lithic surface scatters on the terraces of the Beles river, a northern tributary of the Blue Nile, and also in the Metema region west of Gondar and near the Sudan border. The industry is quite different from that of Benishangul, and is based mostly on blades and bladelets, knapped from fine-grained stones, chert and agate, with the typical Later Stone Age appearance. The most common technique was simple blade production from agate pebbles with a prepared, usually unfacetted platform; retouched tools included mostly end scrapers, backed blades and a few microliths. Except for the smaller geometric component at the Beles sites, the industry is not very different from that recorded at the terminal Pleis120

tocene and early Holocene sites of the Khasm el Girba area by the Atbara river in Eastern Sudan (MARKS 1987; MARKS, PETERS & VAN NEER 1987). This evidence once again suggests that the Sudanese hunter-gatherer groups took refuge in the Ethiopian elevated areas where there was still a grassland and savanna ecosystem during the period of extreme aridity of the Last Glacial Maximum around 18,000 bp (CLARK 1988: fig. 3), and returned to the plains when the climate became wetter after the end of the Pleistocene period. The arrival of pottery to West Ethiopia Interestingly enough, in the Bel K’urk’umu layers pottery types appear “correctly” arranged from a chronological point of view (Tab. 13): the earlier types are situated below the more recent, even though the deposits appear to have been disturbed by post-depositional movements such as the conspicuously abundant animal burrows. Firstly, the lower Units 12–18 that form Level F, where the majority of lithic material was recovered (57.8 % of the total weight), are completely devoid of pottery sherds but a few are recorded in its upper part, Unit 12. Since there is no perceptible change in the lithic industry from Level F to Level E, the sudden appearance of the sherds suggests that the people carrying the pottery, or the pottery or its actual technology, came to the site at a certain moment of its occupation, i.e. sometime after the group of local LSA people began to live there. The age of this contact may be confidently placed around 5000–4500 bp (3800–3070 cal BC), as these are the radiocarbon dates from two charcoal samples extracted in Units 10 and 12, deposited shortly after the appearance of pottery at the site (see Tab. 7). At the deepest levels there are sherds decorated with Wavy Line incised motifs (Fig. 27: 1–2; Fig. 28: 1) and rocker-impressed points, including the varieties of packed and spaced zigzags (Fig. 27: 5–11; Fig. 28: 4–10 ) that are characteristic of the Mesolithic period in Sudan (also known as Early Khartoum, ca 8000–6000 bp). The rocker type is also typical of the beginning of the subsequent Neolithic period (Shaheinab, ca 6000– 5000 bp), yet the decoration (big dots), material (mineral temper) and surface treatment (smoothed instead of burnished) of the Bel K’urk’umu sherds are more reminiscent of the Early Khartoum period (CANEVA 1983: 155–190; Caneva 1988: 67–114; FERNÁNDEZ et al. 2003a: figs. 42–43, 52–55; FERNÁNDEZ et al. 2003b: figs. 27–34, 39–40, 45–50). Higher in the strata a few Dotted Wavy Line (DWL) sherds were unearthed (Fig. 27: 3–4; Fig. 28: 2–3), which are typical of the whole pre-pastoral period (Mesolithic) in the central Saharan regions and begin to appear in the Middle Nile at the



end of the phase (ca 6500–6000 bp), suggesting that the desert populations probably arrived at the Nile when the desert was particularly arid (CANEVA 1991). Another sherd of this type, bigger and better preserved, was recorded in the lower levels of the nearby rock shelter of Bul K’aito A (Fig. 28: 14). The apparent time lag in the pottery reaching the escarpment area may be attributed to the long distance from the Central Sudan region, although it might be merely the result of the radiocarbon dating method. Pottery decoration types characteristic of the later phases in Central Sudan, i.e. the Shaheinab Neolithic (ca 6000–5000 bp) and even the poorly known subsequent period, usually called Late Neolithic or Jebel Moya phase (ca 5000–3000 bp), were found in the upper units of Bel K’urk’umu. Thus, the only sherds with plain comb rocker impression and with undulating polished surfaces (Ripple ware, Fig. 27: 15), unknown at the Sudanese Mesolithic sites and common in the Shaheinab ones (CANEVA 1988: fig. 5: 12–15; fig. 17: 1, 5), were found in Units 2 and 3. Moreover, three out of four sherds found with simple comb impression (Fig. 27: 12–14; Fig. 28: 12) also appeared in the upper Units 3 and 4. As has been suggested elsewhere, a gradual change from rocker impression (pivoting comb) to simple impression (independently applied comb) in the decoration of the Central Sudanese pottery vessels occurred before and after the transition from Early (Saheinab) to Late Neolithic (Jebel Moya) Middle Nile cultures, during the period 5000–4500 bp (CANEVA & GAUTIER 1994: 72, tab. 2; FERNÁNDEZ 2003b: 88–89; FERNÁNDEZ et al. 2003a: 258–260). Another indication of Sudanese Neolithic influence is the finding of a cylindrical grinder of granite (Fig. 27: 18), and a partially polished adze (Fig. 27: 17), both in Unit 5, and a fragmented “net sinker” or pendant made out of a pottery sherd found in Unit 7 (Fig. 27: 16), similar to others recovered in Sudanese Mesolithic sites (ARKELL 1949a: pl. 86: 2; HAALAND 1992: fig. 3; FERNÁNDEZ et al. 2003b: fig. 76: 13). Other curious finds from Level D are the relatively large number of unburned clay pellets with plant impressions, very thin and probably made with grasses or some other variety of small plants (Fig. 28: 13). In Sudan they have been interpreted as some kind of platform or support for querns or working surfaces, or as part of temporary windscreens similar to those currently used by the Nilotes during the dry season (ARKELL 1949a: 79, 107–108, pl. 55:1; CANEVA 1983: 18, fig. 5; FERNÁNDEZ et al. 2003b: fig. 33: 12–17). Several “pencils” in red ochre, probably used to decorate pottery vessels or the human body, were also recorded in Bel K’urkumu (Fig. 27: 19–20), of a similar type to that found in Level D of K’aaba (Fig. 27: 21).

Since no faunal remains were preserved at either of the sites, the important question of the economic orientation of these border groups cannot be determined. The finding of abundant dung-loving fungi of Sordaria type, often associated with domestic cattle, in the pollen record of the LSA levels of K’aaba and in Bel K’urk’umu may be an indication of some kind of domestication practices at the sites, perhaps related to the arrival of Sudanese herders from the plains. Conversely, the general archaism mentioned previously and the continuity of the lithic technology and tools from the lower MSA-like levels to the upper occupation at Bel K’urk’umu, which may be dated to the beginning of the Christian era or even later according to the available radiocarbon dates (see Tab. 7), seems to fit fairly well with the enduring nature of hunting-gathering practices until a very recent date. The continuity of the old pottery types up to the first millennium AD also recalls the archaic features of the current “pre-Nilotic” peoples in the border region between Sudan and Ethiopia (GROTTANELLI 1948). Some of these traits, such as the relevance of hunting, plant gathering and fishing, lack of big livestock, some matrilineal kinship remnants, incisor teeth extraction (MURDOCK 1959: 170–180; BENDER 1975: 9–19), and even the racial morphological characteristics (ARKELL 1949a: 114) are to some extent reminiscent of the Khartoum Mesolithic features. A similar scenario has been presented for the Southern Sudanese region of Eastern Equatoria. The Lokabulo tradition, named after a rock shelter 200 km east of Juba and 600 km south of Assosa, even though poorly known because of the interruption of the research due to the recent war in Southern Sudan, presents some characteristics reminiscent of the Central Sudanese and Benishangul sites (DAVID et al. 1981). The pottery is quartz-tempered and decorated mostly with rocker impression, including some DWL sherds (ibid.: fig. 6, pl. 1), and it appears at the Lokabulo site at ca 3800 bp above an aceramic phase with an undiagnostic flaked quartz industry with rare microliths. The faunal remains of Lokabulo consist only of hunted wild fauna and the excavated deposits yielded quite a good number of mollusc shells, though they were devoid of fish remains (DAVID et al. 1981: 11–19; DAVID 1982: 52–53). Even though linguistic data suggest the presence of a food-producing economy in Southern Sudan since the third millennium BC (EHRET 1982: 28), the picture resulting from the excavation of Lokabulo and other sites in the Eastern Equatorian region implies a Later Stone Age hunter-gatherer economy well into the first millennium AD (DAVID 1982: 53). On the contrary, the site of Jebel Tukyi, 120 km northwest of Juba and of more recent date (2130 bp) produced large domestic cattle (ibid.: 51) together


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with rocker-impressed pottery which Randi Haaland has identified as belonging to the Shaheinab Neolithic tradition (HAALAND 1992: fig. 11, 61–62). Climatic changes that occurred around 6000 bp have been identified as the “great mid-Holocene arid phase” in the Sahara (MUZZOLINI 1995: fig. 30), which corresponds to the lower sea surface temperatures recorded in the Mediterranean after 5900 bp (HASSAN 2002: 322) and the “Post-Late Neolithic arid phase” of the Nabta Playa sequence in the Southwestern desert of Egypt (SCHILD & WENDORF 2002: 24). This deterioration was perhaps the cause of a contraction of the “aqualithic” economy that had been predominant in Central Sudan throughout the preceding millennia during the Early Khartoum period (SUTTON 1974). When faced with climatic deterioration, Africans are forced to choose “between their homes and their environment” (DAVID 1982: 50), and the possibility that some of the Mesolithic people migrated further south where humidity was still high seems highly probable. The sharp differences that have been noticed between the Mesolithic and Neolithic cultural features in Central Sudan, with changes in pottery making, settlement patterns and economic orientation with the arrival of cattle herding from the Sahara, may be interpreted as a consequence of a significant demographic replacement in the region (FERNÁNDEZ 2003c: 414–415). The presence of Mesolithic-like pottery at the West Ethiopian sites, together with the pollen evidence of severe aridity in their LSA levels, are argued in this paper as additional proof for that hypothesis. A second important fracture in the Sudanese cultural sequence took place about one and half millennia later, marking the transition between the Early Neolithic (Shaheinab) and Late Neolithic (Jebel Moya) phases. The progressive intensification of arid conditions in the Sahelian area (WICKENS 1982: 44–47; HASSAN 2002: 323) was one of the most likely causes of the higher mobility of the savannah groups, a process that resulted in a period lacking any archaeological representation either in the Central Sudanese savannah or the Nile river, with the possible exception of some burial mounds (CANEVA 2002). The period roughly corresponds to the interval between 4000 and 2500 bp (ca 2500–700 cal BC), the latest date marking the beginning of the Napatan-Meroitic periods in the first millennium BC. This “vanishing” of the Late Neolithic cultures in Central Sudan has been related to the demise of the Nubian A-Group, and both of them to changes in the balance of power in Egypt and Northern Sudan, namely the emergence of the Egyptian dynastic state and the Kingdom of Kush at Kerma (CANEVA 1988: 371). 122

An external origin for the changes has been alleged by HAALAND (1987: 224–231; 1992: 58–61), who presents a tempting scenario of competition between Nilo-Saharan-speaking groups with multi-resource adaptation (the Khartoum Neolithic) and Cushiticspeaking specialised pastoralists (the Butana/Khashm el Girba traditions; FATTOVICH et al. 1984). The first would have migrated towards the south, preserving their way of life in more humid ecosystems while the Khartoum region was occupied by the fully pastoral groups coming from the Eastern Sudan. The results of a recent survey of the western Butana region near the Blue Nile, however, do not endorse such conclusions, mainly because there appears to be a continuous and gradual change in the material culture of Central Sudan from the Early to the Late Neolithic, even up to the hand-made wares of the Meroitic period (FERNÁNDEZ 2003b: 88). Available data from the Ethio-Sudanese borderlands presented here seem more supportive of an alternative explanation that takes into account the population movements between the Nile-savannah settings and the forested escarpment areas, which could have functioned as a refuge area for the pastoral groups, for ecological reasons and also as a means of resisting the emergence of hierarchical societies (FERNÁNDEZ 2003c). Linguistic and historical data are informative about those interchanges, which eventually resulted in the current distribution of the Nilo-Saharan groups settling the border regions from Western Eritrea to Southwest Ethiopia. The split of the Kunama and Koman linguistic groups from the Nilo-Saharan main stock in the Sahelian plains seems to have occurred first (EHRET 2000: 273–278), followed by the influences of the Meroitic state language on the languages of the borderlands (TRIGGER 1964; BENDER 1981) until the recent arrivals in the refuge area during the crisis of the Sennar sultanate (TRIULZI 1981: 24–25). The rock shelter sites around Assosa are the only occurrences of Sudanese-like impressed pottery recorded in our survey of Benishangul, and, except for some surface finds of uncertain age, lithic tools indicating Middle or Later Stone Age occupation of the interior areas of Benishangul were not found either. Excavations at other sites in the escarpment (e.g. K’unda Damo near Bambasi, south of Assosa) and at those far from the border (rock shelters near Menge, north of Assosa and 35 km inland from the escarpment) produced remains of a different, more recent tradition. The pottery of this period is decorated mostly with simple impressions, incisions and grooved motifs. Radiocarbon dates from K’unda Damo (1985 bp) and Bela Sharafu near Menge (275 bp) show that the chronology of this culture may be placed in the first millennium and first half of the second millennium AD. Data from the excavation at



the two rock shelters of Bul K’aito near Assosa suggest that the pottery decoration gradually evolved in situ from the earlier rocker impressed patterns to the K’unda Damo decoration types, some time before or during the first millennium AD (the sites could not be directly dated). The K’unda Damo pottery’s general patterns are similar to some decorated wares known at Tiya and other sites in Central Ethiopia dated to 750 bp (JOUSSAUME 1995, figs. 101, 311–312) and, to a lesser extent, to some wares of Southern Sudan dated to the later part of the first millennium AD (ROBERTSHAW & SIIRIÄINEN 1985: figs. 19, 32). The grooved decoration of K’unda Damo and Bela Sharafu is also reminiscent of that found in the Turkwell tradition of the Turkana region of north-western Kenya, dated to 870–950 bp at Lopoy and associated with eastern Nilotic speakers (LYNCH & ROBBINS 1979).

ments on the paper, and to Rodolfo Fattovich, David W. Phillipson, Steven Brandt and Roger Joussaume for their experienced assistance at the beginning of our archaeological research in Ethiopia.

Therefore it seems that the earlier cultural contacts with the Sudanese plains may have been restricted to the areas on the edge of the escarpment. A probable scenario for these contacts, as well as explaining the appearance of pottery in Later Stone Age sites, can be inferred from cases recently known in Africa of socially unequal associations between herders and marginalized hunters on the periphery of pastoral societies (SMITH 1998), a situation which later persisted as the border areas became a source for slave raids in historical times (PANKHURST 1977).

Bard, K.A., Coltorti, M., DiBlasi, M.C., Dramis, F. & Fattovich, R. 2000. The environmental history of Tigray (Northern Ethiopia) in the Middle and Late Holocene: a preliminary outline. The African Archaeological Review 17 (2), 65–86.

Acknowledgements The research work was funded by the Spanish Ministries of Culture (Instituto del Patrimonio Histórico Español, Dirección General de Bellas Artes y Bienes Culturales, Ayudas para excavaciones arqueológicas en el exterior, 2001–2003) and Education and Science (Dirección General de Investigación, Project BHA20000710, 2001–2003). We are very grateful to the staff of the Authority for Research and Conservation of Cultural Heritage in Addis Ababa: Ato Jara Haile Mariam, General Manager, Dr. Jonas Beyene, Head of the Archaeology and Anthropology Department, and Ato Gigar Tesfay who helped us in the field. Also to the staff of the Bureau of Education and Culture of the Benishangul-Gumuz Regional State in Assosa: Ibrahim Ziraj, Director, AlMehade Abdurrahim Khojele, Head of the Culture Section, and officials Hamis Bela, Tesfaye Oli and Geremew Feyissa. Andreas Neudorf, from the Summer Institute of Linguistics, and Christoff Herrmann from the German Cooperation were of great help while in Assosa. Finally, our thanks to Elena Garcea for her useful com-

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