Large Cutting Tools at Isimila

isimila aggsbachThis is a large, perfect, “six-hit”- cleaver from Isimila / Tansania made of  Mylonite, a cataclastic microcrystalline rock with a finely divided quartz groundmass of various types and colors (Howell et al. 1962, 64). The Isimila mylonite has good knapping qualities. The best outcrops of this acidic-volcanic-metamorphic rock are found 4–5 miles west of Isimila, but the formation itself can be traced closer to the site.

Isimila  is situated 21 km from the town of Iringa in the southern highlands of Tanzania  and is situated about 1631 m Elevation above Sea Level. D. A. Maclennan (South Africa) discovered the site in 1951 during a car journey from Nairobi to Johannesburg. F. C. Howell, M. R. Kleindienst and G. C. Cole excavated the site for a total of 7 months during 1957–58. An additional season of excavation, directed by Hansen and Keller, took place in 1969, and a small-scale excavation was undertaken by Kleindienst in 1970 (http://www.aggsbach.de/2013/06/a-handaxe-from-isimila/).

The Isimila stream runs through a small valley that  was created by tectonic movement. During the Pleistocene the outlet of the basin was  partially blocked, creating an elongated body of water. This body comprised a combination of marshes and small ponds, sometimes with an overflow. The basin was filled by alternating bands of fine, level-bedded gray-green clay and coarser sandy sediments, which Pickering named ‘Isimila beds’ The depth of the sediments is more than 18 m, and the excavators estimated them to have accumulated over a ‘few  thousand years at most’ (Howell 1961; Howell et al. 1962).

Five distinct beds of coarser sands were identified in the Isimila beds,  separated by layers of finer silty clay sediments.  The main “living floors” and the largest quantities of artifacts originate in the upper layers.  As most artifacts are in mint condition and no evidence of water or other means of transport has been observed, it has been suggested that differences in artifact distribution within the sediments of the various sites should be attributed to human activity. It is still worth while to read the passages of Binfords “Bones: Ancient Men and Modern Myths” about the problems reconstructing ancient landscapes at the Isimila site.

ciidfjddThe short duration of the Isimila bed’s sedimentation process, estimated to be a few thousand years, should be emphasized (Howell et al. 1962), although Hansen and Keller  (1971) have questioned this interpretation. More study is required before a definitive answer can be reached. Typological comparisons with the Late Acheulian assemblages of Olorgesaillie and Kalambo Falls have led Kleindienst to define Isimila as being younger than both (Howell and Clark 1963). Uranium series dating of bones from Sand 4 have yielded a date of 260 k.a. (+40–70 k.a.) but these dates are only a rough estimate. Many scholars feel that Isimila could well be 400 k.a. old. On the other hand late in-situ Acheulian sites with typical LCTs were recently excavated in the Mieso valley in East-Central Ethiopia and radiometrically dated to 212 k.a. The sites are much later than the start of  the MSA in the Etiopian rift valley, beginning more than 60 k.a. earlier! (Gademotta (ETH-72-8B before 276±4 k.a BP; ETH-72-6 after 183±10 k.a BP); (http://www.sciencedirect.com/science/article/pii/S0047248414001559).

The earliest Acheulian in East Africa is dated to ca 1.75 million years ago  and is well  documented at Kokiselei in Kenya, and at Konso in Ethiopia.Even the earliest assemblages from the  Konso sites consist of ‘large cutting tools’  (LCTs) including unifacially and bifacially shaped handaxes  and picks, as well as Mode I (Oldowan) cores, and débitage. Although technologically similar, at  Konso a majority of the bifaces were made on flake blanks, whereas at Gona they were made  equally on cobbles as well as large flakes (>10 cm).

The Acheulian the East African Rift valley, which persisted for over one and a half million years, is attested in diverse environments and over wide geographical expanses. The hallmark of many Acheulian sites in this region is its LCTs, made from “giant cores” primarily handaxes and cleavers.  This mode of production was first recognized by Isaac during the 1960ies.

LCTs very likely emerged in East Africa but have been reported from a wide range of areas, spanning South Africa, Israel (GBY), the Caucasus Region, Eastern Georgia to India (and even beyond the Movius line) to the Iberian Peninsula and Southern France. It is only in Europe north of the Pyrenees and the Garonne valley that a substantial Acheulian presence not accompanied by LFB industries is present. Sharon recently compared  assemblages from geographically diverse sites characterized by the production of  LCTs based on large flakes (defined arbitrary as flakes over 10 cm in maximal diameter) in an attempt to assess their technological,  morphological, and typological suitability for grouping together as a common stage within  the Acheulian techno-complex.

Different techniques of flake (blank) removal from larger clasts are described from the LCD Acheulian. These include bifacial and sliced slab method from giant cores, éclat entame (cobble opening flake), Tabelbala-Tachenghit techniques, Kombewa methods and the Victoria West technique. It is a striking and humbling fact that we still do not know precisely when certain technological milestones and cognitive horizons were first reached.

Sharon noted that there appears to have been a shift from non-LFB industries to LFB industries at ca 800 k.a. and then back to non-LFB or cleaver-less at 500 k.a. Given the insufficient chronological control of many African sites this seems to be somewhat hasty conclusion, regarding the early age of Konso and the late age for Isimila or Calambo Falls. There are several non-LCD ensembles from early middle Pleistocene contextes in East Africa (for example at Melka Kunture). In addition, other regions, such as India, have cleavers that were produced along with broad-tipped handaxes at 500 k.a. and later. The Nile Valley and the Oases in the western Sahara seem to have their own trajectories towards the Acheulian.

The Acheulian culture was originally defined and categorized in accordance with finds from W-Europe, which comprise many  types of handaxes, produced almost exclusively from flint nodules and river cobbles. In the next stage of research, an alternative view of the earliest phases of human culture was established in South Africa (Goodwin and van Riet Lowe 1929), but it too was strongly influenced by European views (Breuil 1930). It comes without surprise that the special features of the African Acheulian came in focus only after the WW II when Africanists began to work with this culture from a post colonialist and anti-Eurocentric view (http://www.southerncape.co.za/history/people/sacsa.php).

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