The Western Rift Valley in January licensed under Creative Commons (http://earth.imagico.de/cc.php)
The Rift Valleys of East Africa extend in a “Y” shape southward from the Red Sea in the north, through Ethiopia, Kenya and Tanzania to Zambia and Mozambique. Overall, the system is about 6,000 kilometers long. What people might assume to be a single rift somewhere in East Africa is really a series of distinct rift basins which are all related and produce the distinctive geology and topography of East Africa. The largest lakes include the Tanganyika, Victoria, Turkana, Malawi, Nyasa and the Albert. These lakes even today hold approximately 27% of the worlds freshwater. They are among the deepest lakes in the world (up to 1,470 meters deep at Lake Tanganyika).
The Rift Valleys of East Africa formed as a result of the area’s complex geological make-up. Driven by forces deep within the earth, three of the tectonic plates that make up the earth’s crust — the Arabian plate, the Nubian plate and the Somalian plate – are slowly moving apart. The resultant cracks between the plates form the Rift Valleys. Over time, water has accumulated in the lowest areas of the valleys, creating the Rift Valley lakes. Their characteristic long, deep shape reflects how the lakes were formed. Associated with the lakes are geysers, earthquakes and volcanic activity, reminders that the area is still geologically active.
The disappearance of the earliest human culture, the Oldowan, and its substitution by a new technology, the Acheulian, is one of the main topics in Paleoanthropology. When hominid remains and early Acheulian tools are associated within any site stratum in Africa, the species is always Homo ergaster or Homo erectus. Raw material utilization in the Acheulean is more localized than during the MSA. People may have been using the large tools as tools and cores for further flaking. This post may be used as a short review of some important East African Acheulian sites, without discussing the topic in depth. Such a coming review should include the discussion of:
- The palaeoenvironmental data during the Middle Pleistocene
- the hominins
- The hominin habitat preferences
- Stone tool technology, function and variability
- Raw material transport, models of site formation
- Models of land use
- Models of subsistence and sociality
Earliest Acheulian in East Africa
The Acheulian stage begins with the early Pleistocene, about 1,75 mya-well after Homo ergaster attains full development in the Turkana Basin. The Acheulian first appears to emerge in the eastern Rift in areas such as Konso-Gardula in Ethiopia, and Kokiselei 4 in Kenia. A little bit later in geological terms it is found at Peninj and Olduvai Gorge in Tanzania (Olduvai Gorge EF-HR Upper Bed II, c. 1.3-1.5 mya). Of great iterest is the fact, that Oldowan assemblages that have been discovered at Olduvai Gorge predate and partially coincide with Early Acheulian assemblages.
The Konso site is dated to 1,75 mya and characterized by a combination of large picks and crude bifaces and unifaces made predominantly on large ﬂake blanks. An increase in the number of ﬂake scars was observed within the Konso Formation handaxe assemblages through time. The local Ethiopian Acheulean is usually divided into three techno-typologically phases (1,6 -0,2 mya): Early, Later, and Terminal (Clark 1994). Melka Kunture, Bodo, and other Middle Awash localities contain lithic material that is commonly considered Later and Terminal Acheulean. Melka Kunture lies in the upper Awash valley, 50 km south of Addis Ababa. At Garba 4D an earlier Acheulian is present (ca 1.5 mya). It was formerly designated as late Oldowan. Garba VIII (900 k.a.), is documenting a set of innovations occurring on the Ethiopian highlands at the end of the Lower Pleistocene: the procurement of large boulders for the extraction of the LCT flake blanks right at the primary source; adoption of the Kombewa method; standardized façonnage for biface and cleaver manufacture and preference for discoid technology among small débitage methods.
An Acheulian younger than 1 mya is well represented by several sites in the area of Gombore II (dated to about 0,8 mya; http://www.aggsbach.de/2014/06/twisted-obsidian-handaxe-from-melka-kunture-gombore-ii/). The latest Acheulian site is Garba I, dated to ca. 0,5 mya, while the end of this long sequence is represented, at Melka Kunture, by the site of Garba III, where there are also Middle Stone Age layers. With the exception of the highland sites of Gadeb, Gondar, and Chilga Kernet, all Ethiopian Acheulian sites are associated with the Rift Valley
Acheulian bifaces are found as far north as the Jordan Valley of Israel (at Ubeidiya) by 1,4-1,6 million years in age. The site consists of several identified “living floors”of concentrations of Acheulean tools such as handaxes, picks, and bifaces, and pebble-core tools and flake-tools. These “living floors” are today suggested to the result of geomorphological activity. Bones found at the site include extinct species of hippopotamus and deer, and molluscs; hominid teeth were found at the site, unidentifiable to species. Gesher Benot Ya’aqov (GBY), located in the Dead Sea Rift valley, is considerably younger, but one of the oldest non-African sites to have yielded evidence for the activities of groups of hominid hunter-gatherers. The excavations recovered thousands of Acheulian period stone tools and animal bones that had accumulated in and around an ancient lake about 800 k.a. ago. The deposits have remained waterlogged virtually ever since, and this unusual circumstance resulted in the excellent preservation of plant macrofossils. The collection of artifacts is dominated by numerous Acheulean hand-axes, cleavers, cores, and flakes and flake tools. Many of the stone tools are made from local basalt. This raw material choice was used to argue for an African origin / tradition of the GBY hominids crossing the gates to Eurasia. Only a single cleaver and 39 handaxes at GBY were produced on flint.
The Turkana Basin has earned its place as the world’s most important repository of evidence of human origins largely through four decades of exploration by the Leakey family through the Koobi Fora Research Project (KFRP).
Roche et al. described an isolated occurrence of an early Acheulean assemblage from the west of Lake Turkana in a sedimentary sequence containing examples of Oldowan assemblages. This assemblage occurs at locality Kokiselei 4, stratigraphically 4.5 m above the top of the Olduvai Subchron (1.78 mya) and is estimated to be 1,72 mya old .
Kilombe is a large Acheulean hand-axe site in the central Rift Valley of Kenya. It was found in the 1970s.Artefacts occur across an area of at least 14 000 sq.m , though density of remains is variable. Its age is estimated in the range 800-980 k.a.
The Kariandusi archaeological site in Kenya lies on the eastern side of the Rift Valley some 120 km NNW from Nairobi, and rests on the Nakuru-Elmentaita basin which occupies the width of the Rift valley, flanked by Menengai crater on the north and the volcanic pile of Mount Eburru, on the south. The Kariandusi site is the first Acheulian site to have been found in Situ in East Africa in 1928 by Luis Leakey. Excavations were performed between1929-1931 and again in 1947-1949 and in 1973–1974. A The sites are well-known for their obsidian hand-axes, but also includes many specimens made of local trachyte lava. Palaeomagnetic analysis of pumice overlying the artifacts confirms they must be at least 730 k.a. old. A date of 980 k.a. was obtained through 40Ar/39Ar comparison of some of the sediments underlying the artifacts.
Discovered and tested by Louis and Mary Leakey in the 1940s, Olorgesailie in southern Kenya was excavated by Glynn Isaac as his dissertation research during the 1960s. Research resumed Olorgesailie in the early 1980s, by researchers of the Smithsonian Institution. Using modern methods of excavations, these people did a lot to reconstruct the Paleolithic landscape. Olorgesailie is best known for an abundance of Acheulean handaxes, associated with several episodes of animal butchering dated to ca 950 k.a. ago. Recent investigations have recovered fossil hominin remains at the site, including a partial cranium KNM-OL 45500 ( H. erectus), in the same stratigraphic level with two Acheulean handaxes and several flakes, and adjacent to dense deposits of handaxes.
New excavations since 2001 have revealed that Acheulean occupations were followed by a long sequence of Middle Stone Age occupations without handaxes, beginning well before 315 k. a and ending before 64 k.a. Levallois technology was present already in the later Acheulean horizons of Members 11 and 13 of the Olorgesailie formation (between 625 and 550 k.a), which further substantiate the claims for a “long Levallois chronology” in Africa, first evidenced from the Kathu Pan 1 site in S-Africa, well before its appearance in the Middle Eastern or Europe.
The Isimila Acheulian Occupation Site in the Iringa Highlands of Tanzania was discovered in 1951 by D.A Marclennanof who on his way from Nairobi to Johannesburg collected some tools from the site. A first scientific report by Clarence van Riet Lowe, at that time the most eminent Prehistorian of South Africa, appeared already in 1951. The first Excavation work at Isimila was carried out 1957-1958 by Clark Howell, later followed by others until 1968. The Acheulian at Isimila, has been dated by U-series to ca. 260 k.a. (Howell et al., 1972), but is now suggested to be 300-400 k.a. old (http://www.aggsbach.de/2013/06/a-handaxe-from-isimila/).
At the southern margin of the Rift valley system, the late (ca 500 k.a. BP) Acheulian Site at Kalambo Falls, situated in the Kalambo River basin near the Tanzanian border in northernmost Zambia, is integrated into the Acheulian settlement system of East Africa. Kalambo Falls is unique in Africa for the length of the cultural and environmental sequence represented: from later Acheulian of the mid-Pleistocene through successive Stone Age (Sangoan and Lupemban) periods of the late Pleistocene and early Holocene, and culminating with materials pertaining to the local Iron Age. The site is best known for waterlogged Acheulean ‘living floors’ that preserved charred wood, seeds and wooden tools. Subsequent research into the formation processes operating at Kalambo led to a substantial revision of the site’s archaeological significance. Fluvial processes apparently created much of the spatial patterning seen in the Acheulean horizons and may even have shaped some of the supposed wooden tools. Renewed excavations at the site were undertaken in 2006 and brought a new Luminescence chronology (Acheulian-MSA transition between 500-300 k.a.) and new informations about site formation- you will find the free text here: http://ac.els-cdn.com/S0047248415001104/1-s2.0-S0047248415001104-main.pdf?_tid=536a488a-53f3-11e5-8318-00000aab0f6b&acdnat=1441474204_3f91eaeabd163fea70d3b1e0f6a69c78