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has yielded reliable ages back to about 35,000 years ago, and in the last few years,
luminescence dating has been applied to sediments several hundred thousand years in
age. As a broad generalisation, the ESA in Africa began around 2.5 Ma ago, with the
Acheulian appearing around 1.5 Ma ago, together with the first signs of fire use; the
MSA is bracketed between about 500/300 and 50 ka, and the LSA dates to between
about 50 to about 11 ka, after which early plant and animal domestication denotes the
inception of the Neolithic.
In desert areas devoid of volcanic ash and other sediments suitable for radiometric
dating, such as the Sahara, Kalahari and Namib deserts, the ages obtained elsewhere
for stone tool assemblages have been used to establish a chronology for environmental
changes evident in the depositional record. This approach was used with some success
at Adrar Bous, a small mountain situated in the heart of the Sahara, some 1,500 km
from the nearest coast (Williams, 1987 ; Williams, 2008 ) and in the piedmont west
and south of Jebel Marra in Darfur, western Sudan (Williams et al., 1980 ; Philibert
et al., 2010 ).
In the latter region, which is semi-arid today, the botanist Gerald Wickens ( 1975a ,
1975b ; 1976a ; 1976b ) found leaf fossils of Combretum and the oil palm Elaeis
guineensis in reworked volcanic tuffs near the village of Umm Mari between Kas
and Nyertete townships ( Chapter 15 , Figure 15.5 ). The oil palm shows the former
presence of tropical rainforest. Wickens believed that the fossils were probably early
Holocene in age and suggested that I revisit the site to check this, which I was able to
do in January 1976, when I found a Developed Oldowan/Early Acheulian stone tool
assemblage comprising fresh basalt choppers immediately beneath the fossil-bearing
tuff, together with bifacial and unifacial choppers, push-planes, discoids, hammer-
stones and flake scrapers (Williams et al., 1980 ). Similar assemblages in East Africa
span a maximum time range from 1.5 to 0.3 Ma and a more probable time range of
1.2 to 0.8 Ma (Clark and Kurashina, 1979 ; Williams et al., 1979 ; Isaac, 1982 ; Gowlett,
1984 ; Clark, 1987 ; Owen et al., 2008 ).
Some 90 km north-east of Umm Mari near the village of Barbis, more than 5 m
of finely laminated diatomites testify to the former presence of a deep freshwater
lake (Philibert et al., 2010 ). A thin layer of sandy alluvium with sporadic basalt and
trachyte gravels overlies the diatomite. Among the gravels were occasional large-
trimmed flakes, flake scrapers, bifacially worked choppers and scrapers, as well as the
broken butt of an Acheulian hand-axe. Some of the artefacts were slightly abraded,
one was very fresh with sharp edges and three were heavily abraded. According to
Dr John Gowlett, who examined the collection, typologically similar artefacts occur
at Olorgesailie in Kenya and Olduvai Bed IV in Tanzania and straddle the Brunhes-
Matuyama paleomagnetic boundary (0.78Ma), so an age range of around 0.8
0.3Ma
is likely for the stone tool assemblage. Later work has confirmed this age estimate
(Isaac, 1982 ; Gowlett, 1984 ; Owen et al., 2008 ). The evidence is circumstantial, but it
is likely that the hominids who made the stone tools now found on the surface of the
±
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