Geoscience Reference
In-Depth Information
Writing on clay tablets or papyrus sheets probably developed from the Neolithic use
of trade-marks, and various forms of alphabets and calendars arose among the later
metal-working cultures of Eurasia and the Americas, none of which were associated
with desert hunter-gatherer societies, among whom there was no perceived need for
such oddities.
17.4 Prehistoric occupation of the deserts and semi-deserts
Analysis of mitochondrial DNA (mtDNA) in extant human populations confirms
movement out of Africa on a number of occasions during the past 1.5 million years
or more (Cann et al.,
1987
; Underhill et al.,
2000
; Cann,
2001
;Hammeretal.,
2001
).
Initial movement out of Africa is associated with small bands of
H. erectus
,whowere
equipped with a relatively unspecialised Acheulian tool-kit and the ability to make
and use fire (Clark,
1975
; Clark and Harris,
1985
; Goren-Inbar et al.,
2004
). Earlier
Homo erectus/Homo ergaster
groups may have brought their Oldowan technology to
Eurasia (Carbonell et al.,
1999
), as evident at Dmanisi in Georgia (Vekua et al.,
2002
),
where a complete
Homo
skull has an age of around 1.8 Ma (Lordkipanidze et al.,
2013
). This suggests that these early migrants were able to obtain enough in the way
of plant and animal foods for survival but that their overall impact on their habitat
was minimal. One probable migration route was across the Sinai and southern Negev
and then across the Dead Sea Rift into Arabia and thence to Asia (Ron and Levi,
2001
; Derricourt,
2005
). The presence of Acheulian bifaces in alluvial river terraces
in the southern Negev Desert and at the site of 'Ubeidiya in Israel (around 1.4 Ma)
is unequivocal evidence of a Lower Palaeolithic human presence during Lower to
Middle Pleistocene times in what are now arid areas (Ginat et al.,
2003
; Goren-Inbar
et al.,
2004
).
Another possible route was across the narrow and shallow Bab el-Mandeb Strait
in the southern Red Sea at times of lower sea level and thence into Arabia and on
to Asia, perhaps along the coast (Stringer,
2000
). Humans were certainly present
on the western side of the Red Sea during the last interglacial (Walter et al.,
2000
).
The Bab el-Mandeb ('Gate of tears' in Arabic) today has a minimum depth of 26 m
(Jarosz,
1997
) and a minimum width of about 4 km. Using published sea level curves
spanning the last 125 ka (Williams et al.,
1998
, p. 119), it is possible to make a
first-order estimate as to when the strait could have been crossed on foot. It could
have been dry or very shallow for most of the time between around 80 and 15 ka
(although possibly flooded from 65 to 60 ka) and dry again, briefly, at around 115 and
105-90 ka. An exodus at any of these times is broadly consistent with the evidence
from both molecular biology and prehistory, neither of which are very precisely dated.
More recent work by Lambeck et al. (
2011
), taking into account isostatic and tectonic
factors, and more recent but unpublished bathymetric surveys concluded that although
there was never a land bridge, the southern Red Sea in places was sufficiently shallow
