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(see
Chapter 15
) found in late Cenozoic fossil soils from northern Kenya and the
Middle Awash region of the Ethiopian Afar Desert offers qualified support for this
hypothesis. They found that the ratio of grassland to tree cover was relatively high
during the time that Pliocene hominids were walking upright in these two localities,
a topic we consider in more detail in
Chapter 17
.
Dealing with a much shorter time scale, measured in thousands rather than millions
of years, Hiscock and Wallis (
2005
) and Hiscock and O'Connor (
2005
)reviewed
archaeological and archival studies of historic desert dwellers in the arid south-west
of the United States, Patagonia, the Kalahari and Australia and concluded that these
modern desert dwellers had undergone a long period of pre-adaptation to living in
deserts by having first occupied these areas when they were not as arid as they are
today. This argument accords with what is known of the Holocene climatic history
of the deserts concerned (see Chapters
18
to
22
) and is reminiscent of Desmond
Clark's (
1980
) suggestion that farming in the Nile Valley, when it did eventually
occur, had been facilitated by a long period of pre-adaptation to agriculture through
more intensive collecting and grinding of wild cereal grasses in the adjoining, less
arid, early Holocene Sahara, a subject discussed in
Chapter 17
.
Some forms of adaptation to seasonally dry conditions have persisted long after
they were no longer necessary - a measure of the reluctance of people long habituated
to aridity to abandon well-tried ways. One example will suffice to illustrate this trait.
To this day, the cattle herders of the savanna grasslands of the southern Gezira in
the central Sudan bring their herds to the White Nile River during the dry season,
although abundant water is available in the canal systems situated well away from
that river. When the author asked them why they continued this practice, they replied
very simply that this was what they had always done.
Over time, many desert communities in widely separated regions of the globe have
become committed to conserving both plant and animal resources. For example, the
Bishnoi tribe in the Thar Desert of Rajasthan revere all living creatures, especially
trees. They will not cut down live trees or branches and will only collect dead wood
for fuel. They attach particular importance to the Kajari, or Khejeri, tree (
Prosopis
cineraria
,
P. spicigera
), because its edible bark provides relief in times of famine.
Elsewhere in semi-arid Rajasthan, it is widely lopped to provide green fodder for
the animals, yielding up to 60 kg per mature tree. The branches are then used as
fences to protect young animals from predators and finally serve as fuel. In the dry
subhumid regions of India, the neem tree (
Azadirachta indica
) is valued and protected,
because its leaves contain oil that repels insects, most notably mosquitoes. The desert
Aborigines of central Australia had a well-developed systems of totems in which it
was forbidden to hunt animals belonging to one's personal totem. In the seasonally
wet tropical north of Australia there were and are strong ritual prohibitions against
burning in the vicinity of patches of monsoon forest; such forests are very vulnerable
to fire and contain abundant valued plant resources. The San hunter-gatherers of
