ABSTRACT
The nature of the adaptation during low, average and double average rainfall is also especially instructive, since extreme variability is a commonly noted feature of low rainfall regimes. In short, the early human condition has been glossed as an adaptation to semi-arid environments, with later secondary radiation into other environments. The amount of land categorized as semi-arid or arid constitutes one-third of the total land surface in the world. For example, the southern Sahel, the border between the true Saharan Desert and the wetter lands to the south in sub-Saharan Africa, is home to some three hundred different groups of people in the 5,000-mile strip between the Atlantic Ocean and the Red Sea/Indian Ocean. In general, the quest for ever greater productivity has intensified exploitation and has carried disturbance by man into less productive and more fragile lands.
