The Indus Civilization (Cambridge History of India, Supplementary Volume) c8.3.3

c8.3.3

The present aridity may have been induced wholly or in part by a northward movement of the Atlantic cyclones, on the hypothesis that these were at one time deflected southwards to the latitude of northern Africa and extended to Arabia, Persia and India. Or it may be that the south-western monsoon then touched the Indus valley. We do not know. In Algeria a similar and perhaps indeed related problem confronts the student of the Roman remains which now lie derelict in a desert environment, and there is a wide agreement that man rather than unaided climate has there been responsible for the deterioration.² In central Asia, Aurel Stein, who was always attracted by this problem in his far-flung fieldwork, similarly regarded destructive barbarian inroads as the major cause. On the other hand, in Kalāt and Makrān the phenomena left him in some doubt as to the bias of the evidence; at one point he observes that the evidence "distinctly pointed to the local climate having undergone a great change since chalcolithic times in its effect upon cultivation", whilst elsewhere he remarks upon an agricultural decadence, even in the vicinity of water, "illustrating once more how in an arid land human factors can within certain limits produce results which centuries hence might easily be mistaken for those of true 'desiccation'".³