With so much through traffic continually passing within her borders, it may be matter for surprise that far more striking evidence of its cultural effect should not have been revealed by archaeological research in Palestine.  Here again the explanation is mainly of a geographical character.  For though the plains and plateaus could be crossed by the trunk-roads, the rest of the country is so broken up by mountain and valley that it presented few facilities either to foreign penetration or to external control.  The physical barriers to local intercourse, reinforced by striking differences in soil, altitude, and climate, while they precluded Syria herself from attaining national unity, always tended to protect her separate provinces, or “kingdoms,” from the full effects of foreign aggression.  One city-state could be traversed, devastated, or annexed, without in the least degree affecting neighbouring areas.  It is true that the population of Syria has always been predominantly Semitic, for she was on the fringe of the great breeding-ground of the Semitic race and her landward boundary was open to the Arabian nomad.  Indeed, in the whole course of her history the only race that bade fair at one time to oust the Semite in Syria was the Greek.  But the Greeks remained within the cities which they founded or rebuilt, and, as Robertson Smith pointed out, the death-rate in Eastern cities habitually exceeds the birth-rate; the urban population must be reinforced from the country if it is to be maintained, so that the type of population is ultimately determined by the blood of the peasantry.(1) Hence after the Arab conquest the Greek elements in Syria and Palestine tended rapidly to disappear.  The Moslem invasion was only the last of a series of similar great inroads, which have followed one another since the dawn of history, and during all that time absorption was continually taking place from desert tribes that ranged the Syrian border.  As we have seen, the country of his adoption was such as to encourage the Semitic nomad’s particularism, which was inherent in his tribal organization.  Thus the predominance of a single racial element in the population of Palestine and Syria did little to break down or overstep the natural barriers and lines of cleavage.

     (1) See Robertson Smith, Religion of the Semites, p. 12
     f.; and cf.  Smith, Hist.  Geogr., p. 10 f.

These facts suffice to show why the influence of both Egypt and Babylon upon the various peoples and kingdoms of Palestine was only intensified at certain periods, when ambition for extended empire dictated the reduction of her provinces in detail.  But in the long intervals, during which there was no attempt to enforce political control, regular relations were maintained along the lines of trade and barter.  And in any estimate of the possible effect of foreign influence upon Hebrew thought, it is important to realize that some of the channels through which in later periods it may have acted had been flowing since the dawn of history, and even perhaps in prehistoric times.  It is probable that Syria formed one of the links by which we may explain the Babylonian elements that are attested in prehistoric Egyptian culture.(1) But another possible line of advance may have been by way of Arabia and across the Red Sea into Upper Egypt.