September 23, 1922] 



NA TURE 



417 



foci of civilisation, each based on well-marked and 

 distinctive geographical conditions. The develop- 

 ment of the three types has been successive and not 

 simultaneous, and there has thus been a steady shift 

 in time of the main focus, a shift westward and north- 

 westward. The three types of human societies alluded 

 to are, of course (a) the river valley type as represented 

 in Babylonia and early Egypt ; (b) the Mediterranean 

 type on parts of the seaboard of the Midland sea ; (c) 

 the forest type of Europe proper, itself becoming pro- 

 gressively more and more influenced by the greater 

 ocean to the west, so that forest influences have steadily 

 given way to maritime ones. 



It is not necessary to consider the geography of these 

 areas in detail. But, beginning with Babylonia and 

 Egypt, I should like to put the causes which seem to 

 me to have promoted fixation quite briefly. Among 

 them we must certainly include the primitive natural 

 resources, scanty though these doubtless were. The 

 birds of the valley marshes, the relatively small number 

 of mammals, the fish of the rivers, must have supplied 

 a certain amount of the animal food. The date palm, 

 in the Tigris-Euphrates areas at least, would, even in 

 its wild state, doubtless yield a fruit of some value in 

 the very early days. 



But as an important factor in the development of 

 cultivation, I would lay especial stress upon the presence 

 of what the botanists call the " open " plant formation. 

 Native trees, as we know, are very few, the date palm, 

 one of the most characteristic, being strictly limited 

 in distribution by its need for water at the roots. For 

 the greater part of the year the ground between the 

 scattered trees is naturally either devoid of vegetation, 

 or is represented only by a few desert plants. But 

 after the periodic flooding by the rivers, an abundant 

 growth of vegetation springs up. The plants may be 

 annuals, the seeds of which ripen as the ground dries, 

 and lie dormant till moisture comes again ; or they 

 may be bulbous and tuberous forms, having but a short 

 period of vegetative activity, but possessing under- 

 ground stems capable of withstanding prolonged 

 drought. The result is that man did not require to 

 clear land for crops ; Nature periodically cleared it for 

 him. He had but to make the fairly obvious deduction 

 that water alone was necessary for the apparently 

 barren soil to blossom like the rose ; from all the choice 

 of plants which the flooded ground offered, he had to 

 pick out those of some use to him, and learn to suppress 

 the rest. As has often been pointed out, he had no 

 need to trouble greatly about renewing the fertility 

 of his lands, for the flood-water did this for him. 



So soon as he had learnt the initial lessons of cultiva- 

 tion, he was tied to the area normally flooded at certain 

 seasons, or to which he could lead the flood-water. 

 He intercalated his crops along one of Nature's lines 

 of weakness, in a transitional area which passed periodic- 

 ally from one climatic zone to another, being, according 

 to the seasons, either a desert or fertile. 



The bordering desert ensured isolation, and, con- 

 tinuing the island metaphor, we may say that it repre- 

 sented the sea. Its effect was to throw the whole 

 energy of the community towards the centre, for the 

 periphery formed an area in which the characteristic 

 mode of life could not be practised. Similarly, it gave 

 protection, for it is unsuited to any save a highly 



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specialised culture, which must have been of relatively 

 late origin. So far as it formed the boundaries of the 

 incipient state, therefore, the desert constituted a 

 barrier preventing the ingress of potential foes. In 

 neither case, of course, was the desert rim complete, 

 and the conditions upstream varied in the two areas, 

 and were, as has often been pointed out, from the point 

 of view of safety, on the whole less favourable in the 

 case of Babylonia than in that of Egvpt. 



As to the third point, it is, I think, easy to show that 

 while the isolation of the areas was markedly conducive 

 to the rise of civilisation and to its growth up to a 

 certain point, in the long run it became a danger. 

 First, the contrast between the belt which could be 

 watered and that to which, with the means available, 

 water could not be carried, was exceedingly sharp. 

 There was little possibility of a gradual spread into 

 areas becoming slowly but progressively different, 

 where new aptitudes could be acquired, new experience 

 gained, and new forms of wealth stored. Specialisation 

 was high within the favoured tract, but the limits set 

 by Nature could not be passed. 



Again, as has often been noted, the conditions led 

 necessarily to a centralised and imperialistic form of 

 social organisation. If there was a sharp line of 

 demarcation between the areas which could and could 

 not be watered, there were great possibilities in the 

 direction of extending by artificial means the belt over 

 which the flood-water spread. This involved the 

 gradual growth of an elaborate irrigation system, and 

 for the maintenance of this a centralised power was 

 essential. This brought with it, as a correlated 

 advantage, the possibility of organised defence when 

 developing neighbouring communities attempted to 

 encroach. But if the attack was made with sufficiently 

 powerful forces, the centralisation became a menace. 

 An attacking foe able to destroy or damage seriously 

 the irrigation system could cut off at its source the 

 basis of prosperity, and render reconstruction on the 

 old scale almost impossible. In other words, the 

 community became adapted to artificial conditions 

 created by itself ; if and when those conditions were 

 destroyed, the survival of the old culture became 

 impossible. 



Turn next to the Mediterranean region, that is, to 

 the area in which the typical Mediterranean climate 

 prevails. In so far as the native plants are concerned, 

 this area shows certain broad general resemblances to 

 the river-valleys, with some striking differences. Thus 

 the characteristic plant formation is alternately open 

 and closed ; closed during the cooler season of the 

 year when the winter rains cause a brief but intense 

 growth of annuals and bulbous or tuberous plants, 

 open during the drought of summer when the trees and 

 shrubs stand apart from each other with bare earth 

 between. But the contrast is due, as indicated, to the 

 rainfall conditions, not to flooding. There is thus no 

 natural renewal of fertility, and plants which require 

 much water can only thrive in the cooler season, so 

 that growth is less intense than in either the Nile or 

 the Euphrates-Tigris valley. 



On the other hand, because of the climatic conditions, 

 trees and shrubs, alike as regards individuals and 

 species, are far more numerously represented in the 

 Mediterranean region. Here, however, we come to a 



