But, on the other hand, this advance in the control of energy was not of a very high order. The geographical conditions and the history of these people, such as it was, placed the emphasis on the small unit. There was nothing to suggest union. The lordship which one group of pueblos exercised over the others was in no sense a kingdom or a government; there was no terri torial extension. There was merely an extortion of tribute with threats—blackmail. There was no corre sponding defence of the area from which tribute was exacted, so that further energy might be saved ; there was no idea of nationality ; it was not even a military despotism like that of Assyria ; the pueblos dominant for a time held their power merely because the other, weaker pueblos were also disunited; tribute was ex torted only because of the fear of utter extinction if it was withheld. The importance of Mexico lay in the fact that here was a more efficient method of saving energy in small communities than elsewhere, for no social or governmental organization of more than an elementary type had been evolved. Not only do we see a continual change in dominant pueblos—the Aztecs being only those whom the Spaniards found dominant, and they had been dominant only for a few generations —but when any outside attack was made there was little or no attempt at union in the face of an enemy, rather was there the reverse. This explains the ease with which the Spaniards were able, with few men, to place themselves in authority so quickly over the whole land.
There was one other area in which the Mexican type of civilization was also developed; possibly, indeed, there is some connection between the two, but at present we know little more than that in the low peninsula of Yucatan to the eastward of Mexico, and separated from it by forest, a people lived who had advanced as far as or farther than any other on the continent. The climate of Yucatan is exceptional on the Gulf coasts, in that it is only for a few months in summer that it receives much rain, while the remaining areas have abundance of rain at all seasons ; these are forest covered, while Yucatan is a grassland, and water is valuable.
In Mexico and Yucatan the conditions are not alto gether unlike those where early advance was made in the Old World. In the other region which we must notice, though there is still a curious fundamental similarity, the more obvious conditions are greatly different. In North America the grasslands are small compared with those of Euro-Asia, and the only animal that might have been, though it was not, domesticated was the bison, so that there were no folk who are com parable to the nomad pastoral tribes of the Old World. In South America even a smaller area is a cool grass ' land, and, though the tropical grassland is of greater extent, we have seen that not even the bison is indigenous ; the desert is of small extent, and the great equatorial forest covers almost all the rest. Thus there does not appear any good reason why a great advance might be expected along the lines followed in the Old World.
But in South America a condition of things exists which is found nowhere else on the globe. Rising abruptly on the west of the great forested plain of the Amazon' is the Andean plateau, two or three hundred miles across, and two miles high, its mountain edges rising a mile higher still—that on the east being forest covered, that on the west overlooking a dry and dusty plain. The lower parts of the central plateau are com
paratively dry and warm, the nights being cool. This climate naturally results from the height so near the equator; farther from the equator, land at this height is too cold, even in this latitude higher lands such as the mountain edges are too cold for primitive people. Nor is the central plateau continuous. The bordering mountains run together and divide the habitable land filth basins, which are accessible to one another, but only with difficulty; while even within each basin the land is by no means flat, but mountain and valley alternate.
Here, then, is another area where, if anywhere in South America, there is the possibility that a higher type of civilization might be evolved, and here the Spaniards found the Incas, as they found the Aztecs in Mexico, a people who had but recently dominated the whole land, and had merely succeeded to a heritage which, no doubt with some setbacks, had been developed under different hands for many centuries. But they had really organized their whole dominion, as the Aztecs had not done, and the organization of their own homeland round Cuzco was probably of a much more ancient date than was the building of the Aztec pueblos. Perhaps, indeed, the development had been proceeding in some form or another for so long a time that in the earlier stages the whole area, which is one known to be liable to unusually rapid changes of level, may have been thou sands of feet lower than it is now, and life made easily possible in spots, where, for example, it is now too cold for grain to ripen.
In the various basins of the plateau, then, protected to some extent by the vacant spaces of high and cold mountain border and other intervening heights, com munities discovered and improved methods of saving energy. With water from the colder mountains they watered fertile lands, and grew and garnered potatoes and maize, the former indigenous, the latter introduced no doubt by invaders from the east, who invigorated, if they first tended to destroy, those they found. But by the employment of the only animal in the New World which was domesticated by non-hunting peoples, they were enabled to use and save energy in many ways possible to no others. The llama, an animal of the camel kind, like its larger relative is a native of dry lands, but unlike the camel its home is on the high plateaus. To the llama, as a beast of burden though not of draught, as a source of food though not of milk, and as a supplier of the raw material of clothing, was in no small- degree due the possibility of the growth of Andean power. Having organized the natural area of which Cuzeo -is the centre, the Incas dominated, and then, not being merely blackmailers like the Aztecs, systematized in a larger whole, the various social organizations-which had been evolved in similar basins to north and south. They did more; they descended on to the western coastal desert, and there also dominated and organized, to form one state, a considerable number of small isolated communities which, each using the waters of a separate river flowing from the heights across the plain, cultivated the irrigated lands around it, and gained control of energy in Egyptian fashion. Even so these communities were far more open to external domination than those in Egypt, and were yet too isolated to make a united defence against men who came with an organized force.