88 THE CLIMATIC FACTOR AS ILLUSTRATED IN ARID AMERICA. 



means are found in the old strands and terraces described in earlier chapters. Even these, 

 however, are not conclusive in certain respects. As to the alluvial terraces there is an 

 alternative theory, that of earth movements, which has hitherto been so widely accepted 

 that the student who has a bias against changes of climate is almost sure to inchne toward 

 it. As to the lakes, there can be little question that their high strands indicate moist 

 conditions in relatively recent times, but when it comes to dating those times, we are 

 once more at a loss to determine convincingly whether they belong to a period before or 

 after the coming of the Hohokam. Taking it all in all, then, we maj^ say that if we accept 

 the reasoning of this volume as to the origin of alluvial terraces, and if we assume that the 

 Hohokam were essentially like the rest of mankind, the evidence in favor of changes of 

 climate is overwhelming. If, on the contrary, we accept the tectonic theory of the origin 

 of terraces, and assume that the Hohokam were a highly peculiar people, we nullify the 

 strongest arguments in favor of climatic changes, but we do not thereby prove that climatic 

 luiiformity has been the rule. We merely leave the matter open. The theory of uni- 

 formity needs exactly as much proof as that of change, for the inherent probability of 

 the one is the same as that of the other. Yet, so far as I am aware, no one has ever ade- 

 quately supported the theory of uniformity by means of an array of well-digested facts and 

 figures, although many people have sought to disprove the arguments advanced as indica- 

 tive of changes. The matter can not be finally settled until actual measurements of 

 specific phenomena at specific dates can be obtained. Such measurements will be pre- 

 sented in later chapters. Meanwhile, the evidence already set forth is in itself so indicative 

 of changes of climate, and agrees so closely with all that has been observed in Asia, that 

 we seem forced at least to believe that a change of climate in the southwestern part of the 

 United States is quite as probable as no change. 



As to whether the supposed change from the past to the present was pulsatory or 

 gradual the evidence is not so strong. The terraces, and to a less extent the lacustrine 

 strands and gypsum dunes, seem to point to a pulsatory character. The human evidence 

 is less conclusive. Since the pre-Columbian inliabitants of America began their work, 

 however, the course of history appears to have been characterized by three chief epochs. In 

 the first epoch man spread over wide areas, lived peacefully in small, unsheltered commu- 

 nities, and apparently was not particularlj^ disturbed as to his supply of water. Then this 

 population of early farmers disappeared. How or why or when, we can not tell. War, 

 pestilence, drought, or any one of a dozen different disasters may have been the cause. 

 Some of the people may have gone at one time, and others centuries later. All that we 

 know is that they went and were succeeded by a people who lived a different sort of hfe. 

 At first these later people may have been as peaceful and untroubled as their predecessors, 

 but before they finally left their niins they were forced to cluster around the main supphes 

 of water, they were compelled to build dams and reservoirs in large numbers, and they 

 were sadly harassed by relentless enemies. In their case, also, we have no exact knowledge 

 as to whether war, pestilence, di'ought, or other causes finally overwhelmed them, but 

 this much can fairly be said: All the disasters which have been suggested as the chief cause 

 of their decline are the sort which would arise when the climate became dry, the crops 

 failed, famine was rife, disease had free rein because of the weakening due to poor nourish- 

 ment, and war and plunder were rampant because of discontent and suffering. How many 

 of this second type of people were displaced at any one time, how long they suffered before 

 they were driven out, and how long they had pre\'iously dwelt in safety no one yet knows. 

 Probably they had disappeared, or their villages had been abandoned and they had become 

 mixed with the invacUng Pueblos at least two or three centuries before the Spaniards 

 arrived about 1600 a. d., for otherwise the early fathers would have heard traditions of 

 them in greater numbers. More than that we can not say. Finally, the last type of 

 aborigines, the Pueblo Indians, have had a history similar to that of their predecessors, but 



