140 WORLD-POWER AND EVOLUTION 



and the early part of 1918, when many weather records were 

 broken in the United States. Solar activity, however, character- 

 istically varies in cycles. When the sun is unusually active the 

 cycles become shorter and the contrast between maximum and 

 minimum increases enormously. In the fourteenth century this 

 tendency was strongly apparent, and during the Glacial Period, 

 and especially during its closing epoch, this must have been still 

 more true. / 



Consider the effect which such extreme and frequent fluctu- 

 ations would have when they first began to prevail in various 

 parts of the Old World, the only place where man appears cer- 

 tainly to have lived at that time. In northern Europe the terrible 

 storms, floods, cold waves, and droughts must have destroyed both 

 animals and plants. Thus the inhabitants were largely deprived 

 not only of the game on which they chiefly subsisted, but of the 

 nuts, berries, and roots which eked out their scanty diet. At the 

 same time the great extremes must have been mentally benumbing. 

 In addition to the famines which must frequently have affected the 

 primitive human inhabitants, diseases like the Black Death 

 probably wiped out others. The few who remained doubtless / 

 subsisted miserably for a while and then migrated southward./ 



In central Europe one of the most marked effects of the early 

 stages of a glacial climate was probably aridity. This is what 

 happens there today on a mild scale when sunspots are numerous. 

 It happened on a much greater scale in the past, as we know from 

 abundant deposits of the yellow, wind-borne dust known as loess, 

 which is found in the valleys of the Rhine, Danube, and other 

 rivers of central Europe. Similarly in North America the 

 relatively poor crops of the central portions of the United States 

 at times of many sunspots have their parallel in the glacial 

 deposits of loess in the valleys of the Mississippi, Missouri, and 

 Ohio. Such aridity was probably not nearly so bad for early man 

 as the incessant storminess and cold farther north. Nevertheless 

 both conditions must have checked progress and wiped out large 



