48 THE ANDES OF SOUTHERN PERU 



home group news that confirms the tribal choice of habitation or 

 sets it in motion toward a more desirable place. Superstitions 

 may lead to flight akin to migration. Epidemics may be inter- 

 preted as the work of a malignant spirit from which men must flee. 

 War may drive a defeated group into the fastnesses of a moun- 

 tain forest where pursuit by stream or trail weakens the pursuer 

 and confines his action, thereby limiting his power. Floods may 

 come and destroy the cultivated spots. Want or mere desire in a 

 hundred forms may lead to movement. 



Even among forest tribes long stationary the facile canoe and 

 the light household necessities may easily enable trivial causes to 

 develop the spirit of restlessness. Pressure of population is a 

 powerful but not a general cause of movement. It may affect the 

 settled groups of the desert oases, or the dense population of fer- 

 tile plains that is rooted in the soil. On the other hand mere 

 whims may start a nomadic group toward a new goal. Often the 

 goal is elusive and the tribe turns back to the old haunts or per- 

 ishes in the shock of unexpected conflict. 



In the case of both primitive societies and those of a higher 

 order the causes and the results of migration are often contra- 

 dictory. These will depend on the state of civilization and the ex- 

 tremes of circumstance. When the desert blooms the farmer of 

 the Piura Valley in northwestern Peru turns shepherd and drives 

 his flocks of sheep and goats out into the short-lived pastures 

 of the great pampa on the west. In dry years he sends them 

 eastward into the mountains. The forest Indian of the lower Uru- 

 bamba is a fisherman while the river is low and lives in a reed hut 

 beside his cultivated patch of cane and yuca. When the floods 

 come he is driven to the higher ground in the hills where he has 

 another cultivated patch of land and a rude shelter. To be sure, 

 these are seasonal migrations, yet through them the country be- 

 comes better known to each new generation of men. And each 

 generation supplies its pioneers, who drift into the remoter places 

 where population is scarce or altogether wanting. 



Dry years and extremely dry years may have opposite effects. 

 When moderate dryness prevails the results may be endurable. 



