SOCIAL i: VOLUTION 



From FotTwr. " Urfwehicbto da* Bumpier*." 



UK 36. Aboriginal Man of tin- M>u-i -rinn Epoch. (Desi 

 by Dr. R. Forrer and Leo Schnug). 



climatic changes and the advancing ice sheet. 

 the tempering of the climate the ice sheet melted back, 

 In its wake, men and animals again pressed north. It 

 required centuries for these changes, and the memory and 

 tradition of a northern habitation must have perished 

 from the minds of these primitive folk. In the inter- 

 vening centuries the old cave dwellings were partially 

 submerged by glacial drift so that when the peoples 

 moved north again and the old caverns were rediscov- 

 ered, the remains of form* -r lial.itation were buried deep 

 below the accumulated drift. In this way, by a succes- 



