Physical Evolution of Man 581 



ductor between the hand or arm and the brain in all or most of 

 the above acts. It only becomes specially stimulated to high- 

 est action when it and the brain, apart from other organs, are 

 acting and reacting directly in relation to each other. 



In the gradual evolution of the nest, the leafy shelter, the 

 hut, the simple home, the embellished house, the palace, and 

 the cathedral, the cooperating and reciprocally stimulating 

 action of hand and brain, with the eye to guide the stimuli 

 passing to and from both, receives striking illustration. As 

 with the orang, the chimpanzee, the Ainu, and some other neo- 

 lithic human races, man's primitive shelter consisted of leafy 

 boughs or piled branches and leaves. The twisting and bend- 

 ing of branches into shape and strengthened connection sug- 

 gested and gradually evolved a more permanent framework or 

 shed, as with ants and beavers. In time the hands were further 

 exercised, so as to ornament, carve, fit together, and trace 

 sculptures or drawings on the walls, like the primitive cave 

 drawings of Central France or the rock and cave drawings of 

 the South African Bushmen, which started "Art in the home." 



The use of brick, plaster, and stone in succession to wood 

 was evolved according to locality conditions, but their use drew 

 out, more and more, the skill and faculty of the hand. This 

 phase in human advance seems first to have been started 

 10,000 to possibly 12,000 years ago, and in the Irano-Assyrian 

 region, where Sumerian and Semite both strove to excel and 

 to rival each other. The first keyed arch to a door or window 

 was a trophy of manual effort in brick, and opened up new 

 possibilities. It probably originated in the Assyrian region, 

 or in the Iranian region northeastward, 6000 to 7000 years 

 ago. 



The climax in combined artistic effort and strength of 

 material may be said to have been reached in the late medieval 

 cathedrals. In these the detailed hand effort and brain stimu- 

 lation that devised and fashioned the massive walls, the gothic 

 windows with their ornate carvings, the huge pillars with 

 widely arched connections, the elaborately tiled floors, the 

 upreared spires and minarets, the paintings and sculptures of 



