18 MAN THE ANIMAL 



But consider the matter more carefully. If a man wields an axe 

 for eight hours a day, week in and week out, he presently adds 

 certain definite, new, useful structures to the physical equipment 

 with which he started. These are the calluses which develop at 

 the main bearing points on his hands. When they are well de- 

 veloped these calluses are as dead as the axe handle itself. But 

 they are highly useful to the man. They are useless and mean- 

 ingless in any other relation. Biologically they are adaptive 

 structures added to man's previous manual equipment. But so 

 precisely is a steam shovel. A modern steam shovel is an adap- 

 tive structure which can be attached to a man's hands. With his 

 hands strengthened by the addition of this equipment his power 

 is so increased as to make the Behemoth a "wee, sleekit, cowrin, 

 tim'rous beastie" by comparison. The man and the steam shovel 

 together constitute one single organism, partly made of flesh, 

 partly made of steel, but operating, if it operates at all, as one 

 single integrated unit. 



All useful machines are additions to the adaptive biological 

 equipment of man as an animal. Some are additions to his motor 

 powers; others to his sensory. But their fundamental meaning 

 is always biological. Except as a part of man's biological equip- 

 ment they have no significance. 



To what does this lead us? The thought has been advanced 

 by not a few persons that the development of machinery is 

 fer se a menace to mankind; that machines will dominate men. 

 But why? Machines are only parts of men. They are merely 

 extensions of, or additions to, his arms, or his legs, or his eyes, 

 or his ears, or to some other organ system. They are added 

 organs. And man is the only animal that is an organ-adder, in 

 any significant degree. This attribute or capacity has been of 

 great, indeed incalculable, value to him in his struggle for 

 survival and in his evolutionary progress. 



In order that the significance of man^s achievements as an 

 environment-maker may be adequately appreciated it will be 

 necessary to digress for a moment to speak briefly of the rela- 



