Essential McLuhan 368 (c) They are exchangeable, enabling man to specialize and to play multiple roles: when carrying a spear, he can be a hunter, or with a paddle he can move across the sea. (d) All of these instruments can be shared communally. (e) They can be made in the community by “specialists” (giving rise to handicrafts). (The Human Animal, 103–4) One thing Hass overlooks is the absence of biological or psychological means of coping with the effects of our own technical ingenuity. The problem is clearly indicated by A.T.W.Simeons in Man’s Presumptuous Brain: But when, about half a million years ago, man began very slowly to embark upon the road to cultural advance, an entirely new situation arose. The use of implements and the control of fire introduced artifacts of which the cortex could avail itself for purposes of living. These artifacts had no relationship whatever to the organization of the body and could, therefore, not be integrated into the functioning of the brain stem. 7 E.T.Hall, The Silent Language, 56–7. However, the notion is of a respectable age: Two generations ago, Emerson made the observation, ‘The human body is the magazine of inventions, the patent office where are the models from which every hint was taken. All the tools and engines on earth are only extensions of its limbs and senses. One definition of man is ‘an intelligence served by organs’” (“Works and Days,” 151). 8 Hass, The Human Animal, 101. In the same vein, Karl Popper wrote, “the kind of extra-personal or exosomatic evolution that interests me here is this: instead of growing better memories and brains, we grow paper, pens, typewriters, dictaphones, the printing press and libraries. These add to our language…what may be described as new dimensions. The latest development…is the growth of computers” (Objective Knowledge, 238–9). The brain-stem’s great body-regulating centre, the diencephalon, continued to function just as if the artifacts were non-existent. But as the diencephalon is also the organ in which instincts are generated, the earliest humans found themselves faced with a very old problem in a new garb. Their instinctive behaviour ceased to be appropriate in the new situations which the cortex created by using artifacts. Just as in the pre-mammalian reptiles the new environment in the trees rendered many ancient reflexes pointless, the new artificial environment which