796 THE POPULAR SCIENCE MONTHLY. 



avoidable disadvantages. Man's adaptations to the conditions of nature 

 are necessarily limited. Thus it might be suj^posed that a perfect ani- 

 mal would be adapted to traverse the water and the air, as well as the 

 land. But such an adaptation would require extra organs, extra weight, 

 and extra consumption of force in their support. Man, on the contrary, 

 has become adapted to the highest field of life, and escaped an adapta- 

 tion to inferior fields which would prove a disadvantage in the struggle 

 for existence with land-animals. 



His extreme sensitiveness to exterior influences gained by his naked 

 skin is, of course, a sensitiveness to temperature as well as to touch. 

 He is thus limited organically to tropical regions, and to some extent 

 to a life in the shade to a forest residence. In fact, he seems more 

 limited in locality and in powers of resistance than most other ani- 

 mals. His unclad skin renders him acutely sensitive to extremes of 

 heat and cold. He has no cortical defense against the attack of his 

 animal foes. His limbs have become adapted to grasping and to sup- 

 port, but have lost their character as offensive weapons. Finally, his 

 adaptation to an arboreal residence has become imperfect. He can 

 not climb like a monkey, run like a deer, swim like an otter, mine like 

 a mole, or crouch like a cat. 



Physically, then, man is one of the most poorly protected of ani- 

 raaih, seemingly a form not likely to survive in competition with his 

 swift-ruining, flying, and climbing neighbors, and with his carnivorous 

 foes, armed yith tearing claws and rending teeth. 



Yet in other 'Respects he has decided advantages. One of these is 

 a feature in which \iyy few animals rival him, a differentiation in his 

 adaptations to nutriment, enabling him to masticate, digest, and assimi- 

 late both vegetable and ail^mal food. This is a decided advantage. 

 Man is at once herbivorous ddA carnivorous, his field of possible food 

 thus being doubled, and his consequent variety of adaptation to nature 

 being likewise doubled. There is no other animal adapted to this 

 double diet to the same degree a? man. By a rather unpleasant re- 

 semblance, the hog most nearly approaches him in this respect. Yet 

 the hog is principally a vegetable feeder, and only occasionally varies 

 his diet to animal flesh. 



A second advantage is the econon^y of muscular force gained by 

 the vertical attitude. The force thuS saved might have been em- 

 ployed in the production of an extren^e agility, enabling man to 

 escape danger by speed and alertness. It h^s fortunately been applied 

 in another direction, that of the production of liiental acuteness. From 

 the time that man first employed the grasping pOwer of his hands to 

 seize stick or stone for defense against his foes, a'p^^cess was begun 

 w^hich is yet far from completion. It was, in its fui^ results, the pro- 

 cess of mental evolution. But, for our present purpos^> ^^'^ must give 

 it a more narrow significance. 



In all probability man, physically, is not now what he-J^'^^ origi- 



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