Epilogue: What Comes of Studying Vertebrates 805 



work, he rigs sails and allows the wind to drive his boat. He builds 

 boats much larger than whales and, as powerful machines have become 

 available, he effects speedy movement by installing at the posterior 

 end of the fish-shaped craft an engine-driven screw propellor analogous 

 to, but not homologous with, the locomotor caudal fin of a fish. His 

 submarines enable him to invade the deeper realm of fishes. As for 

 aerial locomotion, man is not even a good jumper. But here again he 

 brings to his aid machines, and his airplanes carry him at speeds which 

 make the swiftest bird a mere flying tortoise, and he soars to strato- 

 spheric heights quite inaccessible to birds. 



Mammals other than man are more or less restricted to certain 

 habitats by climate. Man in his natural state could tolerate only a 

 moderately warm and equable climate. Some primitive men found 

 refuge from weather by living in caves. In the course of time he con- 

 trived artificial shelters increasing, through the ages, in their elaborate- 

 ness and in capacity for giving him physical comfort. For endurance of 

 cold, mammals need thick fur. Man extended his habitat into cold 

 regions by the simple device of covering his own body with skin and 

 fur removed from other mammals, and, by use of fire, warmed his 

 shelters. Modern man, by manipulation of an elaborate variety of 

 machine-made clothing and by mechanical "air-conditioning" of his 

 intricately complex and highly mechanized artificial caves, is able to 

 live in all zones and climates of the world. 



Most mammals are restricted to a particular diet to which their 

 teeth and digestive organs are adapted. Human alimentary organs are 

 not specialized for a particular diet. Man is omnivorous and his food 

 varies greatly according to the region, climate, and state of human 

 culture in which he lives. Machines and chemical manipulation have 

 come to play an important part in the production and preparation of 

 his foods. 



In the foregoing brief and incomplete sketch of man's relations to 

 his environment may be found the solution of the anomaly of world 

 dominance by an anatomically unspecialized animal. Survival and 

 success of any group of animals require a state of fitness between 

 animal and environment. "A square peg does not fit a round hole." A 

 lit may be made either by rounding the peg or squaring the hole. An 

 animal may acquire anatomic specialization adapting it to a particular 

 environment and mode of living. There is no conceivable way whereby 

 an environment could adapt itself to a particular animal. In any case, 

 the animal could not survive while waiting for the environment to 

 change. But the animal may act upon its environment so as to modify 

 it favorably. The evolution of most mammalian Orders has followed 



