BIOLOGY AND HUMAN TRENDS — PEARL 333 



much more simply and satisfactorily accounted for in the main by 

 the operation of the purely environmental factors of familiar con- 

 tact from childhood, training, easy opportunity of entrance, and 

 the social pressure of tradition ; in short, by " social ", not biological, 

 inheritance. 



Our third unique and universal biological principle, variability, 

 has two aspects, as has already been pointed out. No two living 

 organisms are exactly like each other in all particulars, and no single 

 organism is precisely the same at any two moments in its lifetime. 

 The first of these aspects is the only one that is conventionally called 

 variability. It is mainly caused by the combined interaction of 

 genetic shuffings and recombinations and the environment. The 

 second aspect of organic variability is usually and conveniently 

 called adaptability. It is an odd and remarkable phenomenon. The 

 unique thing is not that organisms are more or less fitted or adapted 

 to the circumstances in which they find themselves. Inanimate ob- 

 jects of various sorts, and particularly that category of them that we 

 call machines, are this. It is true that the adaptations of organisms 

 and machines are brought about in different ways. But the fact of 

 adaptation is present, and in principle identical, in both. We are, 

 however, not concerned here with adaptation, but with self -started 

 and self-controlled adaptability, which organisms have and machines 

 do not. Organisms incessantly change and alter themselves to meet 

 the fleeting changes in their circumstances. No living organism ever 

 stays put. Wlien it does it is dead, and in dying has passed into a 

 wholly different category of matter. 



The process goes even deeper than change and adaptability in be- 

 havior. The very material substance itself that makes up the living 

 organism is constantly changing. What, then, does " personal iden- 

 tity " connote ? What we are pleased to call the same identical man 

 at the age of 70 years is composed of extremely little, if any, of the 

 same material substance that made him up when he was 20 years old. 

 Probably there is not a single molecule in him at 70 that was there at 

 20. In the intervening years the only thing about him that has sur- 

 vived is his pattern, a sort of transcendental or spiritual wraith 

 through which has flowed a steady stream of matter and energy. 

 There is a profound truth embodied in Cuvier's old comparison of a 

 living organism to a whirlpool. It is the pattern that is the essence 

 of the business. It alone endures. And it is constantly altering and 

 adapting itself to changing circumstances. Especially is this true 

 and important of the psychological panel of the total pattern of the 

 human organism. It is this aspect of adaptability, the capacity of 

 organisms for change ending only with death, that seems to be more 

 important in its social consequences than its teleological aspect, if 



