LECTURES IN BIOLOGICAL SCIENCES 



Extinction of biological species is the price which life often pays 

 for this opportunism. The extinct forms are those which were 

 driven by natural selection into blind alleys of adaption to en- 

 vironments which subsequently ceased to exist. But there is 

 another side to the opportunism of selection. Once in a while 

 it endows an organism with novel abilities. The house mouse, 

 the rat, the house fly, the cockroach were probably only moder- 

 ately successful species before the advent of man and his civili- 

 zation. Yet they happened to fit snugly into certain adaptive 

 avenues inadvertently created by man. The same was probably 

 true of the ancestors of most animals and plants which man 

 has domesticated. 



Such accidental emergence of qualities which become useful 

 only in environments which the species encounters in the future 

 is referred to as preadaption. Preadaption does not mean that 

 the evolutionary process somehow has a foreknowledge of the 

 future. It means simply that evolution is a creative process which 

 may lead to appearance of completely new qualities, some of 

 them potentially useful and others devoid of utility or even in- 

 jurious to their possessors. Human evolution doubtless involved 

 occurrences of this sort. Natural selection has endowed man 

 with a genetic equipment which opened up the possibilities of 

 symbolic, abstract and generalizing thought. This novel ability 

 has been highly adaptive because it resulted in the emergence 

 of language. But the same ability brought with it also other 

 developments which proved equally crucial for man. The ca- 

 pacity for abstract thought had as a corollary or a by-product 

 the inception of self-awareness. Man tasted the forbidden fruit; 

 he became conscious of himself and of his environment; he at- 

 tained the status of a person in the existential sense. This was, 

 as we see it in retrospect, the close of the prehuman and the 

 opening of human evolution. 



Perhaps it is this crucial event of the evolutionary develop- 

 ment which the biblical symbolism describes as the Fall. The 

 passing of the happy state of a simple child of nature brought 

 heavy penalties. Man became, and he still remains, a creature 

 rent by internal contradictions. He is a paradoxical being, ca- 

 pable of unspeakable egotism and cruelty, but also of love, 

 abnegation, and self-sacrifice. The subconscious life of man is 



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