238 evolution: the ages and tomorrow 



It was emphasized that nature was gropifig and striviiig 

 toward greater understanding, exploring all possibilities and 

 not knowing a priori how or where success would come. 

 Nature's method is to push Hfe into every nook and cranny 

 of the world's habitats: into the great deeps of the oceans 

 where it must necessarily be compressed and restricted; or 

 out into the driest deserts where thirst is an everlasting 

 problem; or far into the frozen tundra where there is no 

 warmth. Here as elsewhere nature apparently depends on 

 the blind, random forces of genetic variation and natural 

 selection for the evolution of new species— variation in the 

 basic life units (the genes), their additions, deletions, and 

 rearrangements, their drift in a population, and finally the 

 guiding forces of adaptive selection. We pointed out how at 

 many levels in the evolutionary sequence some structural or 

 behavioral characteristic placed restrictions and limitations 

 on the future of a particular group of organisms. Even in 

 man we had occasion to call attention to trends which may 

 halt his further progress, such as failure to adapt sufficiently 

 well to social life, failure to control the total numbers and 

 mental levels of the individuals in his populations; and even 

 the peculiar and very high specialization of his brain where 

 there are probably limiting factors. And, of course, all or- 

 ganisms, whether successful or not, and even the configura- 

 tions of the physical cosmos, are finite. Only the universe as 

 a whole is infinite and eternal. 



One can assume from the record of life, especially on the 

 basis of an over-all trend toward greater mentality, that 

 there has been progress in evolution and that it exists in spite 

 of the innumerable cases of retrogression and extinctions. I 

 have argued for nonanthropomorphic purpose in the uni- 

 verse. Purpose, as a drive toward awareness and intelligence 

 is an innate characteristic of the ?nind-in-matter -energy sub- 

 stance and is as much a descriptive item as any other that 

 analysis of the nature of the space-time continuum may re- 

 veal. Moreover, purpose is partially realized only if and 



