276 i The Process of Evolution 



level of organization within groups of organisms, few biologists 

 would deny that an aardvark is more complex or highly organized 

 than a coacervate droplet. A monarch butterfly is clearly a more 

 complicated apparatus than an amoeba or even a fern. Although 

 relatively simple organisms still are present in some adaptive zones 

 (more conspicuously perhaps in aquatic ones), the superiority of 

 more highly organized types in many situations apparently is attested 

 by their seeming dominance. However, dominance in an ecological 

 situation is an exceedingly difficult thing to measure. Do the pine 

 trees in a coniferous forest "dominate" the fungus that inhabits their 

 roots and without which they could not survive? Do mammals 

 "dominate" the bacteria and other organisms in their intestinal flora 

 that elaborate vitamins necessary for their life? Indeed, careful study 

 of any ecological situation reveals interactions among organisms 

 that make comparisons of "superiority" and "dominance" exceed- 

 ingly difficult. 



Nevertheless an aardvark cannot be produced by amassing co- 

 acervate droplets. Many complex problems of structure and function 

 had to be solved before DNA could use aardvarks or man to make 

 more DNA. These problems apparently were solved slowly, one or 

 a few at a time, over long periods of time. The solutions may well 

 have spelled the doom of less efficient types, and the visible record 

 of life becomes one of increasing complexity or organization. Some 

 more simple organisms also have survived, presumably to become 

 integrated with highly complex ones into complex ecosystems. The 

 basic question remains unanswered: Why should DNA have evolved 

 aardvarks and men for making more DNA when bacteria and other 

 simpler organisms apparently can serve just as well? Perhaps the 

 answer lies in the complexity of ecosystems whose cybernetic mech- 

 anisms result in great stability. But this is a difficult problem to study 

 in the fossil record. A major evolutionary trend intimately associated 

 with increase in complexity is the trend toward increased homeostasis 

 in the individual, population, and ecosystem. 



SUMMARY 



There is no evidence to justify the assumption of an essential dif- 

 ference between the mechanisms that produce gene-frequency 

 changes within populations and those which account for the differ- 

 ences between men and microbes. In view of the time available for 

 the evolutionary process, mutation, recombination, selection, and 

 drift quite adequately account for the diversity of life. The discon- 

 tinuities in variation patterns appear to be the result largely of ex- 



