348 Problems of Organic Adaptation 



man one of the least highly adapted of all animals? Cer- 

 tainly some animals and plants which have the lowest rate 

 of reproduction and elimination have the highest types of 

 differentiation and adaptation. 



One answer to this argument is that one organism is as 

 well adapted as another, and that there are no such differ- 

 ences in fitness as have been assumed. For example, an 

 amoeba may be as well adapted to its environment and needs 

 as a man is to his. If one has reference only to the capacity 

 to survive and leave descendants, this is certainly true. Ev- 

 ery individual or species that persists must be well enough 

 adapted to live and multiply. But adaptations differ greatly 

 in number and complexity in higher and in lower organisms, 

 just as differentiations do, and, since these adaptations have 

 arisen in the course of evolution, those animals and plants 

 that have the more numerous and the more complex adap- 

 tations must have had a longer course or a more rapid rate 

 of evolution. However, the duration of evolution cannot 

 have been longer in higher forms than in lower ones ; if all 

 organisms have had a common origin, all are equally old so 

 far as ancestry and evolution are concerned, and if one con- 

 siders only the different phyla, classes, genera, etc., it is 

 evident that these are much older in the lower than in the 

 higher forms. 



It must therefore follow that the rate of evolution and 

 of adaptation has been much more rapid in higher than in 

 lower organisms in spite of the fact that in general the rate 

 of reproduction and elimination of persons has been lowest 

 in those forms in which adaptation has gone farthest and 

 fastest. A possible explanation of this apparent contradic- 

 tion of the Darwinian theory is found in the fact that higher 

 organisms have more different kinds of genes as well as more 

 differentiated cells and organs than the lower ones, and 



