190 THE PROBLEMS OF EVOLUTION 



havior patterns. Since related species trace ulti- 

 mately to common ancestors, these ancestors must 

 have had more generalized nervous processes than 

 their existing descendants; they must have varied 

 to a degree which permitted them to give rise to a 

 wide range of more or less fixed instincts. But 

 why should an organism with even the rudiments 

 of intelligence give rise to a form whose limitations 

 of instinctive behavior might be its doom.^ The 

 situation is a peculiar one which admits of only 

 one construction. Fixed instincts are valuable in 

 a fixed environment. Since insects much like those 

 of the present have existed through long periods of 

 geological time, it is probable that some of the 

 existing species have developed their fixed instincts 

 through long association with a remarkably con- 

 stant environment. In drawing this conclusion we 

 must remember that the insect is a small creature, 

 capable of occupying a spatially limited environ- 

 ment, and that the possibility of his finding an 

 approximately constant environment of long dura- 

 tion is great; the more complex an environment, the 

 greater is the chance of variation in it. 



These considerations point clearly toward self- 

 maintenance as the goal of the adaptive mecha- 

 nism of the individual, and intelligence need not 

 be excepted. The simpler forms of intelligence 

 enable their possessors to adjust themselves to 

 a greater range of conditions, but the adjustment 



