120 THE EVOLUTION OF MAN 



function of the cerebrum and particularly of the cortex. If 

 animals are arranged in the order of the development of this 

 organ in the nervous system, the relative size and complexity 

 of it will be found standing roughly in parallel with the variety 

 and adjustability of the reaction patterns. That is to say, an 

 animal that has a well-developed cerebral cortex will have a 

 richer type of behavior, being less completely dependent upon 

 instincts and reflexes and being capable of carrying out a larger 

 range of activities than can an animal with less fully developed 

 cerebral structures. 



Man has, as the great differentiation of his own brain from 

 that of most other animals, a very much more delicate internal 

 structure in the cortex and relatively very much larger parts of 

 the cortex devoted to the interconnecting and interrelating of 

 the various parts of that organ with itself. The frontal areas 

 and the so-called association areas are relatively very large. 

 Some of these differences are demonstrable only under the 

 microscope; others, however, are obvious even in the gross 

 anatomy. But despite these differences which are real, no one 

 could ever have inferred from them such marked differences in 

 the expressions of intelligence as do in point of fact distinguish 

 man from even the most highly developed animal. The gen- 

 eral pattern of the human nervous system is, broadly speaking, 

 exactly that of wide ranges of the mammals and more particu- 

 larly of the primates. Nevertheless, the behavior of man is 

 certainly very different (even though the difference be thought 

 of as merely quantitative and not as qualitative), especially on 

 the levels of memory, imagination, thought, and reflection. 

 On the whole, man's development and control over language is 

 unquestionably the greatest single achievement which his in- 

 telligence has compassed, and whether one thinks of it as cause 

 or effect, its presence, more than any other one factor, is re- 

 sponsible for his enormous superiority to his animal neighbors. 

 It has enabled him to achieve social cooperation and the fixa- 



