NERVOUS AND ENDOCRINE CONTROL I 35 



THE BACKGROUND OF HUMAN MENTALITY * 

 RALPH LINTON 



Human behavior is vastly different from the behavior of the other 

 mammals, even that of our cousins the apes. Nevertheless, just as the 

 physical differences between men and apes diminish in importance and 

 cease to be a bar to relationship when they are studied against the back- 

 ground of mammalian variation, the differences in behavior diminish in 

 importance when they are seen in their proper perspective. There is a 

 gap to be sure, and this gap will never be bridged by fossil evidence of 

 the sort which is gradually bringing the structure of men and apes into a 

 continuous evolutionary series. Behavior does not fossilize, and the actual 

 links disappeared when the half-men of the late Pliocene and early Pleis- 

 tocene became extinct. However, human and animal behavior can be 

 shown to have so much in common that the gap ceases to be of great 

 importance. 



The outstanding quality of living as opposed to dead matter is that 

 living matter responds to stimuli in ways which increase its chances of 

 survival. The living being apprehends its environment and acts to adapt 

 itself to it. This irritability of protoplasm, its capacity to receive and 

 transmit stimuli and to react to them purposefully, is the foundation of 

 behavior. It is equally characteristic of the amoeba, that speck of jelly 

 which lies at the root of the animal family tree, and of man, who has 

 perched himself on its highest branch. 



In unicellular organisms such as the amoeba all parts of the individual 

 are sensitive to all sorts of stimuli and the whole individual responds to 

 them. In slightly more complex organisms, where a number of cells have 

 banded together for their mutual advantage, there is a specialization in 

 function. The surface cells receive and transmit stimuli while the interior 

 cells respond to bring about the changes necessary for the survival of the 

 organism. In still more complex organisms, including our own, there is 

 a further specialization in function. All such organisms begin as mere 

 aggregations of cells which become differentiated into a surface layer, 

 highly sensitive to stimuli, and a less sensitive interior. As the individual 

 develops, part of this surface layer remains on the outside and develops 

 into the skin and the various sense organs. Another part is folded in and 

 buried among the less sensitive cells. This becomes the nervous system. 

 The buried part of the original sensitive surface layer specializes in the 

 transmission of stimuli just as the exposed part specializes in their reception. 



In animals organized on the radial principle, such as jellyfish and allied 

 forms, the nerves form a continuous net. In those organized along axial 



• From The Study of Man by Ralph Linton, D. Appleton-Century Company, Inc. 

 Copyright 1936. 



