1. The Social Use of Space 101 



from his primate and preprimate ancestors a physiology transpiring in 

 groups within the range of 10-20 adults. This physiology was fixed some 

 half a million years ago and has not significantly diverged from it since. 

 Development of a larger social group is made possible by a culture in which 

 a normative orientation prescribes values, and sanctions roles of behavior 

 such that the total effect of participation in a larger group so buffers the 

 individual that at any particular time the individual functions socially as if 

 he were a member of a group of 12 individuals. Furthermore, genetic 

 changes of the central nervous system making learned value systems of 

 cultures possible must have arisen under circumstances which prevented 

 division of the basic group size when it reached twice this level. Either an 

 ecological-psychological trap like the behavioral sink (Section XII, C) or 

 any isolated but very abundant source of a needed resource would be ade- 

 quate to demand either a genetic change of physiology making life in large 

 groups tolerable, or a genetic change endowing the central nervous system 

 with the capacity to learn and culturally transmit values. Each increase in 

 group size is associated with a reorientation of the value system. Such in- 

 creases in group size are saltatory. The theoretical basis of why such 

 changes must be saltatory and not transitional is discussed in Section 

 XIII, B, 3. 



XIII. A Formulation of Group Dynamics 



Twelve individuals represent the approximate optimum group size for 

 certain species (Sections VIII, C and XII, E) . Furthermore, such a sized 

 group might be expected to have evolved from home range dynamics. 

 Evidence could readily be assembled that other basic A^'s, NbS, characterize 

 other mammahan species. Some typically live as pairs while others assemble 

 in herds exceeding 100 or 1000 individuals. However, circumstances may 

 force N to diverge markedly from A^6. Elaboration here of the model of 

 social interaction presented in pages 349-354 of Calhoun (1957) provides 

 insight into the consequences of such divergence of A^ from Nb. 



A. The Model of Social Interaction 



On a presumptive basis there are three variables which should determine 

 the mechanics of contact and interaction. These are (a) the number of 

 animals moving about and having opportunity of contacting each other, 

 (b) the length of the refractory period following the response of one animal 

 upon contacting another until it is again capable of exhibiting a similar 



