290 I The Process of Evolution 



riages tend to keep the population in many parts of the world 

 divided into relatively small partially interbreeding groups ( some- 

 what analogous to Wright's model for a population with a structure 

 favorable for evolutionary progress ) . 



In recent years in western countries groups with the highest intel- 

 lectual attainments have voluntarily limited their family size to a 

 greater degree than other segments of the population. Since intelli- 

 gence has a genetic component, this differential is selection against 

 intelligence. There are, however, many complications that make it 

 impossible to predict the consequences of this recent ominous trend. 

 The influence of our primate background on our culture has been 

 profound. The loss of a sharply defined oestrus period in the female 

 and the general helplessness of the primate infant, with the concomi- 

 tant establishment of a family group stable throughout the year, has 

 led to systems of interpersonal relationships that have been vastly 

 elaborated in cultural evolution. On top of the relatively simple 

 male-female and female-offspring relationships of prehuman family 

 groups, cultural evolution has produced the monstrously complex 

 set of phenomena usually included under such topics as love, sex, 

 and kinship. That these phenomena have become deeply and basi- 

 cally interwoven into the entire fabric of our behavior has been 

 amply demonstrated by anthropologists and psychologists. These 

 phenomena enter into choices of political systems and political 

 leaders, legal systems, the characteristics of the deities that men 

 have devised, and even into choices of designs for automobiles. 



Unfortunately, very little is known about the ways in which cul- 

 ture evolves. Some similarities with biological evolution are obvious, 

 but the value of the following analogies is open to considerable 

 doubt. They are given here more as food for thought than as es- 

 tablished fact. 



Many apparent parallelisms may be detected. Virgin births are 

 found in the mythologies of many different cultures. Complex 

 puberty rites are also widespread, ranging from severe tests of 

 manhood involving torture and genital mutilation to ceremonies such 

 as Christian confirmation and Jewish Bar Mitzvah. Ceremonial ap- 

 peals to spirits are nearly ubiquitous— utJe Navajo dancers and San 

 Francisco ministers appealing to their gods for rain. Some examples 

 seem closer to the biological phenomenon of convergence: the ap- 

 pearance of functionally similar structures in very dissimilar entities. 

 An example of this might be the military dictatorships which sprang 

 up in both Germany and Japan between World Wars I and II. The 

 histories of the two cultures in which these phenomena appeared 

 were widely divergent, and yet in many superficial aspects the 



