EVOLUTION AS SEEN IN SEROLOGICAL TESTS 123 



Blood cell substances A and B are not confined to man. Among the 

 great apes, for example, the antigens are distributed as shown in Table 6.1. 

 Although the numbers tested are small, one contrast to the distribution in 

 man seems striking. Apparently species diflferences in possession of one or 

 another of the antigens occur among apes. Thus, chimpanzees seem never 

 to have developed substance B, and the two species of gorillas seem to dif- 

 fer in which of the antigens is present, although here the numbers are too 

 small to afford confidence in conclusions. It is interesting that group O, a 

 large group, frequently the predominant one, in human populations is so 

 poorly represented among the apes. Perhaps the presence of A or B or 

 both, not their absence, was the original condition among ancestral pri- 



Table 6.1. Distribution of Blood Groups in 

 the Great Apes'' 



" Numbers are actual numbers of individuals 

 tested. 



Based on data iu Wiener, 1943; Wiener and Gordon, 

 1960. 



mates. This suggestion, advanced by Wiener, contrasts with the idea fre- 

 quently expressed that group O was the original condition from which 

 groups A and B arose by mutation. 



Wiener and Gordon (1960) called attention to an interesting difference 

 between the blood groups of man and chimpanzee, on the one hand, and 

 of the gorilla, on the other. In man and chimpanzee the A and B substances, 

 when present, are found in the red blood cells, as we have noted. In the 

 gorilla, however, these antigens may be present in the cells of organs and 

 in secretions (as they may also be in man) but are absent from the red 

 blood cells. This absence of A or B from blood cells, even when present in 

 other cells, distinguishes the gorilla from man and chimpanzee and suggests 

 to these authors that the chimpanzee is more closely related to man than is 

 the gorilla. 



A contrast should be noted between the distribution of antigens A and 

 B and that of the serum proteins discussed earlier in the chapter. In gen- 

 eral the serum proteins which we noted as chemically similar in man and 



