this problem as long ago as 1925. In his now classic announcement of the 

 Taung discovery, he stated: 



Few data are available concerning the expansion of brain matter which takes 

 place in the living anthropoid brain between the time of eruption of the first 

 permanent molars and the time of their becoming adult. So far as man is con- 

 cerned, Owen (Anatomy of Vertebrates vol. iii) tells us that "The brain has 

 advanced to near its term of size at about ten years, but it does not usually obtain 

 its full development till between twenty and thirty years of age." R. Boyd (1860) 

 discovered an increase in weight of nearly 250 grams in the brains of male human 

 beings after they had reached the age of seven years. [Dart 1925, p. 197] 



However, in this first paper, as mentioned before, Dart ventured no 

 estimate of the capacity, either of the child or of the adult. Keith, in his 

 comment in Nature a week, later, did make an estimate. He stated that in the 

 fourth year a human child has reached 81 per cent of the total size of its 

 brain, whilst, "at the same period," a young gorilla has attained 85 per cent 

 of its full brain size and a chimpanzee 87 per cent. No statement was made 

 about the sample size nor the origin of the materials upon which these state- 

 ments were based. From these figures Keith chose the value of 85 per cent 

 to apply to the Australopithecus endocast. Based on his estimate of "less than 

 450 c.c," he computed that the adult brain "will not exceed 520 c.c." (Keith 



1925)- 



In his Natural History paper, Dart (1926) gave his estimate of 520 c.c. 



for the child and added 20 per cent, which he described as "a reasonable 

 amount to allow for subsequent expansion." This gave him an adult estimate 

 of 625 c.c. 



Zuckerman (1928) based his estimates on chimpanzee data and pointed 

 out that, by analogy with the chimpanzee, the subsequent growth would 

 have varied with the sex. The average expansion, he stated, after the 

 eruption of the first molar is 8.1 per cent in the chimpanzee, regardless of 

 sex. In the male the average expansion was given as 1 1.3 per cent, and in the 

 female as 3 per cent. The final ca- 

 pacities estimated by Zuckerman regardless of sex 540 c.c. 

 for a Taung adult were therefore as if male 566 c.c. 

 follows: if female 515 c.c. 



These figures, as will be seen, are remarkably similar to those obtained by 

 my latest estimates based on newer comparative material. 



Keith's later detailed study led him to an upward revision of his earlier 



^ >4 



