BRAIN DEVELOPMENT AND EVOLUTION. 531 



another increase in number, variety, and depth, as we have seen 

 in the case of the Bushwoman. And thus these convolutions go 

 on pari ]jassu with increasing manual dexterity and intelligence, 

 multiplying, assuming more varied and complex forms and greater 

 depth, until we reach the most thoughtful and learned members 

 of the highest civilized communities, where the brain surface if 

 smoothed out would measure, on an average, about four square 

 feet. 



What immediately concerns us, however, in this connection, is 

 the fact that not only the savage and the primitive man, but the 

 ape and even certain quadrumana, have already found more con- 

 triving, thinking, remembering, and other kinds of brain work to 

 do than a head and cranial capacity in due proportion to their 

 bodies will admit of. And thus each and all are preserving and 

 perpetuating by natural selection and heredity all the variations 

 of increased cerebral surface resulting from more numerous, 

 varied, and deeper convolutions. 



Is it inconsistent, then, with the theory of evolutionary descent 

 for the savage to have the largest possible cranial capacity and 

 head not out of due and advantageous proportion to his body 

 and the demands of his mode of life ? This question is completely 

 answered by the fact, which has now been fully set forth, that 

 the further growth of head and consequent cranial capacity in 

 his case has been already arrested, as in the case of the ape and 

 the quadrumana, at the point of becoming too large for his body 

 and mode of life, while his still increasing and developing mental 

 and emotional powers and activities have already found a sub- 

 stitute for further cranial capacity, or head growth, in more 

 numerous, complex, and deeper convolutions, thus increasing the 

 brain surface. 



It is surprising that this objection has not been earlier de- 

 murred to on the specific ground of inadequacy. It now appears 

 that as well might the cranial capacity of an ape as that of a 

 savage or a primitive man be made the basis of this objection, 

 since in all three cases further head growth has been checked at 

 the point of undue proportion to the body, and thereafter increas- 

 ing mental activity has found a physical substitute for further 

 head or brain growth in the preservation, as a fitter adaptation, 

 of every fortuitous variation in the direction of these increased 

 convolutions, first foreshadowed in the quadrumana, reaching the 

 highest complexity in civilized man, and co-ordinated to advanc- 

 ing intelligence at every intermediate step. 



Thus we see that this popular objection crumbles at the first 

 touch of a few simple and well-known facts. 



