THE DESCENT OF MAN. 365 



THE DESCENT OF MAN. 



By Professor LIXDLEV M. KEASBEY, 

 beyn mawr college. 



/^ ENERAL evolutionary evidence led anthropologists some time ago 

 ^-^ to postulate a pliocene precursor of man, but their surmise has 

 only recently been substantiated by particular proof. The search for 

 the so-called missing link was at first confined to the temperate zone. 

 Many discoveries were made, but, as the skulls and implements un- 

 earthed were all taken from pleistocene deposits, there was nothing to 

 indicate the existence of man on earth before quaternary times. It was 

 not, indeed, until investigations were transferred to the tropics that 

 earlier vestiges of human life were revealed. In the year 1894 Dr. 

 Eugene Dubois discovered the upper portion of a stall and some skeletal 

 parts of a distinctly human creature buried in the pliocene beds of East 

 Java. These remains have since been subjected to the strictest scientific 

 scrutiny and pronounced genuine. Taking the geological location of the 

 discovery into account, there can be no further doubt, therefore, that in 

 this tropical region the human species was already differentiated from 

 the apes in tertiary times. 



Judging from the size and form of the skull, and from such por- 

 tions of the skeleton as remain, the variation of the human prototype, 

 or to give him his scientific name. Pithecanthropus erectus, was evi- 

 dently along both psychic and physical lines ; the former showing a dif- 

 ference of degree, the latter exhibiting a distinction in kind. 



There are two anatomical tests of intellectual superiority: cranial 

 capacity and the convolutions of the brain, both of which can be applied 

 in the present instance. It is a well-known fact that the frontal bone, 

 which forms the vault of the anterior part of the cranium of young men 

 and apes, is divided by a suture. So long as this line of growth re- 

 mains open, the fore part of the cranium can expand; but if the 

 anterior . sutures of the skull consolidate early in life, the cranium 

 cannot increase in capacity beyond the size reached in early infancy. 

 In consequence of the early closure of these sutures in the anthropoid 

 apes, the cranial capacity of these creatures is restricted, and the fore 

 part of their brain rarely increases beyond the size attained at the end 

 of the first year of life. With man, however, these sutures do not con- 

 solidate until a much later period, and, as the anterior lobes of the 

 brain continue to develop, human cranial capacity increases accord- 

 ingly. As a result, the average human being possesses four times as 



