Physical Evolution of Man 573 



tion so adapted to a high degree as to bring the sense organs 

 into most rapid and perfect contact with environal stimuU. In 

 some turbelhirians and in nemerteans this is effected by the 

 proboscis, whose substance, attachment-area, and orifice of 

 protrusion are very richly nervous, and are situated in the 

 midst of the sense centers; in cephalopods, spiders, ants, and 

 other invertebrates that are highly evolved mentally as well 

 as physically, we have seen that other structures surrounding 

 the brain and the various sense centers act as rapid and varied 

 environal perceptive organs, while in mammals the most per- 

 fect, persistent, and dominant organization, physically and 

 mentally, is associated with increasing specialization of the 

 forelimbs as environal contact organs.* 



The highest exhibition of this is seen in the chimpanzee and 

 orang as outlined in last chapter. Now, if man in his physical 

 organization has evolved by degrees from ancestral forms that 

 had a common ancestry with the gorilla, chimpanzee, and 

 orang, the new details that he has undoubtedly acquired dur- 

 ing the process were a permanently upright habit, and all that 

 this would involve in straightening of the long bones of arms 

 and legs; in perfect plantigrade motion; in total cessation in 

 use of the arms for progression; in condensation and almost 

 vertical placing of the pelvis; in condensation and contoured 

 balancing of the spinal column as related mechanically to the 

 head, arms, and legs; in a more vertical facial angle and larger 

 brain capacity; in greater prominence of the brow and reduced 

 hairiness of the body. 



We believe that it is possible to show that steadily perfected 

 adaptability of the forelimbs for increasingly varied contact 

 of these with environal objects directly or indirectly effected 

 such changes. This gives, therefore, to the fore limbs a ])re- 

 dominant importance in man's physical evolution, but we trust 



* Did space permit an interesting study could be made, and comparison 

 instituted, regarding tlie highly specialized limbs of Artio- and Perisso-dactyla, 

 as connected with race dominance on the one hand, and brain-stagnation on 

 the other, the whole resulting in an evolutionary cul-de-sac. This has in 

 part been referred to by Osborn and others. 



