.".II Comparative Morphology of Chordates 



of this latter sort lie within the line of specialization peculiar to the 

 evolution of the group. Man is gregarious and social. He organizes 

 himself into groups, small and large, social, economic, religious, politi- 

 cal, national. His nations, to a large extent but not entirely, are raeialh 

 distinct. Each group stands for a set of ideas. Among these ideologies 

 there is all manner and degree of conflict, ranging from friendly debate 

 to cataclysmic world wars. The human race is in a state of flux. It is a 

 seething ferment of clashing ideals and objectives. All of this is in utter 

 contrast to what we see in existing races of other mammals. They seem 

 to have arrived at a state of biologic equilibrium. The carnivore must, 

 of course, take his food, but as a rule mammals of a kind do not form 

 groups to make war upon one another. So far as they may have any- 

 thing approaching an idea, they are all in fairly good agreement about 

 it and there is a high degree of uniformity in their well-ordered be- 

 havior. Mammalian groups other than primates are phylogenetically 

 relatively old. The human race is new. It is now in a plastic and 

 formative stage. It has not "found itself." It has already performed 

 miracles in adaptation of the environment, but it is torn by internal 

 disharmonies. 



Vertebrate history is repeating itself again. The human race is in a 

 phase of evolution analogous to that when, in the early days of amphib- 

 ians, reptiles began to emerge; or to that early formative period of 

 reptilian history whence the theromorphs opened the way out toward 

 mammals; or, yet again, to that later period when, in a world of 

 diversifying mammals, a little remnant of the primitive stock somehow 

 held itself aloof from the general tendency toward anatomic specializa- 

 tion and, in the course of long ages, built up the nervous mechanism 

 which eventually put tools into the hands of primates. 



During this present century, the internal disharmonies of the 

 human race have become especially devastating. Dire prophecies are 

 rife. We are told that human civilization is to be destroyed, that man 

 will annihilate himself from the face of the earth, and that the world of 

 I he future will be dominated by insects. If the future may be foreseen 

 in the light of the past, it would seem that a past of a half-billion years, 

 more or less, should afford some reasonable ground for prophecy, and 

 especially so if any consistent trend in that long past can be seen. 



There is certainly such a trend, and it is most clearly discernible in 

 the history of the chordates. From primitive chordate to man, it is a 

 story of continuous progress. It is difficult to imagine any sort of 

 adaptation to environment which has not been successfully achieved 

 by some vertebrate. Finally, as if possibilities of structural adaptation 

 to environment had been exhausted, primate mammals have begun 

 to adapt the environment. Tt is true that many great and once success- 



