Revolutionary evidences 257 



EVOLUTIONARY EVIDENCES 

 BY S. W. WILLISTON 



In the time allotted me T can hope to give little more than a very brief 

 summary of the more important evidences of evolution furnished by 

 vertebrate paleontology during the past ten years; nor could I speak 

 even briefly of much of my subject had not kind friends, especially 

 Doctors Gregory and Eastman, come to my aid. The field of vertebrate 

 paleontology has grown so wide that no longer can any one person make 

 a pretense even to that universal knowledge rightly claimed by our 

 predecessors a score of years ago. 



Perhaps the most encouraging sign of advancement in our science 

 during the past ten years has been the recognition of certain methods or 

 factors of evolution that permit us to orient ourselves better, to discern 

 more clearly the true lines of evolution, and of these I refer more espe- 

 cially to parallel evolution. We have been deceived in the past, time 

 without end, in almost ever}^ branch of animal and vegetable life, by 

 adaptive characters, characters evolved in response to like environmental 

 conditions, so often imputed to real heredity. From the time of Peter 

 Camper, when whales were breathing fishes, to the present, some of the 

 most difficult problems in the determination of real phylogenies have 

 been due in large part to the confusion between adaptive and genetic 

 characters. Such problems will always remain with us, but we are now 

 on guard against their ofttimes insidious deceptions. 



The progress of the past ten 3^ears in most branches of vertebrate 

 paleontology has been very encouraging, in the more careful study of 

 faunas, their relationships and sequences — a progress which has opened 

 up a new science, that of paleogeography, a science yet in its infancy and 

 full of snares and pitfalls for the unwary. The pioneers in vertebrate 

 paleontology left us many things imperfectly or erroneously known. 

 We are no longer dependent to the extent that we were a score of years 

 ago upon a tooth or a vertebra or a limb bone as foundations for specu- 

 lations, no longer tempted as we were to use them as mere springboards 

 for fights of imagination, which too often, alas, reached terra firma 

 again with disastrous results. The impelling spirit of genus and species 

 making has given place to other ideals more in accord with modern 

 science, and the acquisition of facts has largely taken the place of the 

 formulation of vague theories. This, it seems to me, is the province of 

 our science in the immediate future, as our President truly said a year 



