PAPERS PRESENTED AT GENERAL SESSIONS 39 



THE PALEONTOLOGIST'S VIEW OF EVOLUTION 

 T. E. Savage, University of Illinois. 



To the paleontologist, evolution means the progressive 

 change in the life of the earth from age to age, as a 

 result of natural causes. Just as the life of today devel- 

 oped out of the life of yesterday, the life of the present 

 year was derived in a natural way from that of last year ; 

 so the life of the present age evolved in a natural way 

 by slow progressive changes out of the age that preceded, 

 and so on back to the earliest appearance of life on the 

 earth, several hundred million years ago. The causes 

 of these changes were partly inherent in the organisms, 

 but were largely a result of responses to changes in the 

 external environment. There are three main lines of 

 evidence which practically compel the student of fossils 

 to believe in the doctrine of evolution. These are (1) 

 the geologic succession of life on the earth, (2) the num- 

 erous transitional or connecting forms and (3) the law 

 of recapitulation in the life history of the individual. 



1. The fossils preserved in the rocks show us the 

 actual types of life that existed during the time the suc- 

 cessive rock formations were deposited. It is significant 

 that these fossils show a constant advance in the life as 

 we pass from lower to higher, i. e. from older to younger 

 rock strata. For example, the earliest known plants are 

 found in rocks of pre-Cambrian age, and are algae and 

 related forms, representatives of the lowest Phylum or 

 group of plants. The higher, fern-like plants did not 

 appear until much later (Silurian) time; and the highest 

 group, the seed bearing plants, were not developed for 

 a long time later than the ferns. 



Likewise, the earliest animal fossils preserved in the 

 rocks are the lower invertebrate types, which preceded 

 the vertebrate forms by several million years. Of still 

 greater significance is the fact that within any Phylum 

 or group of animals or plants, it is the lowest members 

 of the group that appear earliest, successively higher 

 types being developed later in time, just as among the 

 Vertebrata the fishes appeared before the Amphibia, the 

 Amphibia before the reptiles, and the reptiles before the 



