GREAT STEPS IN ORGANIC EVOLUTION 905 



reptiles and primitive Gymnosperms were widely distributed, but 

 with the early Eocene cold the larger forms died out. Rapid evolu- 

 tion took place where small forms could resist, whence modern 

 mammals and angiosperms. With the return of warmer conditions 

 would come their widening colonisation, and their fuller adaptation 

 also, even to desertic regions and their extreme climates. Such pro- 

 gress in evolution under the influence of Ice Ages thus needed 

 increasing adaptability to physical conditions; thin-skinned amphi- 

 bians thus giving place to scaly reptiles, and these to feathered birds 

 and hairy mammals, with their high blood temperatures. Finally 

 came man, with his practically universal distribution, since 

 beyond such organic advances he has used his intelligence. The rise 

 of modern man in the Northern Hemisphere, most influenced by the 

 last Ice Age, is here significant; and this notably in association with 

 its favouring the growth of grassland in place of the Tertiary 

 forests. Thus even man's civilised and modern development of 

 pastoral and cereal agriculture may be viewed as his continuation 

 of nature's process; and this ever since it may well have been one 

 of the early Ice Ages which led to the emergence and evolution of 

 the first land plants and animals. 



In such colossal world-changes we may also profitably, reflect 

 upon the evolution-processes, generally more separately and speci- 

 ally considered. Thus for the Darwinian schools, what more dramatic 

 and comprehensive forces of natural elimination, leading to natural 

 selection, with survival of the more adaptive forms, than at the 

 stages so critical for life of these great climatic rhythms? Yet 

 also the schools of Lamarckian descent must say, amid such 

 cosmic stress — what organic strain to meet it — what internal need 

 and organic urge towards readjustment — what elan vital — what 

 surpassing of mneme by horme! And so above all in man — and 

 with what intensive arousal of intelligence by difficulties; and 

 towards readaptations of every realisable kind, up to social grouping, 

 towards better resistance to hard environment and even increasing 

 domination of it. 



Hence, too, great influences towards favouring the evolution of 

 sex in higher animals, to its increasing individuation; and also to 

 the advances of mothering and parental care. And this not only 

 as culminant for the reproductive life, but also as reacting on the 

 indi\ddual and self-maintaining organisation as well, and in various 

 measure. Hence, indeed, our insistence upon divergent lines of 

 evolution, and these from varieties and species to larger and larger 

 groups, broadly contrasted as predominantly anabolic and kata- 

 bolic, more passive and more active ; and thus ranging from feminoid 

 and masculoid species (like bee and wasp, etc.) to the very origins 

 of plants and animals themselves. (See Section on Reproduction 

 and Sex.) 



