PROGRESS, BIOLOGICAL AND OTHER 47 



individuals, and differences in the nature and or- 

 ganization of human groups are determined chiefly 

 by what we can best sum up as differences of tradi- 

 tion in the widest sense of the term. The later his- 

 tory of mankind, from a period long antedating writ- 

 ten records, has been one of the rapid rise and equally 

 rapid extinction, not only of one group-unit after 

 another, but of one type of group-unit after another. 

 It is further obvious at first glance that the group- 

 units, the types of society which are at present domi- 

 nant, are far from perfect and far from stable, and 

 indeed that they are evolving, with speed of change 

 hitherto unsurpassed, towards new and unknown 

 forms. 



When the mammalian type first became dominant 

 on the globe — at the transition between the Sec- 

 ondary and Tertiary periods — a somewhat similar 

 history was passed through. The new type of or- 

 ganization gave its possessors marked advantages 

 over other animal types: but the full potentialities 

 of the mammal (excluding man) were not realized 

 until well over half of the Tertiary period had 

 elapsed, and man was being prepared in the womb of 

 circumstance. The Pliocene sees the triumph of the 

 perfected types of mammal: the preceding Miocene, 

 broadly speaking, sees the first rise of these new 

 types, while the Eocene and Oligocene show us a 

 rapid rise and as rapid extinction of variation upon 

 variation on the original theme.^^ With man, how- 



12 See Woodward, '98; Osborn, '10, 



