Geological Aspects of Evolution 89 
Geological Aspects 
of Evolution 
Victor T. ALLEN 
A consideration of the Geological Aspects of Evolution in- 
volves the entire geologic record of nearly two billion years 
as well as the long uncertain stages preceding the known eras. 
From this great store house of information it is necessary to 
Select with care the topics which are to be briefly treated and 
the episodes which are to be regarded as typical illustrations. A 
brief sketch of this inviting subject may be presented under four 
headings: (1) the origin of the earth, (2) the origin of life, (3) 
evolution and the geologic record, (4) the Quaternary or The 
Age of Man, 
The origin of the earth. The first problem of evolution 
with which the geologist is concerned is the origin of the earth. 
This problem is astronomical as well as geological, for the evolu- 
tion of the earth can not be divorced from that of the component 
members of our solar system. The earth is one of nine planets, 
which rotate about and in the same direction as the sun. In 1796 
