ARCHEAN AND PALEOZOIC LIFE 405 
Life in the Archean. — With the dawning of the 
Paleozoic, the waters of the sea were peopled with 
animals and plants, living in great numbers and con- 
siderable variety. Although only the faintest traces of 
life have been found in the rocks of Archean age, there 
is every reason for believing that the ancestors of these 
Paleozoic creatures lived during the Archean time. 
Very careful search has been made for records of this 
ancient life, with almost no success. 
Some geologists believe that the beds of limestone 
and graphite, which occur among these ancient rocks, 
are indications of the presence of life when they were 
deposited. It is to be said, however, that while plants 
can be changed to coal and then to graphite, and while 
shell-bearing animals may construct beds of limestone, 
there are other ways in which both graphite and lime- 
stone may be formed. Hence the mere finding of these 
substances among the Archean rocks, is no proof of the 
existence of life in that period. 
The belief in evolution makes it necessary to as- 
sume that the Paleozoic animals had ancestors in 
pre-Paleozoic times; and there is really some proof 
that life did exist then. Traces of what appear to be 
low types of animals have been discovered; but some 
of these, particularly the Eozoon, which was believed to 
represent the earliest form of life, are thought by some 
scientists to be nothing but a peculiar form of mineral. 
