Chapter VII 



THE FOSSILS 



LATE PRE-CAMBRIAN FAUNAE 



It has been stated already that the fossil record of early life on earth 

 is deplorably scanty. This statement is, perhaps, in need of qualifica- 

 tion, for there is a rather extensive literature on fossils from the pre- 

 Cambrian. But by and large these all come from sediments of late 

 pre-Cambrian times. So they are not so much older, and clearly the 

 precursors of the more fully developed and better preserved Cambrian 

 faunae. 



This late pre-Cambrian life comprises fossil remnants, including 

 Algae, Radiolaria and Crustaceans, indicating the existence of a rich 

 and varied flora and fauna, which was no longer restricted to mi- 

 crobes. These late pre-Cambrian organisms already belonged to 

 higher levels of organization than those we must look for when we 

 study early life on earth and its origin. Crustaceans, segmented 

 animals with a hard outer skeleton, are as far removed from the 

 origin of life as a jet aircraft is from a wheelbarrow. 



Consequently these fossil assemblages of late pre-Cambrian times, 

 which are known from several of the old shields, add but little to the 

 knowledge of early life. They are all from sediments laid down only 

 a little earlier than the base of the Cambrian system. They form the 

 immediate ancestry of the organic world of the Cambrian. Their 

 absolute age will not have been much higher than the 600 my which 

 is now given for the base of the Cambrian; it will, in all probability, 

 be much lower than 1 billion years. 



THE IMPORTANCE OF MICROBES 



This matter of the late pre-Cambrian organisms, which are the im- 

 mediate precursors of those of the Cambrian, and which already 

 show a high level of organization, brings up the importance of mi- 



