Evolution 341 



region, the Holarctic ; Madagascar is recognized as a unique region, the 

 Malagasy ; and the Polynesian and Hawaiian Islands are separated 

 from the Australian region. All the areas are divided into three major 

 groupings and are arranged as follows : 



hawa(1an%, J 



POLYNESIAN 



£. 



Fig. 109. — Map of the world showing zoogeographical regions. (Base map modified 



from map by A. J. Nystrom and Co.) 



THE GEOLOGICAL TIME SCALE 



As based on evidence from radioactive materials, the age of the 

 earth is usually considered to be approximately 3,000,000,000 years. 

 Somewhere in that almost unimaginable extent of time, life began on 



