150 THE MEANING OF EVOLUTION 



far, but must surely be measured in tens of millions 

 of years. 



A\'hen we attempt to study the past we find its vari- 

 ous epochs unequally clear to us. In human history 

 only quite modern times are absolutely clear. The 

 history of the Middle Ages is distinct enough for us 

 to build for ourselves a picture of the time with rea- 

 sonable hope of gaining a correct view of the state of 

 affairs. Back of this comes the long stretch of the 

 Dark Ages, in which here and there we have bright 

 spots, but it will perhaps long be impossible to portray 

 clearly the life of the people. Getting back to the 

 Romans, things once more become reasonably plain, 

 as is true also in the case of Greek history. Back of 

 this stretches the Egyptian with fair precision, and, 

 older than it, the Babylonian and Chaldean. But these 

 past three have not left nearly so definite an account 

 for us as did the later civilizations of Greece and 

 Rome. 



When we try to go back of these we must change 

 our method of study entirely. Writing is absent, and 

 all we know of earlier men must be inferred from a 

 few pictures that were daubed on the rocks or carved 

 in ivory or bone, from tools made of stone or bone, 

 from a few metal or stone ornaments, or from the 

 bones of the men themselves. Even so, the history 

 fades out without tellinc: us its own beciinninsis. It 



