SIXTH STAGE OF THE HISTORY. 



Tumping shrew of East Africa (Petrodromus tetradadylus) . An ancestral and probably not 

 ■* SmSar form of this insectivore is to be looked upon as representmg "^^"^ ancestors in 

 the Eocene period or earlier-a period which is to be dated one or perhaps several millions 

 of year' ago At this time man^s ancestors "lived essentially in an atmosphere of odo s■ 

 ?he sen^se of 'smell was the only one well developed. When they took to an arboreal Me, 

 th-v emancipated themselves from the dominance of this sense of smell, and thus, Dr 

 SmfthThiS started oTthe course which finally led to the evolution of man. Photograph 

 fr-im the Rrooklvn Institute of Arts and Sciences. 

 That trop Si Afrka mav have been the region where man's direct ancestors developed, was 

 sueeested by Darwtn and Dr. Smith looks with favor on the suggestion. Ancestors who 

 dkf not progress w^" fell bv the wayside, are still there, he points out. It may be sup- 

 poLd that they found thei? environment perfectly congenial, had no reason to change 

 ft Ind so stayed where they are and thus lost the impetus to evolution which a change of 

 envSonr^ent Wd have given. Man's direct ancestors, for some reason, left their homes 

 and branched out into nel fields, where variation and natural selection had a chance to 

 accelerate their development. (Fig. 5.) 



387 



