78 HOMOIOTHERMISM 



homes or customs, which are not part of the somatic 

 equipment of each individual, may be passed on from 

 generation to generation to a greater degree than among 

 short-lived animals. 



Long life and the ability to maintain a constant tem- 

 perature have given birds and mammals great advan- 

 tages over other animals. They live without any breaks 

 in their activities and thus have better opportunities for 

 gaining and profiting by experience. Continuity of liv- 

 ing at a constant temperature and a high rate of metabo- 

 lism have probably thus been the chief factors which 

 have made it possible for them to become wiser. 



