428 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1930 



agriculture as it becomes more intense. The more successful and pro- 

 lific an insect injurious to agriculture is the more certainly will it 

 arouse man's destructive energies and the greater the certainty that 

 the all too favorable mutation that is the cause of its success will be 

 the cause of its elimination in whole, or part. 



But mutations of a still more dangerous sort are threatening man- 

 kind, mutations in the world of organisms that live as parasites on 

 the human protoplasm. With the more conspicuous of these para- 

 sites, external and internal, man has learned to cope. One by one the 

 pathogenic bacterial diseases are being eliminated or reduced in fre- 

 quency. But now we face still smaller parasitic particles, the filtra- 

 bie viruses which are, at present, practically inaccessible to man. 

 There seems to be reason to conclude that they are mutating also, 

 and perhaps rapidly. The waves of influenza epidemics that pass 

 round the world in periodic fashion assume slightly different aspects, 

 show somewhat different symptoms, in successive visits. Those who 

 are resistant to the one visitation may show slight resistance to the 

 next. The selections of the past have left the stocks of the more 

 crowded continental areas a hardy resistant people, far more so than 

 the peoples of distant oceanic islands that had not undergone selec- 

 tion for resistance to the ultra microscopic parasites. When one con- 

 templates the high mortality of the influenza epidemic of 1918 one 

 realizes that notwithstanding this high resistance it is quite within 

 the range of possibility that at some future time a mutation shall 

 arise in these viruses such that no human protoplasm is protected 

 against it or can protect itself against it. Then our boasted sky- 

 scrapers might become inhabited by bats and the safe deposit vaults 

 of our cities become the caves of wild animals. 



Whether or not this will occur in the future, the possibility brings 

 home a realization of the fact that man is not merely looking on the 

 process of evolution taking place around him but, as an organism, 

 he is a part of that evolution ; he is acting upon other organisms and 

 being acted upon by them as well as by the inorganic world in which 

 he lives. He is attempting a mastery of that world; and, indeed, 

 upon such mastery his fate may depend. His ability to master that 

 world depends upon his superior gifts of intelligence to see relations 

 and to idealize new ones. How much farther man can go in this 

 direction depends upon the capacity for development of the intelli- 

 gence. There are those who warn us that we are approaching the 

 limit and must sometime in the future wait for further human evolu- 

 tion to make further fundamental progress. To wait until nature 

 affords the desired mutation may mean indefinite postponement. Can 

 not man himself control his evolution ? Two methods are open ; one 

 the production of new and better combinations of traits by appropri- 

 ate matings. This is the method of the applied geneticist interested 



