248 READINGS IN BIOLOGICAL SCIENCE 



We are told that we can not change human nature. But human nature can 

 change. It has changed. We are what we are because it has. There is no 

 good reason to suppose that it has ceased changing. But the process is 

 extremely slow. Further, whatever may be said of human nature, human 

 behavior can be changed, both in the individual and in the mass, and it is 

 behavior that counts. Recent events in Germany may not be proof of any 

 change in the human nature of the Germans; but they certainly bear wit- 

 ness to a change in German behavior; and it is German behavior that the 

 rest of the world has to deal with. It is equally possible to shape human be- 

 havior to good ends. 



IV 



Organisms must adapt themselves to their environment as the very condi- 

 tion of survival. If a satisfactory adjustment has been achieved and then 

 the environment changes, a new adjustment must be effected; and that is 

 always difficult. The course of geological history is strewn with the relics 

 of species that, faihng in adjustment, perished. The application of this 

 principle to man is this: man's body and mind reached its distinctly hu- 

 man state in one type of environment, and he has lived on into a radically 

 different type, which he has himself created, and he is having tremendous 

 difficulty in making the necessary adjustment. 



The environment of early man was that of forest, or forest and plains, 

 suited to hunting; or, if he was near the sea, to hunting and fishing. It was 

 an active life in the open. He needed neither golf course nor gymnasium. 

 He got his food from plants that grew wild, or from animals of the chase; 

 at any odd time, not thrice daily o' the clock. It was one continuous strug- 

 gle against cold and hunger. Eternal watchfulness was necessary that he 

 get the animal before the animal got him, for both were out for a meal. 

 Strength of limb, keenness of eye and ear, accurate knowledge in a narrow 

 field counted for more than familarity with Plato or the calculus would 

 have done. On them hung the issues of life and death. Dense population 

 was impossible; there was not food enough. If population crowded on 

 food supply, then war, starvation or infanticide kept it down. It was a 

 life close to elemental nature, a life in which every normal adult could and 

 did share somewhat equally, had his chance, and was on the whole equal 

 to the situation. 



All that is a matter of far away and long ago. Some thirty thousand 

 years separate us from Cro-Magnon man. Two great environmental 

 changes have taken place. The first, to a settled agriculture, we see already 

 accomplished at the beginning of recorded history, some six or seven thou- 

 sand years ago. Man at that time possessed domestic animals and cultivated 

 grains; and on this basis he had established permanent agriculture on the 

 rich, level, well-watered flood-plains of the old world. This permitted the 

 accumulation of wealth, the growth of dense population, commerce by 



