MAN AS A MAKER OF NEW PLANTS — ANDERSON 477 



Here is a field in which we could very rapidly get down to some of 

 the basic principles concerning closed versus open habitats. In my 

 opinion, the degree to which such associations as the California chap- 

 arral are manmade is a better subject for study than for debate. They 

 have certainly been greatly affected by man. To learn to what degree, 

 I should prefer to look for more facts rather than to listen to more 

 opinions. 



Even among biologists there has been a strong tendency to avoid 

 such problems — to study the plants and plant association of mountain- 

 tops and jungles rather than those of dooryards and gardens, to think 

 of plant and animal communities as they must have been in some bliss- 

 fully innocent era before the advent of man. It seems to me far 

 healthier and far more logical to accept man as a part of nature, to 

 concentrate one's attention as a naturalist on man's activities, since he 

 is the one species in the world we most nearly understand. It is be- 

 cause we know from inside ourselves the problems in which man is 

 deeply involved that we appreciate their bewildering complexity; 

 experiments with laboratory insects would not seem so beautifully 

 simple if we knew as much about them as we do about man. The popu- 

 lation genetics of garbage-pail flies (Dobzhansky, 1949) would appear 

 more complex if we understood from within what it is like to be a 

 Drosophila. The apparently standardized environment of flour in a 

 bottle (Park, 1938) would not seem undifferentiated to any investi- 

 gator who had once been a flour beetle and who knew at firsthand the 

 complexities of flour-beetle existence. Imagine a nonhuman investi- 

 gator of human populations recently arrived from Mars. What could 

 he understand of the relationships of Catholics and Protestants ? How 

 long would it take him to discover that, though most of the shortest 

 girls in New York City get married, the very tallest seldom do ? Hav- 

 ing discovered this phenomenon, how much longer would it take him 

 to understand it ? When we attempt to work with laboratory insects, 

 our ignorance of their social complexities makes them seem far sim- 

 pler material than they really are. 



I must confess that when, from being a student of variation in 

 natural populations, I was of necessity led to being a student of man's 

 upsetting effects on his environment, my own thinking was too much 

 colored by this attitude. Only gradually did I come to realize that, 

 though man is now the world's great upsetter, he is not the first. 

 There were others before him, and they played a similar role in evolu- 

 tion. Stebbins and I have recently suggested (1954) that the great 

 bursts of evolutionary activity in the past, the times of adaptive radia- 

 tion, were caused by such upsets. The formation de novo of a great 

 fresh-water lake such as Lake Baikal produced a new and open habitat 

 in which the organisms from various river systems could meet and 



