Evidence from Experiments 91 



§10. Experimental Evidence. 



The story of domestication and cultivation is a long 

 record of experiments in evolution. There are over 

 two hundred well-marked breeds of domestic pigeon, 

 but all have been derived under man's care from the 

 blue rock-dove, Columba livia. Similarly there is 

 very strong evidence that the multitudinous breeds 

 of poultry (see Figure 13) are descended from the 

 jungle fowl, Gallus bankiva, still found wild in some 

 parts of India and Malay. The origins of most of 

 our cultivated plants are unknown, but the evidence 

 is strong for tracing most of the wheats to the wild 

 wheat still growing on Mount Hermon, and for trac- 

 ing the cauliflower, broccoli, Brussels sprouts, curly 

 greens, and the like to the Wild Cabbage that grows 

 by the shore. And everyone knows how the aristocrats 

 of the orchard owe their origin to the plebeian crab- 

 apple of the wayside. Darwin's question was, If Man 

 has been able to fix and accentuate this and that 

 variety in a comparatively short time, what may not 

 Nature have accomplished in a very long time ? 



There is suggestiveness also in what Man has been 

 able to do within recent years by using the Mendelian 

 clue in his practical transformism. He has been able, 

 so to speak, to pick out desirable characters from one 

 breed of animals or race of plants, and assemble them 

 again in another which has some good points of its 

 own. Very interesting also are those few cases, such 

 as Professor Tower's experiments with potato-beetles, 

 where man has been able to provoke heritable changes 

 by some deeply saturating environmental change. In 



