THE HEREDITARY BASIS 21 



the case might be different. The latter variety might not yield 

 more than a fourth of the former in either of the fields. In this 

 instance the choice of the best seed would be more important than 

 the choice of the best field. 



When we compare the influence of heredity and environment 

 it is necessary to state what particular hereditary conditions we 

 are comparing with what given range of environmental conditions. 

 We then have a soluble problem, at least theoretically. We might 

 make a rough estimate of the relative importance of the heredi- 

 tary conditions that are commonly found within the limits of the 

 species or variety with the conditions that are produced by the 

 variations of environment to which the species is commonly ex- 

 posed. Leaving out of account the variations in heredity that 

 might occur and taking the average of such variations as are 

 actually met with, and leaving out of account what environmental 

 conditions might accomplish and considering in general only what 

 is actually done, we may obtain results that can be compared. 

 We might find our species to be remarkably uniform in its heredi- 

 tary constitution, and that the bulk of the diversity within it 

 could be attributed to the effect of external conditions. On 

 the other hand, the species might possess much hereditary 

 variability like the mixed breeds of many of our domestic plants 

 and animals in which the differences of innate constitution 

 are much more conspicuous than those produced by the 

 environment. 



Homo sapiens, the species in which we are particularly inter- 

 ested in the present connection, contains a high degree of heredi- 

 tary diversity. Not only does each of the major divisions of the 

 species (if we may be permitted to group all mankind into one 

 species) contain numerous minor groups which are commonly 

 further subdivided, but most peoples, especially among civilized 

 nations, represent racial mixtures of many different stocks. A 

 little observation of the multitudes we encounter in going along a 

 street cannot fail to impress one with the heterogeneity of his 

 fellow creatures, and it does not require extensive dealings with 

 our kind to convince one that they are as diverse in mental 



