382 EVOLUTION OF PHYSICAL CHAKACTERS 



varieties, and a turning of lethal selection to the building up of 

 immunity against disease. 



7. There are one or two other points connected with germinal 

 change about which a word may be said. Of the origin of 

 mutations we know nothing, but since in all probability the 

 ultimate cause of mutations may have to be sought in some 

 kind of environmental change, it should be borne in mind that, 

 as man is subject to an immense variety of environmental stimuli, 

 mutations may be more frequent in man than in any species 

 in a state of nature. It has been suggested that the germinal 

 constitution may be adversely affected by certain factors, especially 

 by the use of alcohol. Of this there is no certain evidence.^ It 

 has been supposed that there may be some connexion between 

 the difference in age of the parents on the one hand and the 

 germinal constitution of the offspring on the other. It has been 

 supposed, for instance, that the offspring are innately more 

 vigorous when the parents are at a certain age. So far as investiga- 

 tion has gone at present, it has not been established that there is 

 any such connexion — of sufficient importance at least to deserve 

 consideration here. In other words, the fact that among certain 

 races young men have wives of considerably greater age than 

 themselves and older men young wives, does not to any note- 

 worthy extent affect the germinal constitution of the race. Again 

 it has been stated that the first-born are innately inferior to the 

 later-born children.^ This conclusion has been criticized.^ As, 

 however, the preponderance of first-born children among the 

 offspring as a whole would not appear to be markedly greater 

 at any one period of history than at another, the inferiority of the 

 first-born, if it exists, would make no difference between men of 

 different races at the same or at different times. 



The correlation of characters one with another should not be 

 forgotten. The favouring of one character may involve the 

 favouring of quite other characters. Of this what was said regard- 

 ing the ductless glands is an example. It has been supposed that 

 liability to disease is correlated with pigmentation and that, 

 owing to selection through disease, a change in the average pig- 



1 An admirable summing up of what is known as to the effect of alcohol on the 

 germinal constitution will be found in Popenoe and Johnson, loc. cit., ch. ii. 



^ Pearson, ' Problem of Practical Eugenics ', Eugenics Laboratory Lecture Series, 

 No. 5. 



* Greenwood and Yule, J. R. S. S., vol. Ixxii, 1914. See Pearson's reply ' On the 

 Handicapping of the First- bom ', Eugenics Laboratory Lecture Series, No. 10. 3 



