MULTIPLICATION OF THE HUMAN KACE. 487 



men of unusual mental activity leave no offspring. But 

 f'lcts of this kind admit of another interpretation. The re- 

 action of the brain on the body is so violent — the overtaxing 

 of the nervous system is so apt to prostrate the heart and 

 derange the digestion ; that the incapacities caused in these 

 cases, are probably often due more to constitutional dis- 

 turbance than to the direct deduction which excessive action 

 entails. Such instances harmonize with the hypothesis ; but 

 how far they yield it positive support we cannot say. 



§ 368. An objection must here be guarded against. It is 

 likely to be urged that since the civilized races are, on the 

 average, larger than many of the uncivilized races ; and since 

 they are also somewhat more complex as well as more active ; 

 they ought, in conformity with the alleged general law, to 

 be less prolific. There is, however, no evidence to prove that 

 they are so : on the whole, they seem rather the reverse. 



The reply is that were all other things equal, these 

 superior varieties of men should have inferior rates of in- 

 crease. But other things are not equal ; and it is to the 

 inequality of other things that this apparent anomaly is 

 attributable. Already we have seen how much more fertile 

 domesticated animals are than their wild kindred ; and the 

 causes of this greater fertility are also the causes of the 

 greater fertility, relative or absolute, which civilized men 

 exhibit when compared with savages. 



There is the difference in amount of food. Australians, 

 Fuegians, and sundry races that might be named as having 

 low rates of multiplication, are obviously underfed. The 

 sketches of natives contained in the volumes of Livingstone, 

 Baker, and others, yield clear proofs of the extreme 

 depletion common among the uncivilized. In 



quality as well as in quantity, their feeding is bad. Wild 

 fruits, insects, larvae, vermin, &c., which we refuse with 

 disgust, often enter largely into their dietary. Much of this 

 inferior food they eat uncooked ; and they have not out 



