Chap. V. INTELLECTUAL FACULTIES. 159 



The lower animals, on the other hand, must have 

 their bodily structure modified in order to survive under 

 greatly changed conditions. They must be rendered 

 stronger, or acquire more effective teeth or claws, in 

 order to defend themselves from new enemies ; or they 

 must be reduced in size so as to escape detection and 

 danger. When they migrate into a colder climate they 

 must become clothed with thicker fur, or have their 

 constitutions altered. If they fail to be thus modified, 

 they will cease to exist. 



The case, however, is widely different, as Mr. Wal- 

 lace has with justice insisted, in relation to the intel- 

 lectual and moral faculties of man. These faculties are 

 variable ; and we have every reason to believe that the 

 variations tend to be inherited. Therefore, if they were 

 formerly of high importance to primeval man and to 

 his ape-like progenitors, they would have been per- 

 fected or advanced through natural selection. Of the 

 high importance of the intellectual faculties there can 

 be no doubt, for man mainly owes to them his pre- 

 eminent position in the world. We can see that, in 

 the rudest state of society, the individuals who were the 

 most sagacious, who invented and used the best weapons 

 or traps, and who were best able to defend themselves, 

 would rear the greatest number of offspring. The tribes 

 which included the largest number of men thus endowed 

 would increase in number and supplant other tribes. 

 Numbers depend primarily on the means of subsistence, 

 and this, partly on the physical nature of the country, 

 but in a much higher degree on the arts which are there 

 practised. As a tribe increases and is victorious, it is 

 often still further increased by the absorption of other 

 tribes. 2 The stature and strength of the men of a tribe 



2 After a time the members or tribes which are absorbed into another 

 tribe assume, as Mr. Maine remarks (' Ancient Law,' 1SG1, p. 131), that 

 they are the co-descendants of the same ancestors. 



