MODERN EVOLUTION. 239 



if some one species had wings developed in a re- 

 markable manner in comparison with the other spe- 

 cies of the same genius." And when this exceptional 

 development of any part or organ occurs, we may 

 conclude that the modification has arisen since the 

 period when the several species branched off from 

 the common progenitor of the genus; and this period 

 will seldom be very remote, as species rarely endure 

 for more than one geological period. 



How completely this applies to man, the latest 

 product of organic evolution. The brain is that part 

 or organ in him which has been developed " in an 

 extraordinary degree, in comparison with the same 

 part " in other Primates, and which has become 

 highly variable. Whatever may have been the favour- 

 ing causes which secured his immediate progenitors 

 such modification of brain as advanced him in intel- 

 ligence over " allied species," the fact abides that 

 in this lies the explanation of their after-history; the 

 arrest of the one, the unlimited progress of the 

 other. Increasing intelligence at work through vast 

 periods of time originated and developed those social 

 conditions which alone made possible that progress 

 which, in its most advanced degree, but a small 

 proportion of the race has reached. For in this ques- 

 tion of mental differences the contrast is not be- 

 tween man and ape, but between man savage and 

 civilized; between the incapacity of the one to count 

 beyond his fingers, and the capacity of the other to 

 calculate an eclipse of the sun or a transit of Venus. 



