THEORY OF NATURAL SELECTION. 199 



Mr. Mivart then asks (and this is his second objection), 

 if natural selection be so potent, and if high browsing be 

 so great an advantage, why has not any other hoofed quad- 

 ruped acquired a long neck and lofty stature, besides the 

 giraffe, and, in a lesser degree, the camel, guanaco, and 

 macrauchenia ? Or. again, why has not any member of the 

 group acquired a long proboscis ? With respect to South 

 Africa, which was formerly inhabited by numerous herds of 

 the giraffe, the answer is not difficult, and can best be given 

 by an illustration. In every meadow in England, in which 

 trees grow, we see the lower branches trimmed or planed to 

 an exact level by the browsing of the horses or cattle ; and 

 what advantage would it be, for instance, to sheep, if kept 

 there, to acquire slightly longer necks ? In every district 

 some one kind of animal will almost certainly be able to 

 browse higher than the others ; and it is almost equally 

 certain that this one kind alone could have its neck elon- 

 gated for this purpose, through natural selection and the 

 effects of increased use. In South Africa the competition 

 for browsing on the higher branches of the acacias and other 

 trees must be between giraffe and giraffe, and not with the 

 other ungulate animals. 



Why, in other quarters of the world, various animals 

 belonging to this same order have not acquired either an 

 elongated neck or a proboscis, cannot be distinctly answered; 

 but it is as unreasonable to expect a distinct answer to such 

 a question as why some event in the history of mankind did 

 not occur in one country while it did in another. We are 

 ignorant with respect to the conditions which determine the 

 numbers and range of each species, and we cannot even con- 

 jecture what changes of structure would be favorable to its 

 increase in some new country. We can, however, see in a 

 general manner that various causes might have interfered 

 with the development of a long neck or proboscis. To reach 

 the foliage at a considerable height (without climbing, for 

 which hoofed animals are singularly ill-constructed) implies 

 greatly increased bulk of body ; and we know that some 

 areas support singularly few large quadrupeds, for instance 

 South America, though it is so luxuriant, while South Africa 

 abounds with them to an unparalleled degree. Why this 

 should be so, we do not know ; nor why the later tertiary 

 periods should have been much more favorable for their 

 existence than the present time. Whatever the causes may 

 &ave beem, we can see that certain districts and times woullj 



