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 conjecture what changes of structure would be favourable
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 favourable for their existence than the
present time. Whatever the causes may have been, we can see that certain
districts and times would have been much more favourable than others for
the development of so large a quadruped as the giraffe.
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