So we see that while the vegetable-feeding animals have three characters in common, namely, large flat grinders, a capacious stomach, and defensive weapons, their defences, on the other hand, may be of three different kinds, and they may depend upon horns, hoofs, or teeth for protection.
Now in the beginning, when we first meet with the milk-givers, these defences were not so complete in any of the vegetable-feeders as they are now. Of the elephants alone it may perhaps be said that they had large and formidable ancestors.[159] As to the rest, the huge hippopotamus and sharp-tusked boar were only represented by small animals;[160] and even later, when the hogs branched off in a line of their own, they had at first only ordinary teeth, which did not grow out as tusks.
So, too, the fierce horned rhinoceros had as an ancestor a hornless tapir-like creature,[161] and the graceful hoofed horse a little creature no larger than a fox, with five separate toes on his feet.[162] Lastly, all the horned animals which chew the cud,—oxen, buffaloes, antelopes, and deer,—were nowhere to be seen, and in their place were only some small elegant creatures without horns.[163]
It is only at a later period when the flesh-feeding animals grew strong and dangerous, and the vegetable-feeders had to struggle for their lives, that we begin to find the remains of hogs and hippopotamuses with tusks, rhinoceroses with nose-bones, and fleet horses which could take to their heels, or bite and kick their enemy to death; of stags with antlers, ever increasing in size; and of bulls and buffaloes, goats and antelopes, with true horns. For not only by this time were they persecuted by the flesh-feeders, but they themselves were becoming very numerous, and it was the strongest only that could secure feeding-grounds or carry off wives.
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It is very curious to see the different ways in which the three chief lines of vegetable-feeders secured these advantages to themselves. First, there were the hogs and hippopotamuses. The hogs did not grow to any enormous size, but their thick skins were a great protection to them, and their eye-teeth became their defence, growing out from the lower, and sometimes from both jaws into huge tusks; while their broad, round, flexible snouts served them to turn up the ground, and so get at roots and underground fruits such as other grass-feeding animals could not find; though at the same time they did not despise snakes or toads, and have become omnivorous animals. And so they have spread nearly all over the world; in Europe and Asia as wild hogs, and their wives the sows; one peculiar form, the Babirusa, being found only in Celebes; in Africa as large Wart-hogs, some as big as donkeys, with two pair of strong tusks curling out of the mouth; while in South America the family is represented by the small Peccaries, which travel about in herds, and have no tusks to show; but which, nevertheless, are bold and fearless, for they have within their lips short lancet-shaped tusks, which inflict fearful wounds. Only in North America, north of Texas, no wild creature of the hog family now lives, though in ancient times there were plenty of them.
Fig. 67.
The Babirusa; the double-tusked hog of Celebes.
Meanwhile the warmth-loving hippopotamuses, the hog’s nearest relations, with huge grinding teeth behind, sharp front teeth, and tusks within their lips, took to a water-life in the Old World.[164] When we look at their immensely powerful bodies, and their short stout legs with four strong hoof-covered toes, and learn how rapidly they can gallop on land, and how furiously they charge an enemy in the water, snapping their great jaws which will kill a large animal at one crunch, we do not wonder that they can hold their own, especially as they always live in herds. Yet large and powerful as they are, they have not spread far over the earth, for though in past ages the hippopotamus swam in the river Thames, and grazed and left his bones in the ground upon which London streets now stand, yet after a time they crept down to warm Africa, where they may now be seen lazily basking on the surface of the Nile or of the river Zambesi by day, and making tracks by night into the swamps and jungle to feed on the coarse rank grass. They are well fitted for their life, for their thick naked skin, with pores which give out a fatty oil, keeps them from chill in the water; their eyes are set well back on their heads, so that as they float deep they can still look around, and the slits of their nose, and the openings of their ears, can both be closed and made water-tight when they dive, while their slow breathing enables them to remain a long while under water.