Page:Popular Science Monthly Volume 34.djvu/209

Rh remain in this respect on the lowest mammalian level. Their teeth approximate rather to the type which occurs in horses and some other outlying ungulate groups than to the type which occurs in the true ruminants. They have always canines in both jaws; but these canines are not lengthened out into regular tusks, nor do they serve to any noticeable extent as weapons of warfare. In short, the camels by many points of their structure point back to a time when the ancestors of the ruminants had not diverged at all widely from the ancestors of the horse, the pig, or the hippopotamus, and they still retain in many particulars the early "generalized," or rather unspecialized, type of the common progenitor of the entire group.

The llamas and alpacas may be looked upon as the best living representatives of the camel tribe in its primitive state, before it had begun specially to assume its camel-stage. They do not possess the adaptive peculiarities which fit the camel for its desert existence; and, on the other hand, they exhibit to the full that awkward, ungainly, misshapen type which so often betrays Nature's first rough draught of an evolving order. They are, as it were, the sketchy outline only of the perfected ruminants. Compare for a moment the ugly, shambling, ungraceful alpaca with the red deer, flying over the open Scotch moorland; the gazelle, springing lightly along the Syrian plains; the antelope, careering across the South African veldt; or the chamois, leaping from crag to crag among the frozen Alps, and you will see at once what is meant by the difference between a specialized and a generalized type—the difference between Nature's early attempts in a given line, and her fully evolved and carefully molded final product.

The antelopes and deer, with their various allies, such as the gnu, the eland, the ibex, the buffalo, the bison, the sheep, the bighorn, and the musk-ox, represent for us the developed ruminant types, produced by fierce competition in the struggle for life in the great continents. Their fleetness of foot, their exquisite horns, their agility, their grace of movement, all depend upon the existence in their native countries of highly evolved beasts of prey, from whose fierce attacks they have had to save themselves by speed and acuteness. To the same cause they owe also the keenness of their senses, the slimness of their legs, and to some extent also the elegance and beauty of their entire bodies. The smaller kinds, like the gazelles, are remarkable for their vigilance, their timidity, and their alertness, the hereditary result of ages spent in avoiding the attacks of predatory enemies. Natural selection, in short, has given to the advanced ruminants generally their distinctive rapidity, lightness, and beauty of shape. To sexual selection, on the other hand, they owe their twisted horns or branching antlers, their dappled coats and exquisite markings,