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Some Early Mammals and the Story of the Horse: Australia

SOME EARLY MAMMALS Thus, the Tapir from Sumatra, or Central and South America, is the nearest living relative of the Palæothere; while, if we go back still further into Jurassic times, we must fetch marsupials from Australia to match some of the little mammals whose jawbones are found in some of the deposits of that age. To the geologist and naturalist, South America and Australia are countries which have, as it were, lagged behind; for their faunas are not "up to date," as the saying is; and thereby hangs a long story-into which we must not be led now, and one which shows how closely the sciences of Geology, Natural History, and Geography are interwoven.

As already stated, Cuvier's great results in restoring Eocene animals were due, in a large measure, to the use he made of his principle of "correlation; " of which he writes: "I doubt whether I should ever have divined, if observation had not taught me, that the ruminant hoofed beasts should all have the cloven foot, and be the only beasts with horns on the frontal bone." 1 Again, it is found though no one knows why-that only those hoofed animals which have their hoofs in one or two pairs, have horns in one or two pairs on the frontal bones: whilst those with three hoofs, if they have horns at all, have either one or two placed one behind the other (example, the Indian rhinoceros with one horn and the African two-horned rhinoceros). There must be secret reasons for these curious facts-who shall win immortality by discovering them? Other relationships, such as that between teeth and hoofs, might be given; but the above example is sufficient for our present purpose (see p. 7). In dealing with this subject, however, it should be mentioned that Cuvier's law is not infallible, and does not always apply to some of the ancient and generalised types discovered since his day. 1 Ossemens Fossiles, tom. i. p. 184. (1834.) The great theory of Evolution was first dimly suggested by Greek philosophers, such as Anaximander (B.C. 610), who may have derived the idea from Egyptian, Babylonian, or Hindu sources; then revived, in a more scientific form, by Lamarck last century. Fifty-two years ago it was placed on a truly scientific basis by the illustrious Charles Darwin, and is now generally accepted by naturalists and palæontologists. Indeed, it is hard to be a paleontologist in these days without being also an evolutionist-so abundant is the evidence derived from a study of extinct animals. Year by year the evidence is accumulating, and many workers in various parts of the world are discovering long-lost types which appear to link together some of the branches of the great Tree of Life. Marsh and Cope in America; Owen, Huxley, and others in England; have all been directing our ideas in the same course. At Pikermi in Attica; in the far Western States in America; at Sansans, Allier, Lebéron and other localities in France, such great and important additions have been made of late to our knowledge, that it is now possible to make out certain lines of evolution in the Mammalia since their first important outburst at the beginning of the Tertiary period.

We now propose to trace, in the light of recent discoveries, the history of one important living group, as represented by the horse.

The series of fossil horses now known is so complete, that hardly a single important gap is left between the original fivetoed ancestor, and the horse of to-day, with only one toe to each foot! Here, then, we have the most perfect evidence of the evolution of an animal from distant ages in the earth's history that has ever been presented to the world! Professor Cope's SOME EARLY MAMMALS researches on the history of camels as illustrated from fossil remains have brought to light another line of evolution equally interesting if not quite so complete. According to the latter palæontologist, the very earliest ancestor of all the hoofed animals (and therefore of the horse) was the Eocene Phenacodus, with five toes. But this conclusion is not generally accepted now.