The hippopotamus (H. major) is a good one to start with, for Flower and Lydekker[83] say that it "cannot be specifically distinguished from H. amphibius" of Africa. This gigantic brute used to live in the rivers of England and Western Europe. The text-books generally say in "Pliocene times," because, I suppose, no one has the courage to suggest that it lived under the ice of the "Glacial period." We are always pointed to the wool on the rhinoceros and the mammoth as indicating a somewhat cool climate, but the well known amphibious habits of the hippopotamus cannot be so easily disposed of. But if, as I believe, this world never saw a foot of ice at the sea level till the end of the "Pleistocene period," to speak after the current manner, the problem becomes very simple. In that case the time of the Hippopotamus in England was neither earlier nor later than that of the palms and acacias of the "early" Tertiary or Mesozoic rocks, or than that of the mammoth, lion, and hyena of the Pleistocene. There is as we now know absolutely nothing but an out-of-date hypothesis to indicate that they did not all live there together. We may, if we choose, try to dovetail those conditions into the present on the basis of uniformity and slow secular change, by assuming a few million years for the process, but there is neither a particle of evidence nor of probability that the hippopotamus was not contemporary alike with the palms of the Eocene and the elephants and lions of the post-Tertiary.
As for the mammoth itself, which Flower and Lydekker have intimated may turn out identical with E. Columbi and E. armeniacus, and thus the direct ancestor of the modern Asiatic elephant (E. indicus), some have argued that its average size was not greater than that of the existing species of India and Africa. But Nicholson says that it was:
"... considerably larger than the largest of living elephants, the skeleton being over sixteen feet in length, exclusive of the tusks, and over nine feet in height."[84]
Dana is equally positive:
"The species was over twice the weight of the largest modern elephant, and nearly a third taller."[85]
The upper incisors or tusks were very much longer than in the modern species, being from ten to twelve feet long, and sometimes curved up and back so as to form an almost complete circle. As these tusks continue to grow throughout life, their enormous length is, I take it, a proof of much greater longevity and thus of greater vitality than in the cases of the modern species. The latter is simply a degenerate.
And so I might go on with the Edentates, the Ungulates, the Rodents, the Carnivores, etc., for the same thing must be said of all.
As Sir William Dawson[86] remarks:
"Nothing is more evident in the history of fossil animals and plants of past geological ages than that persistence or degeneracy are the rule rather than the exception.... We may almost say that all things left to themselves tend to degenerate, and only a new breathing of the Almighty Spirit can start them again on the path of advancement."
In spite of the long popular views of Cuvier, every modern scientist admits that the great lion and hyena of the Pleistocene are identical with the living species of Africa. Many say the same thing of the fossil bear as compared with the modern brown bear and the grizzly, though, as Dana remarks of all three, lion, hyena, and bear, "these modern kinds are dwarfs in comparison."