| LIFE. | Archæan Time. | The Beginning. Includes the long lapse of time when the globe could not support life, but towards its close faint traces of life, both animal and vegetable appeared. | |
| Paleozoic Time. | The Period of Old Life Forms. Forests of flowerless trees; but pines grew in the coal measures. Animal life largely invertebrate; but amphibians and reptiles among the vertebrate appear at the close. | ||
| Mesozoic Time. | The Period of Middle Life Forms. Flowering trees increasing in number and importance. Deciduous trees make their appearance. Animal life largely reptilian. The class Mammalia represented by marsupials. | ||
| Cenozoic Time. | Tertiary, or Age of Mammals. | Eocene. Miocene. Pliocene. | |
| Quaternary, or Age of Man. | Glacial or Pleistocene. Recent. | ||
At the close of the Mesozoic time, great elevations of land took place in both America and Europe, especially in the northern portions.21 This could not fail to have a great effect on life, both animal and vegetable.
During the Eocene, or first division of the Tertiary Age, we have simply to note the steady progress of life. There were forests of species of oaks, poplars, maples, hickories, and other common trees, and others now found only in tropical regions. Palm trees were growing in the upper Missouri region of the United States. And England was decidedly a land of Palms, as no less than thirteen species are known to have been growing there. Cypresses, yews, and pines graced the scene.22 Our special interest centers, however, in the mammals of this epoch.
In the preceding epoch marsupials only were represented. But in beds of the middle and closing portions of the Eocene period we meet with a sudden increase of Mammalian life. Whale-like animals were especially abundant in the seas; and on our Western plains were animals like the tapirs of India, and rhinoceros-like animals as large as elephants23 but having no trunks, and diminutive little animals not larger than foxes, from which have come our horses. Europe also had a varied Mammalian fauna. There were numerous hog-like animals. Animals, like the tapirs of tropical Asia and America, wandered in the forests and on the banks of the rivers. Herds of horse-like animals, about the size of Shetland ponies, fed on the meadows.24 Animals that chew the cud were present, or at least had near representatives.25
Among the flesh-eating animals were creatures resembling foxes, wolverines, and hyenas.26 This shows what a great advance had been made. But, besides all these, we are here presented with representatives of the order of Quadrumana, or four-handed animals. Several genera of lemurs are found in both America and Europe.
Now the Quadrumana are the order below man. Therefore it seems that in the Eocene period, all the forms of life below man are represented. The time seems to be at hand when we can look, with some confidence, for traces of the presence of man himself. We must therefore be more cautious in our investigations.
The epoch following on after the Eocene is designated as the Miocene. We must remember that, though recent in a geological sense, yet it is immensely remote when measured by the standard of years. We must inquire into all the surroundings of this far away time. The geographical features must have been widely different from the present.
In the first place, the elevation of land to the north must have been sufficient to have connected the land areas of the Northern Hemisphere—North America, with Asia27 and Greenland; and this latter country must have been united with Iceland, and, through the British Islands, with Europe. But, to compensate for this land mass to the north, large portions of Central and Southern Europe were beneath the waves.28 The proof of this extended mass of land is to be found in the wide distribution of similar animals and plants in the Miocene time. All the chief botanists are agreed that the north Polar region was the center from which plants peculiar to the Eocene and Miocene epochs spread into both Europe and America.29 We may mention that the famous big trees of California are simply remnants of a wide-spread growth of these trees in Miocene times. They can be found in a fossil state at various places in British America, in Greenland, and in Europe. They are supposed to have originated somewhere in the north, and spread by these land connections we have mentioned into both Europe and America. But this is not the only tree that grew in the Miocene forests of both continents. The magnolia, tulip-tree, and swamp cypress are other instances.30 Eleven species, growing in the Rocky Mountain regions in Rocene times, found their way to Europe in the Miocene times,31 driving before them the plants of a tropical growth that had hitherto flourished in England. Now this implies land connection between the two continents. Furthermore, animals both large and small are found common to the two countries.32 The climate over what is now the North Temperate Zone, and even further. north, must have been delightful. There is ample testimony to this effect in the rich vegetative remains over wide areas.