^60:4.2 This period also witnesses the end of the continental drift and the building of the modern mountains of Urantia. But the pressure of the continental masses and the thwarted momentum of their agelong drift are not the exclusive influences in mountain building. The chief and underlying factor in determining the location of a mountain range is the pre-existent lowland, or trough, which has become filled up with the comparatively lighter deposits of the land erosion and marine drifts of the preceding ages. These lighter areas of land are sometimes 4,572 to 6,100 m thick; therefore, when the crust is subjected to pressure from any cause, these lighter areas are the first to crumple up, fold, and rise upward to afford compensatory adjustment for the contending and conflicting forces and pressures at work in the earth’s crust or underneath the crust. Sometimes these upthrusts of land occur without folding. But in connection with the rise of the Rocky Mountains, great folding and tilting occurred, coupled with enormous overthrusts of the various layers, both underground and at the surface.

^60:4.3 ¶ The oldest mountains of the world are located in Asia, Greenland, and northern Europe among those of the older east-west systems. The mid-age mountains are in the circumpacific group and in the second European east-west system, which was born at about the same time. This gigantic uprising is almost 16,000 km long, extending from Europe over into the West Indies land elevations. The youngest mountains are in the Rocky Mountain system, where, for ages, land elevations had occurred only to be successively covered by the sea, though some of the higher lands remained as islands. Subsequent to the formation of the mid-age mountains, a real mountain highland was elevated which was destined, subsequently, to be carved into the present Rocky Mountains by the combined artistry of nature’s elements.

^60:4.4 The present North American Rocky Mountain region is not the original elevation of land; that elevation had been long since leveled by erosion and then re-elevated. The present front range of mountains is what is left of the remains of the original range which was re-elevated. Pikes Peak and Longs Peak are outstanding examples of this mountain activity, extending over two or more generations of mountain lives. These two peaks held their heads above water during several of the preceding inundations.

^60:4.5 Biologically as well as geologically this was an eventful and active age on land and under water. Sea urchins increased while corals and crinoids decreased. The ammonites, of preponderant influence during a previous age, also rapidly declined. On land the fern forests were largely replaced by pine and other modern trees, including the gigantic redwoods. By the end of this period, while the placental mammal has not yet evolved, the biologic stage is fully set for the appearance, in a subsequent age, of the early ancestors of the future mammalian types.

^60:4.6 ¶ And thus ends a long era of world evolution, extending from the early appearance of land life down to the more recent times of the immediate ancestors of the human species and its collateral branches. This, the Cretaceous age, covers 50,000,000 years and brings to a close the premammalian era of land life, which extends over a period of 100,000,000 years and is known as the Mesozoic.

^60:4.7 [Presented by a Life Carrier of Nebadon assigned to Satania and now functioning on Urantia.]

PAPER № 61

THE MAMMALIAN ERA ON URANTIA

^61:0.1 The era of mammals extends from the times of the origin of placental mammals to the end of the ice age, covering a little less than 50,000,000 years.

^61:0.2 During this Cenozoic age the world’s landscape presented an attractive appearance — rolling hills, broad valleys, wide rivers, and great forests. Twice during this sector of time the Panama Isthmus went up and down; three times the Bering Strait land bridge did the same. The animal types were both many and varied. The trees swarmed with birds, and the whole world was an animal paradise, notwithstanding the incessant struggle of the evolving animal species for supremacy.

^61:0.3 The accumulated deposits of the five periods of this 50,000,000-year era contain the fossil records of the successive mammalian dynasties and lead right up through the times of the actual appearance of man himself.

1. THE NEW CONTINENTAL LAND STAGE

THE AGE OF EARLY MAMMALS

^61:1.1 50,000,000 years ago the land areas of the world were very generally above water or only slightly submerged. The formations and deposits of this period are both land and marine, but chiefly land. For a considerable time the land gradually rose but was simultaneously washed down to the lower levels and toward the seas.

^61:1.2 Early in this period and in North America the placental type of mammals suddenly appeared, and they constituted the most important evolutionary development up to this time. Previous orders of nonplacental mammals had existed, but this new type sprang directly and suddenly from the pre-existent reptilian ancestor whose descendants had persisted on down through the times of dinosaur decline. The father of the placental mammals was a small, highly active, carnivorous, springing type of dinosaur.

^61:1.3 Basic mammalian instincts began to be manifested in these primitive mammalian types. Mammals possess an immense survival advantage over all other forms of animal life in that they can:

^61:1.4 1. Bring forth relatively mature and well-developed offspring.

^61:1.5 2. Nourish, nurture, and protect their offspring with affectionate regard.

^61:1.6 3. Employ their superior brain power in self-perpetuation.

^61:1.7 4. Utilize increased agility in escaping from enemies.

^61:1.8 5. Apply superior intelligence to environmental adjustment and adaptation.

^61:1.9 ¶ 45,000,000 years ago the continental backbones were elevated in association with a very general sinking of the coast lines. Mammalian life was evolving rapidly. A small reptilian, egg-laying type of mammal flourished, and the ancestors of the later kangaroos roamed Australia. Soon there were small horses, fleet-footed rhinoceroses, tapirs with proboscises, primitive pigs, squirrels, lemurs, opossums, and several tribes of monkeylike animals. They were all small, primitive, and best suited to living among the forests of the mountain regions. A large ostrichlike land bird developed to a height of 10 m and laid an egg 22 by 33 cm. These were the ancestors of the later gigantic passenger birds that were so highly intelligent, and that onetime transported human beings through the air.

^61:1.10 The mammals of the early Cenozoic lived on land, under the water, in the air, and among the treetops. They had from 1 to 11 pairs of mammary glands, and all were covered with considerable hair. In common with the later appearing orders, they developed two successive sets of teeth and possessed large brains in comparison to body size. But among them all no modern forms existed.

^61:1.11 ¶ 40,000,000 years ago the land areas of the Northern Hemisphere began to elevate, and this was followed by new extensive land deposits and other terrestrial activities, including lava flows, warping, lake formation, and erosion.

^61:1.12 During the latter part of this epoch most of Europe was submerged. Following a slight land rise the continent was covered by lakes and bays. The Arctic Ocean, through the Ural depression, ran south to connect with the Mediterranean Sea as it was then expanded northward, the highlands of the Alps, Carpathians, Apennines, and Pyrenees being up above the water as islands of the sea. The Isthmus of Panama was up; the Atlantic and Pacific Oceans were separated. North America was connected with Asia by the Bering Strait land bridge and with Europe by way of Greenland and Iceland. The earth circuit of land in northern latitudes was broken only by the Ural Straits, which connected the arctic seas with the enlarged Mediterranean.