^61:5.2 Simultaneously with these land elevations the ocean currents shifted, and the seasonal winds changed their direction. These conditions eventually produced an almost constant precipitation of moisture from the movement of the heavily saturated atmosphere over the northern highlands. Snow began to fall on these elevated and therefore cool regions, and it continued to fall until it had attained a depth of 6 km. The areas of the greatest depth of snow, together with altitude, determined the central points of subsequent glacial pressure flows. And the ice age persisted just as long as this excessive precipitation continued to cover these northern highlands with this enormous mantle of snow, which soon metamorphosed into solid but creeping ice.

^61:5.3 The great ice sheets of this period were all located on elevated highlands, not in mountainous regions where they are found today. 50% of the glacial ice was in North America, 25% in Eurasia, and 25% elsewhere, chiefly in Antarctica. Africa was little affected by the ice, but Australia was almost covered with the antarctic ice blanket.

^61:5.4 The northern regions of this world have experienced six separate and distinct ice invasions, although there were scores of advances and recessions associated with the activity of each individual ice sheet. The ice in North America collected in two and, later, three centres. Greenland was covered, and Iceland was completely buried beneath the ice flow. In Europe the ice at various times covered the British Isles excepting the coast of southern England, and it overspread western Europe down to France.

^61:5.5 ¶ 2,000,000 years ago the first North American glacier started its southern advance. The ice age was now in the making, and this glacier consumed nearly 1,000,000 years in its advance from, and retreat back toward, the northern pressure centres. The central ice sheet extended south as far as Kansas; the eastern and western ice centres were not then so extensive.

^61:5.6 ¶ 1,500,000 years ago the first great glacier was retreating northward. In the meantime, enormous quantities of snow had been falling on Greenland and on the north-eastern part of North America, and ere long this eastern ice mass began to flow southward. This was the second invasion of the ice.

^61:5.7 These first two ice invasions were not extensive in Eurasia. During these early epochs of the ice age North America was overrun with mastodons, woolly mammoths, horses, camels, deer, musk oxen, bison, ground sloths, giant beavers, sabre-toothed tigers, sloths as large as elephants, and many groups of the cat and dog families. But from this time forward they were rapidly reduced in numbers by the increasing cold of the glacial period. Toward the close of the ice age the majority of these animal species were extinct in North America.

^61:5.8 Away from the ice the land and water life of the world was little changed. Between the ice invasions the climate was about as mild as at present, perhaps a little warmer. The glaciers were, after all, local phenomena, though they spread out to cover enormous areas. The coastwise climate varied greatly between the times of glacial inaction and those times when enormous icebergs were sliding off the coast of Maine into the Atlantic, slipping out through Puget Sound into the Pacific, and thundering down Norwegian fiords into the North Sea.

6. PRIMITIVE MAN IN THE ICE AGE

^61:6.1 The great event of this glacial period was the evolution of primitive man. Slightly to the west of India, on land now under water and among the offspring of Asiatic migrants of the older North American lemur types, the dawn mammals suddenly appeared. These small animals walked mostly on their hind legs, and they possessed large brains in proportion to their size and in comparison with the brains of other animals. In the 70^th generation of this order of life a new and higher group of animals suddenly differentiated. These new mid-mammals — almost twice the size and height of their ancestors and possessing proportionately increased brain power — had only well established themselves when the Primates, the third vital mutation, suddenly appeared. (At this same time, a retrograde development within the mid-mammal stock gave origin to the simian ancestry; and from that day to this the human branch has gone forward by progressive evolution, while the simian tribes have remained stationary or have actually retrogressed.)

^61:6.2 ¶ 1,000,000 years ago Urantia was registered as an inhabited world. A mutation within the stock of the progressing Primates suddenly produced two primitive human beings, the actual ancestors of mankind.

^61:6.3 This event occurred at about the time of the beginning of the third glacial advance; thus it may be seen that your early ancestors were born and bred in a stimulating, invigorating, and difficult environment. And the sole survivors of these Urantia aborigines, the Eskimos, even now prefer to dwell in frigid northern climes.

^61:6.4 ¶ Human beings were not present in the Western Hemisphere until near the close of the ice age. But during the interglacial epochs they passed westward around the Mediterranean and soon overran the continent of Europe. In the caves of western Europe may be found human bones mingled with the remains of both tropic and arctic animals, testifying that man lived in these regions throughout the later epochs of the advancing and retreating glaciers.

7. THE CONTINUING ICE AGE

^61:7.1 Throughout the glacial period other activities were in progress, but the action of the ice overshadows all other phenomena in the northern latitudes. No other terrestrial activity leaves such characteristic evidence on the topography. The distinctive boulders and surface cleavages, such as potholes, lakes, displaced stone, and rock flour, are to be found in connection with no other phenomenon in nature. The ice is also responsible for those gentle swells, or surface undulations, known as drumlins. And a glacier, as it advances, displaces rivers and changes the whole face of the earth. Glaciers alone leave behind them those telltale drifts — the ground, lateral, and terminal moraines. These drifts, particularly the ground moraines, extend from the eastern seaboard north and westward in North America and are found in Europe and Siberia.

^61:7.2 ¶ 750,000 years ago the 4^th ice sheet, a union of the North American central and eastern ice fields, was well on its way south; at its height it reached to southern Illinois, displacing the Mississippi River 80 km to the west, and in the east it extended as far south as the Ohio River and central Pennsylvania.

^61:7.3 In Asia the Siberian ice sheet made its southernmost invasion, while in Europe the advancing ice stopped just short of the mountain barrier of the Alps.

^61:7.4 ¶ 500,000 years ago, during the fifth advance of the ice, a new development accelerated the course of human evolution. Suddenly and in one generation the six coloured races mutated from the aboriginal human stock. This is a doubly important date since it also marks the arrival of the Planetary Prince.

^61:7.5 In North America the advancing 5^th glacier consisted of a combined invasion by all three ice centres. The eastern lobe, however, extended only a short distance below the St. Lawrence valley, and the western ice sheet made little southern advance. But the central lobe reached south to cover most of the State of Iowa. In Europe this invasion of the ice was not so extensive as the preceding one.