Now we have a good knowledge of man as he was in the later stage of the Ice-Age at least a million years later and may thus institute a useful comparison and form some idea of the advance made. In the later stages of the Pleistocene a race of men lived in Europe of whom we have a number of skulls and skeletons, besides vast numbers of stone implements.
They never made fire, and, like the other surviving fragments of early humanity, they had no tribal organisation, and no ideas of religion or morality. The first effect of the Ice-Age on this primitive humanity would be to lead to a beginning of the development of racial characters.
Europe and America were ushering in the great Ice-Age, which was to bury five or six million square miles of their territory under a thick mantle of ice. Such is the general outline of the story of the Tertiary Era.
There are a few works still in circulation in which popular writers, relying on the obstinacy of a few older geologists, speak lightly of the "nightmare" of the Ice-Age. But the age has gone by in which it could seriously be suggested that the boulders strewn along the east of Scotland fragments of rock whose home we must seek in Scandinavia were brought by the vikings as ballast for their ships.
First, to the southward, come the mountain ranges passing eastwards into high plateau. Then, north of this line, from the Lower Danube, as far as China, stretches a belt of grassland or steppe-country at a lower level, a belt which during the milder periods of the ice-age and immediately after it must have reached as far as the Atlantic.
The great lakes of North America are permanent memorials of its Ice-Age, and over more than half the country we trace the imprint and the relics of the sheet. South America, Australia, Tasmania, and New Zealand had their glaciated areas. North Asia was largely glaciated, but the range of the ice-sheet is not yet determined in that continent.
The suggestion that the disk of the sun is appreciably smaller since Tertiary days is absurd; and the idea that the earth has only recently ceased to allow its internal heat to leak through the crust is hardly more plausible. The cause remains to be discovered. We turn now to consider the effect of the great Ice-Age, and the relation of man to it.
In other words, if we suppose that the axis of the earth does not consistently point in one direction that the great ball does not always present the same average angle in relation to the sun the poles will not always be where they are at present, and the Pleistocene Ice-Age may represent a time when the north pole was in the latitude of North Europe and North America.
However that may be, the Ice-Age would restrict all the Primates to the south. It will be seen, on a glance at the map, that a line of ice-clad mountains would set a stern barrier to man's advance in the early Pleistocene, from the Pyrenees to the Himalaya, if not to the Pacific. He therefore spread westward and southward.
It would therefore seem that the precursors of man made singularly little, if any, progress during the vast span of time between the Miocene and the Ice-Age, and that then something occurred which quickened the face of human evolution.