climate has changed radically since the death of the mammoths; and as the bodies of the animals were found not decomposed but well preserved in blocks of ice, the change in temperature must have followed their death very closely or even caused it.
There remains to be added that after storms in the Arctic, tusks of mammoths are washed up on the shores of arctic islands; this proves that a part of the land where the mammoths lived and were drowned is covered by the Arctic Ocean.
The Ice Age and the Antiquity of Man
The mammoth lived in the age of man. Man pictured it on the walls of caves; remains of men have repeatedly been found in Central Europe together with remains of mammoths; occasionally the settlements of the neolithic man of Europe are found strewn with the bones of mammoths.1
Man moved southward when Europe was covered with ice and returned when the ice retreated.
Historical man witnessed great variation in climate. The mammoth of Siberia, the meat of which is still fresh, is supposed to have been destroyed at
4 See G. F. Kunz, Ivory and the Elephant in Art, in Archaeology, and in Science (1916), p. 236.
1 In Predmost in Moravia a settlement has been excavated in which remnants of a human culture and remains of men were found together with skeletons of eight hundred to one thousand mammoths. Shoulder blades of mammoths were used in the construction of human graves.
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the end of the last glacial period, simultaneously with the mammoths of Europe and Alaska. If this is so, the Siberian mammoth was also the contemporary of a rather modern man. At a time when in Europe, close to the ice sheet, man was still in the later stages of neolithic culture, in the Near and Middle East—the region of the great cultures of antiquity—he may already have progressed well into the metal age. There exists no chronological table of neolithic culture because the art of writing was invented approximately at the advent of the copper—the early—
period of the Bronze Age. It is presumed that the neolithic man of Europe left pictures but no inscriptions, and consequently there are no means of determining the end of the Ice Age in terms of chronology.
Geologists have tried to find the time of the end of the last glacial period by measuring the detritus carried by rivers from the glaciers and the deposits of detritus in lakes. The quantity carried by the Rhone from the glaciers of the Alps and the amount on the bottom of the Lake of Geneva, through which the Rhone flows, were calculated, and from the figures obtained the time and velocity of the retreat of the glacial sheet of the last glacial period were estimated. According to the Swiss scholar Francois Forel, twelve thousand years have passed since the time the ice sheet of the last glacial period began to melt, an unexpectedly low figure, as it was thought that the ice age ended thirty to fifty thousand years ago.
Such calculations suffer from being only indirect evaluations; and since the velocity at which the glacial mud had been deposited in the lakes was not constant and the amount varied, the mud must have assembled on the bottom of a lake at a faster rate in the beginning when the glaciers were larger; and if the Ice Age terminated suddenly,'the deposition of detritus would have been much heavier at first, and there would be little analogy to the accumulation of detritus from the seasonal melting of snow in the Alps. Therefore, the time that has elapsed since the end of the last glacial period must have been even shorter than reckoned.
Geologists regard the Great Lakes of America as having been formed at the end of the Ice Age when the continental glacier retreated and the depressions freed from the glacier became lakes.
In
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the last two hundred years Niagara Falls has retreated from Lake Ontario toward Lake Erie at the rate of five feet annually, washing lown the rocks of the bed of the falls.2 If this process has been going m at the same rate since the end of the last glacial period, about seven thousand years were needed to move Niagara Falls from the mouth of the gorge at Queenston to its present position.
The assumption that the quantity of water moving through the gorge has been uniform since the robin-bobin
end of the Ice Age is the basis of this calculation, and therefore, it was concluded, seven thousand years may constitute "the maximum length of time since the birth of the falls." 3 In the beginning, when immense masses of water were released by the retreat of the continental glacier, the rate of movement of Niagara Falls must have been much more rapid; the time estimate "may need significant reduction," and is sometimes lowered to five thousand years.4 The erosion and sedimentation on the shores and the bottom of Lake Michigan also suggest a lapse of time counted in thousands, but not in tens of thousands, of years. Also the result of paleontological research in America carries evidence which constitutes "a guarantee that before the last period of glaciation, modern man, in the form of that highly developed race, the American Indian, was living on the eastern seaboard of North America" (A. Keith).5 It is assumed that with the advent of the last glacial period the Indians retreated southward, returning to the north when the ice uncovered the ground and when the Great Lakes emerged, the basin of the St. Lawrence was formed, and Niagara Falls began its retreat toward Lake Erie.
If the end of the last glacial period occurred only a few thousand years ago, in historical times or at a time when the art of writing may
2 The recession has been 5 feet per year since 1764; at present it is 2.3 feet on the sides of the horseshoe cataract, but substantially more in the center.
3 G. F. Wright, "The Date of the Glacial Period," The Ice Age in North America and Its Bearing upon the Antiquity of Man (5th ed., 1911).
4 Ibid., p. 539. Cf. also W. Upham in American Geologist, XXVIII, 243, and XXXVI, 28S. He dates the uprise of the St. Lawrence basin 6,000 to 7,000 years ago; the St. Lawrence must have been freed from ice before Niagara Falls could come into full action. Not dissimilar figures were obtained from the retreat of the Falls of St. Anthony on the Mississippi at Minneapolis.
5 Keith thinks that the development of the human skull went through a process of advance and retrogression during exceedingly long ages.
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have been already employed in the centers of ancient civilization, the records written in rocks by nature and the records written by man must give a coordinated picture. Let us, therefore, investigate the traditions and the literary records of ancient man, and compare them with the records of nature.
The World Ages
A conception of ages that were brought to their end by violent changes in nature is common all over the world. The number of ages differs from people to people and from tradition to tradition.
The difference depends on the number of catastrophes that the particular people retained in its memory, or on the way it reckoned the end of an age.
In the annals of ancient Etruria, according to Varro, were records of seven elapsed ages.
Censorinus, an author of the third Christian century and compiler of Varro, wrote that "men thought that different prodigies appeared by means of which the gods notified mortals at the end of each age. The Etruscans were versed in the science of the stars, and after having observed the prodigies with attention, they recorded these observations in their books."*
The Greeks had similar traditions. "There is a period," wrote Censorinus, "called 'the supreme year' by Aristotle, at the end of which the sun, moon, and all the planets return to their original position. This 'supreme year' has a great winter, called by the Greeks kata-klysmos, which means deluge, and a great summer, called by the Greeks ekpyrosis, or combustion of the world. The world, actually, seems to be inundated and burned alternately in each of these epochs."