Chapter I
PREHISTORIC MAN COMES TO NORTH AMERICA
Archeological studies of human remains from all over the world have shown beyond serious question that man originated in the Eastern Hemisphere about a million years ago. Meager remnants of prehistoric skeletons of man and his tools, hearths, and debris heaps have been found in deposits of late Cenozoic time, Chapter Five of earth’s history. This late Cenozoic period starting about a million years ago is called the Pleistocene or Ice Age. These discoveries show the orderly processes of survival of the fittest and of evolution developing successive generations of man with refined physical and mental qualities, ultimately producing modern man.
During the Ice Age there were four separate times during which ice formation on all continents of the earth increased tremendously. Just what caused changes in climate to make this possible is not definitely known. Slight changes in amount of carbon dioxide in the air, which could have been affected by the amount of volcanic activity or by major changes in the amount of plant life in existence, may have affected the climate. Slight variations in the orbit of the earth in its course around the sun may also have had their influence. Even today it would require a drop of only a few degrees in the average annual temperature of the earth’s climate to produce a large increase in ice formation. All that is required is that a little more snow falls each winter than will melt in the summer. Thus, each year the excess would gradually build up glaciers and continental ice sheets, producing another “ice stage” in a few thousands of years.
The area of ice in the world today is relatively small: under 6 million square miles, about the same as that existing during each of the four interglacial (warm climate) stages of the Pleistocene. During the four glacial stages of the Ice Age, continental ice sheets increased their areas by three or four times, also becoming larger in size in each successive cold cycle. The latest and most extensive of these glacial times, the Wisconsin Stage, actually saw two ice advances with a brief recession separating them about 60,000 years ago.
During each glacial stage tremendous amounts of water were removed from the oceans and deposited on the continents as ice fields. This involved amounts of as much as 20 million cubic miles of water, causing world-wide lowering of sea level of about 150 or 200 feet. Today the sea between Alaska and Siberia is very shallow. It is not difficult to realize that lowered sea level during the glacial stages of the ice age drained the water from this and other shallow sea floors exposing these as land links or “land bridges” which extended between continents and islands. This state of affairs made possible the overland migration of man to the Western Hemisphere.
In his illuminating paper “Early Relations of Man to Plants” Sauer has pointed out that early man’s migrations to the New World were not the result of mere aimless wanderings. Peking Man of the first interglacial stage about 900,000 years ago in Asia used fire in established hearths. He ate both cooked meats and vegetables. This evidence indicates at least a semi-sedentary family life. Since he had learned to make himself more comfortable generally by remaining in one favorable place, it follows logically that even primitive Peking Man migrated only when he could improve his lot by doing so. He moved on only when he was forced to do so by a failing food supply or because of crowded conditions caused by increasing numbers of his fellow men. It is believed that not only Peking Man, but his descendants were as sedentary as their food supply allowed them to be. Dr. Sauer observes that
“... the history of human population (numbers) is a succession of higher and higher levels, each rise to a new level being brought about by the discovery of more food either through occupation of a new territory or through increase in food producing skill.”
The invention of a better tool, improved food preparation, discovery of new foods, better storage, or utilization would bring about this increase in food availability.
Apparently the twin circumstances of the need for more food and the existence of a dry land connection between Asia and North America enabled a series of migrations of prehistoric men to the New World. The migrations did not occur just during one glacial stage, nor during the last 15 or 25,000 years as some have claimed, but continued interruptedly over a period of many thousands of years. Perhaps such migrations started as long ago as 300,000 years—whenever land connections permitted and other conditions warranted. As a result, we find a number of stocks of Old World Man at various levels of cultural development coming into the Americas. Naturally a variety of plant and animal species migrated in both directions between the Old and New Worlds of their own accord, in addition to those which might have been brought along by prehistoric man.
A classic example of plant migration to the New World is that of California’s celebrated redwoods. In China just a few years ago the little changed ancestors of these trees, the still-growing Metasequoia were discovered. In rocks of the most recent era (Chapter Five of earth’s history) the step by step migration of the changing redwood ancestors can be followed by studying successively younger rock layers in Siberia, Alaska, and in Canada and northwest United States. These relics and imprints of the foliage, fruits, and even of wood texture of these ancient trees were covered by sands and muds, and thus preserved in stone as fossils. This has made it possible to identify the ancestral redwood species and to demonstrate their march to California. It is interesting to note how the redwoods changed in the process, evolving by degrees to cope with new conditions of climate and soil during their slow migrations. At length today two distinct and unique Sequoias are to be found living only in California. One, the Coast Redwood, has adapted itself to coastal fogs and reproduction by sprouting root shoots. The other, restricted to drier areas of the west slope of the Sierra, the Sierra Redwood or Big Tree, has its needles reduced to small scales to withstand the drier climate, and reproduces only by seed.