Page:Popular Science Monthly Volume 34.djvu/30
THE POPULAR SCIENCE MONTHLY.
By W J McGEE,
OF THE U. S. GEOLOGICAL SURVEY.
DURING the unlettered youth of the race there were no written records from which the antiquity of man can be read. So the anthropologist on the one hand, and the geologist on the other, have sought to construct an early human history from prehistoric relics, and from the formations in which they are imbedded or the fossils with which they are associated. Lubbock divided prehistoric time into four great epochs, viz.: 1. The Paleolithic or rough stone epoch, during which primitive man flourished; 2. The Neolithic or polished stone epoch, during which higher development was reached; 3. The Bronze age; and 4. The Iron age. These divisions, at first supposed to represent successive eras, are now regarded as representing cultural phases rather than periods of time (in fact, all are found among the present population of the world), and they are accordingly valueless as measures of the antiquity of man upon the globe. The geologist classifies later geologic time as Cenozoic or the era of modern life, divides it into Tertiary and Quaternary (or Pleistocene), and subdivides the Tertiary into Eocene, Miocene, and Pliocene. But no part of the geologic record, as hitherto interpreted, is more indefinite than that of the transition from Tertiary to Quaternary, or from Pliocene to Pleistocene; and this indefiniteness is especially unfortunate for American anthropology, since it was about this period that the autochthon — the primeval inhabitant of the continent — first appeared. It is, indeed, customary to recognize the geologically recent glacial period, during which northern United States was overspread by an ice-sheet extending southward to the thirty-eighth parallel, as the initial episode of the Quaternary; but it is becoming apparent that this period is too long and too vaguely defined to satisfy inquirers for a date of man's origin.
Recent researches in the Great Basin of western America, in the Mississippi Valley, and in the Atlantic slope, have shown (1) that the glacial period consisted of two epochs of humid climate and glaciation (the later comprising two or more sub-epochs); (2) that these cold and wet epochs were preceded, separated, and followed by climatal conditions much like those of to-day; (3) that the intervening a glacial epoch was of considerable dura-
- "Prehistoric Times," American edition, 1875, pp. 2, 3.