We feel that the life-story of prehistoric man can best be divided—certainly for the purposes of this book—into a Paleolithic, or Old Stone Age, which included the making of artifacts out of wood, bone, shell, and chipped and sometimes polished stone, and a Neolithic, or New Stone Age, which was defined by the invention of agriculture and the perfecting of pottery, of weaving, and of the polishing of stone. This may reduce a little the confusions that are inevitable in the study of early man tens of thousands to hundreds of thousands of years ago. Conflicts of evidence and opinion will remain, of course. We need not let them deter us from judging early man in the Americas. Indeed, they should free us from paying too much heed to the dogmas of scientific conservatism.
_Speak to the earth, and it shall teach thee._ —JOB 12:8
The dead hand of another system of classification lies across a still larger area than the Stone Age itself or the Age of Man. This area is the entire life of our earth since it took sufficient shape to support cellular life. As it is so large an area and much of it is so remote in time, changes in the definition of most of its various divisions do not much affect the present discussion.
Once upon a time there were four great divisions, neatly numbered in Latin as the Primary, the Secondary, the Tertiary, and the Quaternary. The first two went by the board when newer scientists found older ages and stretched the life of the earth a couple of billion years. The Tertiary is still a respected appellation, but the good name of the Quaternary—the area of time with which this book is mainly concerned—is seriously questioned. Defined as the Age of Man, it was supposed to harbor all evidence of his existence; but hints of his presence in the Tertiary have rather sullied the scientific standing of the later period.
[Illustration: THE LIFE STORY OF THE EARTH
_This summary of the story of the earth is a combination of charts in Arthur Holmes’_ Principles of Physical Geology, _Earnest A. Hooton’s_ Up from the Ape, _and George Gaylord Simpson’s_ The Meaning of Evolution, _with modifications by William C. Putnam and James Gilluly. *The divisions marked with an asterisk used to be called, respectively, Secondary and Primary._]