You can see that the more we dig and find, the more clearly the main facts begin to stand out. We begin to be more sure of which people lived at the same time, which earlier and which later. We begin to know who traded with whom, and which peoples seemed to live off by themselves. We begin to find enough skeletons in burials so that the physical anthropologists can tell us what the people looked like. We get animal bones, and a paleontologist may tell us they are all bones of wild animals; or he may tell us that some or most of the bones are those of domesticated animals, for instance, sheep or cattle, and therefore the people must have kept herds. More important than anything else--as our structure grows more complicated and our materials increase--is the fact that “a sort of history of human activity” does begin to appear. The habits or traditions that men formed in the making of their tools and in the ways they did things, begin to stand out for us. How characteristic were these habits and traditions? What areas did they spread over? How long did they last? We watch the different tools and the traces of the way things were done--how the burials were arranged, what the living-places were like, and so on. We wonder about the people themselves, for the traces of habits and traditions are useful to us only as clues to the men who once had them. So we ask the physical anthropologists about the skeletons that we found in the burials. The physical anthropologists tell us about the anatomy and the similarities and differences which the skeletons show when compared with other skeletons. The physical anthropologists are even working on a method--chemical tests of the bones--that will enable them to discover what the blood-type may have been. One thing is sure. We have never found a group of skeletons so absolutely similar among themselves--so cast from a single mould, so to speak--that we could claim to have a “pure” race. I am sure we never shall. We become particularly interested in any signs of change--when new materials and tool types and ways of doing things replace old ones. We watch for signs of social change and progress in one way or another. We must do all this without one word of written history to aid us. Everything we are concerned with goes back to the time _before_ men learned to write. That is the prehistorian’s job--to find out what happened before history began. THE CHANGING WORLD in which Prehistoric Men Lived [Illustration] Mankind, we’ll say, is at least a half million years old. It is very hard to understand how long a time half a million years really is. If we were to compare this whole length of time to one day, we’d get something like this: The present time is midnight, and Jesus was born just five minutes and thirty-six seconds ago. Earliest history began less than fifteen minutes ago. Everything before 11:45 was in prehistoric time.