Now these automobiles and radios will eventually wear out. Let us suppose we could go to some remote part of Turkey or to Timbuktu in a dream. We don’t know what the date is, in our dream, but we see all sorts of strange things and ways of living in both places. Nobody tells us what the date is. But suddenly we see a 1936 Ford; so we know that in our dream it has to be at least the year 1936, and only as many years after that as we could reasonably expect a Ford to keep in running order. The Ford would probably break down in twenty years’ time, so the Turkish or Timbuktu “assemblage” we’re seeing in our dream has to date at about A.D. 1936-56. Archeologists not only “date” their ancient materials in this way; they also see over what distances and between which peoples trading was done. It turns out that there was a good deal of trading in ancient times, probably all on a barter and exchange basis. EVERYTHING BEGINS TO FIT TOGETHER Now we need to pull these ideas all together and see the complicated structure the archeologists can build with their materials. Even the earliest archeologists soon found that there was a very long range of prehistoric time which would yield only very simple things. For this very long early part of prehistory, there was little to be found but the flint tools which wandering, hunting and gathering people made, and the bones of the wild animals they ate. Toward the end of prehistoric time there was a general settling down with the coming of agriculture, and all sorts of new things began to be made. Archeologists soon got a general notion of what ought to appear with what. Thus, it would upset a French prehistorian digging at the bottom of a very early cave if he found a fine bronze sword, just as much as it would upset him if he found a beer bottle. The people of his very early cave layer simply could not have made bronze swords, which came later, just as do beer bottles. Some accidental disturbance of the layers of his cave must have happened. With any luck, archeologists do their digging in a layered, stratified site. They find the remains of everything that would last through time, in several different layers. They know that the assemblage in the bottom layer was laid down earlier than the assemblage in the next layer above, and so on up to the topmost layer, which is the latest. They look at the results of other “digs” and find that some other archeologist 900 miles away has found ax-heads in his lowest layer, exactly like the ax-heads of their fifth layer. This means that their fifth layer must have been lived in at about the same time as was the first layer in the site 200 miles away. It also may mean that the people who lived in the two layers knew and traded with each other. Or it could mean that they didn’t necessarily know each other, but simply that both traded with a third group at about the same time.