In Sum
Ten years ago, we knew that men in America had once killed, skinned, and eaten animals now extinct, for we had found their weapons and a few of their bones mingled with the fossils of mammals long extinct. We could not question the association, because it often involved the remains of campfires; spear points and bones might be moved about in the course of time, but not fragile heaps of charcoal. We knew, too, that the bones and tools of man had been found sealed away by the chemistry of the ages. But when we tried to date man securely by animals that were dead and gone, or by the earths that lay above him, we began to guess. The guesses of conservative glacialists gave him at least 15,000 years in the New World. Other speculations—supported by rather plausible evidence as well as not implausible theory—placed him still earlier. Now, at last, through the miraculous time clock of radiocarbon, we know that man was here before the chill of the last Ice Age settled upon the land.