ABSTRACT
During the late eighteenth and early nineteenth centuries, geology opened up a vast and unfamiliar vista of earth history. The study of rocks and fossils showed that the history of the earth had not covered the same stretch of time as the history of mankind, but extended back immeasurably before the advent of homo sapiens. It also appeared that prehuman earth history had not been a single period of continuity, but a great chain of successive worlds (that is, of periods of geological history), each with its own distinctive flora and fauna. Moreover, it emerged that the nature of the historical succession had been progressive: Successive worlds increasingly resembled our present world, with respect both to its inhabitants and the environmental conditions under which they had lived. This new vista of earth history equaled the Copernican revolution in its intellectual implications, reducing the relative significance of the human world in time, just as earlymodern astronomy had diminished it in space.
