Ideas: A History of Thought and Invention, from Fire to Freud

by Peter Watson

It was by now difficult to contradict the evidence of the rocks, where the basic picture was clear. ‘The earliest rocks [600 million years ago] yielded only the remains of invertebrates, with the first fish appearing only in the Silurian [440–410 million years ago]. The Mesozoic [250–65 million years ago] was dominated by the reptiles, including the dinosaurs. Although present in small numbers in the Mesozoic, the mammals only became dominant in the Cenozoic [65 million years ago the present], gradually progressing to the more advanced creatures of today, including the human species.’69 (The dates in square brackets were not, of course, accepted in the nineteenth century.) It was hard for people not to read some sort of ‘end’ in this progression, ‘leading’, via stages, to humans, ‘and thus revealing a divine plan with a symbolic purpose’. In books of the time, most ‘trees of life’ showed a main stem, thicker than others, leading directly to man.