Historical Record of Organic Evolution
Almost one and one-half centuries ago ( 1809) Lamarck compared the process of evolution to the movement of the hour hand of a clock. A creature whose lifetime lasted one second would perceive no motion at all in the hour hand. Even thirty consecutive generations of such a creature might doubt whether the hand really moves. With respect to observing evolution in geological time, man is in the position of such a creature.
Since Lamarck, biologists did find ways to perceive some motion in the hour hand of the evolutionary clock. They used for this purpose the speeded-up processes of evolution by polyploidy, evolution under domestication (Chapter 9), and the experimental evolution, chiefly in microorganisms (Chapter 5). But with respect to the evolution which has actually taken place in the history of the earth, an observer of only the now-living animals and plants is still in a position of judging a long movie film by only the last picture frame. Let us, though, give the credit which is due to this observer: from the only picture at his disposal he has correctly inferred that there was a story back of this picture. Moreover, he has successfully used the experimental method to find out some of the mainsprings of action in the story. He can even make intelligent guesses as to what kinds of events could and could not have occurred. But to learn what events did actually occur and in what sequence, the last picture frame is not enough. Fortunately, some fossil remains of the living beings of the past epochs are preserved in the geological strata. They furnish us with some torn-up fragments of the preceding picture frames of the story. It is the business of paleontologists to restore these fragments as much as possible, and to arrange them in the proper sequence.