In his essay of appraisal of Lamarck , Ernst Mayr mentions an argument for evolution which Lamarck made which is quite acute and yet which is one that I have never heard made. In essence he stood Paley on his head.
William Paley  and others who propounded Natural Theology pointed to the marvelous degree to which life is adapted and co-adapted. The instances of this extensive adaptation and its degree of perfection are innumerable. Consider, for example, the fig and fig wasp. The fig wasp lives inside the fig fruit. That is the only place that it lives; it can live nowhere else. The fig tree is constrained to provide a home for the fig wasp because it is the fig wasp and no other insect that can fertilize the fig tree. The fig has many adaptations that permit the wasp to exist without taking too much and to both force and allow wasps to go from one fig tree to another. The fig locks out all others save the fig wasp; in turn the fig wasp has special adaptations which give it the key to lock.
To Paley et al this profound degree of interdependent adapation was clear evidence that life had been designed as an entirety by a designer of no mean order. Each animal, each plant is just as it must be to suit its place in the world. In short, it is part of the nature of life that each species be well adapted.
This was all very well. However in 1800 it was quite clear that the world had not always been just as it is now. The geologists had determined that the Earth was old rather than young, and that it had changed slowly over time. Mountains had grown and had eroded away. Sea beds had filled with sediment which turned to rock and then was lifted up to become land.
If it is in the nature of life to be well adapted to its environment and if environments change slowly but inexorably over time then it inevitably follows that life must also change slowly but inexorably. To argue otherwise is to argue that the perfection of lifes adaptation is a matter that only occurs now and that life in the past was ill adapted to the world.
In short, Paley's argument has been stood on its head. Paley argued that the perfection of the adaptation of life implied that it was created just as it is now. His argument presupposed the fixity of the Earth. But the Earth is not fixed in its form; therefore the perfection of life must have followed its changes. Ergo life evolved.
 Mayr, Ernst, 1976: Essay 17, pp 223-249, Lamarck Revisited in _Evolution and the Diversity of Life, Selected Essays, Belknap Press, paperback edition 1997, ISBN 0-674-27105-X (adapted from an article in J. of the History of Biology, 5, no.1 (1972) pp 55-94)
 Paley, WIlliam, 1902: Natural Theology: Or, Evidences of the Existence and Atributes of the Deity, Collected from the Appearances of Nature. London; R. Fauldner (cf from )
 Mayr, Ernst, 1982: The Growth of Biological Thought, The Belknap Press of Harvard University Press, ISBN 0-674-36446-5.
This page was last updated November 22, 1997.