Charles Darwin's theory of evolution was no big bang in biology. In the 18th century, several researchers had already developed similar ideas, included among them, Erasmus Darwin, Charles's grandfather. Based on the fossils of extinct animal species, he had postulated as early as 1794 that all life had originated from small, microscopic mollusks.
In the first half of the 19th century, the French naturalist Georges Cuvier developed his theory of catastrophes. Accordingly, fossils show that animal and plant species are destroyed time and again by deluges and other natural cataclysms, and that new species evolve only after that.
One of the sharpest critics of Cuvier's theory of cataclysms was Jean-Baptiste Lamarck (1744 to 1829),who was convinced that all living things had originated from simple organisms, and were therefore related to each other. The various species were merely the result of different environmental conditions: Thus, intensive use of certain organs has lead to their strengthening and enlargement; their disuse on the contrary has lead to a reversal of their development, and eventual disappearance. The properties thus acquired are passed on to the offspring.
Lamarck illustrated his theory using the example of the evolution of giraffes. They had short-necked ancestors that had tried all their lives to reach for the juicy leaves of trees. By constantly stretching their necks, they grew longer and longer, a property which they passed on to their offspring. The long neck of the giraffe is said to have come into existence in this manner over generations.
Darwin was, on the other hand, convinced that such features are the result of natural selection. Accordingly, certain giraffes had longer necks through pure chance, and thereby had an advantage over other members of their species in reaching sources of food that had been hitherto inaccessible to them. The animals passed on this "whim of nature" to their offspring, who, for their part, were better able to survive periods of food scarcity. Over long periods, long-necked giraffes survived and flourished.