By 1800, European naturalists knew a great deal about plants and animals. They collected specimens, carefully studied them and even classified similar species in groups. But only a few bold thinkers, including Jean-Baptiste Lamarck and Erasmus Darwin, Charles's grandfather, speculated that species had evolved--that is, that all life shared a common ancestor.

Why didn't more people grasp that similarities in skeletal structures--so clearly visible--were a clue that species are related? In part, no one could convincingly explain how evolution worked. How could distinctive features, like the anteater's long nose, have taken shape over time? How could new species arise? Few naturalists, however, were even asking such questions. Most were comfortable with the prevailing view that each species resulted from an act of special creation by a Creator.

Evolution Before Darwin

Early evolutionists like Jean-Baptiste Lamarck had difficulty explaining how new species arose. Lamarck saw that many animals seemed to have acquired useful adaptations. The giraffe's long neck, for instance, was perfect for feeding on high leaves. But how did the giraffe get its neck? Lamarck thought it resulted from the constant effort of reaching for food. Constant use of a body part, he argued, made it larger and stronger.

But there was one key problem. Can changes produced during an animal's lifetime be passed on to its offspring? Does a father lifting weights produce a muscular baby? Lamarck argued that such acquired traits could be inherited, but few others were persuaded. A convincing mechanism for evolution had yet to be discovered.