While the fixity of species was the generally accepted view before Charles Darwin, he was not the first to propose that evolution, understood as the transformation of one species into another, occurred. The ancient Greek philosopher Anaximander maintained that people had evolved from fish, and the zoologist and botanist Jean-Baptiste Lamarck (1744–1829), as well as Darwin's grandfather, Erasmus Darwin (1731–1802), were also proponents of evolution.

Lamarck, for instance, argued, in his Philosophie Zoologique (1809), that life resulted from ongoing spontaneous generation and that each lineage, beginning with simple forms, was driven by an inner tendency to complexity and perfection. On his view, more complex creatures belonged to older lineages, with our own the oldest. Adaptation and diversity was explained by the inheritance of acquired characteristics. Different environments caused organisms to have different needs in response to which they would use or not use their various organs: Use would cause...