In the eighteenth century, many Europeans and Americans embraced a world-view in which the natural world was seen as complete, full, and perfect, as created by God. Within this worldview, no species ever became extinct because such an event would destroy the perfection of nature. Toward the end of the eighteenth century, the concept that no species had ever become extinct was increasingly challenged by evidence from the fossil record. By the early nineteenth century, a new paradigm, the “former-worlds” view of Earth history, began to emerge.

Buffon had argued that New World quadrupeds were degenerate varieties of Old World...