Before we tackle evidence of evolution head-on, let's briefly review the history of evolutionary thought. Recall that early ideas about the natural world were heavily influenced by Plato and Aristotle, who believed that species were fixed and unchanging. Early Christians built upon this idea, and concluded from the biblical account of creation that God had created each of these species individually. The belief in divinely created, unchanging species dominated for centuries, but by the 18th century, the tide had begun to turn in favor of evolution. At this point, people still weren't quite sure how evolution happened—Charles Darwin and Alfred Russel Wallace hadn't thought of natural selection yet, and Jean-Baptiste Lamarck's inheritance of acquired characteristics was the most commonly accepted mechanism for evolutionary change. Early believers in evolution might have been wrong about how evolution happened, but props to them for at least understanding that it did happen. What evidence led them to abandon old ideas about species being fixed entities, and to conclude that evolution had occurred?
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