It’s all about having enough Gorillas spending long enough, as per the infinite monkey theorem. Even producing the works of Shakespeare is inevitable — eventually.
A less complex text would likely be produced sooner:
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And so with the theory of evolution. There is variation within species. In certain circumstances, having certain characteristics, on the average, make survival more likely — resulting in differential reproductive success. Meaning the next generation has a higher proportion of individuals with the beneficial characteristic. And so on. That’s evolution, right there. Plenty of well documented examples. Our understanding of genetics has advanced enormously since Darwin, so he wasn’t right about that aspect. But on the issue of over-reproduction, the environment acting on variability resulting in differential reproductive success, causing change — Darwin absolutely gave us a rational explanation for observations that were previously inexplicable.