While this is true under nominal operation in most cases, 'most cases' is not adequate for a safety-critical function.
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The Chesapeake bay was once so full of oysters you couldn't sail in it enough. Natives regularly ate oysters so large that colonists said they used the shells as dinner plates - we've found oyster shells 7 inches long. But now, the biggest oysters are a fraction of that size, and if we had seen the original oyster population we'd call them critically endangered.