In technology, as in biology, we like to imagine evolution proceeding onward and upward. As new species and technologies appear, their primitive ancestors drop by the wayside, right? Not exactly. Mammals, birds, and flowering plants-all relatively recent innovations-might seem to rule the earth today. But far older designs, from barnacles to crocodiles, are doing just fine in their respective niches, thank you. New species don't always evolve to replace old ones; they also fill vacant niches, which in turn can actually solidify the standing of older species. So it is with technology.

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