PerspectiveEvolution

The treacheries of adaptation

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Science  25 Oct 2019:
Vol. 366, Issue 6464, pp. 418-419
DOI: 10.1126/science.aaz5189

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Summary

One of Darwin's great insights was that he took the widespread observation that organisms are exceptionally well-suited to their environment and turned it on its head. He argued that behind the constructive process of adaptation lies, counterintuitively, a destructive one: Progeny with favorable variations obscure the many progeny who are less well suited and either do not survive or, at best, have fewer offspring. This insight—which Darwin owes in part to Thomas Malthus and shares with Alfred Wallace—is a cornerstone in the theory of evolution by natural selection and raises an important question in biology: What is the nature of the tradeoff between the capacity for adaptation and the cost of producing less-fit offspring? On page 490 of this issue, Johnson et al. (1) find that as adaptation proceeds and fitness gains are expected to diminish, the cost of mutation becomes more severe.

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