The Paradox of Stasis and the Nature of Explanations in Evolutionary Biology

Recently, Estes and Arnold claimed to have "solved" the paradox of evolutionary stasis; they claim that stabilizing selection, and only stabilizing selection, can explain the patterns of evolutionary divergence observed over "all timescales." While Estes and Arnold clearly think that they have identified the processes that produce evolutionary stasis, they have not. Instead, Estes and Arnold identify a particular evolutionary pattern but not the processes that produce that pattern. This mistake is important; the slippage between pattern and process is common in population and quantitative genetics and contributes to a persistent misunderstanding of the nature of explanations in evolutionary biology.