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Summary
Many of the cell's macromolecular machines appear gratuitously complex, comprising more components than their basic functions seem to demand. How can we make sense of this complexity in the light of evolution? One possibility is a neutral ratchet-like process described more than a decade ago (1), subsequently called constructive neutral evolution (2). This model provides an explanatory counterpoint to the selectionist or adaptationist views that pervade molecular biology (3).
