Evolving the improbable

The debate about the evolutionary roles of natural selection and molecular drive cannot be resolved by assigning probabilities with hind-sight to unique events in the evolution of complex adaptations. Hoyle dismisses natural selection by calculating, erroneously, the improbability of assembling by chance a string of amino acids in the order in which they occur in a given protein. Dawkins dismisses molecular drive on the same false grounds of the improbability of making the right decision, by chance, at each step in a long series of steps in the evolution of a given trait. Calculation of the probability, at any given step, of a successful match between fortuitous genetic variation and fortuitous environmental heterogeneity requires detailed knowledge of all parameters at that step. Such information is an essential requirement for quantifying the roles of natural selection and molecular drive in the evolution of one actual series of steps out of many potential series.