Substitution rates not consistent with neutralist expectations.
Data therefore supports selectionist view.
This in turn means that the effective rate of production of neutral mutations is likely to be higher for those organisms, which would tend to counteract the expected generation time effect and perhaps completely compensate for it. V. Is the molecular clock episodic. The issue 1. Neutral theory has traditionally assumed that amino-acid substitution caused by drift is a process that can be modelled as a poisson process. It is therefore legitimate to ask whether actual amino-acid substitutions occur according to a Poisson process.