Handicapped individua in evolutionary processes.

Usually, when considering an evolutionary development, the fittest individua and their successful mutations receive most attention. The less fit ones, existing due to selection-mutation equilibria, are regarded, as an inevitable waste. It appears that these handicapped individua play an important role in evolution, as they make escapes from evolutionary traps possible. It is concluded that crucial improvements come from mutations of mutants. The implications seem to account to some extent for the observed speed and mode of evolution. An appropriate stochastic model is introduced, numerical experiments reported and results discussed.