Crowding

• some individual is more fit and so copies of this individual and very similar individuals quickly take over
• this lowers the diversity of the population and slows further progress by the GA - in worse case down to mutation
• Solutions: use tournament or rank selection
• fitness sharing - the fitness of an individual is reduced by the presence of other similar individuals
• restrict the kinds of individuals allowed to recombine - multiple subspecies - related approach is to spatially distribute individuals and allow only nearby individuals to recombine