However, if a separate advantageous mutant (B) of gene b arises before A has gone to fixation, and happens to arise in an individual who does not carry A, then individuals carrying B and individuals carrying A will be in competition.
Porén, se un mutante vantaxoso distinto (B) do xene b se orixina antes de que A chegue á fixación, e se orixina casualmente nun individuo que non porta A, entón os individuos que porten B e os individuos que porten A estarán en competición.