Are you referring to genetic drift? This is a statistical phenomenon by which alleles that are near neutral for viability change in frequency until one becomes

Are you referring to genetic drift? This is a statistical phenomenon by which alleles that are near neutral for viability change in frequency until one becomes fixed. This doesn't mean that neutral mutations will invariably push the wild type out of the genome. Actually, that would be improbable in the absence of a selective pressure or an accident of history.