It was sloppily worded. The gene under discussion is presumably a mutated version of one which exists in more primitive primates. Natural selection (i.e., death by incompetence or other inability to survive and reproduce) gradually filtered out those individuals who did not possess the mutated gene, thus assuring the predominance of the changed gene in the population. There is no "override," to speak of. Just a higher reproductive success rate for those possessing the mutation.
Hmmm. . .then that question that gets laughed at by evolutionists so much comes to mind. If 'natural selection' means death by incompetence or other inability to survive and reproduce, why are there still apes? Shouldn't they have ceased to exist based on these criteria? If not, why wouldn't some forms of life between apes and man exist? Why would they be less 'competent' to survive than apes?