The naturalistic evolutionary account of the development and origin of homo sapiens sapiens tells the truth. This true narrative tells of no more significance or purpose of homo sapiens sapiens than that of any other species. If that is the only true account of the origin and development of humanity, nihilism is correct.
Grant that the evidence for this evolutionary narrative is better than any supplementary account of the origin and development of humanity, an anthropology, which finds a special significance and purpose for human beings. This is not to grant that there is no evidence for the supplementary account.
Maintaining that one is not entitled to allow belief in any account with weaker evidence than that for evolution is incompatible with nihilism. It presupposes that there is a source of obligations on how to use our reason. It is presupposed that there is a way we ought to be with respect to our rationality. Accepting that there is a way we ought to be is to accept that there is a point to our living.
Holding fast to assertions of nihilism because that is what duty to truth requires is an instance of a stoic stance defying nihilism. If there is no God, still the truth and our duty to it stand against not being – nothingness.