Many theists and atheists alike concur on this point. Michael Ruse, a noted agnostic philosopher of science, explains, The position of the modern evolutionist is that . . . Considered as a rationally justifiable set of claims about an objective something, ethics is illusory. I appreciate that when somebody says 'Love thy neighbor as thyself,' they think they are referring above and beyond themselves. Nevertheless, such reference is truly without foundation.
Morality is just an aid to survival and reproduction . . .
I think that Friedrich Nietzsche was right. But we must be very careful here. I'm not claiming that we must. I think that we can. Like Prof. Ruse, I don't see any reason to think that in the absence of God, the morality evolved by homo sapiens is objective.