Can objective morality exist in Atheism?

[Darwinian]

To say that morality is "objective" is to say that notions of "right" and "wrong" are universal and fixed for all times. What are "right" and "wrong" today will be that way for all times and all cultures.

Objective morality is a problem for evolution because some evolutionary theorists believe that our sense of right and wrong develop historically, and that it is open to change as we evolve throughout the generations. If it is the case that our brain develops over thousands and thousands of years, some evolutionary thinkers might say, then our understanding of right and wrong might change as well.

Accordingly some evolutionary thinkers base their understanding of ethics on genes (See the book "The Selfish Gene"). If it is the case that genes and evolution determine what morality is, then it is difficult to see how it can be universal for all places and times and for all "variations" of the human species. If "reason" is historically conditioned, then even our capacity to reason might change as well.

You should be aware, though, that "evolution" does not mean the same as progress. It might be the case that we will evolve further, but that does not mean what we will evolve into will be "better" than what we are. Evolution is an adaptation to one's environmental changes, not necessarily a self-improvement process though in many cases the way we evolve might indeed benefit us in the long run.