Looking at some non-theological interpretations of materialism that are not as bleak as the existential crisis brought on by pure materialism...
This is NOT to deny that evolutionary psychology (i.e. sociobiology) doesn't have some important truths to tell us, both in the animal kingdom and to the human experience. But deep down, even we don't believe it, in our heart of hearts. It's not a theist/nontheist thing. Some of the most moral people I know of are nontheists, like the late Isaac Asimov or the living Harlan Ellison. Indeed, many nontheists are outraged by what they perceive of a fictional God acting nonmorally---without realizing the very standards they hold God and others is mysterious in origin, a thing so close to us that we don't see how unexplainable it is.
I hope I don't need to point out that I do NOT advocate a euthenasia program, either for low-IQ children or the senile. I'm just pointing out that the evolutionary imperative to eliminate the unfit is strangely absent in most cultures' sociology, despite its evolutionary logic.
Those who devote their lives to helping others--without even kin-selection benefit---like Schweitzer, or Annie Sullivan spending her life bringing one individual, Helen Keller, to true intellectual flowering-- are almost universally admired, despite any personal failings they might have.
Next time: SOCIAL RELATIVISM ISN'T RELEVANT