In studying evolutionary biology, “group-selection” has a specific meaning, an individual sacrifices its own fitness in order to improve the group fitness.
I think it’s quite limiting to think strictly in terms of genetics, because there is more than one level of description going on when it comes to selection pressure.
It is interesting to take that step back and view the culture as an individual. The human super-organism (e.g., a tribe, or more generally, a culture) competes with others for resources. It consumes, metabolizes, and excretes, which is to say that it lowers entropy locally and raises it globally. With others, it fights, defends, cooperates, and merges/assimilates. It gets sick, fights the antigens, heals itself, or dies. New super-organisms are spun off of or otherwise born from parents. We may look at the “evolution of language” through the lens of the human super-organism. Language is the DNA of culture, to make a rough analogy.
The dynamics that propagate the super-organism are not reducible to genetics. It’s a different level of description, because culture emerges from the interaction of large numbers of individuals. And you can’t deny that if one culture has guns and confronts another that doesn’t, that dynamic is going to place a harsh selective pressure indeed on the culture without the firepower. So genetics is not the whole story, and that’s what I mean by group selection.
There may be a selection effect in that cultures with guns are more likely to persist, but that’s different from saying that selection pressures play a really important role in designing the particular features of a culture.
That’s what I’m saying—selection pressures are important in determining cultural features, because those features in turn determine a culture’s viability. The global-level organization of a culture—including its moral code, political organization, and other important social structures—are key considerations in what makes a culture healthy or stable, and thus competitive in an arena of limited resources. Keep in mind, I think these ideas lend themselves more easily to ancient history, in which the boundaries between cultures were so much clearer, rather than the globalized cultures of our modern world.
A lot of these ideas come from Jared Diamond’s fascinating Guns, Germs, and Steel, which talks in depth about cultural evolution throughout human history.