I know you are talking about evolutionary physcology, which is okay per se. I was just trying to bring out two points:
1) That it is very easy to come up with what Stephen J. Gould called "Just-So-Stories" that darwinize every aspect of human behavior without any evidence to support the story. This is where I threw in the cautionary note. I agree that all human behavior evolved, but what caused it to happen in many areas of behavior is still unknown. For these areas, there is no end to conjecture.
2) I'll admit that perhaps it was a bit unwarrented for me to say your premise may be false. I realize there is more to evolutionary therory than "Natural Selection." It isn't the only process going on. Sexual Selection also exists (which is it's own entity, not a subcategory of natural selection). "Group selection," or some varient of it, is what you seem to be thinking about here. From what I can tell this is a controversal theory since it seems contradictory to natural selection. But what do I know, maybe they are complimentary. Time for me to do some more reading...