I agree with you here, but I still stick with my point that the Bible's sexist definition of adultery is justified, while the modern non-sexist definition of adultery is unjustified, based on evolutionary reasoning. I'm not Christian either. I don't know anything about the Lakota, but any religion/traditions that includes exercises in self-discipline which makes morality possible is fine with me. My friends, no. But anyone chasing after my wife isn't my friend, and such people really will destroy the human race based on my values. What is the reasoning behind this? (I don't believe this.) This doesn't actually happen with humans, so this explanation may be true in a vestigial sense. But even so, the purpose wouldn't necessarily have been variety and much as encouraging males to compete for the female so as to have the strongest male win. Of course it is generally subconscious. In my personal case it isn't because I am disgusted with humanity in its present state.
Actually all religious and spiritual belief systems have their own exercises in self-discipline which makes morality possible--but this morality is either archaic and borrowed from another time, or it is based on the zeitgeist----and this was exactly Hegel's point when he coined the term, zeitgeist---spirit of the times---i.e. the cultural and social values of the people within the context of the times that they live in. I have several titles for you to read---it is late, I am tired, and I can't think of them offhand, but I do have several titles on my bookshelves that get into this very subject. But an example of this is the fact that not all sperm are suited for fertilization---there are those that are intended more for fighting the sperm of other partners. This is how the strongest mate tends to win from inside the womb. I hope you are not referring to female vocalizations during sex (there is a special name for them---I can't think of it---its late). If your partner(s) are not being more vocal than you then, well, ...umm, ...there is a problem. If it is just because you are extremely vocal, then I would say, stop acting like a porn star, and sit back and actually enjoy it ;-) Seriously though I assume you are referring to the part about potential mates showing up---that is common even among apes. In humans, it would be unusual for your neighbor's wife to be noisy enough for you to show up at their bedroom, upon which you watch and wait---in case you get a turn... But this certainly plays into the dynamic of the human sexual experience. This is why many humans enjoy porn. We can't exactly go to our neighbors window, but we can certainly explore our voyeuristic inclinations through porn. It is not exactly like our ape cousins, but we certainly enjoy it as a species just the same.