No bashing seen in any way. Your point is as valid as anyone else's! Maybe I can give you a prod in the right direction here or at least waste some time typing a post. Let's see what science tells us before we even get into all the religious complications. Lets start on the fact that maaaaany animals mate for life including gibbon apes, wolves, termites, coyotes, barn owls, beavers, bald eagles, golden eagles, condors, swans, brolga cranes, French angel fish, sandhill cranes, pigeons, prions (a seabird), red-tailed hawks, anglerfish, ospreys, prairie voles (a rodent), black vultures and many, many more. Primates, fish, birds, all forms. Not all do of course. Consider also the fact that mating is a basic instinctual act. Marriage is the highly ritualized ceremony that occur in many cultures, some which do not even believe in a singular god and still it's considered a lifetime bond. Not that you'll ever find a culture, not in all history, that was atheist by choice and simply worshiped nothing. Due to the overwhelming evidence as seen in our, and all prehistoric times, its seems in our biology, for some reason, to worship a higher power. Although we do not know for certain why, we see evidence of an area of the brain geared specifically for this and we have seen this play out in experiments involving psychedelic and hallucinogenic drugs where people actually believe they had a religious experience. Perhaps certain chemicals create an enlightenment in an instant that takes holy people (monks,etc.) years to achieve. So if our basic desire is to believe, we would have to choose NOT to believe in a higher power due to lack of evidence (or whatever reason). Regarding religions now. That's not quite as easy. A religion is also a highly developed ritualistic practice that evolved from another basic biological desire (just like marriage did). Marriage and religions didn't come first. The biological need came first and the highly advanced and ritualized behaviors formed much later and have been evolving ever since.
Marriages fail often today. This is a fact. But why? Is it because of promiscuity? Is that the reason? Unlikely. In fact, impossible. We most strongly bond to our "first love" and bond less tightly to each subsequent relationship. How many divorces are on the grounds of infidelity? Very few. If there is infidelity there is usually something problematic first that then became adulterous.
All of this is a "Which came first?" ideology. Which formed first? Belief in a higher power or disbelief? Which happened first? Mating for life or promiscuity? which came first? Mating for life or marriage? Which came first? Belief in a higher power or the religions of the world? When you consider what came first, you have the answer to your basic questions of "are people this way or are they that way?"
Look at a male's jealousy. Why should a person care if a particular woman mates with someone else? What's the mechanism? After all, why should he care? The answer is not "just because". Jealousy is a higher emotion that evolved to gaurd one specific thing. A male's desire to see to it that his sperm reaches a female's egg before another male's. If a female has multiple mates in a particular month, the chances of passing on his genes would be greatly diminished. And let's not underestimate the power of the desire to reproduce. Parents will die for their children. A man will kill another man if he feels that man threatens his chances of reproduction with a particular female. Ro murder in a "jealous rage" is simply the ultimate expression of the male's desire to reproduce. So first comes the desire to reproduce, then comes the desire to ensure ones genes are passed on correctly, then comes jealousy, etc.
More on this later. I'm starving.