I recommend reading JFK Fuller "The Decisive battles of the western world and their influence on history" or any book about ancient history, which i define as before the battle of hasting. And you will learn about the sheer amount of war there has been all over europe, really rampant. Example is during the great migration era. My point with all this is that in war their usually is rape, alot, which per definition is that the male chooses their spouse.

For more modern example read Catherine Merridale "Ivan's Wa. The Red Army 1939-45". Where their was extensive rape and pillage done by the red army. Rough translation, i have a swedish copy. "Among the Soviet soldiers that fell on the preussian refuges that streamed out from Insterburg and Goldap was a young Officer by the name off Leonid Rabitjev. Decades later would this man gather the strength that is required to write about the offences he saw were being committed. "Women, mouther and children lie right and left along the road, and infront of each one their stands a screaming armada of men with their pants down", he wrote."

My point is that we can't really compare the trends of peaceful today with history in terms of reproduce, because a lot of women bore children of war, even up to relative modern times.

And unsuccessful men can go die in a war for the successful men who'll remarry multiple times.

Again, you are not accounting for rape in war. Which the "unsuccessful men" on the winning side will do. Just look up conflict in Africa, rape is being used as a weapon.

Not true. The men who die in the fighting tend to be the unsuccessful ones. The ones who did not die, in addition to having the opportunity for rape (and in ancient times to take concubines home), would also come back as heros and have the opportunity to marry women from their own tribe.

These pressures are much more pronounced in polygamous societies, such as fundamentalist Muslim countries today, or ancient Jewish culture as documented in the Old Testament.