[mixtupcpl]

Thats exactly correct and old Europe is a great example that is similar to modern Islam.

The original impetus for the trend was necessity (fewer men). As the population evens out, the cultural tradition doesn't automatically reverse, so you end up with a situation that is largely untenable.

So what happens is a class discrimination where the powerful, as usual, consume more resources than they need.

But I dont think any of this is a "natural" process. It is all man made and the result of being sentient. The species goes to war because we think. We kill each other off (because we DONT think really), to the point where there is a population imbalance. We are thinking enough to devise a mechanism to repair it. This mechanism is something nicely abused by powerful men (who generally rule the planet) moving forward so it stays in place.

All of that is interesting and worthy of study, but I dont see how any of it points to a biological tendency towards a genuine "poly" structure. It is more further evidence that the male of the species is often quite horrible in his treatment of his fellow humans.