Women are far more important than men

This is one of my first and most basic premises. I'm not sure when I arrived at it, but I think a little argumentation can easily demonstrate its truth.  Imagine a society (a primitive band) with 100 people, 99 men and 1 woman.  Turn the clock forward by 20 years.  At that point, that society might have increased in size to perhaps 110 people, minus any deaths that occurred.

(I am imagining that for some reason the 99 men didn't fight each other, kill each other, over access to the lone woman).

Now consider a society of 100 composed of 1 man and 99 women.  Twenty years hence, it might increase in size to around 1,000 members.  (Unless, of course that one male died!).

This same logic applies exactly in breeding many animals.  A breeder needs only a few males to service a large number of females.  (The ram-to-ewe among sheep ratio might be 1:40 or so).  And indeed, extra males may be a waste, since they are costly to feed and care for without producing any additional "value added."

The same is true for people.  That is the reason that men (and not young women) are the ones mostly sent off to war.  That is why the most dangerous jobs are typically allocated to males.  That is why there is a rule in dealing with emergencies to save the "women and children first."  Those are good ideas, in almost any society and almost any situation, because the women are more important than the men.

A group that is trying hard to increase its numbers might for these reasons encourage polygamy (as the Mormons did) or condemn birth control (as Catholics have done).

In a society that is running out of resources, however, the opposite circumstance might apply.  Then, you don't want too many fertile women producing too many children.  And I suppose that we on Earth are perhaps approaching that situation now.  Still, social customs take a very long time to change.