How do I limit resources to make polyandry the most effective survival option?

Question

It was quite common for families to have boatloads of kids in the middle ages, with women normally producing 10 or more children. These children were a security blanket to take care of their parents in old age and to support whatever business the family was in. It was also expected that most would die before reaching adulthood, meaning that these families had to be large in order to sustain themselves. This situation was hazardous to many women and children, who would often die in childbirth.

This story played out differently in the nation of Sheba, a nation that existed in the medieval period but isolated from most of the world. The Queen of Sheba, Jezebel Iscariot, rules over a matriarchal society in which lineage is passed down through matrilineal lines. It is common for women to have multiple husbands. Scarce resource situations may force cultural features that give offspring a higher chance of survival. In such situations, having large numbers of children and hoping that most survive is unlikely to be successful. In polyandrous societies however, an offspring would have multiple fathers to take care of it.

If this system concentrates resources and effort on fewer children for the purposes of making sure that most survive to adulthood, it can out-compete other possible strategies. How can I ensure that society develops along this path?

Answer 1

Males have enormously reduced fertility.

In your world, the chance of any given man fathering a child on any given attempt is next to nil. Your men are nearly infertile. This is not genetic because the women are quite fertile; it is male specific. They produce almost no sperm. The reason for this is not known but may be due to their consumption of vast quantities of cannabis.

The result is that many, many sexual encounters must take place before conception very eventually occurs. Getting these encounters to take place is also problematic for the woman - the men are not very energetic in this regard, possibly as a result of the same problem which reduces sperm count. For a woman to become pregnant, she must try multiple times. Given the lack of enthusiasm men in your world have for the endeavor, multiple husbands improve her odds of getting pregnant or at least occasionally trying to get pregnant.

The other result of this system is that all the husbands will consider any child to have been fathered by their cooperative efforts (such as they are) and so each of these many placid and gentle daddies has an equal stake in the child. This means more parental care and resources for the child.

Answer 2

I think you are looking in the wrong direction.

• Matrilineal vs patrilineal societies are not a product of the locally available resources. In the ancient Mediterranean region the old matrilineal societies were overtaken by patrilineal invaders (source), without any change in the available resource.
• concentrating resources and effort on fewer children can make sense if you have quite some developed means. If you rely on your arms for farm a field, you better have as many arms as possible. It's only when you have a tractor that you can go easy on the arm count. Same for health care: if you have the means to take care of sick/wounded people, then it make sense to invest in few of them, but if all you have is murmuring some hulla hulla and spreading mud mixed with saliva, you better have faith in the big numbers and make as many kids as possible, since by chance some of the will survive.

I heard stories from my grandmother that in her times, just 100 years ago, for a pregnant woman it was common to go work in the fields until the very last moments before delivery and then get back there as soon as possible, the concept of maternity leave being not even an abstract idea.

This is maybe the only difference you can play on: with more men at disposal, a pregnant woman can be relieved from heavy duties and be better taken care of during her pregnancy, delivery and after delivery, increasing the chances that she can survive and proceed further in the baby making job.

Answer 3

Simple, make sure the society has everything it needs and a bit over for a bit of hedonism. We're seeing it in modern/westernized societies; with increased quality of life, the birth rate goes down - sometimes to the point of not being enough for replacement. Very likely it has some relation with the Maslow's pyramid of human needs.

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Not quite the "how to limit resources" that you expect, but under scarcity a smaller number of children will simply not happen.