Consider each person as an agent with a hierarchy of desires. Each agent’s objective in the game of life is to maximize the satisfaction of their desires, starting from the base level desires of subsistence to the higher level desires of love, sex, and power.

Every person for themselves

Now, in the beginning of time, there was a vast fertile land in Farmtopia that sustain a small populace of farmers. Each person farms on a separate tile of land and lives in a separate wooden house. If you live in Farmtopia, your survival algorithm is fairly simple:

1. Plant seeds at a certain time of the year

2. Harvest at a certain time of the year

3. Find a mate with whom you can satisfy your desires of love and sex

4. If you have a child, feed your child and teach the child your way of life

All is well. The population is small but steady, and everyone is happy.

Every couple for themselves

One day, a guy named Smith decide to move in with his sexual partner. At first, everything seems to go as usual. They both work at the fields. They plow twice the land and planted twice the seeds. The work is split equally.

Then, their problems come. They have one child, then another, then another, and yet another. Now, in the old days, each agent only has one child to feed and teach on average. Now, each of them has two children on average. In fact, feeding and teaching 4 children become so laborious that it’s about as much work as farming the lands. The Smiths know that specialization leads to greater productivity, so they make a deal with each other: one of them will only tend to the children while the other will only cultivate the land. They called the deal “marriage.” The deal isn’t great for the husband because he now has to cultivate twice the land as he needed to before. The deal isn’t great for the wife because she now has to tend to quadruple the children as she needed to before.

But the Smiths blossomed in Farmtopia. The first 2 Smiths give rise to 4 young Smiths. And the 4 young Smiths, being taught the way as they are, inherit their parents’ survival algorithms; they produce 8 younger Smiths. In this way, the Smiths’ population doubles every generation while the population of every other household remains the roughly constant. Soon, the Smiths become so numerous on the lands of Farmtopia that the other agents either have to copy the Smiths’ survival algorithm or simply go extinct.

All is still well. The population is large and steadily growing, and everyone is still mostly happy.

Every family for itself

One day, another person named Smith decided to do something for her 4 children. You know, in the old days, when the parents of a household die, the children move out of their parents’ house out of respect for the deceased; they get married and build their own house, plow their own fields, and harvest their own food. Smith is kind-hearted and wants to help her children. So, she teaches to her children that when she and her husband are dead, her 4 children should split the furnitures, and stockpile of grains inside the house equally amongst themselves. They should likewise split the plowed fields equally amongst themselves.

In the old days, everybody has roughly equal wealth: they produce about equal amount of wealth in their life and their wealth is reset after their death. Their children, out of homage to the deceased, don’t take the deceased’s properties into their own hands. The Smiths have a slightly different survival algorithm. Because each generation of the Smiths inherit the furniture of the previous generation, their number of furnitures grow larger. Because each generation of Smiths inherit the grains of the previous generation, their stockpile of grains grow higher. Because each generation of Smiths inherit the farmlands of the previous generation, the area of their plowed field grow larger. The quality of life just keep increasing for the Smiths because each generation grow richer than the previous. Perhaps most importantly, with their abundant resources, the Smiths have a higher chance of surviving through a famine than other families. Eventually, everyone in Farmtopia adopts the Smiths’ practice—bestowing their properties to the next generation. The few families who decide not to die out due to recurrent famines.

All is well. The population is large and steadily growing, and everybody is getting richer and happier.

There is a slight problem. Some families are a tiny bit more hardworking than others. So, they grow more grains, they build more and larger furnitures, they plow a larger area of fields, and they pass on these grains and furnitures to their children. Some of their children are also hard-working, and so they grow more grains and build even more furnitures, and plowed even larger fields, and pass them onto their own children. Eventually, several families in Farmtopia have a much larger stockpile of grains, a much larger number of furnitures, and much larger area of plowed field to grow food in than other families.

But all is fine. Everybody is still getting richer and happier on average.

Every landlord for themselves

One day, something very very bad happens: a huge famine swept Farmtopia. Food is not growing at its regular pace in the fields.

You know, in the old days, to grow enough food for one person only required one Farmtopian acre of land. Now, because the land is dry and the precipitation is low, growing enough food for one person requires two acres of land. This is fine for the richer families, because they have a large enough stockpile of grains to survive through the famine. They also have larger plowed fields to grow food on. This is terrible for the poorer families, because they don’t have a large enough stockpile of grains nor large enough plowed fields to survive the famine.

The desperate poor Farmtopian families turn to their richer neighbors for help. Their richer neighbors, being kind-hearted Farmtopian people, gladly offer to give them part of their stockpile of grains to help the poorer families get pass the famine.

But there was one particularly cold-hearted rich household: the Smiths’ household. When several poor Farmtopian neighbors turn up to the Smith family to beg for some grains, the Smith family offered them a deal: the Smith family will feed them if they give the Smith family their farmlands in turn. Not only so, they have to work on those farmlands that now belong to the Smith family. The Smith family call this contract “serfdom.”

The poor Farmtopian neighbors of the Smith are desperate for food, so they turn in their plowed fields to the Smith and work on those fields for the Smiths. The famine thus passed.

With this contract, the Smiths family grow larger and richer, with an ever larger area of farmlands and an ever greater number of serfs working for them.

On the other hand, the other rich households of Farmtopia grow poorer and poorer over the years as they kind-heartedly give away their stockpile of grains to poorer farmers who need them during famines. Eventually, their wealth decline so much that they have to either adopt the Smiths’ practice or risk becoming so poor that they are liable to being struck down to serfdom by famines themselves.

After many years, all is not well in Farmtopia. Most farmers become propertyless serfs who work for a few number of rich landlords. On average, the people of Farmtopia are less rich and less happy than before.

Concluding remarks

Now, if you have no idea what I am trying to tell you, I’m sorry. This allegory is not intended as a historic account of how societal structures such as “marriage,” and “serfdom” came about. These societal constructs, amongst many others, are common across almost all well-developed ancient civilizations. The point I’m trying to make is that this is not a coincidence. The reason that people across different parts of the globe all adopt these social constructs as parts of their cultures is……evolution. Evolution drives the development of cultures that are most suited for survival in the environments in which they developed. And certain cultural constructs are beneficial to the survival of the culture across many different environments. These include “marriage” and “serfdom.” They apply widely to almost all ancient agricultural civilizations.