Evolutionary sociology - a possible origin of social classes

Our hunter-gatherer ancestors lived in a classless, egalitarian society. Agriculture allowed harder-working individuals to accumulate more goods and therefore also status. However, social hierarchy doesn’t explain the creation of social classes. Many animals evolve hierarchies, but no other animal has ever evolved classes. Classes are different from mere hierarchies in being at least partially impermeable through endogamy or assortative mating.

Interestingly the tripartite social division we know nowadays (upper, middle, lower class) also characterizes early agricultural societies, in particular in the Fertile Crescent, e.g all Indo-Europeans had very much a three-class system. Of course, the longer and more complex these societies got, the more stratified they tended to become (as in the case of Egyptians). The three classes typically comprised:

Upper class	king, priests, landowners, high-ranking soldiers
Middle class	warriors. artisans and merchants
Lower class	labourers, slaves (who often constituted the lowest class)

Social stratification is often explained in terms of division of labour and functional.  However, the division of labour doesn’t explain endogamy and why not all people strove to achieve an occupation with a higher status.

We now know that social class partially genetically determined, with individuals with high IQs and the personality traits conscientiousness and openness achieving the highest status in our contemporary society and at the same time these are also some of the most important criteria in assortative mating. Somebody who struggles in school, might not strive to become, say, a manager or university professor.

Going back to complex ancient farming societies, the development of classes might have been influenced by genetic traits. The earliest farmers had to become extremely hard-working and conscientious, working from dawn to dusk during the planting and harvesting seasons. This is in contrast to hunter-gatherers who rest frequently and work in short bouts. Moreover, farmers would have had to become more “planning” and forward-looking than hunter-gatherers.

Fast forward a few thousand years and evolution might have selected for the above-mentioned traits in farmers. Moreover, the descendants of those early farmers had not only inherited theses genes but also a lot of property. Their surplus goods most likely attracted neighbouring pastoralists and hunter-gatherers, the latter probably increasingly less able to feed themselves due to overpopulation and destruction of animal habitats.

I have argued before, that these early modes of subsistence had an impact on personality. Farmer types (SJ in Myers-Briggs - J types being known as "planners") being high in serotonin. Pastoralist types being high in dopamine, with higher activity levels. In fact, what I call “pastoralist” types are often called “artisans”, entrepreneurs”, or even “warriors” in the Myers-Briggs groupings (SP-types). It seems therefore not unlikely that these herders traded goods with the rich farmers, leaving the hunter-gatherers (N-types) with low-skilled, low-wage work.

Fast forward again a few thousand years and you will a tripartite class system in a complex agricultural society, whose members will prefer to choose their partners from their own class due to evolved sexual preferences: farmers according to productivity and wealth, pastoralists according to physical strength and dexterity, and hunter-gatherers according to their egalitarian mindset.  

Upper class: early farmers (SJ)	king, priests, landowners, high-ranking soldiers
Middle class: pastoralists (SP)	warriors, artisans, and merchants
Lower class: hunter-gatherers (N)	labourers, slaves (who often constituted the lowest class)

Of course, the system was rarely this neat. Take the Magyars, as an example: this pastoralist tribe invaded Hungary, established themselves as a ruling class and imposed their language on the local population. However, they left few of their genes, due to intermarriage. Being pastoralists, their descendants got replaced by hard-working farmer types on top of the social hierarchy again.

Something similar might have occurred in Rwanda.

The Twa were the earliest hunter-gatherer inhabitants. The Hutu were Bantu farmers that settled the region around 500 AD. The Tutsi were a nomadic (pastoralist) people that most likely superimposed themselves as minority rulers over the Hutu. However, centuries later, not all Tutsi constitute the upper class and they are often indistinguishable from the Hutu from a socio-economic point of view. The Tutsi are genetically similar to Bantus but also have some Cushitic pastoralist admixture. Genetic studies found 22.2% of E1b1b in a small sample of Tutsis from Burundi, but no bearers of the haplogroup among the local Hutu and Twa populations, which suggests that the ancestors of Tutsis in this area may have assimilated some Southern Cushitic-speaking pastoralists

Even though there is no class system due to ethnic origin nowadays, it isn’t hard to see that there once was one, with the Tutis (also defined as the ones close to the king) as former upper class, the Hutu as middle class and the Twa hunter-gatherers as lower class.

Social class is much more permeable nowadays and mostly defined by income. If we have a look at the distribution of income according to MBTI types some interesting patterns emerge:




P types tend to populate the lower-income-class and J types the upper-class. N types (hunter-gatherer types) also populate mostly the lower half of the income spectrum, but also part of the top (ENTJ/INTJ). N types are typically characterized by greater “openness” in the Big 5 inventory, being more “planning” and conscientious than the NP types enables them to compete with the SJ types.