The hardest problems for evolutionary psychology - part two: voluntary childlessness

The basis of evolution is differential reproduction, so all life is programmed to survive and reproduce. Therefore the most perplexing problems in evolutionary psychology are when life seems to be programmed to self-destruct or voluntarily give up genetic reproduction.  I will try to provide a tentative answer to these riddles, based on personality types.

If all life is programmed to survive and reproduce, voluntarily childlessness (genotypical suicide) is a similar problem as suicide (phenotypical suicide). So, how can this paradox be explained?

The most common answer you get when you ask people why other people don’t want to have children is “selfishness”, i.e. they want to have an easier life without children. Why should people want to have easier lives, when life for humans is getting easier all the time and not harder, though? Another problem with this answer is that evolutionary theorists maintain (and they are right) that it is actually selfishness (on a genetic level) that should people have children instead of none. So what kind of buggy selfish genetic program codes for phenotypical selfishness that leads to genotypic suicide?

As not all people would want to live childlessly, the answer most likely can be found in their personality types. As you can see in the table, the top common types are S types, whereas the N types populate the lower half of the table. Given that personality type is about .5 heritable we can assume that N types tend to have fewer children. Why should that be so?  N types have inherited more hunter-gatherer traits than S types, who have inherited more early farmer traits.

Hunter-gatherers rely much more on alloparenting than farmer, where most of the parenting is done in the close circle of the family. There is a saying “It takes a village to raise a child”. The village has gone and the burden of child-rearing lies nowadays mostly with mums. It is, therefore, no big surprise that women want to have fewer children nowadays. For “hunter-gather” women this burden may seem much bigger than for “farmer” women, as in the past farmer women already had to adapt to the burden of additional child-rearing chores. This might be one reason why “hunter-gatherer” women don’t want to have any children at all nowadays.

That is not all there is to the story, however. Everybody knows how important self-actualization is nowadays. Many people don’t want to have children before they feel self-actualized.

For farmers, this means acquiring the desired social status and material wealth for founding a family. This is easier for the more conscientious and ambitious -J types than the “lazier” P types. Moreover, introverted S types seem to want to have more children. This is likely due to the fact that their introversion limits their ability to climb up all the way to an alpha position, so they probably want to settle down earlier than the ES types whose possibilities in modern work environments are less restricted. Introverts earn considerably less money than extroverts and have high early-retirement numbers.

There is another highly interesting pattern visible in type distribution. For N types the opposite holds true: the more ambitious J types have fewer children than the less ambitious P types. What is more, the NJ types tend to be in the average to high-income segment. According to standard evolutionary theory, they should, therefore, have more offspring than the less successful NP types. So, what is going on here?

My point is that self-actualization for “farmers” and “hunter-gatherers” are different. Whereas farmers will be content to settle down once they have achieved the desired material success, hunter-gatherers are not programmed to achieve material success, but their reproductive success rather depends on reputation and achievement for the group. So, hunter-gatherers would rather go for jobs that are less well paid than managers, bankers, etc., but bring them a higher reputation, e.g. university professors or artists. For a university profressor, the highest kind of reward is most likely not monetary compensation, but publication in a prestigious scientific journal. 

NJ types tend to become experts and therefore find fewer potential partners who share their interests. Think of a university professor who finds it hard to find an equal. What is more, N types, are more egalitarian than S types, they don’t easily conform to the “man the breadwinner cliche” and so both man and woman might prefer to follow a prestigious career, which might leave little time for children.

These are the reasons why ISTJ/ISFJ are the most common types and INTJ/INFJ are the least common types. If this trend continues it can be expected that in the future there will be fewer hunter-gatherer genes in our gene pool.