Have you ever met a man or woman over 20 years of age, but when you briefly spoke to them, you felt as though their manner of speech and choice of topic was chilldike? Such people have an IQ of around 70. They have the mental ability of a normal 10-year-old. And about 1-in-50 grown-ups you meet seem to be stuck at this level.

Indeed, recent studies all agree that general intelligence (called ‘g’) is heritable up to 50-80%. The other part is apparently determined by the environment, but it isn’t clear how. Studies of identical twins who were separated at birth show that intelligence is well over 90% heritable. But this fact still ignores the question: What exactly is the thing being inherited?

Is one’s adult IQ score (or rather, one’s percentile class, since IQ scores may vary across different tests) inherited from one’s parents in the form of a point value? I.e., if your father has an IQ of 120 and your mother has one of 80, do you inherit the average, meaning 100?

Though IQ scores do appear to be highly heritable, the thing being inherited is likely a range rather than a point. You may be born with a genetic and heritable potential for an intelligence quotient of 90 to 130, and effectively manage to score 125 due to your specific circumstances.

The identical twin studies, even the ones separated shortly after birth, show high IQ similarity among such siblings, and this may be explained by them having shared the same womb. Correct, the environmental influences on differences in intelligence start even before you were born. It is, therefore, likely that the 9 months spent inside your mother also have had the greatest impact on the further development of your brain.

Contrary to popular perception (also known as feminism), women score a bit lower than men in every culture. Men also excel at spatial tasks, on average. For white people, women’s brains tend to stop developing around age 18, whereas men’s brains continue to develop up to age 25.

Feminism has turned this phenomenon into a joke, saying women can do in 18 years what men do in 25, suggesting it’s the men who are “slow”. In truth, men and women develop their brains at a similar pace up to age 18, when women’s brain development stops. Men’s brains then continue to develop spatial and mathematical abilities, i.e., they grow a bit more intelligent.

In other words, in the primitive world, a man won’t be a good hunter until around age 25. And in that primitive world, a man of 25 would indeed be a father of a small family, and his hunting skills would have to be optimal. Women logically prefer somewhat older men precisely for this reason. The bit older men have more experience and greater intelligence.

Some argue that women do better at EQ tests (emotional “IQ”) and this should be considered a form of intelligence. EQ tests actually measure only one’s conformity, one’s agreeableness, and mindfulness. These qualities are needed to maintain good social standing but actually harm women’s success in business and science, where competition requires men to beat the others.

EQ is about being nice, whereas IQ is about one’s ability to see solutions to problems. Still, with all this talk of heritability, genes, and IQ, we are ignoring something crucial, and that is the possibility that having a high IQ is a response to difficulties presented in early childhood, combined with the child’s genetic predisposition to absorb such difficulties and later overcome them.

A man named William Sidis, for example, was a child prodigy with an apparent IQ of over 200. He taught himself Latin and Greek by age 2, and learned to speak over 40 languages before age 20. But his childhood biography reveals something acutely telling: Sidis’s parents were both academics, and they confronted their baby with extreme intellectual demands.

In order to win his parents’ love and affection, baby Sidis had to overcome immensurable intellectual hurdles that his overly academic and insensitive parents threw at him. This, I believe, is what set the stage for Sidis’s intelligence, though surely combined with a genetic/heritable ability to do so. The genes provide the stage, the environment triggers a response.

Indeed, I argue that the only environmental factors truly influencing our adult intelligence are the experiences in our mothers’ womb and our early weaning (specifically: the demands imposed on us as small children in order to win our parents’ nurture and affect).

In a sense, our adult intelligence may be a coping mechanism. If our intelligence is above-average, it is because we were confronted with great difficulty trying to win the affection of our (perhaps absent-minded or deliberately condescending) parents. If our intelligence is very low, it is perhaps because we truly failed to receive the necessary nurture (food and love) to fuel our brain’s development.

Mind you, I do not believe intelligence and other cognitive ability is some universal quality among all groups of human beings. Some dog breeds are naturally smarter than others. Some breeds are more obedient than others. And so on, and so forth. But the processes explaining differences between high-IQ and low-IQ members of a certain group probably are universal.

Within-group differences in intelligence show up as different levels of psychological maturity. Less intelligent people continue to enjoy certain childish play throughout their lives, whereas more intelligent people soon grow bored with them and require higher quality stimulation of their minds.

We also know, for example, that birth order matters. A mother’s first-born child tends to have a bit higher IQ than subsequent siblings. The reason is that the mother was younger. The first-born child is usually also the only one that received both parents’ full attention (until #2 is born).

Children with fewer siblings also tend to have higher IQs, for parents can spend more time nurturing each individual child. Having too many children, then, may mean all of them to fall short of the love and affection they need to develop their minds properly. School is not a substitute for raising children. Schools are only meant for preparing children for the economy (“fitting them in”).

The following processes, then, determine one’s present general intelligence:

• one’s genetic potential, probably inherited in the form of a range (min. 80 – max. 150, for example, or narrower: 120-135, etc.);

• the quality and quantity of nurture received in the womb and in early infancy (food and love, intellectual stimulation, also abuse or difficulty);

• the duration of one’s brain development (less than 18yrs, 18-25 yrs, or more than 25yrs);

• the speed at which one matures psychologically (more intelligent children outgrow “childish” games more quickly);

• the actual use of one’s mind to stimulate it for learning and acquiring new skills throughout life (intellectually lazy people don’t use their full potential, and will score lower on IQ tests);

The most intelligent people in our world must have had top genetic potential, received all the best food they needed to grow their physical brains, were then confronted with intellectually challenging surroundings (either from supportive or abusive parents!), had the longest overall brain development (over 25 years), matured their psychologies rapidly (a consequence of having a high intelligence), and consistently used their minds to actually train their thinking (so they end up doing well on IQ tests).

Some in the scientific community are trying to tweak our genome in order to breed children with higher intelligence. I believe these attempts will remain unfruitful, for the materialist sciences inherently deny the existence of heritable souls. If our intelligence is not derived from some molecular code, but rather drawn from a non-physical source, then no amount of tweaking DNA will increase anyone’s intelligence.