Intelligence Decline in the average intelligence of the population in advanced industrial nations

[Dagne]

I find it really sad is that humanity will have less and less IQ because clever women are less reproductive. It is likely that men can inherit their IQ only from their mothers...

"some studies suggest that intelligence is inherited from the mother. These findings were initially found in studies on mice, but confirmed when extrapolated to human brains. This was carried out by a study conducting a survey on >12,000 people. Paternal genes tend to accumulate in the limbic system, which is concerned with aggression, hunger, e.t.c. basic instincts. No paternal gene is found in the cerebral cortex, which is concerned with advanced functions like learning, reading, e.t.c.
Intelligence genes are carried by the X chromosome, which are 2 with women. Even if it comes from the X chromosome of the father, it gets deactivated. "https://www.newtimes.co.rw/section/read/228963

"15 IQ points decreases women's odds of parenthood by 21–25%. Because women have a greater impact on the average intelligence of future generations, the dysgenic fertility among women is predicted to lead to a decline in the average intelligence of the population in advanced industrial nations".https://reason.com/2014/07/31/smart-...t-have-babies/

Clever men often do not mind marrying a woman who is pretty though not so intelligent, but it means that his genes for intelligence may be lost if he has only boys as offsprings. Still if woman's IQ is average but her father is of high IQ, she may have deactivated IQ genes for an offspring with high IQ. So men should really scrutinise wife's family for IQ because his IQ genes may be passed only to girls and they will be deactivated until the next generation.
On the other hand, some men may feel somewhat intimidated if their woman is much smarter than himself, so smart women may not be seen as perfect marriage material by average men.

Besides, smart women themselves may tend to skip marriage and children if they cannot find a smart man for herself. I don't think that they always dislike the idea of children and family, only that smart women want a man who is even smarter than herself, someone to look up and to be worth of sacrificing or compromising her professional ambitions or whatever else she wanted to do in her life. Still, family is a structure which supports men's goals in live. A woman may also take some career, but her goals are somewhat secondary. In many cases this is how the woman feels, too, because fighting for contracts or doing big business requires a lot of male aggressiveness not so much IQ and it would not make women happy to adapt to male world too much, where roles in family were reversed with husband staying home to take care of children and her fighting for money/status, etc.


Technically the humanity would be better off under matriarchal system where clever women had many offsprings with whatever - either smart or handsome or men with strong instincts, instead of the opposite where the classical ideal is "clever man + pretty woman" (or man with status has a harem of beauties).

Female genes are more important in carrying intelligence while in case of other features like height - male genes behave more "aggressively" and some of female genes get deactivated (conditioned) so that children will get to inherit more of their father's features, especially girls, apart from IQ, as far as it is understood now.
Pity I don't remember where I read a study about it.

 

[ToBeOrNotToBe]

Lol, men do not only inherit IQ from their mothers, that's so dumb. The only unique thing you get from your mum is mtDNA - that's precisely the reason it's useful for distinguishing population migrations when the autosomes are all muddled up (and Y DNA is still much more useful than mtDNA)

 

[Dagne]

I think studies about how much our IQ or other features can be passed by genes and who's genes are very exciting.

To put it very simply, possibly half or even up to 80% of what we call IQ is inherited, and mostly it depends on X chromosome that we get from our mothers in case of men or mother and father in case of women.

Inheritance of IQ is complex, meaning that it depends on many genetic variants (about 500) scattered across genome and how those fragments interact among each other and get influenced by environmental factors.

But what I find fascinating is the so called "conditioned genes" - which is something new - it seem that certain gene variants are shut down depending if they come from mother or from father. So for a woman, it seems, that I technically could not have inherited my fathers phenomenal memory, but I might still have it (or not) among my gene variants but they are conditioned (shut down) in my case. Still, I could pass it to my children if I were lucky. My brother, and his children however, don't have this possibility, as he inherited only my mother's gene variants from her X chromosome in case of intelligence. Earlier, common sense was that we inherit our intelligence from both parents. It is like my cousin who is a very bright mathematician, but his daughters are not interested in maths and find it rather difficult (which is somewhat a bit disappointing for parents). But now, in the light of this study, it is clear that father cannot expects his children to inherit his intellectual capacities, you have to look for that on mother's side (in my case, mother or her family are not into maths, too.) The bright side is that my nieces who are not good at maths may have children who are brilliant (like grandfather...) of course if one is lucky...

On the other hand it seems that we inherit something about our emotions and intuition from fathers, not from mothers.


"A category of genes known as “conditioned genes” are thought to work only if they come from the mother in some cases and the father in other cases. Intelligence is believed to be among the conditioned genes that have to come from the mother.
Laboratory studies using genetically modified mice found that those with an extra dose of maternal genes developed bigger heads and brains, but had little bodies. Those with an extra dose of paternal genes had small brains and larger bodies.
Researchers identified cells that contained only maternal or paternal genes in six different parts of the mouse brains which controlled different cognitive functions, from eating habits to memory.
Cells with paternal genes accumulated in parts of the limbic system, which is involved in functions such as sex, food and aggression. But researchers did not find any paternal cells in the cerebral cortex, which is where the most advanced cognitive functions take place, such as reasoning, thought, language and planning."
https://psychology-spot.com/did-you-know-that-intelligence-is/

https://www.rd.com/advice/parenting/inherit-intelligence-from-mom/

It seems that the best predictor of intelligence is mother's IQ, child's IQ varied only an average of 15 points from that of their mother.

 

[ToBeOrNotToBe]

True actually, men also get their X chromosome only from their mother (even if it isn't matrilineal), I was too quick there. I still doubt what you're saying is correct though.

 

[Dagne]

I don't think too that everything about IQ inheritance is clear.
Typically men are better at spacial thinking, besides men's brains are larger, so it may mean that male hormones and, subsequently, Y chromosome has some important enhancement qualities. This is just my own thinking, it is not from studies.

 

[Angela]

Except that those "on average" slightly better visual/spatial abilities are present before most of the testosterone kicks in.

Something worrisome is going on because they tracked a decline even within families, so no influence from migration or higher IQ women having fewer children etc., although I think those things have an influence. That's the benefit of a longitudinal study.

Perhaps it's something in the environment, or in how children are now being reared. Yes, there's a correlation of upwards of 60% (and probably more) of intelligence with genes, but something environmental, perhaps neo-natal, may also be involved.

Or, the parents to be were exposed to something which caused mutations in the genes governing intelligence, or "switched" them off.

I've always had a hunch that all the drugs ingested by some people when they were teen-agers, and immoderate use of alcohol as well, has had an effect on the number of children born with developmental delay, learning problems, autism, etc.

We'd better find out what it is. If the latter turns out to be the cause, the science deniers will be out in full force. They wouldn't want to admit they were wrong in saying it was all harmless.

While we're at it we'd better find out why sperm counts are dropping.

 

[Dagne]

Angela, do you have link to a study which refers to IQ decline in families?

I was reading a critical review about some Norwegian study which concluded that IQ within Norwegian families were declining. The criticism was because it was assumed that genetic differences between siblings are the same now as in the past, without taking into consideration that within a number of different Norwegian population registries biological siblings or half-siblings are not distinguished by law which should lead to distorted results.

 

[Angela]

I think studies about how much our IQ or other features can be passed by genes and who's genes are very exciting.

To put it very simply, possibly half or even up to 80% of what we call IQ is inherited, and mostly it depends on X chromosome that we get from our mothers in case of men or mother and father in case of women.

Inheritance of IQ is complex, meaning that it depends on many genetic variants (about 500) scattered across genome and how those fragments interact among each other and get influenced by environmental factors.

But what I find fascinating is the so called "conditioned genes" - which is something new - it seem that certain gene variants are shut down depending if they come from mother or from father. So for a woman, it seems, that I technically could not have inherited my fathers phenomenal memory, but I might still have it (or not) among my gene variants but they are conditioned (shut down) in my case. Still, I could pass it to my children if I were lucky. My brother, and his children however, don't have this possibility, as he inherited only my mother's gene variants from her X chromosome in case of intelligence. Earlier, common sense was that we inherit our intelligence from both parents. It is like my cousin who is a very bright mathematician, but his daughters are not interested in maths and find it rather difficult (which is somewhat a bit disappointing for parents). But now, in the light of this study, it is clear that father cannot expects his children to inherit his intellectual capacities, you have to look for that on mother's side (in my case, mother or her family are not into maths, too.) The bright side is that my nieces who are not good at maths may have children who are brilliant (like grandfather...) of course if one is lucky...

On the other hand it seems that we inherit something about our emotions and intuition from fathers, not from mothers.


"A category of genes known as “conditioned genes” are thought to work only if they come from the mother in some cases and the father in other cases. Intelligence is believed to be among the conditioned genes that have to come from the mother.
Laboratory studies using genetically modified mice found that those with an extra dose of maternal genes developed bigger heads and brains, but had little bodies. Those with an extra dose of paternal genes had small brains and larger bodies.
Researchers identified cells that contained only maternal or paternal genes in six different parts of the mouse brains which controlled different cognitive functions, from eating habits to memory.
Cells with paternal genes accumulated in parts of the limbic system, which is involved in functions such as sex, food and aggression. But researchers did not find any paternal cells in the cerebral cortex, which is where the most advanced cognitive functions take place, such as reasoning, thought, language and planning."
https://psychology-spot.com/did-you-know-that-intelligence-is/

https://www.rd.com/advice/parenting/inherit-intelligence-from-mom/

It seems that the best predictor of intelligence is mother's IQ, child's IQ varied only an average of 15 points from that of their mother.

Well, not to be cruel, but I have noticed that some of the very intelligent men I've known who have married women based solely on looks are sometimes disappointed their children don't have intellects matching their own. You'd think doctors, in particular, might have figured out that genetics has something to do with IQ.

Btw, it was indeed the Swedish study to which I was referring, which stated there was a drop even within families over time. I certainly hope there was some statistical error. That would be very worrying.

 

[bigsnake49]

Well, not to be cruel, but I have noticed that some of the very intelligent men I've known who have married women based solely on looks are sometimes disappointed their children don't have intellects matching their own. You'd think doctors, in particular, might have figured out that genetics has something to do with IQ.

Btw, it was indeed the Swedish study to which I was referring, which stated there was a drop even within families over time. I certainly hope there was some statistical error. That would be very worrying.

Ah, have they figured out that the good looking trophy wives did not marry the doctors for their good looks? They might or might not get better looking kids but they certainly won't get smarter kids.

 

[Angela]

Ah, have they figured out that the good looking trophy wives did not marry the doctors for their good looks? They might or might not get better looking kids but they certainly won't get smarter kids.

Most of us are prone to seeing what we want to see, don't you think? You have to actively work against it. Some men are quite clearheaded about it, though, in my experience: it's why they chose a profession where they could make a lot of money. I just don't think some of them thought ahead to their future children. I know of one case of a doctor, as a matter of fact, who left his wife (from a family of doctors), for his office receptionist and had a second set of children. The second wife made her life, her husband's life, and the life of her daughters a misery trying to ensure that they would succeed the way his first set of children had, to absolutely no avail. They weren't Harvard material, they weren't going to play first violin in an almost professional orchestra, and that was that.

My dearest friend and I, now passed, who tended to look at the world and other people the same way, used to chat, after a club dance, or some big event, and play the "now why did she marry him, or vice versa", or sometimes, "how could such a nice person marry such a complete ____". I'm sure you know what I mean.

Human beings are infinitely fascinating to observe.

 

[bigsnake49]

Most of us are prone to seeing what we want to see, don't you think? You have to actively work against it. Some men are quite clearheaded about it, though, in my experience: it's why they chose a profession where they could make a lot of money. I just don't think some of them thought ahead to their future children. I know of one case of a doctor, as a matter of fact, who left his wife (from a family of doctors), for his office receptionist and had a second set of children. The second wife made her life, her husband's life, and the life of her daughters a misery trying to ensure that they would succeed the way his first set of children had, to absolutely no avail. They weren't Harvard material, they weren't going to play first violin in an almost professional orchestra, and that was that.

My dearest friend and I, now passed, who tended to look at the world and other people the same way, used to chat, after a club dance, or some big event, and play the "now why did she marry him, or vice versa", or sometimes, "how could such a nice person marry such a complete ____". I'm sure you know what I mean.

Human beings are infinitely fascinating to observe.

Well, it was not better couple of generations ago in Greece in the era of arranged marriages.The criteria was rather severe. They looked at when your grandmother and grandfather died, what did they die off? Any mental illness in the family? Were they lazy or hard workers. Good with their hands? Did they lose their hair early? Did the female members of the family have problems with their pregnancies, etc. etc. There was a lot of selection going on. The matchmaker was a valued member of the community.

 

[Dagne]

Btw, it was indeed the Swedish study to which I was referring, which stated there was a drop even within families over time. I certainly hope there was some statistical error. That would be very worrying.

Well, I would be interested to see the methodology of such studies, just in case.
Another problem with such long term studies might be that the easiest to use data from Scandinavian registries (which are really popular among geneticists)
IQ data are taken from the records on conscripts. Each conscript is doing an IQ test and this information is included in the registry. The registry is public, available for scientific purposes. So the researches can find information on the IQ of several generation of men.
The conclusion on decreasing IQ within families could be derived only by comparing differences between men from different generations (brothers, father, uncles, etc.) where the link might be the weakest.

Mothers / daughters/ granddaughters should be included as test subjects, too, but the freely available data on them do not exist.

Besides, if we want to take into consideration "conditioned IQ genes" of fathers, then we should be comparing intelligence of every second generation (children and their maternal grandparents).

If we had these type of studies, that would be really interesting.

 

[Dagne]

Perhaps it's something in the environment, or in how children are now being reared. Yes, there's a correlation of upwards of 60% (and probably more) of intelligence with genes, but something environmental, perhaps neo-natal, may also be involved.

The simple answer is that IQ like height depends on nutrition. But I suppose it is OK now. Though the pollution (air pollution especially) might be a big factor.
Another factor - "secure emotional bond between mother and child" - poor women, again it all depends on them

"Mothers have also been found to play an extremely significant role in this non-genetic part of intelligence, with some studies suggesting a secure bond between mother and child is intimately tied to intelligence.

Researchers at the University of Washington found that a secure emotional bond between a mother and child is crucial for the growth of some parts of the brain. After analysing the way a group of mothers related to their children for seven years, the researchers found children who were supported emotionally and had their intellectual needs fulfilled had a 10 per cent larger hippocampus at 13 on average than children whose mothers were emotionally distant. The hippocampus is an area of the brain associated with memory, learning and stress response".
https://www.independent.co.uk/news/...erit-inheritance-genetics-genes-a7345596.html

 

[Dagne]

Well, it was not better couple of generations ago in Greece in the era of arranged marriages.The criteria was rather severe. They looked at when your grandmother and grandfather died, what did they die off? Any mental illness in the family? Were they lazy or hard workers. Good with their hands? Did they lose their hair early? Did the female members of the family have problems with their pregnancies, etc. etc. There was a lot of selection going on. The matchmaker was a valued member of the community.

That's how it was in Lithuania, too, one would want to marry someone form "a good family" only...

 

[Dagne]

Air pollution is a factor, too:


"The paper shows that air pollution, like inadequate nutrition and stimulation, and exposure to violence during the critical first 1,000 days of life, can impact children’s early childhood development by affecting their growing brains:

• Ultrafine pollution particles are so small that they can enter the blood stream, travel to the brain, and damage the blood-brain barrier, which can cause neuro-inflammation.
  
• Some pollution particles, such as ultrafine magnetite, can enter the body through the olfactory nerve and the gut, and, due to their magnetic charge, create oxidative stress – which is known to cause neurodegenerative diseases.
  
• Other types of pollution particles, such as polycyclic aromatic hydrocarbons, can damage areas in the brain that are critical in helping neurons communicate, the foundation for children’s learning and development.
  
• A young child’s brain is especially vulnerable because it can be damaged by a smaller dosage of toxic chemicals, compared to an adult’s brain. Children are also highly vulnerable to air pollution because they breathe more rapidly and also because their physical defences and immunities are not fully developed."
  https://reliefweb.int/report/world/...n-can-affect-brain-development-young-children
  The paper quoted is a Unicef paper attached to the article.
  
  Besides, air pollution, especial such as diesel traffic residues, affect brains of the adult people, too, "on more polluted days Chinese students do on average worse in their exams"
  
  Air pollution is really a bad factor for many issues, especially ultra small particles.

 

[Angela]

The simple answer is that IQ like height depends on nutrition. But I suppose it is OK now. Though the pollution (air pollution especially) might be a big factor.
Another factor - "secure emotional bond between mother and child" - poor women, again it all depends on them

"Mothers have also been found to play an extremely significant role in this non-genetic part of intelligence, with some studies suggesting a secure bond between mother and child is intimately tied to intelligence.

Researchers at the University of Washington found that a secure emotional bond between a mother and child is crucial for the growth of some parts of the brain. After analysing the way a group of mothers related to their children for seven years, the researchers found children who were supported emotionally and had their intellectual needs fulfilled had a 10 per cent larger hippocampus at 13 on average than children whose mothers were emotionally distant. The hippocampus is an area of the brain associated with memory, learning and stress response".
https://www.independent.co.uk/news/...erit-inheritance-genetics-genes-a7345596.html

Except that the lungs of ancient samples don't look so great from inhaling all that smoke from open fires in windowless huts, so I don't know.

Again, my hunch is that it is what is happening to men, not women. It's male sperm counts that are down, not eggs. A woman is born with all her eggs, but sperm is constantly being produced, and so is prone to damage from pollutants of all kinds, including the ingestion of drugs and alcohol.

It's like all the studies which showed it was older men, not women, producing less fit offspring, although a lot of men here were vociferous in their denial. Over time, mutations accumulate.

Of course, what happens during the time the child is in utero is also extremely important. One reason the U.S. lags in terms of child mortality is not because of worse health care; it's because of the high numbers of women from the "underclass" who continue to use drugs and consume high quantities of alcohol during pregnancy. We also have Amerindian populations who seem to have tremendous difficulties with alcohol processing who give birth to children with Fetal Alcohol Syndrome, which is an absolutely horrible thing.

As for that longitudinal study, wouldn't grandfathers and grandsons show up, the "skipping a generation" part which would even things out?

As for that "skipping a generation" thing on the male line, I think it might apply to things besides intelligence, and I've seen it in my own family .My paternal grandfather was not terribly stable mentally in mid life. Not one of his eleven children showed any sign of it: all stable and healthy mentally and physically. Yet, among the over thirty grandchildren, two have had problems.

On the maternal family side of the equation, I met a family here where the mother developed a mental illness after the birth of her children. Two of her four children have done the same. The husband/father is an absolute saint, trying to care for all of them, keep their lives solvent and together.

 

[Angela]

Well, it was not better couple of generations ago in Greece in the era of arranged marriages.The criteria was rather severe. They looked at when your grandmother and grandfather died, what did they die off? Any mental illness in the family? Were they lazy or hard workers. Good with their hands? Did they lose their hair early? Did the female members of the family have problems with their pregnancies, etc. etc. There was a lot of selection going on. The matchmaker was a valued member of the community.

It was just the same with us.

I sometimes wonder if it was a "bad" or a "good" system. Perhaps good for the village or community, not so good in a lot of cases for the individuals. Those old women were responsible for a lot of broken hearts. Yet...seventeen year old hearts can mend, and perhaps some of those girls, for example, were glad in the end that they didn't saddle themselves with a man who worked too little and drank too much, and gave them too many children to feed, or the man who married the prettiest girl in the village against the counsel of his elders grew unhappy with the slovenly house, the bad food, and the poorly cared for children.

I drank up all those stories as a child, because I was the kind who followed the grandparents and great aunts and uncles and great-grandparents around and begged for stories as they worked. I'm pretty sure they sunk in, and that's why I was prone to believe in the effect of family "blood" lines long before all these papers on genetics, as unpopular as the ideas were.

No matter how infatuated I was with my husband to be, no matter how much I suffered from that "colpo di fulmine", I really doubt I would have eventually married him had I not instantly liked his family, seen how hard working and ambitious they were, how stable, and most importantly, how kind and loving and respectful they were to one another, and how important family life was to them. Had I seen alcoholism, or abuse, or even just disorder and lack of stability, I think I would have run for my life. My nonna always said I was born old. Perhaps I was.

 

[davef]

Stress might play a role, though I'm not sure if it's any worse for kids these days. I think I read that kids in the US are constantly being bombed with tests as part of this common core thing and it's messing with their mental health but I'm not sure if it's any worse than what students went through prior to this shift (I mean, you can't have school without tests-I'm no teacher but how else can you measure how much a student learned?).

 

[Dagne]

As for that longitudinal study, wouldn't grandfathers and grandsons show up, the "skipping a generation" part which would even things out?

I agree that skipping generation is somehow important for inheritance. But in case of IQ, if we presume that boys inherit their IQ from mother's side, then comparing men from families with the same surname (grandfather - father - son) would not be meaningful. But that is the easiest way to identify family members from public registry, isn't it?

 

[Dagne]

Small particle air pollution (which gets into blood) affects IQ. So it must be that world's mean IQ reduced due to pollution, too.

Also I watched really fascinating 2min bbc animated reel (link in the article below), where they say that there is evidence (not just correlation) that more polluted air means more violent crimes. Totally insane, but it is true.

http://www.bbc.com/future/story/20190415-how-air-pollution-is-doing-more-than-killing-us