Here the only philosopher worth reading offers a possibility: "And first, if we consider how little odds there is of strength or knowledge between men of mature age, and with how great facility he that is the weaker in strength or in wit, or in both, may utterly destroy the power of the stronger; since there needs but little force to the taking away of a man’s life; we may conclude that men considered in mere nature, ought to admit amongst themselves equality; and that he that claims no more, may be esteemed moderate." Hobbes, Thomas. The Elements of Law: Natural and Politic (modernised) (pp. 71-72). So those of lesser wit are able to destroy those of greater in the state of nature. Elsewhere the philosopher remarks that those of greater wit seek to dominate those of lesser, thereby bringing an early death to those of greater wit given the equal ability of all to kill everyone else.
I think there is. I want to say I read that you can’t have such high an IQ and be relatable to people. So very high isn’t desirable from an interaction perspective. Something around the 115-120 range I think they said is where the intelligence and relatability intersect positively.
The question has always been, at least for me, is why do people with high IQ make horrible decisions? Are we just defined by our ability to be good at math? There’s a lot of exceptionally smart people still wearing masks (not to harp on that topic too much but COVID broke the IQ factor for me).
Everyone makes horrible decisions. I'd bet the house that high IQ people make less simple mistakes. If they are making more decisions of a complex variety, they might still make as many or more wrong decisions but that would be comparing apples and oranges.
Also, note that it is easier to see a decision was "stupid" when we look at it in hindsight.
Agreed regarding the hindsight comment. Maybe regarding the assumption that high IQ makes fewer poor decisions. I think we want that to be true. Also, the impact of poor decisions from those with high IQ may have much greater ramifications because these people may be in positions of incredible responsibility.
Bull. I have no doubt plenty of high IQ people relate perfectly well. Do they relate less well? I'm skeptical so show me some evidence.
Some don't relate wellv and they stand out. Does an average intelligence person who can't relate stand out in the same way? I don't think so.
Maybe you are right due to secondary effects such as autism spectrum characteristics that make them less relatable but that's a secondary affect. So even if that is true, I see no reason to think just havinh high IQ and no other issues makes someone less relatable, given they are smarter and have more ability to figure out how to relate. Note that relating to others isn't just having the same IQ. It's also about finding a topic or activity to relate on. Again, high IQ should help finding and using this commonality.
I'd also note that in a community where many people are high IQ, including many university town and urban communities, high IQ doesn't have to be an anomaly.
I'm high IQ (except math) married to someone much smarter. (high-energy physics, engineering, business). He's one of the best judges of character I've ever met & positively Machiavellian in his ability to understand & manipulate people,, seductively charming with women.
He's also met some of the smartest men (physics Nobelists) in the world, who all had great social skills. There are some famous exceptions: Kurt Goedel (likely on the spectrum) stands out. But John von Neumann was socially skilled & a ladies man.
Speaking of physics: wearing a well-fitted N95 mask or respirator WILL block aerosol-carried virus particles.
David Friedman's subsequent post (linked in Arnold's footnote) explains why average intelligence would tend to increase over generations even if genius tends to be socially maladaptive for genius:
"If true, that implies that in a society with an average IQ of 100 an IQ of 150 may reduce instead of increase reproductive success. But as long as an IQ of 115 increases reproductive success, intelligence is being selected for and should increase. When the average gets to 115, 130 should increase reproductive success, and so on up. So although this is a reason why evolution might increase intelligence more slowly, it is neither a reason why it wouldn’t increase it nor an upper limit on how high it would eventually go."
Arnold writes: "I think that all it takes for a society to continue to produce people without genius IQs is for there to be some point at which higher IQ actually reduces fitness on average. There are many ways that a high-IQ person could be more fragile."
Another complication: Whether an IQ of, say, 150 (on the current scale) in a later (evolutionarily accessible) cohort makes a person 'fragile' might depend on the prevalence of persons of IQ 150 in the later cohort. Frequency-dependent effects matter in some evolutionary contexts.
Why do stupid people exist? Because they benefit the group. The existence and reproductive success of a particular human group depends on the mixture of traits of the group as compared to the mixture of traits of other groups. In order for the group to be reproductively successful it needs dumb people to do the stuff that dumb people do best. What is it that dumb people do better than smart people? They work for the smart people, and it’s in the interest of the smart people to keep the dumb people around. In fact, the existence of smart people depends on dumb people. Being smart and staying smart requires work. Dumb people are like labor saving devices that free up time for smart people; making it possible for smart people to get even smarter.
I’m grateful for the dumb people in this world. They do work that smart people won’t do, and thus make the world a better place.
I think one answer is that marginal IQ hasn't been strongly selected for until quite recently. Being noticeably smarter than your neighbors doesn't do you a lot of good if you're a hunger-gatherer or a subsistence farmer -- at best, you can maybe come up with a better snare or an improved crop rotation method, but you're still so subject to time and fate that it doesn't make a huge difference to your family. It might help if your whole society took up your innovation, but most small-scale societies are incredibly conservative about these things. It takes a whole lot of "cultural technology" to end up in a situation where a smart person can meaningfully increase their chances of passing on their genes purely due to intelligence!
Individual fitness in the evolutionary sense may be more related to wisdom (the ability to use knowledge and experience to make sound decisions) than on IQ (that is ability to quickly understand and solve problems). Of course, one cannot be wise if stupid, but there are many high IQ people quite lacking in wisdom, often due to being caught up in and blinded by dysfunctional heuristics (e.g., ideology). I call such people "self-enstupidated."
I guess we'd have to distinguish what "high IQ" is. But in any case while I can see somebody with an IQ of 150 *originating* an ideology that is replete with bad ideas - such is ego, and to an extent creativity - it is harder for me to believe someone at that level would be captivated by ideology, absent some deformation of their mental powers.
There are two effective strategies to solving problems. Create your own solution (rare), or copy or borrow one from somewhere else (vast majority aka culture). It doesn’t take much upstairs to copy or mimic or use tools or processes created by others. However, if just about everyone is copying the majority, this creates a competitive niche strategy of creating novel solutions. But this requires more intelligence to use imagination, consider tradeoffs, avoid potential new risks, and to combine ideas or transfer similar solutions from one domain to another.
This tracks closely to the hypothesis that there must be costs to intelligence (energy or such), but adds that the cost may actually be less copying and more wasted time energy and risk with novelty.
Thus the dominant strategy would be cultural copying, which is efficient and safe and doesn’t require much thinking, and the niche strategy would be to explore/create novelty which requires brain power.
Watching Carl Lewis perform at the Olympics several decades ago led me to wonder: why isn’t everyone athletic to that degree? Perhaps that thought should have been prompted by Bruce Jenner, who, as a decathlete, displayed a broader range of athleticism; I may have been influenced by Lewis’s remarkable gracefulness, and the fact that his events—sprints and long-jump—rely more on natural talent and less on training and practicing technique. But even the decathlon does not cover the full range of athletic talents, which include performance in weight-lifting, gymnastics, marathon running, swimming, horseback riding, hitting a baseball, shooting a basketball, etc.; truly general athletic accomplishment would make one good at more than a mere ten sporting events. (True, achieving anything like *excellence* in both weight-lifting and marathon running would be remarkable.) And then there are the fine-motor skills involved in drawing, sewing, playing the piano, etc., which are not considered “athletic.” Putting these all together, we may ask: why does the average human being not have more natural talent for *general physical performance*?
I think part of the answer is that Natural Selection “cares” about more than performance; just subsisting is also important: surviving shortages of food and water, hibernating or estivating (or just sleeping) during unpromising times—in general, passively dealing with privation. Another part of the answer is that Natural Selection works slowly and crudely: it is remarkable that it has produced creatures are impressive as us, though, of course, we *could* be even more impressive.
Now that we have mastered biotechnology and Artificial Intelligence we are ready to take over from Natural Selection, and produce some *really impressive* creatures.
From Scott Alexander's ACX Open Thread 346 (September 9, 2024):
ACX commenter Metacelsus is a Harvard bio PhD who the excellent De Novo blog; he also reviews most ACX posts and grants on biology for me. He recently co-founded a startup, Ovelle, to commercialize his academic work on gametogenesis (turning arbitrary cells into eggs). If this worked, it could replace the complicated and invasive egg harvesting process of IVF with a simple blood draw or mouth swab. But beyond that, it would allow women to circumvent menopause by creating eggs at any age (women can safety become pregnant well into their 50s, they just lose the ability to create eggs naturally), and maybe (this is still speculative) allow gay couples to have biological children. And with a couple of extra steps, you could turn this into a supercharged version of embryo selection that could essentially end all genetic disease (existing techniques don’t give you enough rerolls for more than incremental gains). This technology already works in mice, and some companies (including one backed by Sam Altman) are working on translating it to humans - but IIUC Metacelsus is coming from an academic lab that’s gotten significantly further. Ovelle is looking for people who want to invest or work for them (remember, investing in biotech is a minefield best left to professionals, and working in biotech is terrible and soul-sucking). You can contact them here.
Diversification of cognitive abilities does lower the average, but may benefit the community or species as a whole.
Even primitive social organisms such as bumblebees can solve reasonably interesting puzzles and then teach the colony to modify the innate behaviours to accommodate the new skill. Researchers find that ”there are huge inter-individual differences: most bees will require either step-wise training or the chance to observe a skilled conspecific to master the task on their own. A very small minority of individuals even solve the task by individual trial-and-error learning.” (see Bee Cognition/Current Biology/vol 27/19/Oct 2017)
Now imagine that some individuals in a colony are particularly stubborn and just cannot learn the winning strategy discovered by the smart bumblebees. Why this can be a winning strategy for a colony? Because a short-term winning strategy can harm the species in the long term. Stubborn, conservative individuals then save the colony.
Nature optimizes not for the skill, but for the species’ survival.
This and one other comment are arguments for group selection. Standard evolutionary theory is that you are evolving to compete against other members of your species, not to help each other out. But people may be different since so much of our success comes from cooperation.
I was trying to make a point that diversity of skills is advantageous overall. Changing environment requires quick adaptation. Diverse species just adapts better/faster: it has seed individuals better adapted for the new environment. Too much specialization is unsustainable in the long term - using Arnold's perspective.
(I'm not the David Friedman referred to in the post.)
It seems plausible that before the modern era there was a hard limit on low intelligence. The less intelligent you are, after all, the less you can do for the tribe: growing food, tracking game, storing resources, etc., all require some level of cognitive ability. But as society industrialized and became wealthier (at least in the west), our ability to house and feed the unintelligent improved. So maybe today we see a greater range of intelligence in the population, overall, because we can afford to feed and house the less intelligent.
While there are a lot of good points in both the article and the comments, I think the most likely answer is Thomas L. Hutcheson’s in the comments here. “Stupid” is relative, and we were a lot more stupid in the past. Intelligence has been selected for, but not everywhere all the time, due to all the different factors folks here have mentioned. Evolution is usually a slog.
It may also be that there's no feasible way for new mutations to improve the average or reduce the variance of human intelligence much, or to do so without introducing other non-adaptive traits. One can't always assume that every trait exists solely because it's adaptive compared with other imagined possibilities. To reiterate an old joke about this aspect of evolution: there's a reason why deer don't have built-in laser cannons to protect them from predators, and it isn't because that wouldn't be adaptive.
Or it may be that greater intelligence can only be achieved by (combinations of) genes that have adverse maladaptive side effects. For example, genes for greater intelligence may correlate with risk of relatives developing disabilities. Highly intelligent people are more likely than average to have autistic siblings, this is pretty well confirmed.
Friedman seems to only be addressing male reproductive success vs IQ, when it's important to note that women have greater influence over their child's IQ than men do (I think this has to do with children inheriting mitochondrial DNA only from their mother, but I could be misremembering), and high IQ seems to negatively impact women's reproductive success in the modern world. Educated, economically successful women seem to not want to settle for a partner whose own achievements aren't on the same level, but successful men do not have the same filter when selecting a partner of their own (youth, fertility markers, etc. you know the drill), thus you wind up with a fairly large group of high IQ women who are destined to be unsuccessful in the marriage market. Not to mention there are the pets and self-gratification angles Friedman discusses that affect women as well as men, which further affects the reproductive success of high IQ women.
Edit: a couple more comments worth adding, I think:
1. I think DF's sports car analogy is correct, but he's not drawing the correct conclusion from it. Sports cars aren't inherently more complicated than other vehicles. The reason they spend a lot of time in the shop is that to get the high performance, you have to increase the thrust to weight ratio of the car relative to other vehicles, so the component parts are very lightweight, but have more force applied to them, and thus prove to be far less durable than components for other cars. The basic issue is that in complex systems, there are always trade-offs that have to be made. It's not necessarily that "something went wrong," it's that maximizing for trait A means probably means you have to accept a higher likelihood of lower trait B scores or what have you.
2. I think Friedman is right that you have to consider just good ol specialization, comparative advantage, ROI, etc. Consider that if you live in a village of relatively skittish people circa 8,000 BC, the returns to being fearless are probably pretty high. But if everyone in the village is fearless, you probably get an excess of violence, and thus it might become an advantage to be skittish, since you avoid physical conflicts that are debilitating or deadly to your peers. Since brains are biologically expensive, as Friedman notes, you can imagine circumstances where minimizing the investment in energy intensive tissue would be a winning strategy, and would continue to work into the modern era, because after all, somebody still needs to dig ditches, take out the trash, etc.
I believe I saw somewhere that independent of hypergamy, high-IQ women are less likely to want children, and being smart, can make damn sure they never get pregnant. I'm high-IQ in a long-time marriage to a higher-IQ man (he's taller, too, but I'm only average female height). Both of us (as well as his ex-wife, even smarter than me cause she got the math chip) knew from childhood we didn't want children & got sterilized in our 20s.
When I was at university, I had a friend with an extremely high IQ. I mean, over the top. Fundamentally, that meant that everyone he interacted with was, to him, stupid. He suffered greatly, and eventually became addicted to various illegal drugs. The drugs had the effect of reducing his intelligence and made life bearable.
Reminds me of the Warren Buffett line about getting chased by a lion and crying out, “But I’m good at capital allocation.” Doesn’t do you much good.
Here the only philosopher worth reading offers a possibility: "And first, if we consider how little odds there is of strength or knowledge between men of mature age, and with how great facility he that is the weaker in strength or in wit, or in both, may utterly destroy the power of the stronger; since there needs but little force to the taking away of a man’s life; we may conclude that men considered in mere nature, ought to admit amongst themselves equality; and that he that claims no more, may be esteemed moderate." Hobbes, Thomas. The Elements of Law: Natural and Politic (modernised) (pp. 71-72). So those of lesser wit are able to destroy those of greater in the state of nature. Elsewhere the philosopher remarks that those of greater wit seek to dominate those of lesser, thereby bringing an early death to those of greater wit given the equal ability of all to kill everyone else.
do high IQ people find it harder to fit in with average people? Is there a huge benefit to just agreeing with the crowd?
I think there is. I want to say I read that you can’t have such high an IQ and be relatable to people. So very high isn’t desirable from an interaction perspective. Something around the 115-120 range I think they said is where the intelligence and relatability intersect positively.
The question has always been, at least for me, is why do people with high IQ make horrible decisions? Are we just defined by our ability to be good at math? There’s a lot of exceptionally smart people still wearing masks (not to harp on that topic too much but COVID broke the IQ factor for me).
Everyone makes horrible decisions. I'd bet the house that high IQ people make less simple mistakes. If they are making more decisions of a complex variety, they might still make as many or more wrong decisions but that would be comparing apples and oranges.
Also, note that it is easier to see a decision was "stupid" when we look at it in hindsight.
Agreed regarding the hindsight comment. Maybe regarding the assumption that high IQ makes fewer poor decisions. I think we want that to be true. Also, the impact of poor decisions from those with high IQ may have much greater ramifications because these people may be in positions of incredible responsibility.
Bull. I have no doubt plenty of high IQ people relate perfectly well. Do they relate less well? I'm skeptical so show me some evidence.
Some don't relate wellv and they stand out. Does an average intelligence person who can't relate stand out in the same way? I don't think so.
Maybe you are right due to secondary effects such as autism spectrum characteristics that make them less relatable but that's a secondary affect. So even if that is true, I see no reason to think just havinh high IQ and no other issues makes someone less relatable, given they are smarter and have more ability to figure out how to relate. Note that relating to others isn't just having the same IQ. It's also about finding a topic or activity to relate on. Again, high IQ should help finding and using this commonality.
I'd also note that in a community where many people are high IQ, including many university town and urban communities, high IQ doesn't have to be an anomaly.
Indeed.
I'm high IQ (except math) married to someone much smarter. (high-energy physics, engineering, business). He's one of the best judges of character I've ever met & positively Machiavellian in his ability to understand & manipulate people,, seductively charming with women.
He's also met some of the smartest men (physics Nobelists) in the world, who all had great social skills. There are some famous exceptions: Kurt Goedel (likely on the spectrum) stands out. But John von Neumann was socially skilled & a ladies man.
Speaking of physics: wearing a well-fitted N95 mask or respirator WILL block aerosol-carried virus particles.
David Friedman's subsequent post (linked in Arnold's footnote) explains why average intelligence would tend to increase over generations even if genius tends to be socially maladaptive for genius:
"If true, that implies that in a society with an average IQ of 100 an IQ of 150 may reduce instead of increase reproductive success. But as long as an IQ of 115 increases reproductive success, intelligence is being selected for and should increase. When the average gets to 115, 130 should increase reproductive success, and so on up. So although this is a reason why evolution might increase intelligence more slowly, it is neither a reason why it wouldn’t increase it nor an upper limit on how high it would eventually go."
This assumes all else being equal which Arnold very specifically denies being the case.
Arnold writes: "I think that all it takes for a society to continue to produce people without genius IQs is for there to be some point at which higher IQ actually reduces fitness on average. There are many ways that a high-IQ person could be more fragile."
Another complication: Whether an IQ of, say, 150 (on the current scale) in a later (evolutionarily accessible) cohort makes a person 'fragile' might depend on the prevalence of persons of IQ 150 in the later cohort. Frequency-dependent effects matter in some evolutionary contexts.
Why do stupid people exist? Because they benefit the group. The existence and reproductive success of a particular human group depends on the mixture of traits of the group as compared to the mixture of traits of other groups. In order for the group to be reproductively successful it needs dumb people to do the stuff that dumb people do best. What is it that dumb people do better than smart people? They work for the smart people, and it’s in the interest of the smart people to keep the dumb people around. In fact, the existence of smart people depends on dumb people. Being smart and staying smart requires work. Dumb people are like labor saving devices that free up time for smart people; making it possible for smart people to get even smarter.
I’m grateful for the dumb people in this world. They do work that smart people won’t do, and thus make the world a better place.
I think one answer is that marginal IQ hasn't been strongly selected for until quite recently. Being noticeably smarter than your neighbors doesn't do you a lot of good if you're a hunger-gatherer or a subsistence farmer -- at best, you can maybe come up with a better snare or an improved crop rotation method, but you're still so subject to time and fate that it doesn't make a huge difference to your family. It might help if your whole society took up your innovation, but most small-scale societies are incredibly conservative about these things. It takes a whole lot of "cultural technology" to end up in a situation where a smart person can meaningfully increase their chances of passing on their genes purely due to intelligence!
Individual fitness in the evolutionary sense may be more related to wisdom (the ability to use knowledge and experience to make sound decisions) than on IQ (that is ability to quickly understand and solve problems). Of course, one cannot be wise if stupid, but there are many high IQ people quite lacking in wisdom, often due to being caught up in and blinded by dysfunctional heuristics (e.g., ideology). I call such people "self-enstupidated."
I guess we'd have to distinguish what "high IQ" is. But in any case while I can see somebody with an IQ of 150 *originating* an ideology that is replete with bad ideas - such is ego, and to an extent creativity - it is harder for me to believe someone at that level would be captivated by ideology, absent some deformation of their mental powers.
Another hypothesis.
There are two effective strategies to solving problems. Create your own solution (rare), or copy or borrow one from somewhere else (vast majority aka culture). It doesn’t take much upstairs to copy or mimic or use tools or processes created by others. However, if just about everyone is copying the majority, this creates a competitive niche strategy of creating novel solutions. But this requires more intelligence to use imagination, consider tradeoffs, avoid potential new risks, and to combine ideas or transfer similar solutions from one domain to another.
This tracks closely to the hypothesis that there must be costs to intelligence (energy or such), but adds that the cost may actually be less copying and more wasted time energy and risk with novelty.
Thus the dominant strategy would be cultural copying, which is efficient and safe and doesn’t require much thinking, and the niche strategy would be to explore/create novelty which requires brain power.
Watching Carl Lewis perform at the Olympics several decades ago led me to wonder: why isn’t everyone athletic to that degree? Perhaps that thought should have been prompted by Bruce Jenner, who, as a decathlete, displayed a broader range of athleticism; I may have been influenced by Lewis’s remarkable gracefulness, and the fact that his events—sprints and long-jump—rely more on natural talent and less on training and practicing technique. But even the decathlon does not cover the full range of athletic talents, which include performance in weight-lifting, gymnastics, marathon running, swimming, horseback riding, hitting a baseball, shooting a basketball, etc.; truly general athletic accomplishment would make one good at more than a mere ten sporting events. (True, achieving anything like *excellence* in both weight-lifting and marathon running would be remarkable.) And then there are the fine-motor skills involved in drawing, sewing, playing the piano, etc., which are not considered “athletic.” Putting these all together, we may ask: why does the average human being not have more natural talent for *general physical performance*?
I think part of the answer is that Natural Selection “cares” about more than performance; just subsisting is also important: surviving shortages of food and water, hibernating or estivating (or just sleeping) during unpromising times—in general, passively dealing with privation. Another part of the answer is that Natural Selection works slowly and crudely: it is remarkable that it has produced creatures are impressive as us, though, of course, we *could* be even more impressive.
Now that we have mastered biotechnology and Artificial Intelligence we are ready to take over from Natural Selection, and produce some *really impressive* creatures.
From Scott Alexander's ACX Open Thread 346 (September 9, 2024):
ACX commenter Metacelsus is a Harvard bio PhD who the excellent De Novo blog; he also reviews most ACX posts and grants on biology for me. He recently co-founded a startup, Ovelle, to commercialize his academic work on gametogenesis (turning arbitrary cells into eggs). If this worked, it could replace the complicated and invasive egg harvesting process of IVF with a simple blood draw or mouth swab. But beyond that, it would allow women to circumvent menopause by creating eggs at any age (women can safety become pregnant well into their 50s, they just lose the ability to create eggs naturally), and maybe (this is still speculative) allow gay couples to have biological children. And with a couple of extra steps, you could turn this into a supercharged version of embryo selection that could essentially end all genetic disease (existing techniques don’t give you enough rerolls for more than incremental gains). This technology already works in mice, and some companies (including one backed by Sam Altman) are working on translating it to humans - but IIUC Metacelsus is coming from an academic lab that’s gotten significantly further. Ovelle is looking for people who want to invest or work for them (remember, investing in biotech is a minefield best left to professionals, and working in biotech is terrible and soul-sucking). You can contact them here.
Diversification of cognitive abilities does lower the average, but may benefit the community or species as a whole.
Even primitive social organisms such as bumblebees can solve reasonably interesting puzzles and then teach the colony to modify the innate behaviours to accommodate the new skill. Researchers find that ”there are huge inter-individual differences: most bees will require either step-wise training or the chance to observe a skilled conspecific to master the task on their own. A very small minority of individuals even solve the task by individual trial-and-error learning.” (see Bee Cognition/Current Biology/vol 27/19/Oct 2017)
Now imagine that some individuals in a colony are particularly stubborn and just cannot learn the winning strategy discovered by the smart bumblebees. Why this can be a winning strategy for a colony? Because a short-term winning strategy can harm the species in the long term. Stubborn, conservative individuals then save the colony.
Nature optimizes not for the skill, but for the species’ survival.
This and one other comment are arguments for group selection. Standard evolutionary theory is that you are evolving to compete against other members of your species, not to help each other out. But people may be different since so much of our success comes from cooperation.
I was trying to make a point that diversity of skills is advantageous overall. Changing environment requires quick adaptation. Diverse species just adapts better/faster: it has seed individuals better adapted for the new environment. Too much specialization is unsustainable in the long term - using Arnold's perspective.
(I'm not the David Friedman referred to in the post.)
It seems plausible that before the modern era there was a hard limit on low intelligence. The less intelligent you are, after all, the less you can do for the tribe: growing food, tracking game, storing resources, etc., all require some level of cognitive ability. But as society industrialized and became wealthier (at least in the west), our ability to house and feed the unintelligent improved. So maybe today we see a greater range of intelligence in the population, overall, because we can afford to feed and house the less intelligent.
While there are a lot of good points in both the article and the comments, I think the most likely answer is Thomas L. Hutcheson’s in the comments here. “Stupid” is relative, and we were a lot more stupid in the past. Intelligence has been selected for, but not everywhere all the time, due to all the different factors folks here have mentioned. Evolution is usually a slog.
It may also be that there's no feasible way for new mutations to improve the average or reduce the variance of human intelligence much, or to do so without introducing other non-adaptive traits. One can't always assume that every trait exists solely because it's adaptive compared with other imagined possibilities. To reiterate an old joke about this aspect of evolution: there's a reason why deer don't have built-in laser cannons to protect them from predators, and it isn't because that wouldn't be adaptive.
Or it may be that greater intelligence can only be achieved by (combinations of) genes that have adverse maladaptive side effects. For example, genes for greater intelligence may correlate with risk of relatives developing disabilities. Highly intelligent people are more likely than average to have autistic siblings, this is pretty well confirmed.
Maybe intelligence HAS been drifting up over the eons.
Friedman seems to only be addressing male reproductive success vs IQ, when it's important to note that women have greater influence over their child's IQ than men do (I think this has to do with children inheriting mitochondrial DNA only from their mother, but I could be misremembering), and high IQ seems to negatively impact women's reproductive success in the modern world. Educated, economically successful women seem to not want to settle for a partner whose own achievements aren't on the same level, but successful men do not have the same filter when selecting a partner of their own (youth, fertility markers, etc. you know the drill), thus you wind up with a fairly large group of high IQ women who are destined to be unsuccessful in the marriage market. Not to mention there are the pets and self-gratification angles Friedman discusses that affect women as well as men, which further affects the reproductive success of high IQ women.
Edit: a couple more comments worth adding, I think:
1. I think DF's sports car analogy is correct, but he's not drawing the correct conclusion from it. Sports cars aren't inherently more complicated than other vehicles. The reason they spend a lot of time in the shop is that to get the high performance, you have to increase the thrust to weight ratio of the car relative to other vehicles, so the component parts are very lightweight, but have more force applied to them, and thus prove to be far less durable than components for other cars. The basic issue is that in complex systems, there are always trade-offs that have to be made. It's not necessarily that "something went wrong," it's that maximizing for trait A means probably means you have to accept a higher likelihood of lower trait B scores or what have you.
2. I think Friedman is right that you have to consider just good ol specialization, comparative advantage, ROI, etc. Consider that if you live in a village of relatively skittish people circa 8,000 BC, the returns to being fearless are probably pretty high. But if everyone in the village is fearless, you probably get an excess of violence, and thus it might become an advantage to be skittish, since you avoid physical conflicts that are debilitating or deadly to your peers. Since brains are biologically expensive, as Friedman notes, you can imagine circumstances where minimizing the investment in energy intensive tissue would be a winning strategy, and would continue to work into the modern era, because after all, somebody still needs to dig ditches, take out the trash, etc.
I believe I saw somewhere that independent of hypergamy, high-IQ women are less likely to want children, and being smart, can make damn sure they never get pregnant. I'm high-IQ in a long-time marriage to a higher-IQ man (he's taller, too, but I'm only average female height). Both of us (as well as his ex-wife, even smarter than me cause she got the math chip) knew from childhood we didn't want children & got sterilized in our 20s.
When I was at university, I had a friend with an extremely high IQ. I mean, over the top. Fundamentally, that meant that everyone he interacted with was, to him, stupid. He suffered greatly, and eventually became addicted to various illegal drugs. The drugs had the effect of reducing his intelligence and made life bearable.