I'd like to know how valid the concern about negative selection is. It stands to reason that having a negative correlation between IQ and reproduction, as we appear to have instituted in modern society, should increase the inequality between a highly intelligent minority and an ever increasing class of stupid people, presumably depressing the mean cognitive capacity and increasing its variance under the curve?
As for the question why we're not all geniuses, the answers probably shouldn't be different from asking why we're not all as good-looking as models or not as athletic as star athletes. Cognitive ability is one advantage for survival, athleticism another (for instance). The correlation between the two is likely very modest...
The answers should be of the same sort for looks and athleticism, some combination of bio costs, behavioral costs, and benefit of diversity, but not the same in detail. I can't think of any plausible reason why being better looking would lead to behavior that reduced reproduction.
Probably should have expanded this comment a bit. "I personally know a very ugly and not very smart woman who has 6 children. She's a sweet person, but . . ."
Until fairly recently females began breeding shortly after menarche. Possibly they hadn't had time to display higher intelligence in ways that were obvious to males.
Even today, there's plenty (see, e.g. David Buss) of evidence that the "standards of beauty" are extremely correlated with good physicla health, good ability to withstand parasitesa nd disease, and fertility, or the ability to produce (probably healthy) offspring. This is cross-cultural and appears to be accurate in nearly all cases. And almost all men who want to breed with women want the "most beautiful" woman who will accept them, but many settle for less for reasons other than producung the 'best' offspring. Evolution has made men very horny.
So my argument is, I suppose, that until recently (200 years? Less?) intelligence was a "cloaked variable" hidden amongst more prominent variables. And the idea (I have no proof) that early humans were like similar hominid species busy keeping every possible female pregnant as often as possible.
So perhaps higher intelligence was inadvertantly selected as a by-product of females who met the more visible characteristics that attracted males.
And that's aside from arranged marriages, a social custom that is used for more 'political' reasons.
My argument doesn’t require men to deliberately select women for intelligence. There are three other mechanisms that would link female intelligence to reproductive success:
Smarter women do a better job of mate selection — don’t fall for seduce and abandon, do select, among men who want them, the one who will do the best job of helping rear her children.
Smarter women do a better job of keeping their children alive to adulthood.
Smarter women do a better job of keeping themselves alive to produce children.
I once heard about a study that said that there is a correlation between intelligence and beauty amongst women. Presumably cause smart men get rich and that allows them to attract pretty girls with hwhom they have smart and pretty babies.
Apparently, there is no such correlation amongst men.
I've wondered if that is particularly true of high caste Indian women.
I would expect the correlation to be higher, and the women more beautiful, in polygenous societies and ones with a high level of income inequality and not very high average income. Be neat if one could actually test that, but it requires objective judges of pulchritude who can compare women of differing ethnicities.
I am reading _The Goodness Paradox_ by Richard Wrangham and he comments that brain size has been increasing but then says ' Around 30,000 years ago brains started to become smaller. In Europe modern brains are some 10 to 30 percent smaller than those living 20,000 years earlier'. (Chapter 3, Human Domestication, page 63). His sources are this paper by Maciej Henneberg https://pubmed.ncbi.nlm.nih.gov/9750968/ and Robert Bednarik https://pubmed.ncbi.nlm.nih.gov/25440983/ This was news to me.
The first one seems to be saying that body size decreased as well. The second is more interesting. The theory seems to be that the development of ways of storing information outside the brain, such as writing, reduced the usefulness of large brains, possibly because the extra size was used for memory. Writing doesn't start that early so I'm not sure exactly what he is thinking of.
Richard Wrangham says that when you breed animals for lack of aggression, their brains get smaller. This is true for wolves/dogs, cavies/guinea pigs, foxes, rats, mink ... as far as I know every animal he has studied except for domestic mice. (He didn't mention any other exceptions.) It is very odd. You breed for this one trait only, and you also get floppy ears, white spots, and a smaller brain. But despite the smaller brain, guinea pigs outperform cavies, and dogs outperform wolves and domesticated foxes outperform the wild ones in tests they have designed for intelligence. So, if he is correct that human beings have domesticated themselves by culling the most violent members of their social groups, then the loss of brain size would just be a side-effect of that.
One method for detecting fitness in humans (and humans use it consciously or not) is the length and quality of head hair. It is a uniquely human trait, but it requires a good diet over a long period of time. Does it take intelligence to maintain a good quality diet? To some extent it must. Care and maintenance of hair also requires some degree of intelligence and dexterity. I've often noted in North America, women often cut their hair short after having children. Hmmm.
If intelligence is the ability to learn from others and act on what we learned, possibly against our "instincts", then higher intelligence means higher susceptibility to propaganda.
The efficient mammal hypothesis can't be true, otherwise there would be no such thing as a rapidly proliferating invasive species, and mankind would be confined to Africa on account of our ecological niches across the world having been filled before our ancestors got there. The idea that evolution succeeds in any sense of finality at maximizing fitness is not supported by the facts!
I think you might need to clarify a bit more just what you mean by intelligence. Skill or talent within a given field seems insufficient, as one might be exceptionally good at one sort of thing and bad at another and lumping that all under "intelligence" seems way too broad to try and pin down. If we are just talking aptitude for something then lots of random genetic mixing will be the answer (being tall with wide arm span makes you really good at basketball, having small delicate fingers and good eye sight a good watch maker, whatever).
I think the other question might be varying in intelligence compared to what? We might think that humans vary a lot in intelligence, while squirrels are thinking "Damn, all those humans are super smart! Not like us squirrels... Dave over there is so stupid he eats the shells!" Size varies a lot between animals, intra but especially inter species, so maybe intelligence does too and we just have a harder time noticing outside of an exceptionally clever dog that intelligence is really random (kind of going along with the highly tuned sports car example). Lots of things play into it, and lots of things have to be a certain way to be really smart.
Lastly, the point about women not being able to signal intelligence for selection raises another question: if high intelligence requires a lot of good nutrition in childhood to fully manifest its protentional, the genes that cause high intelligence might be less adopted as the ceiling of nutrition might be lower. That is, if everyone in your tribe gets enough nutrition to have max 110 IQ it doesn't matter much if your genes have the potential for 140 IQ because you can't get there so it won't be selected for. Even if you get lucky and manage to get above that barrier your offspring will have to be so lucky, and if nutrition above that level is based largely on luck (or other things outside the individual's control) then your kids are not likely to be any more successful than other people's.
In all these comments, not ONE mention of either Brave New World or Idiocracy! 😛
I'd like to know how valid the concern about negative selection is. It stands to reason that having a negative correlation between IQ and reproduction, as we appear to have instituted in modern society, should increase the inequality between a highly intelligent minority and an ever increasing class of stupid people, presumably depressing the mean cognitive capacity and increasing its variance under the curve?
As for the question why we're not all geniuses, the answers probably shouldn't be different from asking why we're not all as good-looking as models or not as athletic as star athletes. Cognitive ability is one advantage for survival, athleticism another (for instance). The correlation between the two is likely very modest...
The answers should be of the same sort for looks and athleticism, some combination of bio costs, behavioral costs, and benefit of diversity, but not the same in detail. I can't think of any plausible reason why being better looking would lead to behavior that reduced reproduction.
Probably should have expanded this comment a bit. "I personally know a very ugly and not very smart woman who has 6 children. She's a sweet person, but . . ."
Until fairly recently females began breeding shortly after menarche. Possibly they hadn't had time to display higher intelligence in ways that were obvious to males.
Even today, there's plenty (see, e.g. David Buss) of evidence that the "standards of beauty" are extremely correlated with good physicla health, good ability to withstand parasitesa nd disease, and fertility, or the ability to produce (probably healthy) offspring. This is cross-cultural and appears to be accurate in nearly all cases. And almost all men who want to breed with women want the "most beautiful" woman who will accept them, but many settle for less for reasons other than producung the 'best' offspring. Evolution has made men very horny.
So my argument is, I suppose, that until recently (200 years? Less?) intelligence was a "cloaked variable" hidden amongst more prominent variables. And the idea (I have no proof) that early humans were like similar hominid species busy keeping every possible female pregnant as often as possible.
So perhaps higher intelligence was inadvertantly selected as a by-product of females who met the more visible characteristics that attracted males.
And that's aside from arranged marriages, a social custom that is used for more 'political' reasons.
This is a great discussion, BTW.
My argument doesn’t require men to deliberately select women for intelligence. There are three other mechanisms that would link female intelligence to reproductive success:
Smarter women do a better job of mate selection — don’t fall for seduce and abandon, do select, among men who want them, the one who will do the best job of helping rear her children.
Smarter women do a better job of keeping their children alive to adulthood.
Smarter women do a better job of keeping themselves alive to produce children.
Smarter women become grandmothers would be a real marker.
I once heard about a study that said that there is a correlation between intelligence and beauty amongst women. Presumably cause smart men get rich and that allows them to attract pretty girls with hwhom they have smart and pretty babies.
Apparently, there is no such correlation amongst men.
I've wondered if that is particularly true of high caste Indian women.
I would expect the correlation to be higher, and the women more beautiful, in polygenous societies and ones with a high level of income inequality and not very high average income. Be neat if one could actually test that, but it requires objective judges of pulchritude who can compare women of differing ethnicities.
I am reading _The Goodness Paradox_ by Richard Wrangham and he comments that brain size has been increasing but then says ' Around 30,000 years ago brains started to become smaller. In Europe modern brains are some 10 to 30 percent smaller than those living 20,000 years earlier'. (Chapter 3, Human Domestication, page 63). His sources are this paper by Maciej Henneberg https://pubmed.ncbi.nlm.nih.gov/9750968/ and Robert Bednarik https://pubmed.ncbi.nlm.nih.gov/25440983/ This was news to me.
The first one seems to be saying that body size decreased as well. The second is more interesting. The theory seems to be that the development of ways of storing information outside the brain, such as writing, reduced the usefulness of large brains, possibly because the extra size was used for memory. Writing doesn't start that early so I'm not sure exactly what he is thinking of.
Richard Wrangham says that when you breed animals for lack of aggression, their brains get smaller. This is true for wolves/dogs, cavies/guinea pigs, foxes, rats, mink ... as far as I know every animal he has studied except for domestic mice. (He didn't mention any other exceptions.) It is very odd. You breed for this one trait only, and you also get floppy ears, white spots, and a smaller brain. But despite the smaller brain, guinea pigs outperform cavies, and dogs outperform wolves and domesticated foxes outperform the wild ones in tests they have designed for intelligence. So, if he is correct that human beings have domesticated themselves by culling the most violent members of their social groups, then the loss of brain size would just be a side-effect of that.
One method for detecting fitness in humans (and humans use it consciously or not) is the length and quality of head hair. It is a uniquely human trait, but it requires a good diet over a long period of time. Does it take intelligence to maintain a good quality diet? To some extent it must. Care and maintenance of hair also requires some degree of intelligence and dexterity. I've often noted in North America, women often cut their hair short after having children. Hmmm.
If intelligence is the ability to learn from others and act on what we learned, possibly against our "instincts", then higher intelligence means higher susceptibility to propaganda.
The efficient mammal hypothesis can't be true, otherwise there would be no such thing as a rapidly proliferating invasive species, and mankind would be confined to Africa on account of our ecological niches across the world having been filled before our ancestors got there. The idea that evolution succeeds in any sense of finality at maximizing fitness is not supported by the facts!
I think you might need to clarify a bit more just what you mean by intelligence. Skill or talent within a given field seems insufficient, as one might be exceptionally good at one sort of thing and bad at another and lumping that all under "intelligence" seems way too broad to try and pin down. If we are just talking aptitude for something then lots of random genetic mixing will be the answer (being tall with wide arm span makes you really good at basketball, having small delicate fingers and good eye sight a good watch maker, whatever).
I think the other question might be varying in intelligence compared to what? We might think that humans vary a lot in intelligence, while squirrels are thinking "Damn, all those humans are super smart! Not like us squirrels... Dave over there is so stupid he eats the shells!" Size varies a lot between animals, intra but especially inter species, so maybe intelligence does too and we just have a harder time noticing outside of an exceptionally clever dog that intelligence is really random (kind of going along with the highly tuned sports car example). Lots of things play into it, and lots of things have to be a certain way to be really smart.
Lastly, the point about women not being able to signal intelligence for selection raises another question: if high intelligence requires a lot of good nutrition in childhood to fully manifest its protentional, the genes that cause high intelligence might be less adopted as the ceiling of nutrition might be lower. That is, if everyone in your tribe gets enough nutrition to have max 110 IQ it doesn't matter much if your genes have the potential for 140 IQ because you can't get there so it won't be selected for. Even if you get lucky and manage to get above that barrier your offspring will have to be so lucky, and if nutrition above that level is based largely on luck (or other things outside the individual's control) then your kids are not likely to be any more successful than other people's.