Professor James Flynn himself suggested that intelligence is being selected against:
ISTM that that remark elides a very important difference between “only allowing Group A to reproduce” and “Group A reproducing at a higher rate than Group B but with reproductive mixing between the two groups and sexual selection favoring Group B traits”.
Sure, if you allow only short people to reproduce, the average height of the population will decrease. But that’s not remotely similar to the situation we’ve got with intelligence.
More-educated/wealthy and less-educated/wealthy people are not even reproductively isolated populations, and it’s certainly not true that only the latter are being allowed to reproduce.
Those two groups mix with each other all the time, both by direct pairing between groups and by having offspring move from one group to the other. As long as people with higher education/wealth status are not reproductively isolated from the rest of the population, and as long as higher education and wealth levels increase one’s appeal to potential mates, then I just don’t see how anyone could plausibly predict that average levels of education and wealth would decrease in the population as a whole.
Okay, excuse me if I’m being dense, but this has to be a whoosh, right? You’re not seriously arguing that celibacy of medieval Catholic clergy affected intelligence levels in the general population, much less that a parent’s intelligence level is transmitted only to offspring of the parent’s own gender?
bldysabba writes:
> This is exactly what I meant when I said there is reason to think it can go
> down. The Flynn effect is entirely non-genetic, while the question I have posed
> is based on genetic selection. If the Flynn effect is limited and has reached that
> limit, as it seems it has, upbringing/nutrition/reduced disease burdens can no
> longer boost IQ, at least in rich countries. Read with the post above, it is only
> logical that genetics will play a more important role in the time to come in
> determining intelligence, since genetics is the sole arbiter of the ‘Intelligence
> potential’ of an individual. My original question still remains valid I think.
There’s no proof though that the genetic selection that you claim to exist actually exists. The environmental selection (which has supposedly been raising the average I.Q.) certainly seems to exist, since it has raised the average I.Q. in many countries around the world for most of the past century. The genetic selection that you claim to exist (which has supposedly been lowering the average I.Q.) is either so small that it’s been swamped by the environmental selection up to now or perhaps it doesn’t exist at all.
Your proof that the genetic selection exists consists of saying 1) more educated, richer people tend to have less children and 2) we all know that I.Q. is inherited, so 3) the average I.Q. must be being lowered by the genetic effects (although this may be swamped up to now by the environmental effects).
First, it’s not even consistently true that richer people have more children. If you look at the number of children that people in various socio-economical classes have, what you see is that there is a slow drop in the number of children that people have from the most poor people up to upper-middle-class people. After that there is a quick rise in the number of children that they have up to the richest people of all. The richest people of all have more children than the poorest people of all.
So why do upper-middle-class people have the least number of children on average, when rich people have the most number of children on average? Well, perhaps it has something to do with the fact that upper-middle-class people are exhausted during their child-bearing years, while rich people have the opportunity to take time off. If you don’t have lots of family money, the only way you can hope to retire rich is to spend the first couple of decades of your adult life working yourself into a frazzle. You have to get a good law degree and spend the first few years of your law career working a lot of overtime. You have to get a good medical degree and spend the first few years of your medical career working like crazy to build up your practice. You have to get a good business degree and work long hours at a big corporation to work yourself up the corporate ladder. You have to get a Ph.D. at a top university and publish like crazy to get yourself a top teaching job and eventually a Nobel Prize or whatever. Similarly for other sorts of jobs. On the other hand, if you’re already rich by the time you reach adulthood, you can take time off whenever you want. Do you want to change our society so that upper-middle-class people have time to have as many children as poor people and rich people? Then change the way that our society works so that people trying to rise to the top of their professions don’t have to work themselves into exhaustion during their child-bearing years.
Second, it’s not clear that more educated people are consistently more intelligent people. Have you ever met any poor people? A lot of them are quite smart, but they were discouraged from getting a good education. Heck, I grew up in a struggling working-class family, and I can tell you that there was a lot of pressure among such people not to get a first-class education. In fact, there was a general discouragement of any sort of ambition to rise to a significantly higher level of achievement.
Third, you are assuming that intelligence is inherited. This has been greatly debated. It’s not universally accepted as proven. I don’t want to get into an argument about that in this thread. No, really, I DON’T WANT TO ARGUE ABOUT IT IN THIS THREAD. In any case, unless it’s proven that intelligence is inherited, your entire argument falls apart. It’s as simple as that. Unless it’s proven that intelligence is inherited, there’s no way that any genetic selection could change the average I.Q.
[annoying]“Africa” is not a “traditional society,” but rather a collection of more than 60 countries, a billion people, and thousands of ethnic groups, some of which are shopping at Baby Gap and watching Harry Potter as we speak, and all of which do, in fact, live in a modern, changing, society that is formed by modern conditions[/annoying]
They don’t have to be completely isolated. All that you need is for the less intelligent to generally have more children. And that is what Flynn is referring to, providing education stats as an example. Do you think that college educated people tend to have children with other college educated people? Do you think that maybe people who drop out of High School are somewhat more likely to have children with others with a similar educational background?
I thought everyone accepted that intelligence was partially influenced by the genes you inherit! Oh well, here are some recent studies for you:
Nope, AFAICT that does not automatically mean that the population as a whole becomes less intelligent.
You seem to be thinking of this phenomenon as analogous to some kind of chemical mixing procedure: e.g., the higher-status people are blue paint while the lower-status people are yellow paint, and the amount of yellow paint is increasing faster than the amount of blue paint. So the overall average green color of the population as a whole is gradually getting more and more yellow.
But that’s not really a good analogy for education/wealth status (as a proxy for intelligence) vis-a-vis reproduction. For one thing, the population is on a continuous spectrum instead of just being split into two colors. For another thing, “bluer” parents can often have “yellower” offspring and vice versa. And moreover, “blueness” characteristics (i.e., higher levels of education and wealth) are more attractive overall to potential mates.
Sure, but again, these groups aren’t reproductively isolated. As I pointed out a few posts ago, the percentage of American adults with a college degree has increased from about 5% in 1950 to about 25% now, and seems to be still increasing. That’s not the result of college-educated people having disproportionately more babies: that’s the result of the college-educated population increasing due to other factors.
So we see that the college-educated can physically reproduce less while nonetheless increasing their share of the overall population. If we insist on treating college education as a proxy for intelligence, we’d be forced to conclude that the average intelligence level has been skyrocketing.
These sorts of conclusions based on using rough demographic categories as proxies for genetically and environmentally complicated qualities like intelligence simply don’t reflect, AFAICT, how population genetics actually works.
Things like the SAT are basically IQ tests. So you can in fact make rough predictions. In terms of whether population shifts can occur, again you need to consider assortive mating patterns.
I’d recommend you read some of Hsu’s posts on Greg Clark’s work which discuss how you can get a shift in quantitative, heritable traits like intelligence or height.
For one thing, we can ditch the “education/wealth status (as a proxy for intelligence)” I did that because I wasn’t aware that there are studies that show a direct negative correlation between intelligence and fertility rates. There are, and I’ve cited them in direct response to one of your posts I think.
For another, as far as I know, on an aggregate level, selection should work like the ‘paint mixing’ you speak of. If there are more people on average with one trait(lets say low genetic potential for intelligence - yellow) than people with another(high genetic potential for intelligence - blue) and * if there is no selection pressure for either in terms of survival/reproductive advantages being conferred by that trait*, which in modern developed countries I don’t think there is, then genetic selection should work in the paint-mixing fashion that you’ve described, except that if yellow paint produces more yellow paint and blue paint produces less blue paint the process will get faster with time. One way this will not happen is something I’ve already admitted to you. If the yellow paint randomly (without survival/reproductive advantages) produces enough blue paint to make up for the reduction in blue because of declining fertility in blue, then intelligence will not decline.
Again - nobody’s insisting on treating college education as a proxy for intelligence. And even if that was my initial argument, it was not that intelligence causes college education or that college education/intelligence causes low fertility, it was only that there is a correlation. This is an important distinction (And in fact, the Flynn effect does show that the intelligence level has been ‘skyrocketing’) Other factors could and did increase college education. In fact, as the discussion has evolved, it’s been shown that other factors can and did increase intelligence levels too. There is evidence to show however, that these factors may be reaching the limit of the impact they can have on intelligence. That leaves us with the original question which I will restate here to incorporate the evolution of this thread. In the absence of survival/reproductive pressures in favour of intelligence, and in the presence of reproductive pressures against intelligence(negative correlation between fertility and intelligence), why would the genetic potential for intelligence not reduce/stagnate especially if current trends remain the way they are?
Yeah that’s what I thought too. Funny how picking any ideology be it liberal/conservative/religious/socialist/capitalist often makes people ignore inconvenient facts.
bldysabba,
An interesting analysis by Razib Khan here at Gene Expression.
But your cited example doesn’t just “consider” assortative mating, it assumes the existence of only assortative mating: in other words, the exact condition of reproductive isolation that I objected to as unrealistic!
Yes, and right in the cite that you linked to, it says that the observed correlation effect “is mediated in part by education and income”! So no, this isn’t evidence for some effect of intelligence considered totally in isolation from such proxy measures.
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You haven’t shown evidence for the absence of reproductive pressures in favor of intelligence. You’ve simply asserted that in your opinion, sexual selection these days doesn’t favor intelligence as an attractive trait in potential mates. I know of no reason to think that’s true.
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You haven’t shown evidence for the presence of reproductive pressures against intelligence. All you’ve shown is that in certain simplistic models that make various unrealistic assumptions, artificially isolated groups with different levels of certain characteristics associated with intelligence (e.g., IQ scores, education, income, etc.) will continue to reproduce at different rates over time.
There’s nothing intrinsically wrong with the question you’re wondering about or with trying to find an answer to it. But the two assumptions you’re basing your suggested answer on simply are not convincing as adequate representations of reality.
My request to explain how reproductive isolation is important still stands.
It doesn’t matter what mediates it as long as the correlation holds true! I’m not interested in establishing causality. If intelligent people have fewer children, that is all that matters for my argument, and I HAVE shown evidence for it. As for the correlation not holding true in the future, I’ve already admitted that caveat… ‘If current trends hold’
What would you accept as evidence? My reason to think it’s true is that there really are no survival pressures to speak of in modern advanced societies. Your lack of intelligence is not likely to kill you off(except in the extreme cases of the Darwin awards as noted by one poster 
) . I absolutely agree that more intelligent people may find it easier to get the mates they prefer, but please give me reason(I’m asking for a cite here) to think that 1) This means more intelligent people will reproduce more and 2) That less intelligent people will not get mates or that they reproduce less. In fact, while you may say…
I consider a negative correlation between intelligence and fertility to be very good evidence for reproductive pressures against the genetic component of intelligence, even if you say…
This part I’m having difficulty with, to be honest. How do you think any social science research is done? Do you have reason to believe that the studies I have quoted are methodologically less rigorous than any other research ever quoted by anybody? I have nothing personal invested in these studies and am taking them at face value, but your attacks on them seem to be driven only by your opposition to their conclusion. I’ll be happy to reconsider this view if you have identified mistakes* in what is peer-reviewed, revised and published scientific research.
*(what you call unrealistic assumptions, artificially isolated groups etc. Where is this stuff coming from? And for the 3rd time, what does isolation of populations have to do with anything?)
Around here women with a long education or high on the career level are getting considerable fewer children than average, while successful men (wealth or career wise) are having more children than average. So we are currently selecting for a future with intelligent men and stupid bimbos. But in general the richest most successful part of society are getting more children than average, same as the poorest. It’s the middle class that is being squeezed out.
Well, the explanation is still the same as before: namely, if “smart” and “dumb” people keep mixing their populations by interbreeding, high levels of individual variation, and social mobility, then there’s no reason to believe that the “dumb” ones will “outbreed” the “smart” ones. That could only happen if the two populations were effectively separated—i.e., reproductively isolated—so that the above three “mixing phenomena” wouldn’t be able to occur.
But that doesn’t mean that there aren’t still characteristics that are favored by sexual selection. And as you yourself acknowledge, intelligence is one of them. If intelligence is in general sexually attractive, then people in general will favor intelligence as one of the criteria when selecting mates.
Um, yes, it certainly does matter that some of the mediating factors, such as education and income, are strongly influenced by non-genetic causes.
The fact is that, at least at present, we simply can’t come anywhere close to testing the social effects of genetically determined intelligence by itself. All our yardsticks of intelligence measurement are tangled up with non-genetic factors.
Nope. I just think that the broad-brush inferences you’re attempting to draw from them seem to be methodologically less rigorous than the evidence warrants.
It is certainly not an insult to any piece of scientific research to observe that it uses “simplistic models that make various unrealistic assumptions”. All research depends on formulating models that to some extent simplify and reduce reality to a more unrealistic approximation. And research about a subject as complicated as human intelligence and population genetics certainly has to do so. The models will doubtless get refined over time as we learn more about the genetic mechanisms underlying psychological characteristics, but we have a long way to go.
There’s nothing wrong with reporting that “given this model of population X with these assumptions about reproductive patterns, we predict that the average level of characteristic Y in the population model will change yay-much in Z generations.” What’s not justified, IMO, is using such a finding to jump to conclusions about real-life populations and characteristics that aren’t very closely approximated by the current models.
Where are you referring to? Do you have some stats?
Umm, did you read the mating pattern data in my post above? Hsu’s assumption regarding assortive mating appears to reflect what happens in the real world. Another paper discussing this here.
Like I said to md2000 (who, oddly enough, was postulating a similar “selection effect” but with the genders reversed) in post #63, this has to be a whoosh, right? You’re not seriously claiming that if an intelligent man marries an unintelligent woman, they will produce intelligent sons and unintelligent daughters?
Everybody knows that you don’t inherit heritable traits only from your same-sex parent, right?.. Right? :eek:
Nope, he specifically stated, as I quoted, that he assumed strictly assortative mating: that is, Group 1 mated only with Group 1, Group 2 only with Group 2, etc. That’s not at all what happens in the real world. In the real world, not only do many people mate across group boundaries, but many people migrate from one group to another independent of reproduction.
For instance, your own most recent cite about educational assortative mating highlights the fact that the group populations in educational levels are very fluid. Lots of people get more education than they’re “genetically entitled to” (i.e., a higher education level than their parents had), simply because there are reduced social barriers and increased social incentives for prolonging one’s education.
Actually, the reproductive isolation that you speak of isn’t required. Both men and women have a negative correlation between intelligence and fertility. A smart-smart pairing would produce the least children, smart-dumb pairing would come next, and dumb-dumb would produce the most children. Even if the ‘interbreeding’ that you envisage happens, it does not affect this. I’ll give you an example. Consider a smart-dumb pairing has two children, one smart, one dumb. The smart child is more likely to have fewer children than the dumb one. When you aggregate this at population levels, it suggests a reproductive pressure against intelligence which accelerates if you include isolation, but does not require isolation.
Hang on. You seem to accept my point that there are no survival pressures to speak of. How then do you get to the position that there are in fact ‘still characteristics that are favoured by sexual selection’? I have only ever stated that intelligence was favoured in the past, and this could be due to either survival or reproduction, and I have explicitly stated that neither of these factors apply today.
This is the third time I’m making this point, the second time to you. Intelligent people could definitely be favoured when selecting mates. The only way that this provides an evolutionary benefit however, is* if intelligent people also reproduce more*. I have asked specifically in the last post for your reason for assuming this to be the case, especially considering that it flies in the face of what I have cited, and I ask you again.
Ah. I see what you’re getting at. You’re saying that the IQ-fertility correlation could be entirely or largely due to the non-genetic factors. Ok, you have a point, but it’s a bit of a stretch don’t you think? If high IQ exists in a person, IMHO it’s fairly reasonable to assume that high genetic potential and upbringing both contribute to it and vice versa, especially in a study done in a modern developed country like the USA. So if there is a negative correlation between IQ and fertility, there is a negative correlation between genetic potential for IQ and fertility as well.
Broad brush inferences? I’m practically using the conclusions of the study word for word! Or do you not agree that a negative correlation between intelligence and reproduction amounts to reproductive pressure against intelligence?
Hang on again. The study results don’t mention population genetics at all, merely fertility rates, and those are about as uncomplicated as you can get.
Again, where are you getting this stuff? Which model? What assumptions about reproductive patterns? What predictions? Again, you don’t seem to be concerned with the specifics at hand. These are empirical studies that measure (real) people’s IQ and correlate it with how many (real) children they have, and control for things like wealth, education etc. If you have a specific problem with the results/studies or the way I’m using them, I can try and examine it. Completely made up strawmen I do not wish to engage with.