# Will intelligence be selected against? **URL:** \ **Category:** Great Debates\ **Created:** [September 13, 2011, 5:47pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177 "2011-09-13T17:47:44Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [September 14, 2011, 4:16am UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/41 "2011-09-14T04:16:39Z")
> [@EdwardLost](#): > > It’s my humble opinion that studies WOULD find reproductive success linked with other, non-IQ forms of “intelligence” such as charm, charisma, a dominant personality, a risk-taking personality, etc. Yes; every time a man talks a women into going to bed with him for example that’s someone getting a chance to reproduce by being _clever_. ---
**Author:** ![Ibn\_Warraq](https://avatars.discourse-cdn.com/v4/letter/i/e19b73/32.png) [@Ibn\_Warraq](https://boards.straightdope.com/u/Ibn_Warraq)\ **Post date:** [September 14, 2011, 4:50am UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/42 "2011-09-14T04:50:55Z")
> [@bldysabba](#): > > Research shows a reasonably high correlation(not causation mind you) between intelligence(IQ), education and wealth _on average_. Studies also show that there is an inverse correlation between education & wealth and the number of children that people have - i.e more educated, richer people are more likely _on average_ to have fewer children. (I don’t think these are controversial points, but in case people think so, I can provide cites) > My question is as follows - Intelligence was the main trait that set us apart from other apes. With time(evolutionary time scales), intelligence got selected for and aided in the survival and spread of the human species and we became more and more intelligent. In today’s world (and hopefully tomorrow’s), societies guarantee at least the survival of all, especially in the developed world. If more intelligent people are having fewer kids, and less intelligent people are having more, and both sets are equally likely to survive and reproduce (this last is an assumption of course, but not wholly unrealistic I think?) will we see humankind _on average_ become less intelligent, or at least a reduction in the rate of growth of intelligence? > Please note: This contention is value neutral, I’m not implying that intelligent = good, not intelligent = bad Dude, Eugenics was discredited over a hundred years ago. ---
**Author:** ![bldysabba](https://avatars.discourse-cdn.com/v4/letter/b/ecccb3/32.png) [@bldysabba](https://boards.straightdope.com/u/bldysabba)\ **Post date:** [September 14, 2011, 5:59am UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/43 "2011-09-14T05:59:39Z")
> [@Kimstu](#): > > Actually, one of my points is precisely that there **is** such mobility between groups. In other words, the upwardly-mobile “smart child” would be mixing the genes of his/her “dumb” kin in with the genes of his/her adopted social class. When one of his/her kids takes after Uncle Derpy in being a few sandwiches short of a picnic, then the intelligence gene pool has been stirred up afresh with Nature’s big fuckstick, thus preventing genetic isolation of the different groups. I have never postulated genetic isolation of the groups. Even with social mobility, more intelligent people have lower fertility rates and would end up reducing in numbers. Your point of less intelligent people having smart children randomly could be valid though. I was trying to model it mathematically, and _if_ the proportion of ‘intelligent children born to less-intelligent parents’ is high enough to offset lower fertility rates in intelligent people and the proportion of ‘less-intelligent children born to intelligent parents’ then indeed we would not see a decline in average intelligence. These proportions are impossible to estimate accurately given current knowledge though, but I’ll keep it in mind. Thanks. > [@](#): > > But increasing education and wealth **for a society as a whole** isn’t the same as genetically increasing intelligence of a sub-population **within** a society. So right there you’ve got a huge confounding factor in attempting to correlate intelligence with fertility rates. I’m afraid I don’t see how you’ve arrived at the confounding factor here, but it turns out I don’t need to correlate intelligence with fertility rates, it has been done for me by research studies. See post 28, and quote below. > **[The reproduction of intelligence](https://www.sciencedirect.com/science/article/abs/pii/S016028961000005X)** > > Although a negative relationship between fertility and education has been described consistently in most countries of the world, less is known about t… > [@](#): > > Intelligence is negatively related to the number of children, with partial correlations (age controlled) of −.156, −.069, −.235 and −.028 for White females, White males, Black females and Black males, respectively > [@](#): > > And again, as with your remark about increasing education and wealth across the board in poor countries, college attendance rates can be changed by many factors other than innate intelligence. For example, a few decades ago only about 5% of US adults were college graduates, and now it’s about 25%. Are you suggesting that intelligence levels have increased that drastically in the US over just the past 60 years? :dubious: I don’t think you are. Again, the intelligence-wealth/education-fertility connection would appear to not be needed anymore. I could still establish it, but it doesn’t seem useful anymore. > [@](#): > > If human sexual selection on average favors intelligence (as you seem to agree that it does), and if current fertility patterns are not producing **reproductively isolated** subpopulations with different intelligence levels, then ISTM that average intelligence levels are not likely to decline. I am in fact saying that human sexual selection on average _did_ favor intelligence in the past, but it doesn’t anymore. Also, I’m struggling to see how genetically isolated sub-populations make a difference here, could you please try and explain it to me again? I’ll do my best to understand and respond. > [@dracoi](#): > > Yeah, what I said was kind of awkwardly phrased. > > Basically what I meant is that wealthy people are more intelligent because they are wealthy. Wealth provides better health, diet, education, etc. Because wealth is inherited, intelligence is also inherited, but not in a genetic or evolutionary sense. > > Thus, there may be no genetic difference between rich and poor populations. A poor child elevated to wealth will be intelligent and a wealthy child reduced to poverty will be stupid. Wealth only changes the expression of the trait. > > (Think of it just like the height example others have provided. I’m not taller than my great grandparents because I have “taller genes”. I’m taller because I grew up with a better diet.) Hmm. You’re saying that genetics may have no difference at all on height/intelligence? While within the realms of possibility, it hardly seems likely don’t you think? I may be taller than my g-gps because of my better diet, but on average people with taller grandparents and my better diet would be taller than me. > [@Lemur866](#): > > Please provide a cite that intelligence is negatively correlated with reproductive success. Done. In this post and in post 28. > [@Naxos](#): > > “Good” or “Bad” are irrelevant words. > > You _are_ implying that whatever you mean by the term “intelligence” is important and preferable and an indicator of a special quality some humans possess. Ahem. I am actually not trying to imply any such thing. I have implied that intelligence _was_ important in the past. I have no way of knowing whether it _will_ be important in the future, and I don’t much care actually. I’m just curious. To attribute something to me that is the opposite of something I have explicitly stated just implies a great deal of disrespect for my intellectual honesty in my view. But considering you don’t know me at all I’ll assume you probably wouldn’t make such a statement if we weren’t on the ‘internets’ 🙂 > [@Ibn\_Warraq](#): > > Dude, Eugenics was discredited over a hundred years ago. That is relevant…how? Who said or implied anything needs to be done IF average intelligence is indeed reducing? ---
**Author:** ![Chen019](https://avatars.discourse-cdn.com/v4/letter/c/f19dbf/32.png) [@Chen019](https://boards.straightdope.com/u/Chen019)\ **Post date:** [September 14, 2011, 6:22am UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/44 "2011-09-14T06:22:17Z")
> [@bldysabba](#): > > Research shows a reasonably high correlation(not causation mind you) between intelligence(IQ), education and wealth _on average_. Studies also show that there is an inverse correlation between education & wealth and the number of children that people have - i.e more educated, richer people are more likely _on average_ to have fewer children. (I don’t think these are controversial points, but in case people think so, I can provide cites) > My question is as follows - Intelligence was the main trait that set us apart from other apes. With time(evolutionary time scales), intelligence got selected for and aided in the survival and spread of the human species and we became more and more intelligent. In today’s world (and hopefully tomorrow’s), societies guarantee at least the survival of all, especially in the developed world. If more intelligent people are having fewer kids, and less intelligent people are having more, and both sets are equally likely to survive and reproduce (this last is an assumption of course, but not wholly unrealistic I think?) will we see humankind _on average_ become less intelligent, or at least a reduction in the rate of growth of intelligence? > Please note: This contention is value neutral, I’m not implying that intelligent = good, not intelligent = bad It’s not a question of “if”. It’s an empirical reality in many western countries. Researchers like Seymour Itzkoff have written about this. Also, see William Hamilton’s review of ['Dysgenics](http://onlinelibrary.wiley.com/doi/10.1046/j.1469-1809.2000.6440363.x/pdf)’. A review of Dysgenics: Genetic Deterioration in Modern Populations, Annals of Human Genetics Volume 64, Issue 4, pages 363–374, July 2000. ---
**Author:** ![Chen019](https://avatars.discourse-cdn.com/v4/letter/c/f19dbf/32.png) [@Chen019](https://boards.straightdope.com/u/Chen019)\ **Post date:** [September 14, 2011, 6:24am UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/45 "2011-09-14T06:24:52Z")
> [@Ibn\_Warraq](#): > > Dude, Eugenics was discredited over a hundred years ago. Depends what you mean. Population genetics shows that heritable quantitative traits can shift in prev[alence over time in a population](http://infoproc.blogspot.com/2011/08/demography-and-fast-evolution.html). > [@](#): > > So we have at least two documented cases of the descendants of the rich replacing the poor over an extended period of time. My guess is that this kind of population dynamics was quite common in the past. (Today we see the opposite pattern!) Could this type of natural selection lead to changes in quantitative, heritable traits over a relatively short period of time? > > Consider the following simple model, where X is a heritable trait such as intelligence or conscientiousness or even height. Suppose that X has narrow sense heritability of one half. Divide the population into 3 groups: > > Group 1 bottom 1/6 in X; \< 1 SD below average > Group 2 middle 2/3 in X; between -1 and +1 SD > Group 3 highest 1/6 in X; \> 1 SD above average > > Suppose that Group 3 has a reproductive rate which is 10% higher than Group 2, whereas Group 1 reproduces at a 10% lower rate than Group 2. A relatively weak correlation between X and material wealth could produce this effect, given the demographic data above (the rich outreproduced the poor almost 2 to 1!). Now we can calculate the change in population mean for X over a single generation. In units of SDs, the mean changes by roughly 1/6 ( .1 + .1) 1/2 or about .02 SD. (I assumed assortative mating by group.) Thus it would take roughly 50 generations, or 1k years, under such conditions for the population to experience a 1 SD shift in X. > > Suppose that Group 3 has a reproductive rate which is 10% higher than Group 2, whereas Group 1 reproduces at a 10% lower rate than Group 2. A relatively weak correlation between X and material wealth could produce this effect, given the demographic data above (the rich outreproduced the poor almost 2 to 1!). Now we can calculate the change in population mean for X over a single generation. In units of SDs, the mean changes by roughly 1/6 ( .1 + .1) 1/2 or about .02 SD. (I assumed assortative mating by group.) Thus it would take roughly 50 generations, or 1k years, under such conditions for the population to experience a 1 SD shift in X. > > If you weaken the correlation between X and reproduction rate, or relax the assortative mating assumption, you get a longer timescale. But it’s certainly plausible that 10,000 years is more than enough for this kind of evolution. For example, we might expect that the advent of agriculture over such timescales changed humans significantly from their previous hunter gatherer ancestors. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [September 14, 2011, 9:36am UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/46 "2011-09-14T09:36:00Z")
> [@JoelUpchurch](#): > > Apparently you aren’t familiar with the concept of an analogy. I am not taking about a literal straight flush and I’m not talking about what genetic characteristics we might need in 100,000 years. We are looking for characteristics they will need to compete in a couple of decades. We are going to look for characteristics that will push them to right end of the normal distribution curve. We want smart healthy children, not X-men. > > You end up with a population where the stupid people start at an IQ of 120 and the normal people are 140 and the smart people from 160 up. Leave out the genes for hemophilia and schizophrenia and breast cancer. Just a quick note: you are aware that there is no way for the average IQ to be 140, right? Average is defined at 100. This is why IQ is not the best thing to use for comparing intelligence. It is relative to the others of that generation. ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [September 14, 2011, 11:00am UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/47 "2011-09-14T11:00:52Z")
Regardless of whether there is a correlation between intelligence and fertility, the fact is that, in so far as it can be measured, intelligence has been increasing for most of the past century: > **[Flynn effect](https://en.wikipedia.org/wiki/Flynn_effect)** > > The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores that were measured in many parts of the world over the 20th century. When intelligence quotient (IQ) tests are initially standardized using a sample of test-takers, by convention the average of the test results is set to 100 and their standard deviation is set to 15 or 16 IQ points. When IQ tests are revised, they are again standardized using a new sample of test-takers, Test ... You could argue that I.Q. tests don’t really measure intelligence, but if they don’t, what does? The fact remains that there is no reason to think that the average intelligence of the human race is going down, and there is reason to think that it is going up. ---
**Author:** ![Evil\_Captor](https://avatars.discourse-cdn.com/v4/letter/e/f17d59/32.png) [@Evil\_Captor](https://boards.straightdope.com/u/Evil_Captor)\ **Post date:** [September 14, 2011, 12:34pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/48 "2011-09-14T12:34:59Z")
> [@Little\_Nemo](#): > > Talk’s cheap. What have you done as an individual to reduce the number of humans on the planet? Not really a fair question. The poster you cite may be a highly effective serial killer, but it’s not like he can go around advertising the fact. ---
**Author:** ![MattProle](https://avatars.discourse-cdn.com/v4/letter/m/ed8c4c/32.png) [@MattProle](https://boards.straightdope.com/u/MattProle)\ **Post date:** [September 14, 2011, 12:40pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/49 "2011-09-14T12:40:25Z")
> [@Wendell\_Wagner](#): > > Regardless of whether there is a correlation between intelligence and fertility, the fact is that, in so far as it can be measured, intelligence has been increasing for most of the past century: > > [Flynn effect - Wikipedia](http://en.wikipedia.org/wiki/Flynn_effect) > > You could argue that I.Q. tests don’t really measure intelligence, but if they don’t, what does? The fact remains that there is no reason to think that the average intelligence of the human race is going down, and there is reason to think that it is going up. QTF This is what I came here to say. When you actually look at the evidence there appears very little reason to worry about society “devolving” into a lot of idiots. _Idiocracy_ was not a documentary. ---
**Author:** ![even\_sven](https://avatars.discourse-cdn.com/v4/letter/e/dfb087/32.png) [@even\_sven](https://boards.straightdope.com/u/even_sven)\ **Post date:** [September 14, 2011, 12:43pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/50 "2011-09-14T12:43:31Z")
The problem with “Look at all those people in Africa- they have low IQs and lots of babies” is that [malnutrition](http://www.ncbi.nlm.nih.gov/pubmed/2628311), [malaria](http://en.wikipedia.org/wiki/Malaria#Signs_and_symptoms), and [infectious disease](http://www.economist.com/node/16510958) all have an effect on IQ. In [many areas of Sub-Saharan Africa](http://visualizationstrategies.wordpress.com/2009/04/04/world-malaria-map-plasmodium-falciparum-endemicity-in-2007/), small children can expect to have malaria several times before they hit school-age. The strain that is prevalent- malaria falciparum- is quite likely to escalate to cerebral malaria, which causes neurological damage. We are talking areas where malaria death rates can hit 20% _of all kids_. Everyone gets severe malaria. Everyone spends large chunks of their period of rapid brain development wracked by massive anemia, seizures and periods of extremely high fever that can last for days. Also look at a [map of childhood malnutrition](http://www.restlessbeings.org/projects/dhaka-street-children/child-malnutrition). Both pre-natal and childhood malnutrition can affect brain development. Not surprisingly, areas with huge disease burdens tend to have high child mortality. This naturally leads to high fertility. A family presumably wants at least some children who live in to adulthood- especially in areas with poor social services where children the only insurance you have that you’ll be taken care of in old age. High disease burdens also affect rural populations, which tend to have high fertility because of the way that agricultural economics incentivizes. Of course, having a lot of children (and being mired in poverty) affects a parent’s ability to provide a stimulating learning environment for children aged 0-5, which has a dramatic effect on IQ. There just isn’t a lot in a desert somewhere to stimulate brain development during these critical years. So what you are seeing is that people with huge disease burdens have lots of kids. That’s it. ---
**Author:** ![bldysabba](https://avatars.discourse-cdn.com/v4/letter/b/ecccb3/32.png) [@bldysabba](https://boards.straightdope.com/u/bldysabba)\ **Post date:** [September 14, 2011, 1:05pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/51 "2011-09-14T13:05:45Z")
> [@Wendell\_Wagner](#): > > Regardless of whether there is a correlation between intelligence and fertility, the fact is that, in so far as it can be measured, intelligence has been increasing for most of the past century: > > [Flynn effect - Wikipedia](http://en.wikipedia.org/wiki/Flynn_effect) > > You could argue that I.Q. tests don’t really measure intelligence, but if they don’t, what does? The fact remains that there is no reason to think that the average intelligence of the human race is going down, and there is reason to think that it is going up. Thanks for that link. Did you read the last part of it though? There does seem to be reason to think intelligence is going/can go down, although it is admittedly not conclusive. From that link - > [@](#): > > Jon Martin Sundet and colleagues (2004) examined scores on intelligence tests given to Norwegian conscripts between the 1950s and 2002. They found that the increase of scores of general intelligence stopped after the mid-1990s and declined in numerical reasoning sub-tests.[37] > Teasdale and Owen (2005) examined the results of IQ tests given to Danish male conscripts. Between 1959 and 1979 the gains were 3 points per decade. Between 1979 and 1989 the increase approached 2 IQ points. Between 1989 and 1998 the gain was about 1.3 points. Between 1998 and 2004 IQ declined by about the same amount as it gained between 1989 and 1998. They speculate that “a contributing factor in this recent fall could be a simultaneous decline in proportions of students entering 3-year advanced-level school programs for 16–18 year olds.”[46] The same authors in a more comprehensive 2008 study, again on Danish male conscripts, found that there was a 1.5 points increase between 1988 and 1998, but a 1.5 points decrease between 1998 and 2003/2004. A possible contributing factor to the recent decline may be changes in the Danish educational system. Another may the rising proportion of immigrants or their immediate descendants in Denmark. This is supported by data on Danish draftees where first or second generation immigrants with Danish nationality score below average.[5] > In Australia, 6–11 year olds IQ, as measured by the Colored Progressive Matrices, has shown no increase from 1975–2003.[47] > In the United Kingdom, a study by Flynn (2009) found that tests carried out in 1980 and again in 2008 show that the IQ score of an average 14-year-old dropped by more than two points over the period. For the upper half of the results the performance was even worse. Average IQ scores declined by six points. However, children aged between five and 10 saw their IQs increase by up to half a point a year over the three decades. This would imply the gains have halted, especially if the reasons for the gains were nutrition and more stimulating environment. The article even explicitly mentions that the recent IQ gains were not genetic in nature and suggests that the limits for gains are being reached. ---
**Author:** ![bldysabba](https://avatars.discourse-cdn.com/v4/letter/b/ecccb3/32.png) [@bldysabba](https://boards.straightdope.com/u/bldysabba)\ **Post date:** [September 14, 2011, 1:17pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/52 "2011-09-14T13:17:14Z")
> [@even\_sven](#): > > The problem with “Look at all those people in Africa- they have low IQs and lots of babies” is that [malnutrition](http://www.ncbi.nlm.nih.gov/pubmed/2628311), [malaria](http://en.wikipedia.org/wiki/Malaria#Signs_and_symptoms), and [infectious disease](http://www.economist.com/node/16510958) all have an effect on IQ. > > In [many areas of Sub-Saharan Africa](http://visualizationstrategies.wordpress.com/2009/04/04/world-malaria-map-plasmodium-falciparum-endemicity-in-2007/), small children can expect to have malaria several times before they hit school-age. The strain that is prevalent- malaria falciparum- is quite likely to escalate to cerebral malaria, which causes neurological damage. We are talking areas where malaria death rates can hit 20% _of all kids_. Everyone gets severe malaria. Everyone spends large chunks of their period of rapid brain development wracked by massive anemia, seizures and periods of extremely high fever that can last for days. > > Also look at a [map of childhood malnutrition](http://www.restlessbeings.org/projects/dhaka-street-children/child-malnutrition). Both pre-natal and childhood malnutrition can affect brain development. > > Not surprisingly, areas with huge disease burdens tend to have high child mortality. This naturally leads to high fertility. A family presumably wants at least some children who live in to adulthood- especially in areas with poor social services where children the only insurance you have that you’ll be taken care of in old age. High disease burdens also affect rural populations, which tend to have high fertility because of the way that agricultural economics incentivizes. > > Of course, having a lot of children (and being mired in poverty) affects a parent’s ability to provide a stimulating learning environment for children aged 0-5, which has a dramatic effect on IQ. There just isn’t a lot in a desert somewhere to stimulate brain development during these critical years. > > So what you are seeing is that people with huge disease burdens have lots of kids. That’s it. I haven’t considered ‘All those people in Africa’ at all. Studies solely in the United States have found a negative correlation between intelligence and fertility. Africa will no doubt experience what the poster before linked to - the ‘Flynn effect’ as fewer people suffer the burden of disease and malnutrition, IQ will increase. I think it is highly likely that as that IQ increases, fertility rates will decline, which brings us back to my original question. ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [September 14, 2011, 3:16pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/53 "2011-09-14T15:16:01Z")
bldysabba writes: \> There does seem to be reason to think intelligence is going/can go down, \> although it is admittedly not conclusive. Actually what it implies is that in countries with the highest median incomes and a lot of equality in those incomes, the improvement in I.Q. scores may have topped out in the last decade. Perhaps this means that whatever causes the Flynn effect can’t produce any further increase in those societies. Given that this is only true in a few countries and in the last decade, there’s no reason to think that intelligence will decrease anywhere, just that the Flynn effect can only increase average intelligence to a limited extent (although that extent is more than 20 points over the past century, which is a large increase). There’s some evidence that the Flynn effect works mostly by bringing up the I.Q. of the poorest sectors of any society. In other words, the richest people in every society may have always gotten the nutritional, medical, or intellectual environments that they needed (or whatever is causing the Flynn effect), while the improvements of the past century (in some societies, at least) have been toward giving the poorer people of those societies some of the same environments. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [September 14, 2011, 5:00pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/54 "2011-09-14T17:00:01Z")
> [@bldysabba](#): > > Hmm. You’re saying that genetics may have no difference at all on height/intelligence? While within the realms of possibility, it hardly seems likely don’t you think? I may be taller than my g-gps because of my better diet, but on average people with taller grandparents and my better diet would be taller than me. I’m not saying there’s no effect for height, but for intelligence? There are so many types of intelligence and development is so crucial to intelligence that I don’t think genetics are as important as upbringing. As an extreme example, your “raised by wolves” feral child will NEVER learn to speak or count normally. A feral child Einstein might be smarter than other feral children, but even he will never learn multiplication, let alone calculus. Those kids missed out on necessary learning during a developmental stage; genetics can’t fill that gap. In a more everyday example, researchers found that wealthier parents talk to their young kids nearly twice as much as poorer parents. ([Cite](http://www.universalpreschool.com/how-to/talk-to-your-kids.asp)) Poorer kids showed a lower vocabulary and a lower rate of communication themselves - the kind of thing that can hinder learning in all areas of intelligence. ---
**Author:** ![bldysabba](https://avatars.discourse-cdn.com/v4/letter/b/ecccb3/32.png) [@bldysabba](https://boards.straightdope.com/u/bldysabba)\ **Post date:** [September 14, 2011, 5:37pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/55 "2011-09-14T17:37:38Z")
> [@dracoi](#): > > I’m not saying there’s no effect for height, but for intelligence? There are so many types of intelligence and development is so crucial to intelligence that I don’t think genetics are as important as upbringing. As an extreme example, your “raised by wolves” feral child will NEVER learn to speak or count normally. A feral child Einstein might be smarter than other feral children, but even he will never learn multiplication, let alone calculus. Those kids missed out on necessary learning during a developmental stage; genetics can’t fill that gap. > > In a more everyday example, researchers found that wealthier parents talk to their young kids nearly twice as much as poorer parents. ([Cite](http://www.universalpreschool.com/how-to/talk-to-your-kids.asp)) Poorer kids showed a lower vocabulary and a lower rate of communication themselves - the kind of thing that can hinder learning in all areas of intelligence. As far as I can tell, both factors - heredity and upbringing seem equally important in determining intelligence. A number of sources say this. For instance [http://www.macalester.edu/psychology/whathap/ubnrp/intelligence05/Rconclusion.html](http://www.macalester.edu/psychology/whathap/ubnrp/intelligence05/Rconclusion.html) > [@](#): > > heredity determines one’s potential, but environment determines how far one will reach that potential during his lifetime. In other words, every individual has a destined mental potential, but how much of that potential the individual will be able to gain solely depends on the environment that the individual grows in. “Nature designs blueprints and nurture modifies them each step of the way.” (Dempsey and Zimbardo 164) This view seems to be the consensus. I’m happy to limit my question to the average ‘Intelligence potential’ of humans. ---
**Author:** ![bldysabba](https://avatars.discourse-cdn.com/v4/letter/b/ecccb3/32.png) [@bldysabba](https://boards.straightdope.com/u/bldysabba)\ **Post date:** [September 14, 2011, 5:47pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/56 "2011-09-14T17:47:29Z")
> [@Wendell\_Wagner](#): > > Actually what it implies is that in countries with the highest median incomes and a lot of equality in those incomes, the improvement in I.Q. scores may have topped out in the last decade. Perhaps this means that whatever causes the Flynn effect can’t produce any further increase in those societies. 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. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [September 14, 2011, 5:48pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/57 "2011-09-14T17:48:04Z")
True, the discussion is irrelevant for Africa or any traditional societies where social status and inherited wealth are the primary deteminants of current wealth and scial class is very stratified. We might argue that the whole middle ages was a breeding program to remove the smartest men from the breeding pool, as the smarter ones tended t be given the education and become (allegedly) celibate clergy… or at least the men did. As a result, we have a European race where women mst be on average obviously much smarter than men. Similarly our agrarian societies have bred for docile inhabitants, where those unable to contain their temper quickly were hung for crimes of violence, or joined the army and killed each other off (except, ths just means they also spread their berserker genes across the countryside before their demise.) Except of course, Scandinavia which seems to have bred for berserkers during their Viking phase. Freakonomics goes into a bit more detail about the correlation between parental success and child sucess. The single biggest indicator of the success of a child is the education level of their parents. Indeed, with spread-out suburbs of similar-sized houses, there is a lot less mixing between classes apparently happening now in North America than in past history, where different socio-economic levels lived closer together. ---
**Author:** ![JoelUpchurch](https://avatars.discourse-cdn.com/v4/letter/j/f05b48/32.png) [@JoelUpchurch](https://boards.straightdope.com/u/JoelUpchurch)\ **Post date:** [September 14, 2011, 5:49pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/58 "2011-09-14T17:49:22Z")
> [@BigT](#): > > Just a quick note: you are aware that there is no way for the average IQ to be 140, right? Average is defined at 100. > > This is why IQ is not the best thing to use for comparing intelligence. It is relative to the others of that generation. I am aware of that, but if you had read the previous posts, then you would be aware that was discussing a scenario where only the wealthy could afford to use genetic selection. In that scenario, then those IQ numbers were accurate. If such technology was applied generally then you would be correct. It would be more accurate to refer to a new normal distribution that was a couple of standard deviations to the right to the old normal. ---
**Author:** ![Algher](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@Algher](https://boards.straightdope.com/u/Algher)\ **Post date:** [September 14, 2011, 6:08pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/59 "2011-09-14T18:08:23Z")
From my 20th reunion class book for Stanford: 30% of my class married another Stanford alum 50% of my class has two kids (no data on 1 or 2+ in the class book) 1/6 have no kids So a little real-world data on the college kids marrying each other and making legacy applicants. ---
**Author:** ![New\_Deal\_Democrat](https://avatars.discourse-cdn.com/v4/letter/n/9d8465/32.png) [@New\_Deal\_Democrat](https://boards.straightdope.com/u/New_Deal_Democrat)\ **Post date:** [September 14, 2011, 6:22pm UTC](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177/60 "2011-09-14T18:22:39Z")
The tendency of less intelligent people to have more children is fairly recent. I doubt it will last long. It is becoming increasingly necessary to be of superior intelligence to earn a decent income. The Personal Responsibility and Work Opportunity Reconciliation Act of 1996 ended Aid to Families With Dependent Children as a life time entitlement. For decades this made possible the reproduction of the unemployable. As time goes on I think that those who are able to support themselves will become increasingly unwilling to support the predominately illegitimate children of those who are not. [Previous page](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177.md?page=2) [Next page](https://boards.straightdope.com/t/will-intelligence-be-selected-against/596177.md?page=4)