# Is intelligence hereditery? **URL:** \ **Category:** Great Debates\ **Created:** [March 15, 2003, 10:36pm UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669 "2003-03-15T22:36:26Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![Hermann\_Cheruscan](https://avatars.discourse-cdn.com/v4/letter/h/b782af/32.png) [@Hermann\_Cheruscan](https://boards.straightdope.com/u/Hermann_Cheruscan)\ **Post date:** [March 15, 2003, 10:36pm UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/1 "2003-03-15T22:36:26Z")
I look at my circle of friends, the ones who have children. I notice that the parents who I would consider to be above average intelligence tend to have kids that are pretty smart. I then look at other friends who are not so smart, their kids seem to be rather dull. Now I know that these might just be my own impressions. I realize that “smart” people may tend to spend more time with their kids and teach them things, than other parents. I realize that less intelligent parents may not be able to have have incomes that would pay for additional education for thier offspring. I realize that there could be all kinds of factors which could explain my observations. What I’d like to know is if there have been any kind of studies done on the hereditary nature of intelligence. Can anyone give a cite concerning such studies? ---
**Author:** ![Bob55](https://avatars.discourse-cdn.com/v4/letter/b/e9c0ed/32.png) [@Bob55](https://boards.straightdope.com/u/Bob55)\ **Post date:** [March 15, 2003, 11:26pm UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/2 "2003-03-15T23:26:09Z")
I think you’re right about incomes, and possibly intelligent parents passing down work ethic to their children. While I’ve not seen data on the genetics of intelligence, there are definitely genetic factors that could be passed down. For example, [this](http://www.sandracabot.com/newsletter2/mcb.shtml) site says: “Albert Einstein, still known as one of the greatest thinkers of all times, apparently had a brain, which contained more neuroglia cells than usual. Neuroglia cells give rise to the myelin sheath that expedites the conduction of nerve transmissions (messages). The main constituent of the myelin sheath is polyunsaturated fat, and it must be obtained from the diet. Further, it appears that eating the wrong fats in the diet directly antagonises the utilisation of the beneficial polyunsaturated fats in the nervous system, so that the health of the myelin sheath and other nervous tissue is impaired.” So it appears some aspects of intelligence are definitely genetic. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [March 16, 2003, 12:35am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/3 "2003-03-16T00:35:47Z")
“Smart” is often measured by vocabulary, especially informally. It’s easier to pick up a big vocabulary by osmosis and/or in a family that encourages reading. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [March 16, 2003, 2:11am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/4 "2003-03-16T02:11:33Z")
The “definition” of intelligence, and the whole nature vs. nurture debate is IMHO, obscenely political, so I’ll stay away from it. However, here’s a nice review article on [Mapping Genetic Influences on Human Brain Structure](http://www.loni.ucla.edu/~thompson/PDF/AnnMed2002_v5.pdf) (a small PDF). > [@](#): > > A striking trend in behavioral genetics has been the finding that many cognitive skills are surprisingly heritable, with strong genetic influences on IQ (Bouchard and McGue, 1981; Plomin and Loehlin, 1989), verbal and spatial abilities, perceptual speed (Alarcón et al., 1998), and even some personality qualities, including extraversion and emotional reactions to stress I’d be surprised if each of the individual studies cited _haven’t_ been “debunked” at one time or another, with varying degrees of success. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [March 16, 2003, 2:34am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/5 "2003-03-16T02:34:34Z")
I don’t see much hope of keeping this from developing into a debate, so I’ll just go ahead and move this thread to GD. bibliophage moderator GQ ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [March 16, 2003, 2:47am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/6 "2003-03-16T02:47:13Z")
I always pose this question to people who ask if intellegence is hereditary: Are humans more intellegent than chimpanzees? Assuming a “yes” answer-- why do you suppose it is so? Look at it another way. Assuming you aren’t a creationist, do you think human evolution has entailed an increase in intelligence? What do you think the mechanism for that improved intellegence was? Now, the real question might be HOW is intellegence inherited and what interactions might there be between genes and environment. I can’t see how any scientifically oriented individual could think that intelligence was NOT hereditary. If you are lookng for a cite, do a google search on “intelligence” and “twins”. I think the general consensus is that a person’s “intelligence” (in as much as we can measure such an attribute) is about 50% hereditary. I could be wrong about that, but that’s what I remember. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [March 16, 2003, 3:50am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/7 "2003-03-16T03:50:16Z")
The trouble with the mechanisms involved in the genetic component of intelligence, IIRC, is that they seem to fail and revert to the norm after several generations- that is, a breeding program using nobel prizewinners would perhaps produce greater intelligence in the first generation, all environmental factors being equal- (impractical, but it is only a thought experiment, thank god) - but by the fifth generation the average intelligence would be back to normal. (sorry, no cites, just from memory- probably wrong) It seems likely to me that this phenomenon might not apply to artificial genetic modification- which may be just a little over the horizon, but is scarey none-the- less. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [March 16, 2003, 4:11am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/8 "2003-03-16T04:11:35Z")
It’s a bit too bad that we all learned about genetics thru the tall/short wrinkled/smoothe pea examples in junior high science class. That leads most people to think that if something is genetic, there is ONE gene involved and it’s either dominant or recessive. Many genetic traits do not opperate on those simple principles. 45: I don’t think anyone has carried out the intellegence breeding experiment you discussed. Certainly not out to 5 generations. But, if your “reversion to the norm” were always true, how could evolution proceed? Think about it. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [March 16, 2003, 4:23am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/9 "2003-03-16T04:23:10Z")
Indeed, but intelligence does not seem to be increasing with time since the evolution of H. sap. sap… I lean toward punctuated equilibrium myself. I’ll see if the study that inspired my distorted thought experiment is available anywhere on the web. it definitely showed a reversion to norm effect (but that could have been due to many factors) ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [March 16, 2003, 4:52am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/10 "2003-03-16T04:52:15Z")
45: A few points: 1. Punctuated eq and Gradualism are not mutually exclusive. 2. There is zero data on whether or not intelligence has increased or decreased during the existance of H. sapiens sapiens. I might agree with your claim, but I would still say there is ZERO data either way, so it would be nothing more than an opinion. Based on what we know about the complexity of genetics, I would not be at all surprised if our first attempts to engineer intelligence resutled in some serious unintended consequences. You might bump up IQ, but also increase personality disorders. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [March 16, 2003, 4:54am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/11 "2003-03-16T04:54:29Z")
45: A few points: 1. Punctuated eq and Gradualism are not mutually exclusive. 2. There is zero data on whether or not intelligence has increased or decreased during the existance of H. sapiens sapiens. I might agree with your claim, but I would still say there is ZERO data either way, so it would be nothing more than an opinion. Based on what we know about the complexity of genetics, I would not be at all surprised if our first attempts to engineer intelligence resutled in some serious unintended consequences. You might bump up IQ, but also increase personality disorders. I could be wrong, but my sense is that the “reversion to the norm” concept is a para-scientific theory. I don’t believe it is something that geneticists take seriously. I’m not a geneticist by profession, so I could be wrong on that. Perhaps someone in the field will chime in. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [March 16, 2003, 2:10pm UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/12 "2003-03-16T14:10:39Z")
Yeah. The study Iwas referring to is nowhere to be found; it was part of a long, probably unscientific refutation of eugenics and breeding for intelligence. Obviously intelligence is governed by hundreds if not thousands of genes working together, and perhaps a breeding prgram might bring results in improving intelligence, but it seems to me that before that sort of long term effort suceeded some gene tweaking would also be taking place. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [March 16, 2003, 8:21pm UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/13 "2003-03-16T20:21:47Z")
Genetic engineering is the way to go. There have been some interesting results with mice. The most recent study produced mice brains that were significantly larger than normal and had more “folds” than usual-- along the lines of human brains. Unfortunately, thr mice were destroyed before they matured, but I’m sure future efforts are underway that will allow testing of “mice intelligence” in similarly engineered animals. Multi-generational breeding programs in humans, besides being unethiical, simply aren’t pratical. ---
**Author:** ![Foolonthehill](https://avatars.discourse-cdn.com/v4/letter/f/e274bd/32.png) [@Foolonthehill](https://boards.straightdope.com/u/Foolonthehill)\ **Post date:** [March 16, 2003, 9:16pm UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/14 "2003-03-16T21:16:11Z")
Seems to me we are ignoring the “effects of the ‘effects of genes’” If I have two intelligent parents, I have a greater chance of being intelligent than the offspring of one intelligent parent, (all things being equal). But what seems to be missing from this is the effect that intelligence has on my folks. Growing up in a household with intelligent parents will probably have more books, will probably have more open discussions, will probably be wealthier, allowing more time for for multiple pursuits. All contributing to my growing intellect. The effects of my parents genes don’t stop at fertilization We are getting smarter as a species, (we are also getting healthier), just in extremely small increments, (actually immeasurablely small). The data is there eg; We’ve gone from families & clans to nations, this shows an expansion of kin selection to group selection, certainly a step up the intelligence ladder. Our ability to solve more complex problems thru co-operation as we evolve, transferring altrusism/cheat detection to larger groups of people. Finally, intelligence is our “tooth and claw” and we are so successful as a species because of our continued selection of smarts. Note, however, that intelligence doesn’t infer right or good. Just smart on a local level. Punc eqs is a form of gradualism. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [March 16, 2003, 11:34pm UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/15 "2003-03-16T23:34:01Z")
I’ll stick by my claim that there is no scientific data that H. sapiens has gotten more intelligent. If anyone has a scientific cite that disputes that, then maybe there’s something to talk about. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [March 16, 2003, 11:47pm UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/16 "2003-03-16T23:47:43Z")
The average cubic capacity of the human cranium has not increased, IIRC, for tens of thousands of years, but this does not necessarily have a direct bearing on intelligence. The sophistication of society has certainly increased, and in some ways seems to have developed a collective memory and perhaps even an intelligence of it’s own. (although it does some daft things sometimes). ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [March 17, 2003, 1:32am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/17 "2003-03-17T01:32:07Z")
Clearly the collective knowledge base has increased, but that says nothing about the relative intelligence level of any single person. In fact, one could argue that the selective pressure on intelligence has DECREASED, esp in modern times and could very well have lead to a LOWERING of average intelligence for the species. But that, too, is just speculation. ---
**Author:** ![Tigers2B1](https://avatars.discourse-cdn.com/v4/letter/t/9fc29f/32.png) [@Tigers2B1](https://boards.straightdope.com/u/Tigers2B1)\ **Post date:** [March 17, 2003, 5:39pm UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/18 "2003-03-17T17:39:36Z")
According to research - some of the genes responsible for intelligence appear to be located on the long arm of chromosome 6. Professor Robert Plomin tested blood samples 50 12 to 14 year olds, from various parts of the United States, who had had tested IQs averaging about 160. He looked only at chromosome 6 because past studies had suggested that something might be there. Plomin says he expects to find many more such genes, including at least one on each of the 23 pairs of human chromosomes. Here is a related 2000 article from BBC news. > [@](#): > > **US researchers believe they have identified the parts of the human genome involved in developing a person’s intelligence. > This means scientists could soon test the potential intelligence of new-born babies. > …The researchers, working for the US National Institutes of Health, analysed the DNA of 200 of the brightest kids in America and compared them with the genetic material from ordinary children. > …The team believe more than one gene is involved - and that these genes can make a big difference to a person’s intelligence. The research was led by Professor Robert Plomin.** The LINK [http://news.bbc.co.uk/1/hi/sci/tech/850358.stm](http://news.bbc.co.uk/1/hi/sci/tech/850358.stm) ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [March 20, 2003, 4:22am UTC](https://boards.straightdope.com/t/is-intelligence-hereditery/161669/19 "2003-03-20T04:22:45Z")
\<\\> Ian Stewart &/or Jack Cohen (who sometimes write with Terry Pratchett) use the word “extelligence” for this. I enjoy the word because it’s immediately understandable. This extelligence may make it less necessary to have some kinds of intelligence, since you can rely on others for so much. But it also rewards some kinds of intelligence, which may not have been rewarded in the past. And to have an effect on future generations, it has to be a reward that results in a greater number of offspring. (Although a greater number of nieces and nephews would do it)