Anyone here NOT believe that the brain is genetically controlled like any other organ

[bodecea]

Thousands of studies have shown that brain size shape and function are under heavy genetic control. Not only that, but recent studies have shown that numerous genes have undergone significant selection pressure in just the last 5-10 thousand years, including ones that affect the brain. We are still evolving.
Why do people deny race, which is simply continental genetic clusters? Or that different races have brains that have evolved different size shape and function? Surely it would be unlikely that brains would be the only organ to evolve exactly the same all over the world?
Once differences in brain structure and function are accepted to some degree then it is much easier to explain the disparities in social functioning between the races.
I'm sure I will be called a racist for this but Occam's Razor demands that simple and factually confirmed reasoning be fully examined. I will be more than happy to bring citations to refute any logically argued differences of opinion.

You're theory goes right out the window when you realize that the idea of race being nice neat packages is a social construct only.

I guess this is as close to an opposing argument as I am going to get. You seem to think race is only a social construct. That seems very odd to me when the vast majority of people are instantly recognizible as one of the five main races and usually even finer distinctions can be made. Anthropologists can identify a skeleton's race. Geneticists can identify without ever seeing the person, just from a small piece of tissue.

Interesting that you say there are FIVE main races. I remember it as THREE main races. Why a change? Because it is merely a social construct. Period.

Did you know that 150 years ago, the Irish were not considered white? Neither were the Polish. And when you talk about Africans, are you talking Northern, Southern, Western, or Eastern? They are all different in size, shape, hair, facial structure, skin color...as are Europeans, Asians, etc. We are ALL different. It is only people with tiny minds themselves who try to pigeonhole the human race into a few neat, tidy boxes.

 

[Si modo]

Interesting. Twenty posts and still not a single reference by the OP to even one of those "thousands of studies". One must assume there are none at this point.

 

[AllieBaba]

Thousands of studies have shown that brain size shape and function are under heavy genetic control. Not only that, but recent studies have shown that numerous genes have undergone significant selection pressure in just the last 5-10 thousand years, including ones that affect the brain. We are still evolving.
Why do people deny race, which is simply continental genetic clusters? Or that different races have brains that have evolved different size shape and function? Surely it would be unlikely that brains would be the only organ to evolve exactly the same all over the world?
Once differences in brain structure and function are accepted to some degree then it is much easier to explain the disparities in social functioning between the races.
I'm sure I will be called a racist for this but Occam's Razor demands that simple and factually confirmed reasoning be fully examined. I will be more than happy to bring citations to refute any logically argued differences of opinion.

You're theory goes right out the window when you realize that the idea of race being nice neat packages is a social construct only.

I guess this is as close to an opposing argument as I am going to get. You seem to think race is only a social construct. That seems very odd to me when the vast majority of people are instantly recognizible as one of the five main races and usually even finer distinctions can be made. Anthropologists can identify a skeleton's race. Geneticists can identify without ever seeing the person, just from a small piece of tissue.

Debate 101: Before debate can ensue, you state your case and supporting evidence.

Carry on.

 

[IanC]

You're theory goes right out the window when you realize that the idea of race being nice neat packages is a social construct only.

I guess this is as close to an opposing argument as I am going to get. You seem to think race is only a social construct. That seems very odd to me when the vast majority of people are instantly recognizible as one of the five main races and usually even finer distinctions can be made. Anthropologists can identify a skeleton's race. Geneticists can identify without ever seeing the person, just from a small piece of tissue.

Interesting that you say there are FIVE main races. I remember it as THREE main races. Why a change? Because it is merely a social construct. Period.

Did you know that 150 years ago, the Irish were not considered white? Neither were the Polish. And when you talk about Africans, are you talking Northern, Southern, Western, or Eastern? They are all different in size, shape, hair, facial structure, skin color...as are Europeans, Asians, etc. We are ALL different. It is only people with tiny minds themselves who try to pigeonhole the human race into a few neat, tidy boxes.

Science studied genetic frequencies of alleles and other markers and found that the most meaningful division was into five clusters. Which, not surprisingly, match continental populations. Of course the three main races make up the vast majority of the world's population.
What does social prejudice from 150 years ago have to do with modern day science? How many racial slurs does it take to negate one MRI image? I don't really want to discuss racial politics, I want to talk about human biodiversity and how obvious physical and behavioural differences are ignored as contributing factors in many social outcomes.
Since no one has argued against the brain being genetically controlled, can I take that as general agreement by most of us?

 

[IanC]

For those who are not familiar with the concept of genetic clusters-

The exact definition of the metric and the allele labeling are somewhat arbitrary, but you can see it is easy to define a meaningful measure of how far apart any two individuals are in genome space.

Now plot the genome of each human as a point on our lattice. Not surprisingly, there are readily identifiable clusters of points, corresponding to traditional continental ethnic groups: Europeans, Africans, Asians, Native Americans, etc. (See, for example, Risch et al., Am. J. Hum. Genet. 76:268–275, 2005.) Of course, we can get into endless arguments about how we define European or Asian, and of course there is substructure within the clusters, but it is rather obvious that there are identifiable groupings, and as the Risch study shows, they correspond very well to self-identified notions of race.

http://infoproc.blogspot.com/2007/01/metric-on-space-of-genomes-and.html

From an article on brain growth-

Twin studies have also shown that genetic effects vary regionally within the brain, with high heritabilities of frontal lobe volumes (90--95%), moderate estimates in the hippocampus (40--69%), and environmental factors influencing several medial brain areas.Studies revealed that total brain volume is positively correlated with general intelligence. In healthy subjects, the level of intellectual functioning has been positively associated with whole brain, gray, and white matter volumes [Thompson et al, 2001; Posthuma et al, 2002]. More focally, several brain areas were found to be correlated with intelligence. Interestingly, it was also shown that the trajectory changes in cortical thickness throughout adolescence are associated with the level of intelligence.

http://www.sciencedaily.com/releases/2007/10/071016131452.htm

Part of the abstract from a genetic identity study-

We have analyzed genetic data for 326 microsatellite markers that were typed uniformly in a large multiethnic population-based sample of individuals as part of a study of the genetics of hypertension (Family Blood Pressure Program). Subjects identified themselves as belonging to one of four major racial/ethnic groups (white, African American, East Asian, and Hispanic) and were recruited from 15 different geographic locales within the United States and Taiwan. Genetic cluster analysis of the microsatellite markers produced four major clusters, which showed near-perfect correspondence with the four self-reported race/ethnicity categories. Of 3,636 subjects of varying race/ethnicity, only 5 (0.14%) showed genetic cluster membership different from their self-identified race/ethnicity.

Genetic Structure, Self-Identified Race/Ethnicity, and Confounding in Case-Control Association Studies I read an interview with the principle author and he stated that there was greater agreement with the self-selected racial background of the subjects than with the self-selected gender identity of the subjects (genetically).
Genetic cluster info as a crime stopper-

In early March, 2003, investigators turned to Tony Frudakis, a molecular biologist who said he could determine the killer's race by analyzing his DNA. They were unsure about the science, so, before giving him the go-ahead, the task force sent Frudakis DNA swabs taken from 20 people whose race they knew and asked him to determine their races through blind testing. He nailed every single one.

The Inconvenient Science of Racial DNA Profiling

 

[editec]

There are statistically different means of IQ in different races.

So?

 

[IanC]

There are statistically different means of IQ in different races.

So?

If there are statistically different racial means in IQ (and by implication the brain horsepower 'g'), does that lead to predictions about racial disparities in areas that draw on the type of intelligence measured by IQ tests?

 

[AllieBaba]

I guess this is as close to an opposing argument as I am going to get. You seem to think race is only a social construct. That seems very odd to me when the vast majority of people are instantly recognizible as one of the five main races and usually even finer distinctions can be made. Anthropologists can identify a skeleton's race. Geneticists can identify without ever seeing the person, just from a small piece of tissue.

Interesting that you say there are FIVE main races. I remember it as THREE main races. Why a change? Because it is merely a social construct. Period.

Did you know that 150 years ago, the Irish were not considered white? Neither were the Polish. And when you talk about Africans, are you talking Northern, Southern, Western, or Eastern? They are all different in size, shape, hair, facial structure, skin color...as are Europeans, Asians, etc. We are ALL different. It is only people with tiny minds themselves who try to pigeonhole the human race into a few neat, tidy boxes.

Science studied genetic frequencies of alleles and other markers and found that the most meaningful division was into five clusters. Which, not surprisingly, match continental populations. Of course the three main races make up the vast majority of the world's population.
What does social prejudice from 150 years ago have to do with modern day science? How many racial slurs does it take to negate one MRI image? I don't really want to discuss racial politics, I want to talk about human biodiversity and how obvious physical and behavioural differences are ignored as contributing factors in many social outcomes.
Since no one has argued against the brain being genetically controlled, can I take that as general agreement by most of us?

No, you can take it that you haven't provided anything specific to argue with. Your statement that "thousands of studies" is pure fluff and doesn't deserve response. Quote a study and how it pertains to what you're saying.

Otherwise, people will continue to view your posts as the school aged ramblings of someone who thinks his vague statements should stand as "fact".

 

[IanC]

alliebaba- you didnt like

From an article on brain growth-

Quote:
Twin studies have also shown that genetic effects vary regionally within the brain, with high heritabilities of frontal lobe volumes (90--95%), moderate estimates in the hippocampus (40--69%), and environmental factors influencing several medial brain areas.Studies revealed that total brain volume is positively correlated with general intelligence. In healthy subjects, the level of intellectual functioning has been positively associated with whole brain, gray, and white matter volumes [Thompson et al, 2001; Posthuma et al, 2002]. More focally, several brain areas were found to be correlated with intelligence. Interestingly, it was also shown that the trajectory changes in cortical thickness throughout adolescence are associated with the level of intelligence.
http://www.sciencedaily.com/releases...1016131452.htm

from above?

 

[Lonestar_logic]

Thousands of studies have shown that brain size shape and function are under heavy genetic control.


You failed!!


Why is this in a race thread anyhow?


Perhaps your brain function is unfunctionable.

 

[AllieBaba]

Remember the world's leading genetecist who tried to make the argument that black people were less intelligent because of geography and generations of being under-nourished and under-educated?

He was right, of course, those things do lead to lower iqs, but he had to retract...I think he got into hot water with his off the cuff comment that went something like, "c'mon, if you had a choice, would YOU hire one?"

"One of the world’s most respected scientists is embroiled in an extraordinary row after claiming that black people are less intelligent than white people.

"James Watson, a Nobel Prize winner for his part in discovering the structure of DNA, has provoked outrage with his comments, made ahead of his arrival in Britain today....

"The 79-year-old geneticist said he was “inherently gloomy about the prospect of Africa” because “all our social policies are based on the fact that their intelligence is the same as ours - whereas all the testing says not really.". He said he hoped that everyone was equal, but countered that “people who have to deal with black employees find this not true”.

http://www.timesonline.co.uk/tol/news/uk/article2677098.ece#

 

[Ravi]

alliebaba- you didnt like

From an article on brain growth-

Quote:
Twin studies have also shown that genetic effects vary regionally within the brain, with high heritabilities of frontal lobe volumes (90--95%), moderate estimates in the hippocampus (40--69%), and environmental factors influencing several medial brain areas.Studies revealed that total brain volume is positively correlated with general intelligence. In healthy subjects, the level of intellectual functioning has been positively associated with whole brain, gray, and white matter volumes [Thompson et al, 2001; Posthuma et al, 2002]. More focally, several brain areas were found to be correlated with intelligence. Interestingly, it was also shown that the trajectory changes in cortical thickness throughout adolescence are associated with the level of intelligence.
http://www.sciencedaily.com/releases...1016131452.htm

from above?

Linky no worky.

Besides, if you were intelligent at all, you'd see the flaw in the study...

 

[AllieBaba]

Are you talking to me? Which study?

 

[IanC]

ravi- the link works now
alliebaba- I think a more pertinent scientist to bring up is Bruce Lahn. His work on genes that affect brain size, and which evolved recently, and are present only in certain populations, just about cost him tenure at UofC. It is an interesting story of how political correctness laid a heavy boot on scientific research.

The 37-year-old Dr. Lahn says his research papers, published in Science last September, offered no view on race and intelligence. He personally believes it is possible that some populations will have more advantageous intelligence genes than others. And he thinks that "society will have to grapple with some very difficult facts" as scientific data accumulate. Yet Dr. Lahn, who left China after participating in prodemocracy protests, says intellectual "police" in the U.S. make such questions difficult to pursue.

http://seedmagazine.com/content/article/seed_interview_bruce_lahn/
As for Watson, he never recanted the evidence for differences in intelligence but only apologized that some were offended.

 

[IanC]

Thousands of studies have shown that brain size shape and function are under heavy genetic control. Not only that, but recent studies have shown that numerous genes have undergone significant selection pressure in just the last 5-10 thousand years, including ones that affect the brain. We are still evolving.
Why do people deny race, which is simply continental genetic clusters? Or that different races have brains that have evolved different size shape and function? Surely it would be unlikely that brains would be the only organ to evolve exactly the same all over the world?
Once differences in brain structure and function are accepted to some degree then it is much easier to explain the disparities in social functioning between the races.
I'm sure I will be called a racist for this but Occam's Razor demands that simple and factually confirmed reasoning be fully examined. I will be more than happy to bring citations to refute any logically argued differences of opinion.

You're theory goes right out the window when you realize that the idea of race being nice neat packages is a social construct only.

I can understand your opinion on this issue but you are looking at just one aspect and missing the whole picture. Here is a NYTimes op-ed that covers most of the points. The New York Times > Opinion > Op-Ed Contributor: A Family Tree in Every Gene

The dominance of the social construct theory can be traced to a 1972 article by Dr. Richard Lewontin, a Harvard geneticist, who wrote that most human genetic variation can be found within any given "race." If one looked at genes rather than faces, he claimed, the difference between an African and a European would be scarcely greater than the difference between any two Europeans. A few years later he wrote that the continued popularity of race as an idea was an "indication of the power of socioeconomically based ideology over the supposed objectivity of knowledge." Most scientists are thoughtful, liberal-minded and socially aware people. It was just what they wanted to hear.

The error is easily illustrated. If one were asked to judge the ancestry of 100 New Yorkers, one could look at the color of their skin. That would do much to single out the Europeans, but little to distinguish the Senegalese from the Solomon Islanders. The same is true for any other feature of our bodies. The shapes of our eyes, noses and skulls; the color of our eyes and our hair; the heaviness, height and hairiness of our bodies are all, individually, poor guides to ancestry. But this is not true when the features are taken together. Certain skin colors tend to go with certain kinds of eyes, noses, skulls and bodies. When we glance at a stranger's face we use those associations to infer what continent, or even what country, he or his ancestors came from - and we usually get it right. To put it more abstractly, human physical variation is correlated; and correlations contain information.

Genetic variants that aren't written on our faces, but that can be detected only in the genome, show similar correlations. It is these correlations that Dr. Lewontin seems to have ignored. In essence, he looked at one gene at a time and failed to see races. But if many - a few hundred - variable genes are considered simultaneously, then it is very easy to do so. Indeed, a 2002 study by scientists at the University of Southern California and Stanford showed that if a sample of people from around the world are sorted by computer into five groups on the basis of genetic similarity, the groups that emerge are native to Europe, East Asia, Africa, America and Australasia - more or less the major races of traditional anthropology.

 

[Whyte.Devyl]

IanC,

Forgive if I am repeating any points made earlier in this thread, I have not entirely read it.

I take the stand that 'race' is not a factor regarding intelligence.

I also recognize the Lewontin fallacy as merely a red herring. Lewontin was an admitted communist who obviously let his ideology flaw his work... just like that quack Lysenko. That is all that really needs to be said regarding his cult's absurd assertion of "race as a social construct".

Though different 'races' are indeed different, there is no inherent superiority of "intelligence" or any other traits. Granted certain measures could be made to pinpoint current distributions... the subjectivenesss of such measures lead to potentially flawed studies, not to mention the aformentioned possibility of ideology interfering with objectiveness. Even if there are current differentiations, given a just a few generations the dynamic could completely reverse.

This could be an interesting conversation.


I acknowledge that there are empirical studies which "prove" some sort of distribution of "intelligence". Still, I would like to pose a question...

Just what is "intelligence" as you see it?

 

[IanC]

Hi Whyte.Devyl,
I think you are misconstruing my point on this thread. I believe individuals are heavily influenced by their genetics, and racial groups are where we get our genes from. Society says that babies are born as blank slates, and environment and culture shape the individual. But any parent with more than one child knows that babies come out with their own personality; shy or outgoing, happy or morose, sharp or dull. And many other behaviors are genetically influenced as well. Facial expressions, speech patterns, political beliefs, etc are all much more ingrained than people think. Why do I think this? Because of twin studies. Monozygotic twins raised apart are more similar than fraternal twins raised together. There are many examples of separated identical twins who share odd behaviors that are nonexistent in their families. Most of us don't how much of what we do is influenced by genetics because we dont have a twin to compare with.
Here is an article on Executive Function

The executive system is a theorized cognitive system in psychology that controls and manages other cognitive processes. It is also referred to as the executive function, executive functions, supervisory attentional system, or cognitive control.
The concept is used by psychologists and neuroscientists to describe a loosely defined collection of brain processes which are responsible for planning, cognitive flexibility, abstract thinking, rule acquisition, initiating appropriate actions and inhibiting inappropriate actions, and selecting relevant sensory information.

Your ability to control thought and behavior relative to your peers - a set of capacities known as "executive functions" - is almost entirely genetic in origin, according to a newly in-press paper from Friedman et al. Over 560 twins completed tests to measure fundamental components of these executive functions, and the results were analyzed in terms of how similar identical twins performed to one another relative to fraternal twins (all twins in the study were reared together). Astonishingly, the results show that the variance common to all executive functions is correlated roughly twice as much between identical twins as between fraternal twins, and that individual variance in executive function falls directly in line with what would be expected from a perfectly heritable trait.

http://scienceblogs.com/developingintelligence/2008/05/99_genetic_individual_differen.php

Now to go from individuals to population groups we need to see these groups as the partially inbred families that they are. If you go back 25 or 30 generations you have more spots in your family tree than there were people in the world, and people didn't move around much then. The unique combinations of genes that you have received from your ancestors make you recognizible for the race you are. And affect your behaviors in many ways even if those ways are unknown.

 

[IanC]

Though different 'races' are indeed different, there is no inherent superiority of "intelligence" or any other traits. Granted certain measures could be made to pinpoint current distributions... the subjectivenesss of such measures lead to potentially flawed studies, not to mention the aformentioned possibility of ideology interfering with objectiveness. Even if there are current differentiations, given a just a few generations the dynamic could completely reverse.

inherent superiority is a value statement. data are data. measurements are measurements. I see no reason to believe that a huge change could happen in a few generations although I would be happy if it did. What leads you to believe that it might happen? What mechanism? Bruce Lahn investigated a few genes connected to brain growth and development that are on their way to fixation in some populations but the time frame is thousands and ten thousands of years.

 

[Whyte.Devyl]

I think you are misconstruing my point on this thread. I believe individuals are heavily influenced by their genetics, and racial groups are where we get our genes from. Society says that babies are born as blank slates, and environment and culture shape the individual.

Society says that?

In terms of social behaviors, babies are born as blank slates. They depend on those around them to teach them language, manners, customs etc. I am not denying that there are instincts which would be genetically influenced ("executive functions?"). These instincts are basic though, and the influence is minimal compared to that of the nurturing.

Do you have a link that supports the theory that "executive functions" are clearly identifiable by a 'racial' distribution?

The unique combinations of genes that you have received from your ancestors make you recognizible for the race you are.

No argument here, 'race' is absolutely measurable by breeding patterns.

data are data. measurements are measurements.

Lewontin or Lysenko would say exactly the same thing.

What leads you to believe that it might happen?

First I need you to answer a question...
Just what is "intelligence" as you see it?

intelligence - Definition from the Merriam-Webster Online Dictionary

1 a (1) : the ability to learn or understand or to deal with new or trying situations : reason; also : the skilled use of reason (2) : the ability to apply knowledge to manipulate one's environment or to think abstractly as measured by objective criteria (as tests) b Christian Science : the basic eternal quality of divine Mind c : mental acuteness : shrewdness
3 : the act of understanding : comprehension

 

[IanC]

The Meaning and Measurement of Intelligence

1. Intelligence is a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. It is not merely book learning, a narrow academic skill, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings--"catching on," "making sense" of things, or "figuring out" what to do.

2. Intelligence, so defined, can be measured, and intelligence tests measure it well. They are among the most accurate (in technical terms, reliable and valid) of all psychological tests and assessments. They do not measure creativity, character personality, or other important differences among individuals, nor are they intended to.

3. While there are different types of intelligence tests, they all measure the same intelligence. Some use words or numbers and require specific cultural knowledge (like vocabulary). Others do not, and instead use shapes or designs and require knowledge of only simple, universal concepts (many/few, open/closed, up/down).

4. The spread of people along the IQ continuum, from low to high, can be represented well by the bell curve (in statistical jargon, the "normal curve"). Most people cluster around the average (IQ 100). Few are either very bright or very dull: About 3% of Americans score above IQ 130 (often considered the threshold for "giftedness"), with about the same percentage below IQ 70 (IQ 70-75 often being considered the threshold for mental retardation).

5. Intelligence tests are not culturally biased against American blacks or other native-born, English-speaking peoples in the U.S. Rather, IQ scores predict equally accurately for all such Americans, regardless of race and social class. Individuals who do not understand English well can be given either a nonverbal test or one in their native language.

6. The brain processes underlying intelligence are still little understood. Current research looks, for example, at speed of neural transmission, glucose (energy) uptake, and electrical activity of the brain, uptake, and electrical activity of the brain.

Group Differences

7. Members of all racial-ethnic groups can be found at every IQ level. The bell curves of different groups overlap considerably, but groups often differ in where their members tend to cluster along the IQ line. The bell curves for some groups (Jews and East Asians) are centered somewhat higher than for whites in general. Other groups (blacks and Hispanics) are centered somewhat lower than non-Hispanic whites.

8. The bell curve for whites is centered roughly around IQ 100; the bell curve for American blacks roughly around 85; and those for different subgroups of Hispanics roughly midway between those for whites and blacks. The evidence is less definitive for exactly where above IQ 100 the bell curves for Jews and Asians are centered.

Practical Importance

9. IQ is strongly related, probably more so than any other single measurable human trait, to many important educational, occupational, economic, and social outcomes. Its relation to the welfare and performance of individuals is very strong in some arenas in life (education, military training), moderate but robust in others (social competence), and modest but consistent in others (law-abidingness). Whatever IQ tests measure, it is of great practical and social importance.

10. A high IQ is an advantage in life because virtually all activities require some reasoning and decision-making. Conversely, a low IQ is often a disadvantage, especially in disorganized environments. Of course, a high IQ no more guarantees success than a low IQ guarantees failure in life. There are many exceptions, but the odds for success in our society greatly favor individuals with higher IQs.

11. The practical advantages of having a higher IQ increase as life settings become more complex (novel, ambiguous, changing, unpredictable, or multifaceted). For example, a high IQ is generally necessary to perform well in highly complex or fluid jobs (the professions, management): it is a considerable advantage in moderately complex jobs (crafts, clerical and police work); but it provides less advantage in settings that require only routine decision making or simple problem solving (unskilled work).

12. Differences in intelligence certainly are not the only factor affecting performance in education, training, and highly complex jobs (no one claims they are), but intelligence is often the most important. When individuals have already been selected for high (or low) intelligence and so do not differ as much in IQ, as in graduate school (or special education), other influences on performance loom larger in comparison.

13. Certain personality traits, special talents, aptitudes, physical capabilities, experience, and the like are important (sometimes essential) for successful performance in many jobs, but they have narrower (or unknown) applicability or "transferability" across tasks and settings compared with general intelligence. Some scholars choose to refer to these other human traits as other "intelligences."

Source and Stability of Within-Group Differences

14. Individuals differ in intelligence due to differences in both their environments and genetic heritage. Heritability estimates range from 0.4 to 0.8 (on a scale from 0 to 1), most thereby indicating that genetics plays a bigger role than does environment in creating IQ differences among individuals. (Heritability is the squared correlation of phenotype with genotype.) If all environments were to become equal for everyone, heritability would rise to 100% because all remaining differences in IQ would necessarily be genetic in origin.

15. Members of the same family also tend to differ substantially in intelligence (by an average of about 12 IQ points) for both genetic and environmental reasons. They differ genetically because biological brothers and sisters share exactly half their genes with each parent and, on the average, only half with each other. They also differ in IQ because they experience different environments within the same family.

16. That IQ may be highly heritable does not mean that it is not affected by the environment. Individuals are not born with fixed, unchangeable levels of intelligence (no one claims they are). IQs do gradually stabilize during childhood, however, and generally change little thereafter.

17. Although the environment is important in creating IQ differences, we do not know yet how to manipulate it to raise low IQs permanently. Whether recent attempts show promise is still a matter of considerable scientific debate.

18. Genetically caused differences are not necessarily irremediable (consider diabetes, poor vision, and phenalketonuria), nor are environmentally caused ones necessarily remediable (consider injuries, poisons, severe neglect, and some diseases). Both may be preventable to some extent.

Source and Stability of Between-Group Differences

19. There is no persuasive evidence that the IQ bell curves for different racial-ethnic groups are converging. Surveys in some years show that gaps in academic achievement have narrowed a bit for some races, ages, school subjects and skill levels, but this picture seems too mixed to reflect a general shift in IQ levels themselves.

20. Racial-ethnic differences in IQ bell curves are essentially the same when youngsters leave high school as when they enter first grade. However, because bright youngsters learn faster than slow learners, these same IQ differences lead to growing disparities in amount learned as youngsters progress from grades one to 12. As large national surveys continue to show, black 17- year-olds perform, on the average, more like white 13-year-olds in reading, math, and science, with Hispanics in between.

21. The reasons that blacks differ among themselves in intelligence appear to be basically the same as those for why whites (or Asians or Hispanics) differ among themselves. Both environment and genetic heredity are involved.

22. There is no definitive answer to why IQ bell curves differ across racial-ethnic groups. The reasons for these IQ differences between groups may be markedly different from the reasons for why individuals differ among themselves within any particular group (whites or blacks or Asians). In fact, it is wrong to assume, as many do, that the reason why some individuals in a population have high IQs but others have low IQs must be the same reason why some populations contain more such high (or low) IQ individuals than others. Most experts believe that environment is important in pushing the bell curves apart, but that genetics could be involved too.

23. Racial-ethnic differences are somewhat smaller but still substantial for individuals from the same socioeconomic backgrounds. To illustrate, black students from prosperous families tend to score higher in IQ than blacks from poor families, but they score no higher, on average, than whites from poor families.

24. Almost all Americans who identify themselves as black have white ancestors-the white admixture is about 20%, on average--and many self-designated whites, Hispanics, and others likewise have mixed ancestry. Because research on intelligence relies on self- classification into distinct racial categories, as does most other social-science research, its findings likewise relate to some unclear mixture of social and biological distinctions among groups (no one claims otherwise).

Implications for Social Policy

25. The research findings neither dictate nor preclude any particular social policy, because they can never determine our goals. They can, however, help us estimate the likely success and side-effects of pursuing those goals via different means.