Friday, January 01, 2010

Estimating black-white racial tension from 1850 to present   posted by agnostic @ 1/01/2010 08:59:00 PM

As a New Year's gift, here is a free copy of an entry I put up on my data blog (details on that here). It's a quantitative look at the history of race and culture in America, together with qualitative examples that illustrate the story that the numbers tell. Enjoy.

Previously I looked at how much attention elite whites have given to blacks since the 1870s by measuring the percent of all Harvard Crimson articles that contained the word "negro." That word stopped being used in any context after 1970, which doesn't allow us to see what's happened since then. Also, it is emotionally neutral, so while it tells us how much blacks were on the radar screen of whites, it doesn't suggest what emotions colored their conversations about race.

When tensions flare, people will start using more charged words more frequently. The obvious counterpart to "negro" in this context is "nigger." It could be used by racists hurling slurs, non-racists who are quoting or decrying the slur, by tribalist blacks trying to open old wounds to recruit new members, by blacks trying to "re-claim" the term, by those debating whether or not the term should be used in any context, and so on. Basically, when racial tension is relatively low, these arguments don't come up as often, so the word won't appear as often.

I've searched the NYT back to 1852 and plotted how prevalent "nigger" was in a given year, though smoothing the data out using 5-year moving averages (click to enlarge):

We see high values leading up and throughout the Civil War, a comparatively lower level during Reconstruction, followed by two peaks that mark "the nadir of American race relations." It doesn't change much going through the 1920s, even though this is the period of the Great Migration of blacks from the South to the West and Northeast. It falls and stays pretty low during the worst part of the Great Depression, WWII, and the first 10 years after the war. This was a period of increasing racial consciousness and integration, and the prevalence of "negro" in the Crimson was increasing during this time as well. That means that there was a greater conversation taking place, but that it wasn't nasty in tone.

However, starting in the late 1950s it moves sharply upward, reaching a peak in 1971. This is the period of the Civil Rights movement, which on an objective level was merely continuing the previous trend of greater integration and dialogue. Yet just as we'd guess from what we've studied, the subjective quality of this phase of integration was much more acrimonious. Things start to calm down throughout the '70s and mid-'80s, which our study of history wouldn't lead us to suspect, but which a casual look at popular culture would support. Not only is this a period where pop music by blacks had little of a racial angle -- that was also true of most of the R&B music of most of the '60s -- but was explicitly about putting aside differences and moving on. This is most clearly shown in the disco music scene and its re-birth a few years later during the early '80s dance and pop music scene, when Rick James, Prince, and above all Michael Jackson tried to steer the culture onto a post-racial course.

But then the late '80s usher in a resurgence of identity politics based on race, sex, and sexual orientation ("political correctness," colloquially). The peak year here is technically 1995, but that is only because of the unusual weight given to the O.J. Simpson trial and Mark Fuhrman that year. Ignoring that, the real peak year of the racial tension was 1993 according to this measure. By the late '90s, the level has started to plummet, and the 2000s have been -- or should I say were -- relatively free of racial tension, a point I've made for awhile but that bears repeating since it's not commonly discussed.

Many people mention Obama's election, but that was pretty late in the stage. Think back to Hurricane Katrina and Kanye West trying but failing to foment another round of L.A. riots, or Al Sharpton trying but failing to turn the Jena Six into a civil rights cause celebre, or the mainstream media trying but failing to turn the Duke lacross hoax into a fact that would show how evil white people still are. We shouldn't be distracted by minor exceptions like right-thinking people casting out James Watson because that was an entirely elite and academic affair. It didn't set the entire country on fire. The same is true for the minor exception of Larry Summers being driven out of Harvard, which happened during a remarkably feminism-free time.

Indeed, it's hard to recognize the good times when they're happening -- unless they're fantastically good -- because losses loom larger than gains in our minds. Clearly racial tensions continue to go through cycles, no matter how much objective progress is made in improving the status of blacks relative to whites. Thus, we cannot expect further objective improvements to prevent another wave of racial tension.

Aside from the long mid-20th C hiatus, there are apparently 25 year distances between peaks, which is about one human generation. If the near future is like most of the past, we predict another peak around 2018, a prediction I've made before using similar reasoning about the length of time separating the general social hysterias that we've had -- although in those cases, just going back to perhaps the 1920s or 1900s, not all the way back to the 1850s. Still, right now we're in a fairly calm phase and we should enjoy it while it lasts. If you feel the urge to keep quiet on any sort of racial issues, you should err on the side of being more vocal for right now, since the mob isn't predicted to come out for another 5 years or so, and the peak not until 10 years from now. As a rough guide to which way the racial wind is blowing, simply ask yourself, "Does it feel like it did after Rodney King and the L.A. riots, or after the O.J. verdict?" If not, things aren't that bad.

Looking at absolute levels may be somewhat inaccurate -- maybe all that counts is where the upswings and downswings are. So I've also plotted the year-over-year percent change in how prevalent "nigger" is, though this time using 10-year moving averages to smooth the data out because yearly flucuations up or down are even more volatile than the underlying signal. In this graph, positive values mean the trend was moving upward, negative values mean it was moving downward, and values close to 0 mean it was staying fairly steady:

Again we see sustained positive growth during the Civil War, the two bookends of the nadir of race relations, although we now see a small amount of growth during the Harlem Renaissance era. The Civil Rights period jumps out the most. Here, the growth begins in the mid-1940s, but remember that it was at its lowest absolute levels then, so even the modest increases that began then show up as large percent increases. The PC era of the late '80s through the mid '90s also clearly shows up. There are several periods of relative stasis, but I see three periods of decisively moving against a nasty and bitter tone in our racial conversations: Reconstruction after the Civil War (admittedly not very long or very deep), the late '30s through WWII, and the "these are the good times" / Prince / Michael Jackson era of the mid-late '70s through the mid '80s, which is the most pronounced of all.

That trend also showed up television, when black-oriented sitcoms were incredibly popular. During the 1974-'75 season, 3 of the top 10 TV shows were Good Times, Sanford and Son, and The Jeffersons. The last of those that were national hits, at least as far as I recall, were The Cosby Show, A Different World, Family Matters, The Fresh Prince of Bel-Air, and In Living Color, which were most popular in the late '80s and early '90s. Diff'rent Strokes spans this period perfectly in theme and in time, featuring an integrated cast (and not in the form of a "token black guy") and lasting from 1978 to 1986. The PC movement and its aftermath pretty much killed off the widely appealing black sitcom, although after a quick search, I see that Disney had a top-rated show called That's So Raven in the middle of the tension-free 2000s. But it's hard to think of black-focused shows from the mid-'90s through the early 2000s that were as popular as Good Times or The Cosby Show.

(In the top picture, the comparison between Jennifer Beals and Halle Berry shows that a black-white biracial babe actress who came of age during the late '70s and early '80s took a white husband twice, while her counterpart who became famous in the early '90s went instead for black men.)

But enough about TV. The point is simply that the academic material we're taught in school usually doesn't take into account what's popular on the radio or TV -- the people's culture only counts if they wrote songs about walking the picket line, showed that women too can be mechanics, or that we shall overcome. Historians, and people generally, are biased to see things as bad and getting worse, so they rarely notice when things were pretty good. But some aspects of popular culture can shed light on what was really going on because its producers are not academics with an axe to grind but entrepreneurs who need to know their audience and stay in touch with the times.

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Tuesday, July 21, 2009

Genetic background & medicine, HIV & differences between blacks & whites   posted by Razib @ 7/21/2009 01:24:00 PM

The Duffy-null state is associated with a survival advantage in leukopenic HIV-infected persons of African ancestry:
Persons of African ancestry, on average, have lower white blood cell (WBC) counts than those of European descent (ethnic leukopenia), but whether this impacts negatively on HIV-1 disease course remains unknown. Here, in a large natural history cohort of HIV-infected subjects we show that although leukopenia...was associated with an accelerated HIV disease course, this effect was more prominent in leukopenic subjects of European than African ancestry. The African-specific -46C/C genotype of Duffy Antigen Receptor for Chemokines (DARC) confers the malaria-resisting, Duffy-null phenotype, and we found that the recently described association of this genotype with ethnic leukopenia extends to HIV-infected African Americans (AA). The association of Duffy-null status with HIV disease course differed according to WBC but not CD4+ T cell counts, such that leukopenic but not non-leukopenic HIV+ AAs with DARC -46C/C had a survival advantage compared with all Duffy-positive subjects. This survival advantage became increasingly pronounced in those with progressively lower WBC counts. These data highlight that the interaction between DARC genotype and the cellular milieu defined by WBC counts may influence HIV disease course, and this may provide a partial explanation of why ethnic leukopenia remains benign in HIV-infected African Americans, despite immunodeficiency.

Duffy status is a highly ancestrally informative trait. This is a case where the relatively low between population variance found among humans does not apply. Rather, it seems that the Duffy null phenotype is a recent adaptation to malaria among West Africans. Because malaria has such a strong fitness implication many independent genetic adaptations have emerged, many of them with other negative side effects. On net individuals with side effects may still have higher fitness in an environment where malaria is endemic. Sometimes the net benefit is most evidence on a population wide scale, sickle-cell anemia is a deleterious homozygote which exists because of the much higher frequency of heteryzogytes vis-a-vis wild type homozygotes. Many malaria adaptations exhibit the large effect dynamic and suboptimal characteristic which one might except from the early stages of natural selection in a Fisherian model. You deal with the adaptive pressures of the present and let the future take care of itself. In this case, the future involved HIV:
The researchers found that leukopenia was generally associated with a faster disease progression from HIV to AIDS, independent of known predictors of AIDS development. "On average, leukopenic European Americans progressed nearly three times faster than their non-leukopenic African or European counterparts," explained Hemant Kulkarni, MD, first author of this study. "However, leukopenic African Americans had a slower disease course than leukopenic European Americans, even though twice as many African Americans in the study had leukopenia."

The investigators found that the DARC variation, not race, explained the differences in WBC counts in African Americans with HIV. Among those who were leukopenic, only those with the DARC variation experienced a significant survival benefit. Additionally, this survival advantage became increasingly pronounced in those with progressively lower WBC counts, suggesting that the interaction between DARC and WBC counts was the primary influence on slowing HIV disease progression in African Americans.

There are no doubt details in the genetic architecture of those with the null genotype worth future investigation.

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Tuesday, February 17, 2009

Steven Rose: Wrong on the science of race, gender, and intelligence   posted by ben g @ 2/17/2009 08:13:00 AM

In the latest issue of Nature, competing editorials were written on the proposition that scientists should study race and IQ. Steven Ceci and Wendy Williams argued 'Yes', and Steven Rose argued 'No'. In this article I will detail the scientific errors which underly Rose's argument. The scientific reasons offered by him are largely a veneer meant to justify his "radical science" political views, but I will refrain from commenting on his politics until my next post on this.

Rose argues:
the categories of intelligence, race and gender are not definable within the framework required for natural scientific research, failing my first criterion of being well-founded. They also fail the second criterion of being answerable: we lack the theoretical or technical tools to study them.
Let's begin with his critiques of IQ:

to try to capture the many forms of socially expressed intelligent behaviour in a single coefficient — and to rank an entire population in a linear mode, like soldiers on parade lined up by height — excludes most richly intelligent human activities. Social intelligence, emotional intelligence, the intelligent hands of the craftsman or the intelligent intuition of the scientist all elude the 'g' straightjacket
Modern psychometrics isn't claiming that all of a person's intelligence is measured by IQ or g. IQ is used because of its strong and reliable correlations with educational and economic performance, independent of class and race.

Group comparisons of IQ are even more problematic. Attempts have been made to make 'culture-fair' or 'culture-free' tests, as if such a thing were possible, to allow comparisons of 'g' between people from very different societies.
Rose doesn't understand what is meant by "culture fair." It doesn't mean that the test prevents someone's culture from having an effect on their IQ score. Rather, it means that culture does not effect the test's predictive validity. And that is indeed the case. Worldwide the correlations between IQ and economic/educational success are high.

Rose goes on to critique the concept of biological race:

As for 'race', the problem is whether it is a biologically, as opposed to socially, meaningful category. Among geneticists interested in differences in gene frequencies between populations, there is increasing consensus that the word obscures more than it reveals, and should be replaced by the concept of biogeographic ancestry, which makes possible the study of subpopulations for relevant genetic and phenotypic characteristics... Broad divisions between 'white' or 'Caucasian' and 'black' or 'Asian', the groups generally discussed in the context of the IQ debate, especially in the United States, hide genetically important subpopulation differences within these groups.
To begin with, it is biologically meaningful to talk of the 'white race' or the 'asian race.' These categories encapsulate a great deal of genetic variation, and are not arbitrary; as Steve Sailer has pointed out, Cavalli-Sforza's principal components map corresponds to social categories of race.

Furthermore, discussing higher level categories does nothing to obscure lower level categories. If I know someone is a Christian, this doesn't mean I cease to be interested in their denomination. And in fact, psychometricians do study more specific categories than the big 3 races; see for example Jason Malloy's summary of Lynn's worldwide psychometric work.

As for terminology, it is actually irrelevant whether we refer to population groups by their "race" or their "biogeographic ancestry." The former has more social and historical baggage, and the latter is more long-winded, but they both point to the same empirical fact-- group-based genetic differences.

Lastly, the IQ differences between blacks, whites, and asians interest researchers so much simply because the differences in educational/economic outcomes between these groups interest researchers (and the public) more than other group-based differences.

Rose moves on to gender:

the crucial question is whether it is possible to identify a biological — presumably genetic or neurodevelopmental — cause to any difference in the way men and women think and act. The problem is that from the moment of birth, boys and girls are treated differently, which shapes both their growing bodies and brains and how they are expected to behave... Thus, although there are minor average structural and biochemical variations between Western men's and women's brains (such as the volume of some nuclei and the distribution of hormone receptors), speculations on their implications for how men and women may think or behave lack any empirical basis.
There are plenty of research methods that can be used to sidestep the problems that Rose raises here. To name a few, we can look at: kids raised as the opposite gender because of botched genital operations, how hormones correlate with various behaviors, the differences between girl or boy babies in their first months of life, human universals, etc.

Rose closes up the "scientific" portion of his article by citing many of the difficulties which prevent the resolution of the race and IQ debate:

The standard approach of population biologists to estimating the potential genetic contribution to a trait is to make a heritability estimate. Whatever the strengths and weaknesses of this measure within a population, it is essentially just that: a within-population measure, only valid for a given environment. The nature of the equations means that if the environment changes, the heritability estimate changes too...Even if reliable correlations were found between some intelligence test score and a measure of brain physiology or activity held by a specific group, such a correlation says nothing about the direction of causation.
This is an argument for more research, not less. This is an argument for genome-wide association studies, which will allow us to pinpoint the genes that effect intelligence and how they interact with the enviornment. This is an argument for more research on the neuroscience behind IQ and intelligence. This is an argument for further funding of projects to map out the genetic differences between human populations world-wide. This is not an argument for cutting off an important (albeit, politically inconvenient) avenue of science.

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Monday, February 11, 2008

Apes or Angels?   posted by Razib @ 2/11/2008 01:08:00 AM

Imagine a brief which is aimed at both Christianity Today and The Humanist; Cornelius J. Troost's Apes or Angels does just that. Synthesizing the latest research coming out of modern genomics with ideas first mooted by Charles Darwin 150 years ago Troost launches an extended broadside at the pieties of the modern age and the cult of equality. He wields the 'universal acid' of evolutionary thinking and makes a case for a post-supernatural world view which fulfills its promise by making peace with nature; as opposed to pretending as if our dreams of the good and should reflect the truth of a world. Troost asks us to consider the implications of a world wrought in blood, red in tooth and claw. In short, fraternity does not depend upon the reality of equality; at least if fraternity as such already exists while the equality never did. Confronting a many-headed hydra Apes or Angels makes recourse to a wide array of tools to cut its antagonista down to size. In the process Troost surveys the grand arc of the history of evolution, naturalistic philosophy as well as the latest insights from neuroscience. Evolutionary science serves as the sinew, but the bone and flesh of the argument are variegated and diverse.

In The Blank Slate Steve Pinker observed curiously that even into the 21st century we take as our philosophical sages in the domain of human affairs to be men who lived in the 17th and 18th century. Hobbes, Locke, Montesquieu and Hume to name names. All them lived before evolution, before psychology, before even the fissuring of natural philosophy into its manifold faces that we know today as science. It is perhaps a reflection upon our species that decisions we make as to how we order our affairs as a social organism are influenced by the ideas of men who lived before the great flowering of scientific thought; common sense ideas from an a priori world. In Apes or Angels the full arc of the hammer-blow that Darwin's common sense idea about natural selection and descent with modification had upon traditional religion is detailed; from the outraged Victorians to the Scopes Monkey Trial to the Dover fiasco. This is a well known tale and many an enlightened liberal would chuckle at the travails of the yokels who populate the broad expanses of the heartland of this nation. The ignorati who refuse to make their peace with the truths unearthed by science.

But interlaced with this familiar story is a less well known one which suggests that the reality that humans are different in nature, capacity and propensity is being established by the more cutting edge of the human sciences. It is commonly observable that as humans we vary, but the causal factors underlying that variation have long been subject to dispute, and to be frank, the fashions of the day. During the high tide of the blank slate men such as Leon Kamin could claim in polite company that the heritability of IQ was about zero. No more. The waters are retreating and exposing what was once obscured; we need to rapidly prepare ourselves for the new and the surprising. Troost's book is chock-full of research from every cutting edge field relevant to the human sciences. On occasion I would submit that his enthusiasm gets the better of him; results reported do not necessarily imply facts established. Theories propounded are a dime a dozen. Science as a process is riddled with error and noise; its genius is in its rigorous corrective mechanisms. But those mechanisms need time to work so as to shape a better picture of reality. That being said, the tentative findings of one generation are the background assumptions of the next. It is the job of scientists to engage in the process of hypothesis generation and subsequent falsification. It is the job of those who follow science, which should be every broadly educated individual, to determine how science fits into our view of how the world is, should be, and how we can make it be what we believe it should be.


Tuesday, November 20, 2007

The unfortunate consequences of misunderstanding race   posted by p-ter @ 11/20/2007 08:54:00 PM

Reading the links that come in to GNXP, I happened upon this post on what the author referrs to as "scientific racism". This bit caught my eye:
I sat on a grant review committee recently for a national-level competition for multi-million dollar grants of an agency I won't name. The review committee was quite large, probably 25 or more scholars from around the U.S. One of the grant applications that the other reviewers (mostly from the biological sciences) rated the highest was one that proposed to look at the "genetic racial differences among Blacks and whites" to different kinds of treatment for HIV/AIDS. I rated this grant proposal among the lowest I had reviewed because of the methodology: all of the participants in the study would be sorted into the supposedly self-evident categories "Black" and "white" based on self-identification. When I raised this objection among my colleagues in the biological and health sciences, they all blinked hard, and looked at me as if I'd committed some sort of unpleasant faux pas. The chair of the committee finally acquiesced that this was a methodological flaw in the proposal, but the grant was nevertheless awarded millions of dollars.
Biomedical researchers are caught between a rock and a hard place here--none of them enjoy being referred to as scientific racists by their colleagues, I'm sure, but they're also interested in real phenomena.

It's well-known that minorities are less likely to participate in biomedical research (though recent studies suggest this is not because they're less willing). From a geneticist's perspective, the discomfiting implication of this is that tests of a drug's efficacy and safety are done on a range of genetic backgrounds that are strongly biased towards the European mean. That is, drugs are accepted or rejected largely based on how well they perform in a sample of individuals of European descent. This is obviously a problem for the applicability of any results, and the NIH is indeed making minority inclusion a requirement for funding certain projects.

Clearly, none of this would be an issue if everyone responded identically to drugs (or if the correlation between drug response and race were zero). It is, however, an issue. Now, ancestry could be related to drug response through any number of mechanisms, either directly (through genetics) or indirectly (through socioeconomic status, etc). Teasing apart those influences means looking at both of them. But then you have someone like the author, who simply dismisses the correlation altogether! And who evidently has some say in the funding of these studies!

It's worth pointing out that HIV progression does indeed have a genetic component and that certain alleles like CCR5-delta32, which is strongly protective against HIV infection, show marked geographic differences in frequency. A priori, looking for genetic components to differential drug response between populations seems entirely reasonable. Lastly, her main point seems to be that genetic ancestry and self-identified race might not match up. They do.

I'm well-aware that positions like the author's are made possible by people at the other end of the spectrum, who see races as the embodiment of some Platonic ideal. But rejecting idiocy certainly does not require one to embrace blindness!

Related: Cancer and Race

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Wednesday, October 31, 2007

James Watson Tells the Inconvenient Truth: Faces the Consequences   posted by Jason Malloy @ 10/31/2007 11:22:00 AM

... [M]ight it be fair also to say that the champions of 'no difference' in race or sex, or intelligence ... are the guardians of a greater 'untruth' that allows people to live together in mutual harmony, implying that these critics really deserve to be praised as our protectors even when they are factually wrong? ... it is roughly how the self-appointed guardians choose to present themselves - leaving aside, usually, the step of frankly admitting that they are promoting factual untruths when they know that they are.
W.D. Hamilton - ("... one of the greatest evolutionary theorists of the 20th century"). Narrow Roads of Gene Land. Vol. II: The Evolution of Sex, p 332.

The public intellectual forum is being manipulated with intimidation and coercion and you are being lied to. The media is not doing its job, and the scientific community is not playing its proper public role as a beacon of dispassionate truth seeking, as a conduit of knowledge to the public, or in fostering an open and fair intellectual climate. Both are abusing their power and authority to do the opposite of their honor bound social and intellectual roles; facts are being distorted in service of values.

This post is a very long and detailed examination of what James Watson said, what the data reveal about James Watson's claims (i.e. are they, or are they not factually accurate), and what the media and scientists told the public about what the data reveal about James Watson's claims.


It's difficult to name many more important living figures in 20th century biology than James Watson. He ushered in the current age of molecular biology with his achievements in 1953, he built up one of the world's greatest biological research facilities from damn near scratch, and he is a former head of the Human Genome Project.

Given such an august curriculum vitae, you would think that this man perhaps understands just a few things about genetics. But given only the condescending media coverage, you'd think this eminent geneticist was somehow "out of his depth" on this one.

In his interview with the Times on Oct. 14th, we learned that:
... [Watson] is "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", and I know that this "hot potato" is going to be difficult to address.

These thoughts were a continuation of an important theme in his new book Avoid Boring People:
... there is no firm reason to anticipate that the intellectual capacities of peoples geographically separated in their evolution should prove to have evolved identically. Our wanting to reserve equal powers of reason as some universal heritage of humanity will not be enough to make it so.

Although Watson's book had already been out for a month with these more euphemistic, but still obvious, comments on race and intelligence, no one expressed any outrage. In fact the reviews were reverential and universally positive.

The explicit reference to intelligence and people of African heritage in his interview was clearly a violation of a much more formidable taboo. Still I am not aware of there being much noise about it until Oct. 17th when the Independent caused an immediate stir by calling attention to the remarks: Africans are less intelligent than Westerners says DNA pioneer.

There's no point in rehashing the rapid sequence of events in detail: several of Watson's sold-out speaking engagements were cancelled, many critical articles appeared in the British press, trailed by the American press a few days later, hundreds of blogs were fuming with negative commentary, including ones by the editors of Scientific American and Wired Magazine, a number of associations issued statements condemning his words, and soon he was suspended from his chancellorship at Cold Spring Harbor. Watson cancelled his already ruined book tour and flew home to tend to the destruction. It was too late; the eminent biologist retired in disgrace on Oct. 26th.

One thing, though, was conspicuously missing from this whole irritating denouement: any semblance of factual refutation. There is good reason for this: everything Watson got in trouble for saying was entirely correct!


The "scientific community" is a broad and inappropriately encompassing term, but to the extent such a thing exists as a social or public entity (I'm not talking about the research literature), it is fair to say it has pronounced Watson's claims not only false, but also outside the bounds of "legitimate" scientific discourse. Since only a small fraction of scientific disciplines have any relevance to Watson's claims, it is clear almost all of these scientists are just evaluating the claims with the same ignorant, moralized mental framework people in the general public use to look at (and editorialize upon) scientific claims about evolution.

Watson's claim was that intelligence testing shows lower intelligence scores in Africa than Europe. Is this or is this not true? The Science Museum in London responded by canceling Watson's speaking engagement by deeming this claim, not only scientifically false, but outside the realm of "legitimate" scientific inquiry (Whatever that is!) altogether:
In a statement, [The Science Museum in London] said: "We know that eminent scientists can sometimes say things that cause controversy and the Science Museum does not shy away from debating controversial topics.

"However, the Science Museum feels that Nobel Prize winner James Watson's recent comments have gone beyond the point of acceptable debate and we are as a result cancelling his talk at the museum."

Watson's claim was that intelligence testing shows lower intelligence scores in Africa than Europe. Is this or is this not true? Francis Collins, Watson's successor over the Human Genome Project, told the media this is not true:
Dr. Francis Collins, director of the National Human Genome Research Institute, said that "I am deeply saddened by the events of the last week, and understand and agree with Dr. Watson's undoubtedly painful decision to retire in the aftermath of a racist statement he made that was both profoundly offensive and utterly unsupported by scientific evidence.

Watson's claim was that intelligence testing shows lower intelligence scores in Africa than Europe. Is this or is this not true? Rick Kittles told the media this is not true:
Rick Kittles, an associate professor of genetic medicine at the University of Chicago, said Watson's remarks aren't backed by science.

Watson's claim was that intelligence testing shows lower intelligence scores in Africa than Europe. Is this or is this not true? Robert Sternberg told the media that the 'scientific findings' show otherwise:
Robert Sternberg, a prominent researcher on race and IQ at Tufts University, called Watson's statement "racist and most regrettable."

"It is unfortunate that some people with great expertise in one area sometimes lose their sense of perspective and come to view themselves as expert in areas about which they know nothing," Sternberg said Thursday in an e-mail response to questions. "They then proceed to embarrass themselves as well as society in general with their comments that express their own ideology rather than scientific findings."

Watson's claim was that intelligence testing shows lower intelligence scores in Africa than Europe. Is this or is this not true? Steven Rose told the media that the scientific literature shows otherwise:
Steven Rose, a professor of biological sciences at the Open University and a founder member of the Society for Social Responsibility in Science, said: "... If [Watson] knew the literature in the subject he would know he was out of his depth scientifically, quite apart from socially and politically."

Watson's claim was that intelligence testing shows lower intelligence scores in Africa than Europe. Is this or is this not true? The Federation of American Scientists issued a statement condemning Watson, claiming that there is no scientific literature showing this:
The Federation of American Scientists condemns the comments of Dr. James Watson that appeared in the Sunday Times Magazine on October 14th... The scientific enterprise is based on the promotion and proof of new ideas through evidence, however controversial, but Dr. Watson chose to use his unique stature to promote personal prejudices that are racist, vicious and unsupported by science.

Unfortunately our esteemed band of sputtering media scientists forgot to provide, in all of these instances, any of their allegedly voluminous citations to the contrary. Allow me, then, to take a different position, with the added benefit of evidence:

James Watson is one of the most important living figures in American science. The claim in his new book Avoid Boring People, that basic evolutionary logic predicts we should expect intelligence differences between racial groups is, if anything, an uncomplicated truth. Watson's claim in his recent interview with Charlotte Hunt-Grubbe that intelligence testing shows lower scores in Africa than Europe is likewise, entirely supported by the scientific literature. As is Dr. Watson's statement that there are many talented people of African descent, which clarifies he is speaking of different average scores, not that said populations are homogenous.

Below I am adding 65 psychometric intelligence study citations for sub-Saharan Africa, collected in IQ & Global Inequality, Race Differences in Intelligence, and IQ & the Wealth of Nations. The citations cover 47% of SS African countries or 78% of the people by national population numbers. The studies vary in quality, sample size, and representativeness, but broadly agree in their findings. Representative studies of the school age population with large sample sizes do not exhibit higher scores, much less scores that approach anything like European norms.


Sub-Saharan Africa
Countries: 43
W/ data: 20 (47% coun/78% pop)
Studies: 65
IQ: 68

West Africa
Countries: 20
W/ Data: 6 (30% coun/65% pop)
Studies: 15
IQ: 67

Central Africa
Countries: 5
W/ Data: 3 (60% coun/80% pop)
Studies: 9
IQ: 64

East Africa
Countries: 8
W/ Data: 5 (63% coun/93% pop)
Studies: 16
IQ: 72

Southern Africa
Countries: 10
W/ Data: 6 (60% coun/76% pop)
Studies: 25
IQ: 69


The recent August issue of the European Journal of Personality features a paper titled The g-factor of international cognitive ability comparisons: the homogeneity of results in PISA, TIMSS, PIRLS and IQ-tests across nations by German psychologist Heiner Rindermann. This paper includes an open peer commentary by 31 international scholars, as well as a response by Rindermann. The target paper provides valuable new IQ data from sub-Saharan African, or rather let's us know we have an overlooked source of intelligence data. I am adding these papers to the gnxpforum files section for you to access.

Starting in the 1960s and picking up pace in the early 1990s various well-implemented student assessment tests have been conducted for the purposes of international educational comparisons, including the Trends in International Mathematics and Science Study (TIMSS), the International Educational Achievement (IEA) measures, and the OECD's Programme for International Student Assessment (PISA). The cross-cultural test construction, sampling techniques, and quality control for these tests are exemplary. These international tests have also included half a dozen sub-Saharan African countries, and the test construction and sampling techniques are likewise very good. For example Ghana, Botswana, and South Africa were included in TIMSS 2003. For each tested grade level, at least 5000 random students from 150 schools were tested in these countries.

Gene Expression bloggers recognized the strong correlation between these types of tests and IQ as far back as 2004, but recently this has reached the academic literature. Last year Richard Lynn and Jaan Mikk reported correlations of .92-1.00 between IQ and TIMSS 2003 for math and science.

In his paper, Heiner Rindermann takes this sort of analysis to the next level by collecting data from all 20 total international student assessment tests encompassing some 78 countries and comparing them with measured IQ data from 128 countries. Rindermann finds, first of all that the combined national student results correlate perfectly with the combined national IQ data (.98), demonstrating the assessment scores and the IQ scores are the same measured construct. With all these diverse kinds of tests for each nation, Rindermann examines the data together through factor analysis and finds that the g factor of intelligence explains some 95% of the variance in the test results: "Thus, cognitive ability differences across nations are by and large unidimensional". (p 681) The stable differences between nations in all cognitive type tests are explained by the g factor.

Furthermore Rindermann emphasizes that, consistent with previous IQ testing, the g loaded international assessment tests reveal sub-Saharan African IQ scores that characteristically range from 1.5-2.5+ standard deviations below European and East Asian norms:
... I do not believe that the [sub-Saharan testing] scores at the general level are largely incorrect: The low values correspond to too many other variables and aspects standing for low cognitive abilities like results of student assessment and Piaget studies (e.g. Botswana in IEA-Reading 14 year-old pupils 1991 330, as IQ 75; South-Africa in TIMSS 8th graders 1999 259, as IQ 64; Ghana in TIMSS 8th graders 2003 266, as IQ 65; South-Africa in TIMSS 8th graders 2003 254, as IQ 63; plausibility considerations lead to lower results for the youth of Africa because of low school attendance rates and unrepresentative participation of countries), poor quality school systems, high skipping rates, low rates of high school degrees, low patent application rates, no famous universities, and many reports of everyday behaviour from officials, traders, journalists, ethnologists and other scientists in 19th century to this day... (p 770)

Thus typical African IQ scores of 70 and below can still be taken as a reliable finding. It is not simply the manufactured data of racialist researchers, or a byproduct of inadequate testing procedures. And, more importantly from the standpoint of the Watson controversy, certainly no reliable body of evidence has shown anything like parity with typical European scores.

I'd like to reiterate, then, that IQs below 70 do not by themselves signify mental retardation, as it is commonly understood as a pathological state.

There are two types of retardation: familial and organic. The former is caused by normal population variation in intelligence while the latter is caused by diverse individual problems such as genetic defects or head injuries. Related to this, the IQ scores of people with familial retardation correlate normally with their parent and sibling's IQ scores (.50), while the IQ scores of people with organic retardation are not much associated with the IQs in their family.

Retardation is measured by a combination of IQ and adaptive scales. Sometimes an IQ of 70 is used as the threshold of retardation. People with familial retardation and organic retardation of matched IQ perform the same in academic and training contexts, but organically retarded individuals do worse on the adaptive scales which measure things such as self-care, motor skills, and social functioning, signifying a broader range of mental dysfunction and some sort of developmental damage.

In the US, consistent with the normal bell curve, there are proportionately about five times as many blacks (16%) with an IQ of 70 or below than there are whites (3%). But basically the same proportional number of whites and blacks are organically retarded (whites 1.5%, blacks 2.0%). (The g Factor, p 369)

The African scores indicate that there are proportionately about seventeen times as many sub-Saharan Africans with IQs below 70 (50%) than American whites (3%), and possibly even more. While organic retardation is probably somewhat higher among Africans, due to overall more challenging health conditions, this should in no way be regarded as characteristic of their normal intelligence variation.

There is nothing particularly meaningful or necessary about an IQ of 70 as a threshold for 'retardation'. La Griffe Du Lion writes:
In 1959, [the American Association on Mental Deficiency] set the IQ threshold for mental retardation at 85. The civil rights movement of the next decade forced psychologists to rethink this boundary, because half the African American population fell below it. In 1973, responding to this concern, AAMD (by then AAMR) changed the threshold for retardation from IQ 85 to IQ 70. The boundary moved south by one standard deviation! The proportion of blacks below the threshold instantly dropped from about 50 percent to 12 percent.

In other words 50% of modern Africans are no more 'mentally retarded' than 50% of African-Americans were 'mentally retarded' in the 1960s. These are labels of convenience designed for normal within-population variation. But the real world academic and economic consequences of IQs of 70-85 and below are the same no matter what you label them.



Groups of people may differ genetically in their average talents and temperaments ... proponents of ethnic and racial differences in the past have been targets of censorship, violence, and comparisons to Nazis. Large swaths of the intellectual landscape have been reengineered to try to rule these hypotheses out a priori (race does not exist, intelligence does not exist, the mind is a blank slate...)
Steven Pinker - The Edge Annual Question - 2006. "What is your dangerous idea?"

Of course pointing to the testing data alone is hardly sufficient to quell these latter-day inquisitors. There is, sadly, an infinite regress of obscurantist objections designed to intellectually moot these issues entirely. These objections are not scientific, and are at odds with the data, logic, and, more often, both.

Systematic media misrepresentations of psychometric science have been occurring for going on 40 years.

In 1988 Stanley Rothman and Mark Snyderman published The IQ Controversy, the Media and Public Policy. Along with data from their 1987 study of over 1000 scholars in fields familiar with IQ testing, such as psychology, sociology, and behavioral genetics, Rothman and Snyderman took a quantitative look at media coverage of IQ and demonstrated how this media coverage habitually diverged with mainstream scholarly opinion.

This is particularly egregious during times of IQ controversy.

Media reports and editorials were quick to attack Watson on the premise that any statement about intelligence measures is scientifically indefensible, because science cannot study something so immeasurable and indefinable as intelligence. Cornelia Dean reporting for the New York Times did just this:
[T]here is wide disagreement about what intelligence consists of and how - or even if - it can be measured in the abstract.

Laura Blue in Time Magazine asserted:
... science has no agreed-upon definition of "intelligence" either - let alone an agreed-upon method to test it. All kinds of cultural biases have been identified in IQ tests, for example. If there is something fundamental in our brains that regulates our capacity to learn, we have yet to separate its effects from the effects of everything that we experience after we're born.

Similarly, Steven Rose in the New Statesmen:
... the question of what constitutes 'intelligence' is itself problematic - the word has much broader and diverse meanings than what can be encompassed in IQ tests.

Robert Sternberg in the Chicago Tribune:
Sternberg, a critic of traditional intelligence testing, believes intelligence can mean something different for different cultures. In parts of Africa, a good gauge of intelligence might be how well someone avoids infection with malaria -- a test of cleverness that most Americans likely would flunk.

In the same way, for many Africans who take Western IQ tests, "our problems aren't relevant to them," Sternberg said."

First of all, an intelligence test cannot and is not designed to tell you the reasons people score differently. So the fact that the test by itself has nothing to say about genetics is not a failure of the test. Second, the assertion of widespread chaos within science over intelligence is false. The statement that there are a number of theoretical differences about the concept of intelligence is only trivially true. In the practical context of research, provisional understanding, and 'normal science' this is rhetorically equivalent to underlining evolution as "only a theory" in media reports. Intelligence as a working scientific research concept and tool is both widespread (as a search for terms such as 'IQ', 'Intelligence' or 'cognitive ability' on PubMed, Google Scholar, or similar publication databases will show), and broadly consistent in approaches and shared theory, methods, premises, and data. The American Psychological Association's 11 member 'taskforce', assembled for a consensus statement on intelligence research, reported:
... [M]uch of our discussion is devoted to the dominant psychometric approach, which has not only inspired the most research and attracted the most attention (up to this time) but is by far the most widely used in practical settings.

Third, "All kinds of cultural biases" certainly have not been reported in IQ tests. The tests are not "biased" in the sense that psychometricians use this term. Again the APA taskforce showed consensus on this issue:
... the relevant question is whether the tests have a "predictive bias" against Blacks, Such a bias would exist if African-American performance on the criterion variables (school achievement, college GPA, etc.) were systematically higher than the same subjects' test scores would predict. This is not the case. The actual regression lines (which show the mean criterion performance for individuals who got various scores on the predictor) for Blacks do not lie above those for Whites; there is even a slight tendency in the other direction (Jensen, 1980; Reynolds &:Brown, 1984). Considered as predictors of future performance, the tests do not seem to be biased against African Americans.

Similarly Robert Sternberg argues that the tests are biased because they allegedly don't measure the sorts of abilities that are necessary for Africans to succeed in their unique environmental niche. This statement is not only a patronizing and idyllic caricature of African needs, but is also empirically false. This idea was addressed by psychologist Earl Hunt in his peer commentary on Rindermann:
There are two reasons that national-level differences in intelligence have been disregarded. One is that it can be argued that intelligence, as evaluated by these tests, is a Western concept, and that the abilities evaluated by the tests may not be the ones valued by non-western societies. This is a spurious argument for two reasons. First, the economic indicators we are trying to relate to intelligence are also Western concepts. As the commentator Thomas Friedman has said, the world is flat. We are not asking whether or not various national populations have the ability to compete in their own societies, we are asking about their ability to compete in the Western-defined international marketplace. The tests are appropriately designed to address this question. (p 727)

In fact, economists Eric A. Hanushek and Ludger Woessmann report that the association between economic outcomes and measured intelligence appear to be even higher within developing African countries than within Western countries. (pp 13-15) Similarly, at the national level, psychologists Earl Hunt and Werner Wittmann found that the relationship between GDP and national average IQ was stronger for the mostly African developing countries than it was among the developed industrial countries. (0.70 vs 0.58)

In their literature review, Kendall, Verster, and Von Mollendorf found that correlations between employee performance and educational outcomes and cognitive ability did not differ for blacks and whites in Southern Africa. In other words, at school or on the job, an African white with an IQ score of 70 will perform no different than an African black with the same score. Similarly an African black with an IQ of 115 performs the same as an African white with the same score.

So "our problems" certainly are relevant to Africans, and certainly are "their" problems. Unless issues such as child mortality, health, sanitation, rule of law, political stability, material comfort, global influence, and life expectancy are somehow not relevant to Africans.

Appearances to the contrary, the mendacious Robert Sternberg is, in fact, implicitly agreeing with Watson, while nevertheless shouting him down in the media. Sternberg does not deny that psychometric general intelligence is as low as reported in Africa, nor does he deny that this psychometric intelligence has the academic and economic consequences that the "racist... know-nothing" Watson implied it did. In fact, Sternberg himself has conducted intelligence studies in East Africa, and found the same characteristically 70ish IQ scores, as well as correlations between IQ and academic achievement in this region similar to the correlations reported in developed countries. Thus Sternberg's reply to Watson in The New Scientist:
The tests as they stand show some differences between various groups of children. The size of the differences and what groups do best in the tests depend on what is tested. For example, with various collaborators I have found that analytical tests of the kind traditionally used to measure so-called general abilities tend to favour Americans of European and Asian origin, while tests of creative and practical thinking show quite different patterns. On a test of oral storytelling, for example, Native Americans outperform other groups.

Ok, so Sternberg agrees that people of European and Asian descent do better on the analytical and general ability tests that reflect the skills vital for functioning in a first-world globalized economy, and therefore must be claiming that Watson is a racist ignoramus only for privileging these general abstract reasoning abilities with the designation of 'intelligence' over the 'oral storytelling intelligence' of Native-Americans, or the 'mosquito dodging intelligence' of sub-Saharan Africans! But if oral storytelling or mosquito dodging are not useful "intelligences" for lifting an individual or a nation out of 1 dollar a day poverty, then Watson can hardly be faulted for expressing concern about the kinds of intelligence not abundant in Africa.

Sternberg is perhaps the most blameworthy scientist to publicly condemn Watson, because he is familiar enough with the data to know Watson is right. His condescending statement that dodging mosquitoes is what characterizes the extent of African needs, is itself seemingly more "racist" than, if not completely identical in substance to, what Watson said. At least Watson appeared to show some sort of concern for what Africans countries require to industrialize, while Sternberg appears to be relativistically dismissing there are problems at all: "Africans are perfectly intelligent... for living like Africans!"

Actually, I believe Sternberg is taking the stage to condemn the factually correct Watson for his own petty academic reasons: Sternberg believes his own unpopular 'practical intelligence' (PDF) model could become more popular if the dominant psychometric model becomes increasingly professionally and personally dangerous to touch. Like Howard Gardner's empirically unimpressive 'Multiple Intelligences', there is an intellectual market for politically correct ideas like Sternberg's model, and fanning the flames of controversy around psychometrics is one way these ideas can cheat to become more popular.

Media red herrings about the supposed ineffability of intelligence or lies about the scientific worthlessness of intelligence testing are designed to moot honesty and openness on this issue, and simply side step the uncomfortable facts. But avoiding facts does not change reality or help shape it to our liking. Intelligence measures predict the kind of social and personal outcomes that people the world over agree are important and desirable. For this reason we need to start engaging this data instead of shooting the messengers. Especially when the messengers we are so casually discarding are important figures like James Watson.



Population genetics now provides a set of reasonably powerful statistical tools that allow us to determine whether... genes that play a role in the brain evolve much faster in certain human races than in others... The answers to such questions could clearly be awkward, if not incendiary... [O]ne of the most obvious questions about population genetic studies of human beings, especially human races [is s]hould they be performed?... The interesting point - and it's not widely appreciated - is that this question is rapidly becoming moot. Vast quantities of information about the human genome now pour into publicly available databases on a daily basis. These data are collected with the noblest of intentions (often medical) and are also made public for perfectly good reasons: citizens should have ready access to the fruits of publicly funded science. Indeed it's almost impossible to imagine how one could stop the sorts of studies I described above. In previous times, granting agencies, such as the NIH or NSF, could block funding for undesirable experiments or scientific journals could refuse to publish them. But with genomic data, minimal money is required (an Internet connection is enough) and any bright graduate student working in his parents' garage could ask and answer any awkward question he likes. And the Internet thoroughly dashes any chance of preventing the publication of unpleasant results.
H. Allen Orr - 'Talking Genes', The New York Review of Books.

Ubiquitous and prepackaged media tropes about race, perhaps more than intelligence, serve not as rational arguments but as apotropaic charms to ward off inconvenient ideas.

Laura Blue in Time Magazine asserted:
... [T]here is no scientific basis for [Watson's comments] ... For one thing, science has no agreed-upon definition of "race": however you slice up the population, the categories look pretty arbitrary.

Steven Rose in the New Statesman wrote:
Second, the idea that there is a genetically meaningful African 'race' is nonsense. There is wide cultural and genetic diversity amongst African populations from south to north, from Ethiopians to Nigerians. There are, for example probably genetic as well as environmental reasons why Ethiopians make good marathon runners whereas Nigerians on the whole do not.

To group the entire diverse populations of Africa together is a characteristically racist trick.

The Guardian reported:
Other scientists point out that our species is so young - Homo sapiens emerged from its African homeland only 100,000 years ago - that it simply has not had time to evolve any significant differences in intellectual capacity as its various groups of people have spread round the globe and settled in different regions. Only the most superficial differences - notably skin colour - separate the world's different population groupings. Underneath that skin, people are remarkably alike.

The Chicago Tribue reported:
Damaging statements such as Watson's -- and the potential for misuse of research on race -- has led many scientists to avoid the topic altogether. In a 1998 "Statement on 'Race,'" the American Anthropological Association concluded that ordinary notions of race have little value for biological research in part because of the relatively minor genetic differences among racial groups.

Craig Venter offered this rebuttal to Watson:
As Craig Venter, who pioneered much of America's work in decoding the human genome, put it: 'There is no basis in scientific fact or in the human gene code for the notion that skin colour will be predictive of intelligence.'

And our friend Robert Sternberg similarly added:
... [T]here is nothing special about skin colour that serves as a basis for differentiating humans into so-called races... Curiously, we do not apply the concept of "race" to colours of dogs or cats... [These] problems with our understanding of ... race show that the criticism being levelled at Watson is based on science rather than political correctness... race is a socially constructed concept, not a biological one.

Well, it's good to see that Venter and Sternberg are basing their criticisms on SCIENCE instead of political correctness! Of course the purposefully obscurantist conflation between 'skin color' and ancestry is something I've dealt with before.


These individuals would not be classified by geneticists, sociologists, psychologists, physical anthropologists, or any sort of scientist as members of the European race. They would not self-identify as white Americans, nor would they be considered as such. They would be eligible for affirmative action.

Human races, like dog 'breeds', are defined in the biological context by shared ancestry, not by single appearance traits. With ancestry you can predict many genes and many traits, but with single genes or single traits, you can not predict many other genes or traits. Which is why you can still easily identify the ancestry of the depigmented individuals in the above picture. Population ancestry predicts the sum patterns of one's genotype and phenotypical traits (e.g. general racial appearance) while any single variable - in this case, skin color - does not.

Denial of this fact was dubbed Lewontin's Fallacy (PDF) by British geneticist A.W.F. Edwards. 'Skin color' is a false and intentionally misleading straw-definition of race, that dishonorable public scientists such as Sternberg and Venter use to manufacture consent for their ideological viewpoints about human equality.

Steven Rose argues that the racial grouping 'sub-Saharan Africans' racistly lumps "diverse populations", but in the next breath uses such equally problematic and diversity encompassing racial categories as 'Nigerians' and 'Ethiopians'. And that is the problem with 'race' criticism, any population concept is diverse and fuzzy - German, Northwest European, New Yorker, Ashkenazi Jew, Asian - and yet the population concept is an essential cog in evolutionary science. The Neo-Darwinian Synthesis that grounded evolutionary theory in genetics, was the vital fusion of Darwin and population genetics. A population is a race is a population. To deny the population is literally a denial of evolution.

Race critics don't and could never explain satisfactorily why groupings like 'sub-Saharan Africans', 'Mediterranean', or 'Dutch' have no place in science, and more importantly the way scientists do use such groupings in practice belies the alleged uselessness (that is, like intelligence, the population concept clearly allows them to perform 'normal science'). And, yes, Dr. Rose, 'African' is a genetically meaningful entity:
In one of the most extensive of these studies to date, considering 1,056 individuals from 52 human populations, with each individual genotyped for 377 autosomal microsatellite markers, we found that individuals could be partitioned into six main genetic clusters, five of which corresponded to Africa, Europe and the part of Asia south and west of the Himalayas, East Asia, Oceania, and the Americas

You'll note, also, that this coauthor of the extreme anti-hereditarian tract Not In Our Genes also suggests marathon running ability in Ethiopia has a genetic component. This belief has become socially acceptable, but the evidence for genetic differences in population intelligence is hardly less spectacular than the evidence for this difference. I don't recall the large transracial adoption study that tested for marathon running. Each of these inferences can be based on the cross-cultural consistency and physiological correlates (PDF) of performance. It is ideology, not data, which keeps Rose from drawing the same inferences about the intelligence difference. It is also ideology that allows Rose to keep his job for this comment, while Watson lost his job for his substantively identical, yet socially taboo comment.

The claim that there has not been enough time for evolution to act on non-superficial traits is not scientific. First because nonsuperficial traits take no more time to evolve than superficial traits. More importantly, reasonable selection parameters allow for significant differences to arise between populations in 100 years, much less 100,000. Richard Lynn argues that genetics account for 1.3 SD in intelligence between sub-Saharan Africans and Europeans. Genetic anthropologist Henry Harpending illustrates how a 1 SD difference in a hypothetical trait, with a lower additive heritability than intelligence, could evolve in 500 years:
... [A]ssume time preference has an additive heritability of 25%. Assume that everyone with time preference more than 1 sd above the mean of the distribution has double the fitness of everyone else. About 16% of the population then has twice the number of offspring as everyone else on average.

After a generation of reproduction the new mean time preference will be increased by (0.2 * .25) or 5% of a standard deviation. In 20 generations, 500 years, time preference should go up by a full standard deviation.

This is similar to Cochran and Harpending's model (PDF) for the evolution of Ashkenazi intelligence. Also allowing for .5-1 SD higher intelligence in mere centuries.

Biologist Gerhard Meisenberg put it this way (PDF):
... the argument that the 100,000 years or so since the dispersal out of Africa were insufficient for the evolution of genetic differences is invalid. To create an IQ difference of, say, 15 points between two populations in 100,000 years, natural selection would have to drive their IQs apart by only 0.004 points every generation - about 1% of the selective pressure in late 20th-century America

Furthermore, is it true that races only differ in a few appearance related genes? Nope. We already have this data and it's not true by a long shot. Nick Wade reported early last year in the New York Times:
In a study of East Asians, Europeans and Africans, Dr. Pritchard and his colleagues found 700 regions of the genome where genes appear to have been reshaped by natural selection in recent times. In East Asians, the average date of these selection events is 6,600 years ago.

Many of the reshaped genes are involved in taste, smell or digestion, suggesting that East Asians experienced some wrenching change in diet. Since the genetic changes occurred around the time that rice farming took hold, they may mark people's adaptation to a historical event, the beginning of the Neolithic revolution as societies switched from wild to cultivated foods.

Some of the genes are active in the brain and, although their role is not known, may have affected behavior. So perhaps the brain gene changes seen by Dr. Pritchard in East Asians have some connection with the psychological traits described by Dr. Nisbett.

In fact, far from being identical, virtually all genes that are related to individual differences in human health and behavior differ to some degree in their frequency between racial populations. This is something you can and should test for yourself.

Gene Expression blogger p-ter recently wrote a very nice post titled So You Want to be a Population Geneticist. This is a How-2 for several genetic databases that can be used by anyone with an Internet connection to search for allele frequencies or signatures of selection. You can use these to look at the gene frequencies of the four population groups from the International HapMap Project: Utah whites, Nigerian Yoruba, Han Chinese, and Tokyo Japanese.

You'll note then that the International HapMap Project is designed to illuminate the genetic differences between these four "sliced-up", "arbitrary", "diverse", "genetically meaningless" racial populations, that are "defined by skin color". Didn't the HapMap people get the memo from SCIENCE that these categories are a racist biological fiction???

Go into Google News, and look under search terms like 'gene' and 'genes', and pick any random recent news items reporting an association between some gene/s and some sort of individual differences. This would not include studies that e.g. talk about genes that differentiate humans or chimpanzees, or that claim no individual differences.

Take the genes you find in the news and plug them into the HapMap Genome Browser , using p-ter's tips, and look how the frequencies differ. We even have an open thread for you to test your own hypotheses and report your findings from these databases. Unlike Watson's righteous regulators, we don't believe your hypotheses are immoral or "beyond the point of acceptable debate".

Posters on the Half Sigma blog recently used p-ter's post to see how CHRM2, a gene described as the first "yielding consistent evidence of association with IQ across multiple studies conducted by independent research groups", was distributed across the HapMap populations:
T is *way* more present than A in rs324650 among East Asians (91%) relative to Europeans (47%) and blacks (27%). Since T is associated with an increase in 4-5 points of performance IQ (what is that, anyway? Is that different from G?) that is significant.

The poster 'Marc' continued by examining how alleles differed for DTNBP1:
Let's look at rs:760761, rs:2619522 and rs:2619538, all of which are associated with increased or decreased intelligence in DTNBP1.

Regarding rs:760761, 18% of Europeans carry the T allele, which knocks about 8 points off the ol' IQ, compared to around 7% of East Asians and 37% of blacks.

Regarding rs:2619522, the numbers are similar. 18% of whites carry the G allele, which knocks about 7 points off the ol' IQ, versus around 8% of Asians and 35-36% of blacks...

Regarding rs:2619538, 61% of whites carry the T allele, which adds about 6.5 points to one's IQ, versus about 1% of Asians and 67% of blacks...

If 6% more blacks carry the T allele than whites (67% vs. 61%) on rs:2619538, and the T allele codes for 6.5 FSIQ (full scale IQ) points, then this gives blacks an advantage of .4 IQ points over whites from this SNP.

Also, if 60% more whites carry the T allele than Asians, and the T allele codes for 6.5 FSIQ points, than this gives whites an advantage of 3.9 IQ points over Asians from this SNP.

So the cumulative effect thus far would be:
minus 3.6 points for blacks relative to whites;
and minus 0.2 points for East Asians relative to whites.

A difference in one or two "intelligence genes" does not by itself suggest that one population is smarter than another, because evolutionary environments select for phenotypes not genotypes. So when populations have many genetic differences, the genes may interact in different ways, and some of the genes that make individuals more intelligent in one population may not have the same effect in another. (In other words if we'd prefer to not take the above results at face value, we have to accept that races are even more genetically different, not less)

However, several pieces of evidence make it doubtful that most intelligence genes are like this. For one, mixed race people generally have IQ scores about midway between their parent populations. (save one study of Eurasian mixes) So I would say the gradual accumulation of similar results for other "intelligence genes" would certainly serve as evidence for the genetic viewpoint.

These differences do illustrate, in yet another way, the falseness of popular arguments that races are genetically identical, or that genetic differences can somehow only exist for "appearance genes". But virtually any gene showing individual differences that you plug in those databases will also be distributed differently among racial groups and demonstrate the same points.



James Watson implied a belief that the uniquely low intelligence of both continental Africans and African-Americans are probably related to familiar genetic causes. This belief is deemed unacceptable to express in public, even in most academic contexts, or hold in private. This is despite the fact that the research evidence in support of this position is stronger than the research evidence that contradicts it. Thus even top scientists like Watson are punished for holding beliefs that are more scientific and logical, while scientists that hold to less scientific beliefs and illogical arguments are rewarded. This is a rot on the soul of science.

Many statements in the press asserted or implied that various environmental theories account for intelligence differences between ethnic groups. These statements do not, in fact, agree with the evidence.

The Chicago Tribune asserted:
The study of racial differences in IQ is among the most deeply contentious fields in all of science. Most researchers agree that tests have revealed some differences among racial groups -- but even larger differences between people of different income levels.

Steven Rose asserted:
Even where there are such average differences in IQ score, as for instance between Black and White populations in the US, there are no scientifically valid methods to enable one to untangle the many interacting factors of the validity of IQ tests themselves, as measures of anything other than school performance, educational and social deprivation, the history of slave-owners versus slaves and continuing racism, which may account for them.

The Associated Press reported:
Jan Schnupp, a lecturer in neurophysiology at Oxford University, said Watson's remarks "make it very clear that he is an expert on genetics, not on intelligence."

Schnupp said undernourished and undereducated people often perform worse on intelligence tests than the well off.

"Race has nothing to do with it, and there is no fundamental obstacle to black people becoming exceptionally bright," Schnupp said."

Contrary to the above claims, differences in intelligence between income groups are not larger than intelligence differences between racial groups in the US, nor do differences in income or wealth account for the racial differences. Whites from households in the lowest income bracket have higher IQ scores than blacks from households in the highest income bracket:
One of the most disturbing, I think perhaps the most disturbing fact in our whole book is that black students coming from families earning over 70,000 are doing worse on their SATS, on average--it's always on average--than white students from families in the lowest income group. You want to cry hearing that figure. I mean, it's so terrible.

One of the largest modern sociology studies of American students found that ethnicity was the single most important predictor of academic achievement:
Chin quotes with approval a book, "Beyond the Classroom," by Laurence Steinberg, B. Bradford Brown and Sanford M. Dornbusch, which says "of all the demographic factors we studied in relation to school performance, ethnicity was the most important. . . . In terms of school achievement, it is more advantageous to be Asian than to be wealthy, to have non-divorced parents, or to have a mother who is able to stay at home full time."

Contra Rose, a number of experiments are able to test all of these environmental theories. For one transracial adoption experiments control for all the shared aspects of the environment that differ between whites and blacks (parenting, income, nutrition, neighborhood), while structural equation models test for possible uncommon factors between whites and blacks that could be acting on IQ (which would include things like racism). These experiments do not lend support to any existing or plausible environmental theories for the remaining lower intelligence scores of people of African descent in Western societies. The Minnesota Transracial Adoption Study found that, by adulthood, the difference in IQ scores between adopted black and adopted white children raised side by side in the same high income households in mostly homogeneous Northern US upper class neighborhoods was 18 IQ points (p 185):

The Minnesota Transracial Adoption Study

IQ at Age 7        IQ at Age 17

W-W 111.5        W-W 101.5
W-B 105.4        W-B 93.2
B-B 91.4        B-B 83.7

W-W = Adopted children with two white biological parents.
W-B = Adopted children with one black and one white biological parent.
B-B = Adopted children with two black biological parents.

The W-W/W-B difference is 8.3 IQ points. The B-W/B-B difference is 9.5 IQ points. And the W-W/B-B difference is 17.8 IQ points.

The difference in IQ scores between 2 black biological parent adoptees and 1 black biological parent adoptees is nearly 10 IQ points despite the fact that both share the exact same social identity.

Similarly a dozen mixed race children that were raised under some mistaken information that they had two black biological parents nevertheless developed IQ scores like the other mixed race children.

There are no simple or plausible environmental theories to explain these kinds of findings.

An additional popular argument is that the Flynn Effect, the observed rise in IQ scores over time, is evidence that African-Americans or African countries will eventually reach parity with white norms. This typically includes the premise that white intelligence in the recent past was even lower than modern black intelligence. A typical example:
US Blacks, with an average IQ today of 85, have the same IQ as US Whites with an IQ of 100 in 1957. If 1957 US Whites were not stupid, then neither are US Blacks today. It's time to shut up about the "low Black IQ", since by any reasonable standard, it is not really low at all.

These arguments are wrong for the simple fact that the Flynn Effect is not a gain in real g factor intelligence, while the differences between nations and ethnic groups are differences in g factor intelligence. These findings led a 2004 team to state:
It appears therefore that the nature of the Flynn effect is qualitatively different from the nature of B-W [Black-White] differences in the United States... [so] implications of the Flynn effect for B-W differences appear small...

James Flynn, namesake of the secular increase, reiterates (DOC) these points:
Factor analysis is a way of measuring this tendency of some people to do better or worse than average across the board; and it yields something called g (a sort of super-correlation coefficient), which psychologists call the general intelligence factor...

When you analyze IQ gains over time, you often find that they do not constitute enhancement of these latent traits -- they do not seem to be general intelligence gains, or quantitative factor gains, or verbal factor gains (Wicherts et al, in press). In the language of factor analysis, this means that IQ gains over time tend to display 'measurement artifacts or cultural bias'. For a second time, we are driven to the conclusion that massive IQ gains are not intelligence gains or, indeed, any kind of significant cognitive gains. (pp 27-28)

Flynn believes the secular increase represents important changes in specific narrow aspects of developed cognitive style, but not a rise in g intelligence.

It is therefore incorrect that 1945 US whites were less intelligent than 2007 US blacks. The Flynn Effect has little apparent bearing on racial intelligence gaps.

This also applies to developing countries. The Flynn Effect reveals that IQ scores in the developed world were some 1.5-2 standard deviations lower in the beginning of the 20th century. (See this GNXP post for the data) These scores are similar to ones in modern African. Some studies also reveal even faster Flynn gains in developing countries than what we observe in developed countries, and it is argued these countries are simply experiencing, in slight delay, what happened in developed countries during the 20th century. But this interpretation is not tenable if there were no actual rises in g factor intelligence in developed countries. It is incorrect that developed countries had lower g intelligence in the first half of the 20th century corresponding to IQs of 70. Meanwhile, as the Rindermann paper reveals, the scores across modern nations do correspond to real intelligence differences. Likewise, extremely low IQ scores in modern Africa, unlike scores in developed countries prior to the mid-20th century, correspond to genuine deficits in g intelligence.

With improvements in nutrition it is likely that scores in Africa will rise over time. But these increases will probably be genuine and of a different nature than what we observed in developed countries. It is unlikely that scores in Africa will meet or rise above those of African-Americans in the next century.

All of this underlines the fact that IQ can't always be taken at face value. Gains or differences in IQ exceeding 1 SD can sometimes be 'hollow', or unreflective of real general intelligence, being manifested only at the lower order strata of intelligence. (See this paper examining how these false gains can arise through practice effects) Fortunately we have good methods for evaluating the construct validity of the tests and the integrity of the IQ scores.



Many intellectuals refuse to interpret psychometric claims or ideas about human diversity rationally. Despite 100 years of data showing that ethnic groups differ in their general intelligence, these claims are still rejected on moral grounds. Many of those who deny these claims either implicitly believe that 'intelligence' is a reflection of human worth, or believe any claim of such a difference must be a cryptic assertion of racial worth. Either way it prevents the claims from being interpreted fairly, in the factual, rather than normative, manner intended by the people who attempt to discuss this science in an open forum.

Watson's original statements about the lower general intelligence of Africans were interpreted as statements about the lower human worth of Africans. When Watson then publicly apologized that his words were being misinterpreted in this way and clarified that claims about racial intelligence differences are not claims about human worth, the confused media reported that Watson had recanted his claims about intelligence differences!!

The science journal Nature ran an editorial claiming:
Watson has apologized and retracted the outburst... He acknowledged that there is no evidence for what he claimed about racial differences in intelligence.

Time magazine also suggested he retracted his intelligence claims:
Watson said in a statement he issued at the Royal Society Thursday. "That is not what I meant. More importantly from my point of view, there is no scientific basis for such a belief."

And on that much at least, he's right. For one thing, science has no agreed-upon definition of "race": however you slice up the population, the categories look pretty arbitrary. For another, science has no agreed-upon definition of "intelligence" either

And Cornelia Dean at the New York Times asserted, not once, but in two separate reports that Watson retracted his intelligence claims. Even doctoring Watson's apology by cut-and-pasting together two entirely separate Watson quotes:
In an interview published Sunday in The Times of London, Dr. Watson is quoted as saying that while "there are many people of color who are very talented," he is "inherently gloomy about the prospect of Africa."

"All our social policies are based on the fact that their intelligence is the same as ours - whereas all the testing says not really," the newspaper quoted him as saying.

"I cannot understand how I could have said what I am quoted as having said," Dr. Watson said in a statement given to The Associated Press. "There is no scientific basis for such a belief."

And again in another article:
Dr. Watson... was quoted in The Times of London last week as suggesting that, overall, people of African descent are not as intelligent as people of European descent. In the ensuing uproar, he issued a statement apologizing "unreservedly" for the comments, adding "there is no scientific basis for such a belief".

False. False. False.

Dear media,

Please read the actual text of James Watson's apology printed in the Independent, instead of mangling it and interpolating it with your own claims:
To those who have drawn the inference from my words that Africa, as a continent, is somehow genetically inferior, I can only apologise unreservedly. That is not what I meant. More importantly from my point of view, there is no scientific basis for such a belief...

The overwhelming desire of society today is to assume that equal powers of reason are a universal heritage of humanity....

To question this is not to give in to racism. This is not a discussion about superiority or inferiority, it is about seeking to understand differences, about why some of us are great musicians and others great engineers.

Watson would only be retracting his intelligence claims if he considered those claims tantamount to claims of 'superiority' or 'inferiority', which he clearly emphasizes he doesn't. Watson is saying that questioning that all races are equal in intelligence is not racism, it is trying to figure out why the world looks the way it does, with the greatest engineers and the greatest musicians disproportionately coming, in a systematic way, from different racial backgrounds. In other words culturally separated people of African descent have been musical innovators across a diverse range of cultures (in the Middle East, Africa, Europe, North and South America, and the Caribbean), while culturally separated people of East Asian descent have excelled at math and science across a diverse range of cultures (in Asia, Europe, North and South America, and the Caribbean).

This is not a claim of racial 'superiority' or 'inferiority', either in terms of legal worth or even in terms of overall talent - since groups all have different strengths and weaknesses. It is simply the recognition that people of different genetic heritage, on average, reveal different talents wherever they are found in the world, and there is one explanation that best accounts for these observations: evolution.

In other words, Watson was thinking like a scientist. Which is exactly why he was punished.

The moral laws of our society dictate that we are not allowed to think scientifically about some issues. Especially not in public.



According to the media and members of the scientific community, James Watson hurt science itself.

An editorial in the top science journal Nature asserted:
Crass comments by Nobel laureates undermine our very ability to debate such issues, and thus damage science itself.

Similarly the Chicago Tribune featured this:
"The damage to Watson's legacy from his statements may be difficult to mend," said Jerry Coyne, a professor of evolutionary genetics at the University of Chicago.

"He's done tremendous damage to science, to himself and to social equality," Coyne said. "It makes us all look bad."

Along with E.O. Wilson, James Watson is perhaps the most distinguished living figure in American biology, and yet even he was not immune to immediate expulsion from the very lab he created and built up over 40 years of his life, and excommunication from the scientific establishment that celebrated him. All this for one crime: voicing scientific facts and hypotheses that made this community uncomfortable. The same personal and professional fate befell former Harvard president Larry Summers in 2005 for a purely academic discussion of females in science during an economics conference intended for discussing this very subject!

What effect will this continuing intellectual mob violence have on future and current scientists and researchers who want to freely study human genetics, cross-cultural psychology, sociology, or any discipline that may reveal similar facts that have the potential to cause their professional or personal destruction by an intellectual community that resembles the medieval church?

Those who punish, those who lie, those who silence, those who condemn, those who intimidate... they have corrupted science.

They have injured the intellectual openness, freedom, and fairness of our society and our institutions, with untold costs to our collective human well-being.

Not James D. Watson.




IQ: 64
Age: Adults
N: 80
Test: CPM
Ref: Berlioz, L. (1955). Etude des progressive matrices faite sur les Africains de Douala. Bulletin du Centre Etude Recherce Psychotechnique, 4, 33-44.

Equatorial Guinea
IQ: 59
Age: 10-14
N: 48
Test: WISC-R
Ref: Fernandez-Bellesteros, R., Juan-Espinoza, M., Colom, R., and Calero, M. D. (1997). Contextual and personal sources of individual differences in intelligence. In J. S. Carlson (Ed.), Advances in Cognition and Educational Practice. Greenwich, Cnn.: JAI Press.

IQ: 67
Studies: 4

IQ: 80
Age: Adults
N: 225
Test: CF
Ref: Buj, V. (1981). Average IQ values in various European countries. Personality and Individual Differences, 2, 168-169.

IQ: 62
Age: 15
N: 1,693
Test: CPM
Ref: Glewwe, P. and Jaccoby, H. (1992). Estimating the determinants of Cognitive Achievement in Low Income Countries. Washington, D.C.: World Bank.

IQ: 65 (266)
Age: 16
N: 5,100
Test: TIMSS 2003
Ref: Martin, M.O., Mullis, I.V.S., & Chrostowski, S.J. (Eds.) (2004). TIMSS 2003 Technical Report. Chestnut Hill, MA: TIMSS & PIRLS International Study Center, Boston College.

IQ: 67
TIMSS 2003: 266 (65)
TIMSS sum: 301
TIMSS+PIRLS sum: 304
Sum: 300

IQ: 67
Studies: 2

IQ: 63
Age: 5-14
N: 50
Test: AAB
Ref: Nissen, H. W., Machover, S. and Kinder, E. F. (1935). A study of performance tests given to a group of native African Negro children. British Journal of Psychology, 25, 308-355.

IQ: 70
Age: Adults
N: 1,144
Test: SPM
Ref: Faverge, J. M. and Falmagne, J. C. (1962). On the interpretation of data in intercultural psychology. Psychologia Africana, 9, 22-96.

IQ: 69
Studies: 5

IQ: 70
Age: Children
N: 480
Test: Leone
Ref: Farron, O. (1966). The test performance of coloured children. Educational Research, 8, 42-57.

IQ: 64
Age: Adults
N: 86
Test: SPM
Ref: Wober, M. (1969). The meaning and stability of Raven's matrices test among Africans. International Journal of Psychology, 4, 220-235.

IQ: 69
Age: 6-13
N: 375
Test: CPM
Ref: Fahrmeier, E. D. (1975). The effect of school attendance on intellectual development in Northern Nigeria. Child Development, 46, 281-285.

IQ: 79 (401)
Age: 15
N: 2,368
Test: IEA-R 1991
Ref: Elley, W. B. (1992). How in the world do students read? The Hague: IEA.

IQ: 69
ISARS: 34 (69)

Sierra Leone
IQ: 64
Studies: 2

IQ: 64
Age: Adults
N: 122
Test: CPM
Ref: Berry, J. W. (1966). Temne and Eskimo perceptual skills. International Journal of Psychology, 1, 207-229.

IQ: 64
Age: Adults
N: 33
Test: CPM
Ref: Binnie-Dawson, J. L. (1984). Biosocial and endocrine bases of spatial ability. Psychologia, 27, 129-151.

Burkina Faso
Cote d'Ivoire
The Gambia
Sao Tome and Principe


Democratic Republic of Congo
IQ: 65
Studies: 5

IQ: 64
Age: Adults
N: 67
Test: SPM
Ref: Verhagen, P. (1956). Utilite actuelle des tests pour l'etude psychologique des autochones Congolese. Revue de Psychologie Appliquee, 6, 139-151.

IQ: 68
Age: 10-15
N: 222
Test: SPM
Ref: Laroche, J. L. (1959). Effets de repetition du Matrix 38 sur les resultats d'enfants Katangais. Bulletin du Centre d’etudes et Reserches Psychotechniques, 1, 85-99.

IQ: 62
Age: 8
N: 47
Test: KABC
Ref: Boivin, M. J. and Giordani, B. (1993). Improvements in cognitive performance for schoolchildren in Zaire following an iron supplement and treatment for intestinal parasites. Journal of Pediatric Psychology, 18, 249-264.

IQ: 68
Age: 7-12
N: 95
Test: LABC
Ref: Boivin, M. J., Giordani, B., and Bornfeld, B. (1995). Use of the tactual performance test for cognitive ability testing with African children. Neuropsychology, 9, 409-417.

IQ: 65
Age: 7-9
N: 130
Test: KABC
Ref: Giordani, B., Boivin, M. J., Opel, B., Nseyila, D. N., and Lauer, R. E. (1996). Use of the K-ABC with children in Zaire. International Journal of Disability, Development, and Education, 43, 5-24.

Republic of Congo
IQ: 64
Studies: 3

IQ: 64
Age: Adults
N: 1,596
Test: SPM
Ref: Latouche, G. L. and Dormeau, G. (1956). La foration professionelle rapide en Afrique Equatoriale Francaise. Brazzaville: Centre d'Etude des Problems du Travail.

IQ: 64
Age: 17-29
N: 320
Test: SPM
Ref: Ombredane, A., Robaye, F., and Robaye, E. (1952). Analyse des resultats d'une application experimentale du matrix 38 a 485 noirs Baluba. Bulletin Centre d'etudes et Reserches Psychotechniques, 7, 235-255.

IQ: 73
Age: 8
N: 73
Test: SPM
Ref: Nkaye, H. N., Huteau, M., and Bonnet, J. P. (1994). Retest effect on cognitive performance on the Raven Matrices in France and in the Congo. Perceptual and Motor Skills, 78, 503-510.

Central African Republic
IQ: 64
Age: Adults
N: 1,149
Test: SPM
Ref: Latouche, G. L. and Dormeau, G. (1956). La foration professionelle rapide en Afrique Equatoriale Francaise. Brazzaville: Centre d'Etude des Problems du Travail.



IQ: 71
Studies: 4

IQ: 69
Age: 7-16
N: 291
Test: Various
Ref: Fahmy, M. (1964). Initial exploring of the intelligence of Shilluk children. Vita Humana, 7, 164-177.

IQ: 64
Age: 6
N: 80
Test: DAM
Ref: Badri, M. B. (1965a). The use of finger drawing in measuring the Goodenough quotient of culturally deprived Sudanese children. Journal of Psychology, 59, 333-334.

IQ: 74
Age: 9
N: 292
Test: DAM
Ref: Badri, M. B. (1965b). Influence of modernization on Goodenough quotients of Sudanese children. Perceptual and Motor Skills, 20, 931-932.

IQ: 72
Age: 8-12
N: 148
Test: SPM
Ref: Ahmed, R. A. (1989). The development of number, space, quantity, and reasoning concepts in Sudanese schoolchildren. In L. L. Adler (Ed.), Cross Cultural Research in Human Development. Westport, Conn.: Praeger.

IQ: 72
Studies: 6

IQ: 69
Age: Adults
N: 205
Test: CPM
Ref: Boissiere, M., Knight, J. B., and Sabot, R. H. (1985). Earnings, schooling, ability, and cognitive skills. American Economic Review, 75,1016-1030.

IQ: 75
Age: 6-10
N: 1,222
Test: CPM
Ref: Costenbader, V. and Ngari, S. M. (2000). A Kenya standardisation of the Coloured Progressive Matrices. School Psychology International, 22, 258-268.

IQ: 69
Age: 12-15
N: 85
Test: CPM-MH
Ref: Sternberg, R. J., Nokes, C., Geissler, P. W., Prince, R., Okatcha, F., Bundy, D. A., and Grigorenko, E. L. (2002). The relationship between academic and practical intelligence: A case study in Kenya. Intelligence, 29, 401-418.

IQ: 76
Age: 7
N: 118
Test: CPM
Ref: Daley, Y. C., Whaley, S. E., Sigman, M. D., Espinosa, M. P., and Neuman, C. (2003). IQ on the rise: the Flynn effect in rural Kenyan children. Psychological Science, 14, 215-219.

IQ: 89
Age: 7
N: 537
Test: CPM
Ref: Daley, Y. C., Whaley, S. E., Sigman, M. D., Espinosa, M. P., and Neuman, C. (2003). IQ on the rise: the Flynn effect in rural Kenyan children. Psychological Science, 14, 215-219.

IQ: 63
Age: 6
N: 184
Test: KABC
Ref: Holding, P. A., Taylor, H. G., Kazungu, S. D., and Mkala, T. (2004). Assessing cognitive outcomes in a rural African population: development of a neuropsychological battery in Kilifi district. Journal of the International Neuropsychological Society, 10, 246-260.

IQ: 72
Studies: 3

IQ: 78
Age: 13-17
N: 2,959
Test: SPM
Ref: Klingelhofer, E. L. (1967). Performance of Tanzanian secondary school pupils on the Raven Standard Progressive Matrices test. Journal of Social Psychology, 72, 205-215.

IQ: 65
Age: Adults
N: 179
Test: CPM
Ref: Boissiere, M., Knight, J. B., and Sabot, R. H. (1985). Earnings, schooling, ability,and cognitive skills. American Economic Review, 75,1016-1030.

IQ: 72
Age: 11-13
N: 458
Test: WCST
Ref: Sternberg, R. J., Grigorenko, E. L., Ngorosho, D., Tantufuye, E., Mbise, A., Nokes, C., Jukes, M., and Bundy, D. A. (2002). Assessing intellectual potential in rural Tanzanian school children. Intelligence, 30, 141-162.

IQ: 73
Age: 11
N: 2,019
Test: RPM
Ref: Heyneman, S. P. and Jamison, D. T. (1980). Student learning in Uganda. Comparative Education Review, 24, 207-220.

IQ: 64
Studies: 2

IQ: 65
Age: 15
N: 250
Test: SPM
Ref: Lynn, R. (1994). The intelligence of Ethiopian immigrant and Israeli adolescents. International Journal of Psychology, 29, 55-56.

IQ: 63
Age: 14-16
N: -
Test: SPM
Ref: Kazulin, A. (1998). Profiles of immigrant students' cognitive performance on Raven's Progressive Matrices. Perceptual and Motor Skills, 87, 1311-1314.



IQ: 76
Studies: 2

IQ: 77 (366)
Age: 15
N: 5,150
Test: TIMSS 2003
Ref: Martin, M.O., Mullis, I.V.S., & Chrostowski, S.J. (Eds.) (2004). TIMSS 2003 Technical Report. Chestnut Hill, MA: TIMSS & PIRLS International Study Center, Boston College.

IQ: 75 (330)
Age: 15
N: 4,768
Test: IEA-R 1991
Ref: Elley, W. B. (1992). How in the world do students read? The Hague: IEA.

TIMSS sum: 396
TIMSS+PIRLS sum: 398
Sum: 391

IQ: 62
Studies: 2

IQ: 64
Age: 20
N: 149
Test: CPM
Ref: Kendall, I. M. (1976). The predictive validity of a possible alternative to the Classification Test Battery. Psychologia Africana, 16, 131-146.

IQ: 60
ISAMS: 24 (60)

South Africa (blacks)
IQ: 67
Studies: 13

IQ: 63
Age: 9
N: 350
Test: SPM
Ref: Lynn, R. and Holmshaw, M. (1990). Black-white differences in reaction times and intelligence. Social Behavior and Personality, 18, 299-308.

IQ: 67
Age: 8-10
N: 806
Test: CPM
Ref: Jinabhai, C. C., Taylor, M., Rangongo, N. J., Mkhize, S., Anderson, S., Pillay, B. J., and Sullivan, K. R. (2004). Investigating the mental abilities of rural primary school children in South Africa. Ethnicity and Health, 9, 17-36.

IQ: 67
Age: 14-17
N: 152
Test: WISC-R
Ref: Skuy, M., Schutte, E., Fridjhon, P., and O'Carroll, S. (2001). Suitability of published neuropsychological test norms for urban African secondary school students in South Africa. Personality and Individual Differences, 30, 1413-1425.

IQ: 65
Age: 10-12
N: 293
Test: AAB
Ref: Fick, M. L. (1929). Intelligence test results of poor white, native (Zulu), colored, and Indian school children and the social and educational implications. South Africa Journal of Science, 26, 904-920.

IQ: 75
Age: 8-16
N: 1,008
Test: SPM
Ref: Notcutt, B. (1950). The measurement of Zulu intelligence. Journal of Social Research, 1, 195-206.

IQ: 69
Age: Adults
N: 153
Test: WAIS-R
Ref: Nell, V. (2000). Cross-Cultural Neuropsychological Assessment. Mahwah, NJ: Lawrence Erlbaum.

IQ: 64
Age: Adults
N: 703
Test: SPM
Ref: Notcutt, B. (1950). The measurement of Zulu intelligence. Journal of Social Research, 1, 195-206.

IQ: 71
Age: Adults
N: 140
Test: WISC-R
Ref: Avenant, T. J. (1988). The Establishment of an Individual Intelligence Scale for Adult South Africans. Report No. P-91. Pretoria: Human Sciences Research Council.

IQ: 68
Age: 15-16
N: 1,093
Test: JAT
Ref: Lynn, R., and Owen, K. (1994). Spearman's hypothesis and test score differences between whites, Indians and blacks in South Africa. Journal of General Psychology, 121, 27-36.

IQ: 63
Age: 16
N: 1,096
Test: SPM
Ref: Owen, K. (1992). The suitability of Raven's Progressive Matrices for various groups in South Africa. Personality and Individual Differences, 13, 149-159.

IQ: 64 (259)
Age: 16
N: 8,146
Test: TIMSS 1999
Ref: Martin, M. O., Gregory, K. D., & Stemler, S. E. (Eds.) (2000). TIMSS Technical Report: IEA's Third International Mathematics and Science Study at the Eighth Grade (Boston, Intrenational study Center, Boston College).

IQ: 63 (254)
Age: 15
N: 8,952
Test: TIMSS 2003
Ref: Martin, M.O., Mullis, I.V.S., & Chrostowski, S.J. (Eds.) (2004). TIMSS 2003 Technical Report. Chestnut Hill, MA: TIMSS & PIRLS International Study Center, Boston College.

IQ: 69
TIMSS 1995: 270
TIMSS 1999: 259 (64)
TIMSS 2003: 254 (63)
TIMSS sum: 304
TIMSS+PIRLS sum: 328
Sum: 324

IQ: 64
ISAMS: 32 (64)

IQ: 71
Studies: 2

IQ: 77
Age: 13
N: 759
Test: SPM
Ref: MacArthur, R. S., Irvine, S. H., and Brimble, A. R. (1964). The Northern Rhodesia Mental Ability Survey. Lusaka: Rhodes Livingstone Institute.

IQ: 64
Age: Adults
N: 152
Test: SPM
Ref: Pons, A. L. (1974). Administration of tests outside the cultures of their origin. 26th Congress of the South African Psychological Association.

IQ: 70
Studies: 3

IQ: 61
Age: 12-14
N: 204
Test: WISC-R
Ref: Zindi, F. (1994). Differences in psychometric performance. The Psychologist, 7, 549-552.

IQ: 70
Age: 12-14
N: 204
Test: SPM
Ref: Zindi, F. (1994). Differences in psychometric performance. The Psychologist, 7, 549-552.

IQ: 76 (372)
Age: 16
N: 2,749
Test: IEA-R 1991
Ref: Elley, W. B. (1992). How in the world do students read? The Hague: IEA.


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Tuesday, September 25, 2007

Race and medicine   posted by p-ter @ 9/25/2007 09:22:00 PM

Apropos of a previous post on race, PLoS Medicine has just published two (opinion) articles on the use of racial categories in medicine. There's only a cursory treatment of genetics (and the treatment that's there is pretty bad), but it's sometimes useful to see another take on the issue. The message I get is that, well, doctors aren't trained in genetics, so any "race-based" medicine (which is necessarily based on probabilites) is likely to become a sort of "black = medicine X, white = medicine Y" dogma.

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Monday, June 18, 2007

The genetics of racial differences in hypertension susceptibility   posted by p-ter @ 6/18/2007 04:47:00 PM

Part three of the "genetics and race" debate in the pages of The New Republic is up. One point the debaters seem to have oddly fixated on is the racial disparity in the prevalence of hypertension-- for those of you unaware, African-Americans have higher rates and more extreme forms of the disease.

The debaters at TNR seem to be aware of two hypotheses for why this disparity could exist: first, the "slavery hypothesis", according to which the slaves that survived the long trip from West Africa in sub-human conditions were those that were able to retain sodium and resist dehydration (sweating causes the loss of salt, which must then be replaced), leading to a massive selective event for improved salt retention that today manifests itself as hypertension. The alternative, they seem to think, is that discrimination and an abundance of unhealthy fast food restaurants in African-American neighborhoods in conjunction lead to the differential susceptibility.

There's no doubt that environmental factors play a role in hypertension, and it's likely that differential exposures to those factors play a role in this phenomenon. But in terms of genetics, it's certainly not the slavery hypothesis or nothing. I actually see no reason to invoke it-- the key observation (perhaps not a groundbreaking one) is that African slaves came from Africa, which is quite different from North America. One obvious difference between the two continents is climate. Is it possible that West African populations were adapted to an West African climate; perhaps in such a way that increases hypertension susceptibility in the US today? Absolutely.

I present as evidence this (open access) paper, which states (in the title) that "Differential Susceptibility to Hypertension is Due to Selection during the Out-of-Africa Expansion". I strongly recommend at least the introduction for anyone interested in this topic.

The authors look at a number of alleles involved in salt retention and blood pressure, and perform analyses simlar to those done in the paper on tonal languages and two brain-expressed genes-- they examine the correlations of the allele frequencies with distance from the equator. When they compare these correlations with those from randomly chosen loci, they find the salt-retention alleles are outliers, suggesting they've undergone selection in reponse to latitude (which they interpret as a proxy for climate). While in the tonal languages case I urged skepticism about causation, these alleles are already known to be involved in hypertension. This just presents evidence that the differences in allele frequencies between populations is due to natural selection, as opposed to some neutral process.

So African populations (and thus, African-American populations as well) have different allele frequencies of at genes known to be involved in hypertension. There is no doubt that this divergence plays a role in the different susceptibilities of African-American and European-American populations to this disease.

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Saturday, June 16, 2007

Diversity & trust   posted by Razib @ 6/16/2007 08:47:00 PM

The New York Times Magazine has a piece up about Robert Putnam's work which shows that ethnic & racial diversity decreases trust, not just between groups but between and individual and society as a whole.


Fear of a genetic planet   posted by Razib @ 6/16/2007 07:45:00 PM

Gene bashing - dilemma of black geneticists working on the National Institute of Health's Human Genome Project:
"I don't fear science. The [development of the] wheel, fire and aircraft have done a considerable amount of harm...far more than genetic research is likely to do," Bowman says.

Anyway, he adds, "we are already in a eugenic society. "We can collect an ovum from a prospective mother and sperm from a prospective father, allow them to develop to the eight-cell stage, test one cell...and make a diagnosis for pre-symptom colon cancer or breast cancer," says Bowman.

Still, he says, "I'm willing to take my chances with the bad parts. The fears are misplaced."

Life comes at you fast. I don't deny that it is important to reflect upon the implications of science, but substance free hand wringing is time wasted on the tracks as the train is speeding in your direction.


Friday, June 15, 2007

Race, TNR debate   posted by Razib @ 6/15/2007 01:12:00 PM

TNR is continuing the debate on race. Not much to read really, but this caught my attention:
I found your characterization of race as a "cluster concept" provocative and intellectually honest, since you admit its imprecision....

Imprecision? Really? Well:
Of 3,636 subjects of varying race/ethnicity, only 5 (0.14%) showed genetic cluster membership different from their self-identified race/ethnicity.

So let's be precise about the term "imprecision." No doubt Plato would sniff at mistyping rate of 0.14%. Also, since we're talking science here one should be familiar with the distinction between accuracy and precision. I think in fact that as the number of informative loci increase an inference of ancestry is rather precise (reproducible). But perhaps the author of the above piece finds the precision of genetic science wanting? That being said, I am a bit confused as to why then his academic interests lay in history, an even more imprecise field, than in physics or mathematics where his passion for precision might be suitably sated.

Race is a social construction. But it is not one constructed purely from human ideology. That many perceive Greeks as white and Turks as non-white is a reflection of social axioms (Christians are white, Muslims are brown). That may perceive Greeks as white and Thai as non-white is not a reflection of social axioms (Greeks exhibit physical characteristics of the white race, Thais do not). Humanists are well schooled in the interplay between ideology and facts in generating a narrative of the world. To pretend as if there is no factual basis in the outlines of an ideology is a denial of reality, which would less concerning if not for the fact that most Americans parrot this very line about race as if it was universally accepted.


Thursday, April 26, 2007

Earwax and breast milk   posted by the @ 4/26/2007 12:57:00 AM

Miura, Yoshiura, Miura, Shimada, Yamasaki, Yoshida, et al. A strong association between human earwax-type and apocrine colostrum secretion from the mammary gland. Human Genetics.

Here we provided the first genetic evidence for an association between the degree of apocrine colostrum secretion and human earwax type. Genotyping at the earwax-type locus, rs17822931 within the ABCC11 gene, revealed that 155 of 225 Japanese women were dry-type and 70 wet-type. Frequency of women without colostrum among dry-type women was significantly higher than that among wet-type women (P < 0.0002), and the measurable colostrum volume in dry-type women was significantly smaller than in wet-type women (P = 0.0341).

Related from Razib: Here are two posts from me on earwax distributions worldwide.

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Saturday, April 07, 2007

Just don't use the word 'race'   posted by the @ 4/07/2007 03:35:00 PM

That seems to be the conclusion of a recent review of Nick Wade's Before the Dawn published in Nature Genetics:
My reluctance to recommend the book stems also from Wade's discussions of 'race' and biology. I agree with Wade that there is something biological about racial categories. In my opinion, although racial identity is socially negotiated, people use physical traits as cues when 'assigning' a racial identity to themselves or another individual. Racial categorization isn't blind to biology. ... Although one might detect biological differences between races, any highlighting of the racial categories (just a subset of groups with biological correlates) has social costs, according to recent social science research. On the other hand, Neil Risch, cited often in the book, has argued that there are significant (medical) costs of ignoring the relationship between racial categories and biology. I suggest that these different costs be weighed in each circumstance where one might link 'race' and genetics. Wade's broad description of races as clearly delineated biological entities is unjustified in the context of a book about human history intended for a general audience. Why use the term 'race', when 'geographic ancestry' or 'continental origin' are more accurate and less costly in social terms, especially since Wade's definition of 'race' is "continent of origin"? I suggest acknowledging the correlation between racial labels and continents of origin, and saving the term 'race' for contexts in which social costs are outweighed by other costs.

This is not the argument I expected to follow the sentence "My reluctance to recommend the book stems also from Wade's discussions of 'race' and biology." In this case, the author isn't being snide by putting race in quotes, as she really means the word race rather than its referent. How often do scholars write that consternation over race is largely related to extra-scientific concerns?

However, I have to criticize this argument, at least to the extent that I'm able to examine the evidence presented. A footnote to the "recent social science research" showing that using the word 'race' is harmful (but that cryptic synonyms are OK) would be appreciated, as this forms the basis of the argument against discussing 'race'. Is it only harmful to discuss 'race' and 'genetics' or 'biology'? Is the attribution of racial differences to environmental/cultural causes not similarly harmful? Is it really true, as is implied, that Wade is morally obliged to substitute most instances of "race" in his text with "continent of origin"?

There's a lot to commend in this review, largely stemming from the reviewers' honesty and directness, and especially in contrast with this hatchet job published in the sister journal Nature.

Update - full text:
Given the rich content of Nicholas Wade's latest book, Before the Dawn, I wish I could simply recommend the book, describe its highlights and stop there. Wade provides a valuable overview of the last ten years of scientific literature on genetic insights into the history of our species. He is an excellent storyteller, weaving the scientific results into a thrilling tale of human migration and settlement, competition and warfare, cultural and linguistic evolution and environmental challenges. The history of our species is a fascinating one, and Wade brings it to life.

I congratulate Wade for taking great pains to qualify many of his statements with terms such as "seems" and "appears to." In an important, related vein, early in the book he notes that any "intent" suggested in biologists' statements about evolution reflects shorthand communication and is not meant to imply that evolution has any particular goal "in mind." Evolutionary biologists will certainly appreciate that note. Furthermore, given that few readers will be specialists in all the fields represented in the book (paleoanthropology, archaeology, linguistics, genetics and more), many will appreciate Wade's practice of defining terms.

Despite the book's many strengths, I am reluctant to recommend the book unconditionally. I found some sections of the book challenging to read, as I looked for supporting evidence for various claims. For example, Wade suggests that the San, peoples in southern Africa who subsist via foraging, are the "closest living approximation to the ancestral human population." Behaviorally, this might be true. However, Wade goes on to suggest that the San may not have evolved genetically, as "foragers have presumably had much the same environment for the last 50,000 years." Wade appears to be unaware of the diverse environments even today within sub-Saharan Africa; furthermore, the changing global climate over the past 50,000 years has often had dramatic impacts on humans living in Africa.

Although at many points in the book Wade notes the speculative nature of conclusions from genetic, archaeological or geographic data, he occasionally treats those conclusions as fact elsewhere. For example, he writes, "There is no way to know for certain the nature of the interaction between the two human species [anatomically modern humans and Neanderthals]." Yet elsewhere he writes, "...[the Neanderthals] crushed the attempt by anatomically modern humans to penetrate the Levant." The reader is at risk of being lulled by numerous "maybes," "seems" and "appears" into trusting unsupported but confidently stated comments elsewhere in the book.

My reluctance to recommend the book stems also from Wade's discussions of 'race' and biology. I agree with Wade that there is something biological about racial categories. In my opinion, although racial identity is socially negotiated, people use physical traits as cues when 'assigning' a racial identity to themselves or another individual. Racial categorization isn't blind to biology. Yet Wade puts words in the mouths of the American Anthropological Association (AAA) when he states that the AAA "dismisses the idea that biological differences can be recognized between races." He backs up his statement with an AAA quote that makes a different point: "any attempt to establish lines of division among biological populations [is] both arbitrary and subjective." Although one might detect biological differences between races, any highlighting of the racial categories (just a subset of groups with biological correlates) has social costs, according to recent social science research. On the other hand, Neil Risch, cited often in the book, has argued that there are significant (medical) costs of ignoring the relationship between racial categories and biology. I suggest that these different costs be weighed in each circumstance where one might link 'race' and genetics. Wade's broad description of races as clearly delineated biological entities is unjustified in the context of a book about human history intended for a general audience. Why use the term 'race', when 'geographic ancestry' or 'continental origin' are more accurate and less costly in social terms, especially since Wade's definition of 'race' is "continent of origin"? I suggest acknowledging the correlation between racial labels and continents of origin, and saving the term 'race' for contexts in which social costs are outweighed by other costs.

Wade's chapter on language is replete with details of relationships among languages, methodology for reconstructing those relationships and arguments in support of methods that are purported to give ages of languages. Although much of this discussion will undoubtedly provoke many linguists, the most provocative element in this chapter is a more general statement: "The mutability of language reflects the dark truth that humans evolved in a savage and dangerous world in which the deadliest threat came from other human groups." I see little support for this conjecture. Language, at least a language rich in elements, cannot come into being without being mutable. And as Wade notes earlier in the book, "Language would have made small groups more cohesive, enabled long-range planning and fostered the transmission of local knowledge and learned skills." Mutability may reflect these advantages rather than a "savage and dangerous world."

Where I am familiar with the relevant scientific literature, I see the details that Wade includes in this, his latest book, as accurately representing scientific findings. Wade often wraps these scientific details in dramatic stories, thereby creating a book both informative and entertaining. However, some of Wade's general themes, such as his claim of a very high level of aggressiveness of prehistoric hunter-gatherers, are just that—dramatic stories. Readers will benefit most by considering each such claim as one among several plausible interpretations of the data.

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Look, it's a tree!   posted by Razib @ 4/07/2007 02:46:00 AM

A new PLOS paper, free for your perusal, Generalized Analysis of Molecular Variance. If AMOVA is your thing, read closely, but I thought I would highlight a figure of interest. We can rattle on all we want about correlation structure...but a picture is worth a thousand posts. OK, a neighbor-joining tree:


Thursday, February 22, 2007

Race IQ and SES   posted by the @ 2/22/2007 12:31:00 AM

Jensen (1998) makes a point that is worth repeating:
The pernicious notion that IQ discriminates mainly along racial lines, however, is utterly false.

Jensen presents what should be a predictable pattern for a highly heritable trait:
Source % of Variance Average IQ Difference
Between races (within social classes)
14 30 12
Between social classes (within races)
8 6
Interaction of race and social class
Between families (within race and social class)
26 65 9
Within families (siblings)
39 11
Measurement error
5 4
100 17

This can be demonstrated most clearly in terms of a statistical method known as the analysis of variance. Table 11.1 shows this kind of analysis for IQ data obtained from equal-sized random samples of black and white children in California schools. Their parents' social class (based on education and occupation) was rated on a ten-point scale. In the first column in Table 11.1 the total variance of the entire data set is of course 100 percent and the percentage of total variance attributable to each of the sources6 is then listed in the first column. We see that only 30 percent of the total variance is associated with differences between race and social class, whereas 65 percent of the true-score variance is completely unrelated to IQ differences between the races and social classes, and exists entirely within each racial and social class group. The single largest source of IQ variance in the whole population exists within families, that is, between full siblings reared together in the same family. The second largest source of variance exists between families of the same race and the same social class. The last column of Table 11.1 shows what happens when each of the variances in the first column is transformed into the average IQ difference among members of the given classification. For example, the average difference between blacks and whites of the same social class is 12 IQ points. The average difference between full siblings (reared together) is 11 IQ points. Measurement error (i.e., the average difference between the same person tested on two occasions) is 4 IQ points. (By comparison, the average difference between persons picked at random from the total population is 17 IQ points.) Persons of different social class but of the same race differ, on average, only 6 points, more or less, depending on how far apart they are on the scale of socioeconomic status (SES). What is termed the interaction of race and social class (8 percent of the variance) results from the unequal IQ differences between blacks and whites across the Spectrum of SES, as shown in Figure 11.2. This interaction is a general finding in other studies as well. Typically, IQ in the black population is not as differentiated by SES as in the white population, and the size of the mean W-B difference increases with the level of SES.

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Friday, September 29, 2006

Skin color and IQ in the GSS   posted by the @ 9/29/2006 11:42:00 AM

A question from Jason Malloy prompted a quick search of the GSS for data on the cause of the Black-White IQ gap. In 1982, the GSS characterized the skin color of Black participants on a 5-point scale (1:very dark brown to 5:very light brown). The very dark/light categories consist of only 50 and 14 individuals, respectively, and so in the following analysis I merged them with the dark/light brown categories, to give three COLOR levels: dark, medium, and light. In the web application, use COLOR(r:1-2;3;4-5) instead of COLOR. The WORDSUM variable is a 10 question vocabulary test, which I'm treating as a proxy for IQ. It is correlated with educational attainment (~.4), and also correlates (~.4-.5) with tests of reasoning and basic knowledge that were given in some years. These other tests are not available for 1982. In the all-subject all-year GSS data set, WORDSUM varies by SEX, and in 1982 COLOR also varies by SEX. Thus, SEX is controlled for in each analysis. WORDSUM is lower in the youngest and oldest age groups, so an AGE(25-65) filter was used.

Table 1. Mean WORDSUM score by COLOR and SEX with ANOVA

Main Statistics
Cells contain:
-Std Devs
-N of cases
COLOR1: Dark4.15
2: Medium5.39
3: Light6.04

color indicates T-statistic, and thus p-value
Color coding:<-2.0<-1.0<0.0>0.0>1.0>2.0T
Mean in each cell:Smaller than averageLarger than average

Analysis of Variance

Main effects89.443.061329.8146.956.0002


We can quantify the effect size of each skin color class using Cohen's d statistic, which measures the mean difference in standard deviation units. In the 1982 dataset, the overall d for the Black-White gap on WORDSUM is -0.63 (among males d=-0.51, among d=-0.74). For comparison, the 1982 male-female gap among Whites is d=-.12, favoring females.

Table 2. Effect size (d) of COLOR on WORDSUM using "light" as a control group


We can also use Whites as the control group.

Table 3. Effect size (d) of COLOR on WORDSUM using Whites as a control group


Thus, there are substantial (moderate to large effect size) differences in WORDSUM scores between the darkest and lightest Blacks in 1982.

As reported by Rushton and Jensen (2005), Shuey (1966) reviewed 18 studies which used skin color as a measure of racial admixture to compare with IQ. Of those 18, 16 found a significant effect of the kind found here, but the overall correlation with IQ was low (r=.1). In this data, the COLOR WORDSUM correlation is r=.31 among males and r=.18 among females, with an overall correlation of r=.23. Off the top of my head, I'm not certain what the expected correlation would be between IQ and skin color among Blacks for a given measure of "between-group heritability" (BGH) as described by Jensen (1998). I'll leave it as an exercise for our mathematically skilled commentators to derive a formula for this relationship and to evaluate the signficance of this finding in explaining the cause of the Black-White IQ gap.

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Thursday, February 23, 2006

"Black" and "white" twins   posted by Razib @ 2/23/2006 02:59:00 PM

Update: More comments here, here and here.
End update

Desidancer and Diana both pointed me to this story about a mixed race couple who gave birth to daughters of very different phenotypes. The explanation in the story is about right, the loci which give you a gestalt impression of racial identity are a tiny sample of your overall genome. In the story it is reported that 7 genes control skin color and F1 (first generation) hybrids should carry half of the variants of each race (since their parents contribute exactly 50% of the genes to each). But the F2 generation can come out as a range of combinations, so it stands to reason that mixed-race couples will have children who vary a great deal in phenotype as the alleles resegregate themselves into alternative combinations. I lay out the details in By the Punnett Square. South Asians, who often exhibit a wide range of color variation from near white to near black, should not be surprised at this sort of dynamic, as the variance within a family can be rather large in complexion.

In any case, independent assortment implies that even if the coloration of these two children reflects one of their ancestral ethnic groups, other traits do not necessarily line up in such a fashion. Since the twins above are babies it is hard to discern facial traits (they just look like babies), but I wouldn't be surprised if the "white" and "black" baby had facial traits that were more equidistant to the metrics of whites and blacks (this would be expectation, though you expect a lot of variance still). There is a reason that in much of the southern part of the New World where admixture between Africans, Europeans and American indigenes is common, there are dozens of definitions for racial phenotypes, because the full range of appearance is expressed in a large enough mixing population (eg, there are terms for people with Negroid facial features and hair form and Nordic coloration and European facial features and hair form and Sub-Saharan African coloration).

By the way, as personal stories like this become more common hopefully we'll stop hearing about how everyone in the future will be brown because of admixture. More values at each variable will result in an increase in variance for the distribution, not a decrease.

Update: OK, I think I need to repost this link, The incidence of superfecundation and of double paternity in the general population:

Sometimes superfecundation occurs by two different men. The frequency with which this occurs must depend on rates of infidelity (promiscuity). It is suggested that among DZ twins born to married white women in the U.S., about one pair in 400 is bipaternal. The incidence may be substantially higher in small selected groups of dizygotic twin maternities, eg. those of women engaged in prostitution.

In other words, double paternity is a possible explanation, but if the number of loci in question is seven or less than this is surely will the expected range due to variance emerging from heterozygosity in the parents1 (and we are only looking at skin color here from what I can tell, the two infants are still of the "baby race," other features are not at play). I don't think that the expectation of double paternity, evening adjusting for SES, approaches the probability that "white" and "black" color genes will resegregate in this fashion.

Update II: David points out that this is being reported in the British newspapers, which does alter your Bayesian priors, but walk around Lowell, Massachusetts, and observe the range in phenotype of the Cape Verdian community. The general point still stands.

1 - Fisher's 1918 paper dealt in large part with the variance expected from heterozygous parents.

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