Establishing the Gap
It is uncontroversial that racial differences in IQ exist. Meta-analyses of data on more than 6,000,000 people have shown that Blacks in America score about 15 points lower than Whites do (
Roth et al., 2001). East Asians, by contrast, score a few points higher than Whites do.
Of course, this does not mean that every African American has a lower IQ than every European American. Actually, these numbers imply that around one in ten African Americans will have an IQ of 100 or higher (the White average) and one in six Whites will have an IQ of 85 or lower (the Black average). The point is that these groups differ on average.
Why gaps matter
That being said, these gaps do matter. If you control for IQ, many social inequalities between the races disappear. For instance, if you hold IQ constant, Blacks are more likely than Whites to get a college degree and get paid the same for the same work.
(
Murray and Herrnstein, 1994)
Controlling for IQ also eliminates most of the Black-White Incarceration gap.
(
Murray and Herrnstein, 1994)
IQ is also an excellent predictor of national wealth, and changes in national IQ overtime predict changes in economic growth (
Lynn and Vanhanen, 2012;
Pietschnig and Voracek, 2015).
Thus, these differences have social importance aside from the fact that human differences are inherently interesting.
Obvious Environment Causes
At this point, some people may be thinking that the Black-White IQ gap can by explained away by poverty, racism, education, or single motherhood. These explanations have each been refuted.
First, let’s look at poverty. Poverty does correlate with IQ, but controlling for socio-economic status, whether measured by parental income, education, neighborhood, wealth, or any other way, does not eliminate the Black-White IQ gap. This has been shown in more than 60 studies over the last 100 years (
Last, 2016A). In fact, poor Whites do better on standardized tests than rich Blacks do.
(
Black Journal of Higher Education, 2008)
The same is true of single motherhood. Even when just looking at people from two parent homes, the Black-White IQ gap persists (
Prifitera et al., 2005, table 1.4;
Weiss et al., 2016, table 5.6). Moreover, research has shown that the Black-White IQ gap, and the White-East Asian IQ gap, still exists even when only looking at people raised (via adoption) in White homes (
Faulk, 2016A).
(
Loehlin 2000;
Lynn, 2015)
Another possibility is that differences in access to education cause the Black-White IQ gap. This is not possible because the Black-White IQ gap exists by age 3 which is prior to the beginning of formal education (
Malloy, 2013). Moreover, the Black-White IQ gap remains after controlling for parental education (
Prifitera et al., 2005, table 1.4;
Weiss et al., 2016, table 5.6). Further still, Blacks with graduate degrees score worse than Whites without even a four-year degree on tests of cognitive ability (
Faulk and Last, 2016). Clearly then, education is not the cause of racial cognitive differences.
Finally, let’s look at racism. To affect intelligence, racism must impact Blacks through some concrete mechanism. As we’ve seen, racism making Blacks poorer, less educated, or more likely to be from single-parent homes cannot explain the IQ gap. Another possibility is that racism has caused Blacks to internalize negative stereotypes about their intellect which in turn impacts their performance on tests. This hypothesis is refuted by the fact that Blacks score higher than Whites on measures of general self-esteem and are more likely than Whites to describe themselves as being smarter than average (
Twenge and Crocker, 2002).
“Black students estimate their own academic competence more highly than Whites despite their own objective and self reported lower academic achievement (Hare 1985: Table 3; Tashakkori 1993: 97). Black high school seniors in the Coleman study were more apt than Whites to classify themselves as “among the brightest” and less likely to agree that “Sometimes I feel that I just can’t learn” despite poor academic performance (Coleman et al. 1966L 287-288, Tables 3.13.11, 3.13.12). Remarkably, southern rural Blacks, whose academic performance fell below that of all other blacks as well as all Whites, were more apt than other Blacks to classify themselves as Bright and able to learn” – Levin, 2016, page 75
Beyond this, there is no obvious way that racism could lower the intelligence of Blacks. Moreover, the Black-White IQ gap is found all over the world, including in Black countries, and did not fall in America between 1920 and 1970 even though there was a huge decline in racism during this time (
Last, 2016B).
To be fair, some of these potential causes, such as poverty, may contribute a few points to the Black-White IQ gap. However, they cannot account for even half of the difference, let alone all of it.
Evidence for a partly genetic cause
Obviously, these environmental explanations failing does not mean that a genetic explanation will succeed. So, why think genes have anything to do with racial intelligence differences, or, for that matter, intelligence in general?
We know that genes impact intelligence through studies of identical twins raised apart and non-biological relatives raised together. Such studies show that the heritability of IQ rises with age and is well over 50% by adulthood (
Last, 2016C). This is backed up by studies showing that genetic similarity between individuals predicts how similar their IQ scores will be and by recent studies showing that genetic tests can predict standardized test performance (
Last, 2016C,
Selzam et al., 2016). This research also shows that non-biological relatives raised in the same home are no more similar than average in terms of IQ despite a far more similar than average experience in home environment. This suggests that differences in home environment explain little to no variation in intelligence in adults.
Before going any further, you should know that hereditarianism isn’t a fringe theory. Surveys show that most intelligence researchers take the hereditarian view on the Black-White IQ gap.
(Rindermann, Coyle, and Becker, 2013)
Recent advances in genetics are consistent with this viewpoint. For instance,
Piffer (2015) looked at racial differences in 9 IQ related gene variants and found that Whites were more likely than Blacks to have the high IQ related variants of all 9 genes. East Asians were also more likely than Whites to have the high IQ related gene variant in the majority of cases.
Piffer used data on all nine of these gene variants to assign people a “polygenic score”. This polygenic score had an astoundingly high correlation of .93 with a nation’s mean IQ in a sample of 23 countries.
Becker and Rindermann (2016) provided further direct genetic evidence when they analyzed data on 101 countries and found that the more genetically different two populations were the larger the IQ difference between them tended to be.
Another variable which predicts the regional cognitive ability is the average degree of White admixture in a population or, in other words, the degree to which the average person is genetically European.
Fruest and Kirkegaard (2016) found this to be the case in data sets on American nations, states within Latin American nations such as Colombia, Brazil, and Mexico, and in US states.
Indirect evidence also points to a genetic explanation. Consider the fact scores on IQ test questions vary in their heritability. Some cognitive abilities are more heritable than others and it turns out that the more heritable a cognitive ability is the larger the racial gap in that ability tends to be (
Jensen, 1973; Nichols 1970;
Last, 2016D). This finding is easy to explain on the hereditarian view but very hard to explain otherwise.
Research has also shown repeatedly that mixed race individuals have IQ scores in between the mean scores of the races of their parents (
Faulk, 2016B;
Faulk 2016C). One study even found that this was true of mixed race Blacks who incorrectly believed they were fully Black (
Weinberg et al., 1992). Further still, white admixture in African Americans has been shown to correlate with both their income and their educational attainment (
Fuerst, 2014). Once again, this is exactly what the hereditarian viewpoint would predict.
Furthermore, Blacks have smaller brains than Whites, who have smaller brains than East Asians (
Last, 2016E). Contrary to what you may have heard, brain size does predict a person’s IQ score. Moreover, changes in brain size over time predict changes in IQ, and the same genes which influence IQ are known to influence brain size. A plausible explanation for this data is that variation in brain size causes variation in IQ. More on this can be read about
here.
There are several reasons to think that racial differences in brain size have a genetic cause. First, the races differ in brain size even at birth (
Schultz, 1922;
Rushton, 1997;
Ho et al., 1980). Research also shows that the races differ in dozens of traits which tend to co-evolve with brain size in a way that is consistent with the brain size differences (
Rushton and Rushton, 2003). (For instance, women need larger hips to give birth to larger brained children.) Furthermore, several studies have shown that mulattoes have an average brain size in between that of Blacks and Whites (
Pearl, 1934;
Bean, 1906). Finally, the Black-White brain size gap did not shrink in the 100 year period between 1880 and 1980 even though the Blacks and Whites converged in every conceivable measure of social inequality (
Last, 2016E). Given all this, there is reason to think that genetically caused racial brain size differences play a role in racial intelligence differences.
Finally, the racial gap “looks” genetic based on how it changes over time, age, and geography. First, the Black-White-Asian IQ gap is seen all over the world.
Lynn (2006)
As mentioned earlier, the Black-White gap is also known to be present at age 3, and the Black-White IQ gap did not converge at all between 1920 and 1970 even though the social inequality between the races declined markedly between 1920 and 1970. This basic pattern of data is what we would expect if the underlying cause of the gap was genetic and makes explanations which appeal to environmental variables which impact people later in life, or are particular to a specific set of countries, unlikely.
In summary, there are many lines of evidence which converge on racial intelligence differences having a partially genetic cause. This doesn’t mean they are entirely caused by genes. They aren’t. But it does mean that genes are an important factor which we should not ignore.
Environmental Causes
To drive home the point that I am not proposing purely genetic explanation of racial intelligence differences, I’m going to briefly mention a two environmental factors which I do think are involved. This isn’t an exhaustive list, but it shows that I really don’t think racial IQ gaps are 100% heritable.
Child abuse has been shown to negatively impact IQ and, unfortunately, child abuse is more common among African Americans than it is among Whites. This accounts for a small proportion of the Black-White IQ gap in America. I’ve written about this in more detail
here.
There is also good evidence that breastfeeding raises IQ and African Americans are less likely than White Americans to breastfeed. This too likely contributes to the Black-White IQ gap in America.
Of course, none of this negates, or is mutually exclusive with, the positive evidence for a partially genetic cause. Rather, the take away is that a complex mix of genes and the environment account for racial intelligence differences. Given the strength of the genetic evidence and the high heritability of IQ in the general population, I am inclined to think that racial intelligence differences are at least 50% heritable if not more so, but that still leaves room for plenty of other causes.
Conclusion
This article is meant as an introduction to the hereditarian case on race and IQ. A more comprehensive set of articles can be found
here for those who require further evidence. If the case presented here was compelling to you, here is what I consider to be the key take away: racial inequalities are probably a permanent feature of society that we’ll have to learn to deal with and they aren’t anybody’s fault. If society can internalize that truth, we’ll have made real progress towards understanding ourselves as a species.
https://thealternativehypothesis.org/index.php/2017/01/07/race-and-iq-the-case-for-genes/
