Everyone Is African (15 page)

The crux of their argument that these differences cannot be fully explained by environment, and therefore must be partly attributable to genetic differences between ethnic groups, is best stated in their own words:

Suppose that all the observed ethnic difference in tested intelligence originate in some mysterious environmental differences—mysterious, because we know from material already presented that socioeconomic factors cannot be much of the explanation. We further stipulate that one standard deviation (fifteen IQ points) separates American blacks and whites and that a fifth of a standard deviation (three IQ points) separates east Asians and whites. Finally, we assume that IQ is 60 percent heritable (a middle-ground estimate).
Given those parameters, how different would the environments for the three groups have to be in order to explain the observed difference in these scores?

…The
average
environment of blacks would have to be at the 6
^th
percentile of the distribution of environments among whites, and the average environment of East Asians would have to be at the 63
^rd
percentile of environments among whites, for the racial differences to be entirely environmental.

Environmental differences of this magnitude and pattern are implausible…. An appeal to the effects of racism to explain ethnic differences also requires explaining why environments poisoned by discrimination and racism for some other groups—against the Chinese and the Jews in some regions of America, for example—have left them with higher scores than the national average.

…The heritability of individual differences in IQ does not necessarily mean that ethnic differences are also heritable. But those who think that ethnic differences are readily explained by environmental differences haven't been tough-minded enough about their own argument.
²¹

After comparing arguments favoring a predominantly genetic explanation and a predominantly environmental explanation of the differences, they draw their final conclusion:

It seems highly likely to us that both genes and the environment have something to do with racial differences. What might the mix be? We are resolutely agnostic on that issue; as far as we can determine, the evidence does not yet justify an estimate.
²²

Though Herrnstein and Murray's book does not venture an estimate of how much genetic variation contributed to this difference, Rushton and Jensen's 2005 article does. They set up the controversy as a dichotomy of two contrasting models to explain average racial differences in IQ: a culture-only model, which they propose as 0 percent genetic and 100 percent environmental, and a hereditarian model, proposed as 50 percent genetic and
50 percent environmental. By the end of their article, they fully reject the culture-only model and recommended revision of their hereditarian model to 80 percent genetic and 20 percent environmental.
²³
They also speculate that a Darwinian approach explains their claim of a large hereditary difference between European, Asian, and African races for intelligence and other behavioral traits:

Evolutionary selection pressures were different in the hot savanna where Africans lived than in the cold northern regions Europeans experienced, or the even colder Arctic regions of East Asians. These ecological differences affected not only morphology but also behavior. It has been proposed that the farther north the populations migrated out of Africa, the more they encountered the cognitively demanding problems of gathering and storing food, gaining shelter, making clothes, and raising children successfully during prolonged winters. As these populations evolved into present-day Europeans and East Asians, the ecological pressures selected for larger brains, slower rates of maturation, and lower levels of testosterone—with concomitant reductions in sexual potency, aggressiveness, and impulsivity; increases in family stability, advanced planning, self-control, rule following, and longevity.
²⁴

These sorts of speculations—considered by many to be overtly racist and biased against African Americans—prompted a firestorm of responses. The scientific journal
American Psychologist
devoted an entire issue to the topic in 2005, titled
Genes, Race, and Psychology in the Genome Era
. The journal
Psychology, Public Policy, and Law
invited responses to Rushton and Jensen's article from prominent psychologists, responses that could hardly have been more polarized. For instance, educational psychologist Linda Gottfredson of the University of Delaware supported Rushton and Jensen's hereditarian view:

In summary, Rushton and Jensen (2005) have presented a compelling case that their 50%–50% hereditarian hypothesis is more plausible than the culture-only hypothesis. In fact, the evidence is so consistent and so quantitatively uniform that the truth may lie closer to 70%–80% genetic, which is the within-race heritability for adults in the West. The case for culture-only
theory is so weak by comparison—so degenerated—that the burden of proof now shifts to its proponents to identify and replicate even
one
substantial, demonstrably
non
genetic influence on the Black–White mean difference in
g
[general intelligence].
²⁵

Richard Nisbett of the University of Michigan drew a completely opposite conclusion in his review:

J. P. Rushton and A. R. Jensen (2005) ignore or misinterpret most of the evidence of greatest relevance to the question of heritability of the Black–White IQ gap. A dispassionate reading of the evidence on the association of IQ with degree of European ancestry for members of Black populations, convergence of Black and White IQ in recent years, alterability of Black IQ by intervention programs, and adoption studies lend no support to a hereditarian interpretation of the Black–White IQ gap. On the contrary, the evidence most relevant to the question indicates that the genetic contribution to the Black–White IQ gap is nil.
²⁶

Yale University professor of psychology Robert J. Sternberg (currently at Cornell University and former president of the American Psychological Association) condemned not only the scientific but also the public-policy views expressed in the article:

J. P. Rushton and A. R. Jensen (2005) purport to show public-policy implications arising from their analysis of alleged genetic bases for group mean difference in IQ…. None of these implications in fact follow from any of the data they present. The risk in work such as this is that public-policy implications may come to be ideologically driven rather than data driven, and to drive the research rather than be driven by the data.
²⁷

The core of the hereditarian controversy as it relates to differences between racial groups centers on three major issues: 1) how races are defined and categorized as supposedly distinct genetic entities, 2) how human intelligence is measured, and 3) how those measurements are interpreted in terms of genetic and environmental causes.

The first issue—the biological and social bases of racial classification—is
one we've already discussed in detail in this book. The dispute focuses on the claim that racial categories represent genetically distinct groups as opposed to the idea that racial categorization is more of a social construct than a biological one. As Sternberg puts it:

Where does race fit into the genetic pattern we have been discussing above?…In fact, it does not fit at all. Race is a socially constructed concept, not a biological one. It is a result of people's desire to classify. People seem to be natural classifiers: they try to find order in the natural world…. Any set of observations of course can be categorized in multiple ways. People impose categorization and classification schemes that make sense to them and, in some cases, that favor their particular, often nonscientific, goals.
²⁸

Classification of people into a few racial categories (usually based on self-identification) grossly oversimplifies and obscures the genetic complexities of ancestry that underlie the realities of human diversity. Therefore, claims that IQ differences between races are largely genetic is scientifically flawed from the outset.

The second issue—measuring intelligence—has generated volumes of discussion, along with a variety of hypotheses to explain the meaning of metrics used to quantify intelligence. Much of the current psychological literature is focused on measuring IQ and an associated value called
g
, which is proposed as a numeric representation of general intelligence.
²⁹
Some have argued that
g
is a real and measurable aspect of human nature and that IQ tests reliably quantify it, particularly if components of IQ tests are weighted toward certain aspects of intelligence most relevant to
g
, a procedure called
g
-loading. Others counter that IQ and
g
are too narrow to encompass the complexities of human intelligence, and a one-dimensional measurement misrepresents true intelligence.

According to several reviews of the topic, there are three prominent theories. The first, often called CHC theory—after psychology professors Raymond Cattell, John Horn, and John Carroll—is a synthesis of several related theories. It posits
g
as a measure of general intelligence and proposes subdivision of
g
into
g-f
(fluid ability) and
g-c
(crystallized ability). Fluid ability is the capacity to think rapidly and deal successfully with new situations and previously unknown factors. Crystallized ability consists of the store of knowledge relevant to daily tasks that a person retains and can recall, such as vocabulary.
Modern IQ testing and measurement of
g
are largely based on CHC theory, measuring aspects of both
g-f
and
g-c
, and such testing serves as the foundation for a large body of research on measuring intelligence.

An alternative is Gardner's theory of multiple intelligences, named after Harvard professor Howard Gardner. He disputes the validity of
g
as a general measure of intelligence and instead has proposed that intelligence falls into multiple categories: linguistic, mathematical, spatial, musical, bodily-kinesthetic, interpersonal, and intrapersonal. Although Gardner's theory of multiple intelligences has its proponents, a majority of psychologists have opted instead for the more simplistic CHC theory.

The third theory is the triarchic theory developed by Sternberg during the time he was a professor at Yale. It proposes three broad categories of intelligence: creative, analytical, and practical. He maintains that intelligence in each of these categories can be measured and that measurement of all three areas can “improve prediction of both academic and nonacademic performance in university settings and reduce ethnic-group differences.” Furthermore, he argues that this theory is important for education because “teaching that incorporates the various aspects of intelligence increases academic performance relative to conventional teaching.”
³⁰

Sternberg, along with Yale colleagues Elena Grigorenko and Kenneth Kidd, determines that “intelligence is, at this time, ill defined. Although many investigators study ‘IQ' or ‘
g
' as an operational definition of intelligence, these operationalizations are at best incomplete, even according to those who accept the constructs as useful.”
³¹

Critics of intelligence tests also often question the validity of IQ tests because of culture bias. Certain cognitive skills may carry a higher value in one cultural tradition than in another, and tests—however well designed to avoid cultural bias—may still favor or disfavor people on the basis of their cultural background.

Nisbett and his colleagues, in their 2012 review of the current state of psychological research on human intelligence, sum up the situation as follows:

The measurement of intelligence is one of psychology's greatest achievements and one of its most controversial. Critics complain that no single
test can capture the complexity of human intelligence, all measurement is imperfect, no single measure is completely free from cultural bias, and there is the potential for misuse of scores on tests of intelligence. There is some merit to all these criticisms. But we would counter that the measurement of intelligence—which has been done primarily by IQ tests—has utilitarian value because it is a reasonably good predictor of grades at school, performance at work, and many other aspects of success in life.
³²

They are quick to point out, however, that “types of intelligence other than the analytic kind examined by IQ tests certainly have a reality” and that “measuring nonanalytic aspects of intelligence could significantly improve the predictive power of intelligence tests.”
³³

In spite of the inability of IQ tests to fully represent the complexity of human intelligence, and largely for their predictive value regarding academic and employment success, IQ scores are widely used as the standard for much of the research on intelligence. However, because IQ scores do not fully represent human intelligence, Sternberg has cautioned that the language used in reference to intelligence is important: IQ represents a subset of cognition and should be referred to specifically as
IQ
, not as overall intelligence.
³⁴

We now move to the third issue at the core of the hereditarian controversy, which is perhaps the most contentious of the three. It is sometimes called the “nature versus nurture” debate, although a more accurate term is the
heritability of intelligence
. The term
heritability
means the proportion of overall variation in a population attributable to genetic variation. Body height, for instance, varies considerably among adults. Part of this variation is attributable to genetics (the combination of variants in DNA inherited by each person that influence body growth), and part is due to environmental variation (such as poor nutrition or diseases that may stunt growth during childhood). The heritability of body height in any population is simply a numerical value that defines what proportion of the overall variation for height is attributable to underlying genetic variation. It is often expressed as a percentage value between 0 and 100. A value of 80 percent heritability for body height in a particular population, for example, implies that 80 percent of the variation is attributable to genetic variation and 20 percent to nongenetic variation, presumably environmental variation.