Intelligence, Race, and Genetics

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Intelligence, Race, and Genetics
Robert J. Sternberg, Elena L. Grigorenko, and Kenneth K. Kidd
Yale University
In this article, the authors argue that the overwhelming
Nor do any tests, except dynamic tests (see Sternberg &
portion of the literature on intelligence, race, and genetics
Grigorenko, 2002a) that require learning at the time of the
is based on folk taxonomies rather than scienti?c analysis.
test, directly measure ability to learn. Rather, traditional
They suggest that because theorists of intelligence disagree
tests focus much more on measuring past learning, which
as to what it is, any consideration of its relationships to
can be the result of differences in many factors, including
other constructs must be tentative at best. They further
motivation and available opportunities to learn.
argue that race is a social construction with no scienti?c
Some theories of intelligence extend this de?nition by
de?nition. Thus, studies of the relationship between race
suggesting that there is a general factor of intelligence,
and other constructs may serve social ends but cannot
often labeled g, that underlies all adaptive behavior (Brand,
serve scienti?c ends. No gene has yet been conclusively
1996; Jensen, 1998; see essays in Sternberg & Grigorenko,
linked to intelligence, so attempts to provide a compelling
2002b). In many theories, including the theories most
genetic link of race to intelligence are not feasible at this
widely accepted today (e.g., Carroll, 1993; Gustafsson,
time. The authors also show that heritability, a behavior-
genetic concept, is inadequate in regard to providing such

1994; Horn, 1994), other mental abilities are hierarchically
a link.
nested under this general factor at successively greater
levels of speci?city. For example, Carroll has suggested
that three levels can nicely capture the hierarchy of abili-
ties, whereas Cattell (1971) and Vernon (1971) suggested
number of scholars claim to have studied rela-
tionships among intelligence, race, and genetics
two levels that were especially important. In the case of
(e.g., Herrnstein & Murray, 1994; Rushton,
Cattell, nested under general ability are ?uid abilities of the
1995). The thesis of this article is that these studies are not
kind needed to solve abstract reasoning problems such as
grounded in scienti?cally derived constructs but rather in
?gural matrices or series completions and crystallized abil-
folk beliefs about them. There is a big difference between
ities of the kind needed to solve problems of vocabulary
studying relationships between constructs and folk beliefs
and general information. In the case of Vernon, the two
regarding such relationships. The bigger problem, how-
levels corresponded to verbal– educational and practical–
ever, is when one studies the latter but believes one is
mechanical abilities. What we know about group differ-
studying the former.
ences largely involves so-called g and major group factors,
In this article, we ?rst review the nature of intelli-
such as verbal and spatial skills. More modern theories
gence. We then discuss the relationship between intelli-
extend intelligence much further, for example, to creative
gence and race. Finally, we re?ect upon the relationships
and practical as well as analytical abilities (Sternberg,
among intelligence, race, and genetics.
Robert J. Sternberg, PACE Center, Yale University; Elena L. Grigorenko,
PACE Center and Child Study Center, Yale University; Kenneth K. Kidd,
To study the interrelationships among intelligence, race,
Department of Genetics, Yale University.
and genetics, we need to know what intelligence is. We do
Preparation of this article was supported by National Science Foun-
not know. Hence, any conclusions about its relationships to
dation Grant REC-9979843; by a government grant under the Javits Act
other constructs will be, at best, tentative.
Program (Grant R206R000001), as administered by the Institute of Edu-
cational Sciences, U.S. Department of Education; by U.S. Department of
Formal Theories of Intelligence
Education, Institute for Educational Sciences Award 31-1992-701, as
administered by the Temple University Laboratory for Student Success;
One way to ?gure out what intelligence is has been to ask
and by National Institutes of Health Grants AA09379 and GM57672 and
experts. Two major symposia have done so (“Intelligence
National Science Foundation Grant BCS0096588. Grantees undertaking
such projects are encouraged to freely express their professional judg-
and Its Measurement,” 1921; Sternberg & Detterman,
ment. This article, therefore, does not necessarily represent the positions
1986). Each of the roughly two dozen de?nitions produced
or policies of the U.S. government, and no of?cial endorsement should be
in each symposium was different. There were some com-
mon threads, such as the importance of adaptation to the
We are grateful to Julian Elliott, Jeremy Gray, Linda Jarvin, Jennifer
environment and of the ability to learn, but these constructs
Jordan, Scott Kaufman, Richard Nisbett, David Preiss, Steven Stemler,
and Karin Weis for comments that helped improve this article.
themselves are not well speci?ed. Moreover, very few tests
Correspondence concerning this article should be addressed to Rob-
of intelligence directly measure either one. Tests do not
ert J. Sternberg, PACE Center, Yale University, Box 208358, New Haven,
offer adaptive tasks one is likely to face in everyday life.
CT 06520-8358. E-mail: [email protected]
January 2005 ? American Psychologist
Copyright 2005 by the American Psychological Association 0003-066X/05/$12.00
Vol. 60, No. 1, 46 –59
DOI: 10.1037/0003-066X.60.1.46

conventional tests. But it is not clear that tests of IQ
measure the same construct among all people to whom the
tests are applied (Sternberg, 2004a, 2004b). The more
culturally distinct the people, the greater the differences in
what the items measure. In part, this is because IQ test
items are largely measures of achievement at various levels
of competency (Sternberg, 1998, 1999, 2003). Items requir-
ing knowledge of the fundamentals of vocabulary, infor-
mation, comprehension, and arithmetic problem solving—
so-called measures of crystallized abilities (Cattell, 1971;
Horn, 1994)—are clearly measures of achievement. Items
requiring ?uid abilities (Cattell, 1971; Horn, 1994) involv-
ing abstract reasoning, once thought to be culture fair
(Cattell & Cattell, 1963), have proven even more suscep-
tible to effects of cultural and other environments than tests
of crystallized abilities (Flynn, 1984, 1987; Neisser, 1998),
suggesting they are in no way “culture fair.” Western-style
schooling even more extensively inculcates these ways of
thinking than it does those measured by tests of crystallized
Robert J.
In summary, it is probably more accurate to refer to
existing studies as assessing the relation between “IQ” or
“psychometric g” and what is labeled as race than as
assessing “intelligence” and these other constructs. Does
the language we use matter? Yes. We need to acknowledge
1997; Sternberg et al., 2000) or to eight distinct multiple
that we are using convenient, partial operationalizations of
intelligences (Gardner, 1999a, 1999b).
the construct of intelligence, and nothing more. As profes-
sionals, some of us may understand that there is a large gap
Informal Theories of Intelligence
between the conceptualization and operationalization of
Lay conceptions of intelligence are quite a bit broader than
intelligence. Others of us may act as though IQ tests
conceptions of psychologists who believe in g (Berry,
somehow provide the kind of measurement of intelligence
1974; Sternberg & Kaufman, 1998). For example, in a
that a tape measure provides of height. When we are
study of people’s conceptions of intelligence (Sternberg,
dealing with the lay audiences who learn about our work,
Conway, Ketron, & Bernstein, 1981; see also Sternberg,
it is especially important that we acknowledge that we
1985), Sternberg and his colleagues found that laypersons
have nothing even vaguely close to a “tape measure” of
had a three-factor view of intelligence as comprising ver-
bal, practical problem-solving, and social competence abil-
ities. Only the ?rst of these abilities is measured by con-
Intelligence and Race
ventional tests. Experts in different occupations in the
“Out of Africa”
United States have somewhat different conceptions of in-
telligence, with their views of the relevant attributes tend-
Most scientists who study such matters believe that those
ing to match the requirements of their occupations (Stern-
humans of whom we are descendants all lived in Africa
berg, 1985). And conceptions of intelligence around the
(e.g., Tishkoff et al., 1996; Tishkoff & Kidd, 2004; Walter
world vary even more than they do in the United States
et al., 2000). They ?rst appeared roughly 200,000 years
(Grigorenko et al., 2001; Sternberg, 2004b; Yang & Stern-
ago. For whatever reasons—to ?nd food, to satisfy wan-
berg, 1997a, 1997b).
derlust, to ?nd better protection against predators, to ?nd
The way intelligence is usually de?ned in studies of
more land—small numbers of unrepresentative people
the alleged relationships among intelligence, race, and
started to migrate out of Africa about 100,000 years ago
genetics is in terms of Boring’s (1923) operational de?ni-
(Stringer, 1990).
tion of intelligence as whatever it is that IQ tests measure.
The “out-of-Africa” hypothesis places the ?rst immi-
This de?nition is unsatisfactory for at least three different
grants from Africa in southwestern Asia. Over the course
reasons. First, it is circular, de?ning the construct in terms
of tens of thousands of years, that initial non-African
of the operation and the operation in terms of the con-
population expanded until now at least some of its descen-
struct. Second, so-called IQ tests do not all measure the
dants can be found on all continents and in most regions of
same thing (Mackintosh, 1998). Third, as indicated, theo-
those continents except for Antarctica, which, in general, is
rists of intelligence do not themselves agree as to what
too cold to be hospitable, at least for modern humans. As
intelligence is.
people migrated, they adapted so as better to ?t their
For convenience, we can follow Boring and operation-
environments. Much of that adaptation was cultural— dif-
ally de?ne intelligence in terms of IQ as measured by
ferent clothing, different foods, for example— but some of
January 2005 ? American Psychologist

may be very different from those in the parent population.
As the new population grows over a few generations, the
magnitude of the sampling error per generation decreases,
and the new population will continue to have very different
frequencies from the parent population. This extreme form
of random genetic drift is referred to as a “founder effect,”
because the population expanded from very few founders
with a relatively restricted gene pool. For example, avail-
able evidence suggests that a small group of individuals left
Africa and over time allele frequencies changed markedly
from those in the African populations left behind.
The third mechanism is gene ?ow or genetic ex-
change, by which interbreeding among certain groups of
individuals potentially results in those populations becom-
ing increasingly similar to each other. Two populations that
start off quite different genetically, if they mate, can pro-
duce offspring that represent the genes present in both of
the original populations.
The fourth mechanism is natural selection, by which
organisms with gene patterns that are adaptive to a given
Elena L.
environment become more prevalent over time. For exam-
ple, organisms that can adapt to changing climatic patterns
are at an advantage over those that adapt only with great
Migration and Adaptation
it was genetic. However, it is dif?cult to prove that traits
seen to differ are truly the result of different selective
Although all of these mechanisms are of importance, here
pressures, that is, genetic adaptations. A major reason for
we illustrate only that of natural selection. Consider the
the dif?culty is that at the genetic level there are quantita-
following example. During the Industrial Revolution in
tive differences in frequencies of genetic variants, not
late-19th-century England, a particular dark-colored moth
qualitative genetic differences, among populations. When
became more prevalent than a related light-colored moth.
multiple forms of a DNA sequence, either a coding se-
Why? It is believed industrial pollution had blackened the
quence or a noncoding sequence, are present, the sequence
forests and improved the darker moth’s camou?age against
is referred to as polymorphic and the forms as alleles at the
predators such as birds. The light-colored moth was too
polymorphism. Among populations of various kinds, allele
visible to survive. More recently, however, with restric-
frequency differences at polymorphisms are the rule be-
tions on air pollution, the light moth has made a comeback
cause of the chance effects known as random genetic drift.
(Cook, 2003). The point, of course, is that natural selection
In other words, as a result of both natural and social events,
is a constantly shifting process. It is in?uenced not only by
only some genotypes are transmitted through generations;
an organism’s biology, but also by the interaction of that
the others are lost. The lack of predictability in who will
biology with environmental conditions (Sternberg, 2004c).
have children and who will not introduces powerful ran-
Is it better from the standpoint of adaptation to the
dom noise into allele frequencies between generations.
physical environment to be a black moth or a light-colored
Thus, observing different allele frequencies does not, in
moth? It depends on the interaction between the organism’s
and of itself, imply that local selection has operated.
attributes, including color, and the particular environment.
Is it better from the same adaptive standpoint to be a Black
Mechanisms of Genetic Influence
person or a light-colored person? The answer is the same,
Four mechanisms have in?uenced the genetic evolution of
of course. In zones with more intense exposure to sunlight,
populations (Templeton, 2002). We consider each in turn.
darker skin puts individuals at an adaptive advantage. The
The ?rst is mutation, by which genes change in
melanin that acts as a pigmentation to produce darker skin
random ways. Mutation results in the rise of both func-
better protects individuals against the damage that large
tional (i.e., coding) and nonfunctional (i.e., noncoding)
amounts of ultraviolet radiation can cause to the skin. Left
unchecked, this radiation increases susceptibility to skin
The second is random genetic drift, by which alleles
cancer, especially melanoma, a form of skin cancer that
in ?nite populations may change in frequency over time as
easily can become fatal. In zones with weaker exposure to
a result of the accumulation of random sampling error in
sunlight, lighter skin is an advantage.
the passing on of alleles from generation to generation.
One explanation of lighter coloration pertains to vita-
When a very small number of individuals migrate and start
min absorption. People rely on sunlight to produce active
a new population, the sampling error (random genetic drift)
vitamin D in the capillaries. The active form does not
is very large, and allele frequencies in the new population
occur in great quantities in the food most people eat.
January 2005 ? American Psychologist

humans indirectly resulted from the pattern of expansion
and migrations accompanied by random genetic drift. Over
the years, frequencies of DNA variants changed only
slightly in terms of total DNA composition but changed
enough to produce differences, many of which we still do
not fully understand. The changes are numerous. Less than
1% of human DNA varies globally, in the 3 billion nucle-
otide positions in the human genome; however, that 1%
creates a large number of potential differences between any
two people. Some regional differences are observable, and
others less so. For example, one will see larger proportions
of blond hair and blue eyes in people born in European
countries than in those born in Asian ones. In addition, one
will see shorter people, on average, among those born in
Asia than among those born in Europe, and one will see
wider noses in West Africa, on average, than in East
Africa. In other words, within geographic groups, there is
variation, and, as it turns out, tremendous variation.
Race as a Social Construction
Kenneth K.
Where does race ?t into the genetic pattern? Actually, it ?ts
nowhere. Race is a socially constructed concept, not a
biological one. It derives from people’s desire to classify.
People seem to be natural classi?ers. Perhaps this tendency
re?ects, in part, what Gardner (1999a, 1999b) has referred
Indeed, often milk is supplemented with vitamin D to
to as “naturalistic intelligence.” Or perhaps it merely re-
prevent de?ciencies. Lighter skin allows greater bodily
?ects a need to discern order in or even to impose it on
production of vitamin D . De?ciencies in vitamin D can
nature. Any set of observations can be categorized in
cause rickets in children and osteoporosis in adults (O’Neil,
multiple ways. People impose categorization and classi?-
cation schemes that make sense to them and that, in some
A second explanation is of a different kind. There is as
cases, favor their particular goals.
yet no conclusive evidence of positive selection for light
If one looks at geographic patterns, one will ?nd many
coloration. Instead, evidence to date may indicate that light
attributes that correlate with geography; nearby populations
pigmentation in climates distant from the equator repre-
tend to be similar and distant populations dissimilar. This
sents a lessening of the selective factors that lead to dark
pattern is similar to common ideas of socially de?ned races
pigmentation near the equator rather than to any particular
but is more complex (K. K. Kidd, Pakstis, Speed, & Kidd,
factors leading to lighter pigmentation per se (Harding et
2004; Rosenberg et al., 2002; Tishkoff & Kidd, 2004).
al., 2000). Individual moths or other animals do not radi-
People in different places come to demonstrate different
cally change in color in the course of their lifetimes.
characteristics by adaptations to different environments,
Rather, over time, those descendants that are better adapted
such as heterozygosity for sickle-cell hemoglobin as a
are more likely to survive and reproduce, and thus distri-
partial protection against malaria, as well as by accumula-
butions of traits change. Human populations adapt over
tion of random genetic drift. But as is so often the case, the
many generations, but not all organisms do. Some adapt
same trait that may be adaptive in one circumstance may be
very rapidly. Generations of bacteria, for example, adapt
maladaptive in another. For example, there is no advantage
rapidly because of their extremely rapid rates of reproduc-
of sickle-cell hemoglobin in the absence of malaria, and the
tion. It is for this reason that the same medication, amoxi-
anemia that results in homozygotic individuals poses a
cillin, that was effective in treating ear infections in the
serious disadvantage.
children of 20 years ago is so much less effective in treating
Other adaptations are equally ?ckle. Today, our pop-
ear infections in the children of today. Bacteria have
ulation is paying the price of tens of thousands of years in
adapted, in the same way that malaria parasites have
which people became genetically programmed to enjoy fats
adapted to many quinine-based treatments and in the same
and sugars and to eat as much of them as they could when
way that the HIV virus is adapting to the medications being
they had the opportunity. In the contemporary environ-
used to treat it. All biological populations adapt, whether
ment, the result is high levels of overweight and obesity.
bacterial, human, or anything else.
Some people have more of a genetic predisposition to gain
There is another key fact in this story. Aside from the
weight than others. Social strati?cation— classifying peo-
explanations of skin color, there are not many scienti?cally
ple into categories of higher and lower status in a society—
supportable selective explanations for the differences ob-
has already ensued on the basis of weight (Brownell &
served in people from different parts of the world. It is
Horgen, 2003). Whether, ultimately, people with a genetic
probable that much of the variation seen among groups of
predisposition toward fatness will be classi?ed as being of
January 2005 ? American Psychologist

a separate race remains to be seen. The point is that an
Jews who do not view themselves as priests exhibit this
adaptation that is positive at one time or place may be
pattern. What conclusion is to be drawn? Well, the correct
indifferent at another and negative at still another.
conclusion is that different groups of people will differ in
One could pick any of a number of traits correlated
various respects. The authors of the study concluded that
with geographic patterns and ?nd correlations with other
one could infer a genetic Jewish priestly line dating back to
related traits. It would be foolhardy, however, to view any
the biblical Aaron (Skorecki et al., 1997). Other bases for
one of these traits as causative of the others. That is what
differentiation could be chosen as well, including the afore-
people have done who have viewed differences in so-called
mentioned one of girth.
races as somehow causative of differences in IQ. It also
As another example, Fish (2002) has pointed out that
would be foolhardy to group fairly arbitrary sets of traits
people who have lived over many generations in cold
and constructs that one then rei?es as being natural, some-
climates, such as Eskimos, have tended to develop rounded
how God-given categories. One will ?nd a distribution of
bodies to maintain heat and thus stay warmer. Some pop-
traits in any of these groups, with only slightly more
ulations in very hot climates, such as the Masai, have
differentiation in comparisons involving individuals from
tended instead to develop lanky bodies. The hypothesis is
different groups than in comparisons involving individuals
that the high ratio of surface area to volume results in their
from the same group (K. K. Kidd et al., 2004). Why would
radiating a high amount of heat and thus staying cooler.
people do this, then? One reason is to justify existing social
Although reasonable, both adaptation hypotheses lack rig-
strati?cations or to create new ones.
orous scienti?c proof. Possibly, they could be just coinci-
We could of course refer to moths as being of different
dences. Scientists do not know for sure.
“races” (black and white) in the same way we sometimes
In the American folk taxonomy of race, as argued by
refer to humans as being of different “races.” We do not
Fish (2002), lanky and rounded people can represent, re-
typically use the term for moths, presumably because we
spectively, two kinds of Blacks and Whites. But one could
are less interested in creating social strati?cations for moths
as easily decide that a more “basic” taxonomy of races
than for people, and race is one way to help create these
would be in terms of lanky and rounded bodies, in which
strati?cations. Of course, we recognize that our article may
case there would be Black and White members of the lanky
have the opposite effect from that intended: Some believers
and rounded races. One would ?nd a number of genetic
in biological race may realize that moths (and perhaps
patterns that, on average, correspond to lankiness and
dogs, cats, and other animals that come in multiple colors)
roundedness, in the same way one would ?nd genetic
have been sorely neglected in the literature on racial dif-
correlate patterns corresponding to darker versus lighter
ferences and that there is still time to remedy this situation.
skin, Cohens versus non-Cohens, or basketball players
To the extent we de?ne race as simply different sets of
versus wrestlers.
physical features, we could say, of course, that the moths
It has been argued that the challenges faced by those
are of different races. But the term, used in this way,
who migrated to northern climates were greater than those
becomes simply a word for saying the moths look different!
faced by people in southern climates and that this differ-
And the surplus meaning associated with the word, at least
as it is used in human descriptions, vanishes.
ence might have led to higher intelligence levels among
Over time, peoples who migrated changed both by
those who went northward (see Rushton, 1995). However,
chance and by adaptation to their environments in various
anyone who has spent any signi?cant time in Africa might
ways. What is “good” depends on the adaptations that need
well dispute this claim. One of the greatest challenges of
to be made, and these adaptations change from time to time
tropical climates is ?ghting tropical diseases to survive, and
and place to place. For example, our ancestors in Africa
the challenges of ?ghting diseases are greater in the tropics
were almost certainly dark-skinned because dark skin pro-
than they are further north. Indeed, children acquire from
vided better protection against the particular challenges of
an early age specialized knowledge, not acquired further
the environment, most notably ultraviolet and other harm-
north, regarding natural herbal medicines that can be used
ful forms of radiation. Other traits, such as straight or curly
to combat tropical illnesses (Sternberg et al., 2001). To the
hair, have no evident adaptive value, and population dif-
extent that warmer climates encourage greater aggression
ferences probably re?ect chance differences. Curiously,
(see, e.g., Nisbett & Cohen, 1996), learning how to com-
then, socially constructed judgments as to how socially to
pete successfully so as to survive in such environments also
stratify people are made on bases that have no relation to
might promote intellectual development. We are not argu-
the original reasons people came to look one way or
ing that people in warmer climates did indeed develop
higher intelligence but, rather, that one could create spec-
There is nothing special about skin color that serves as
ulative arguments supporting greater intellectual growth in
a basis for differentiating humans into so-called races. Any
such climates, as has been done to support the notion that
two groups of people that differ in one way are likely to
there was greater intellectual growth as a result of chal-
differ in a cluster of ways. For example, as noted by Marks
lenges up north. Indeed, post hoc evolutionary arguments
(2002), geneticists have found that 54% of people who
made in the absence of fossils at times can have the
have designated themselves as Hebrew priests, many of
character of ad hoc “just so” stories designed to support, in
whom have the surname of Cohen, have a certain pattern of
retrospect, whatever point the author wishes to make about
two genes on the Y chromosome. In contrast, only 33% of
present-day people.
January 2005 ? American Psychologist

Differences in socially constructed races stem largely
makes one Black to some degree. So one can be light
from geographic dispersions that began about 100,000
Black, medium-skinned, or dark Black, but one is still
years ago and continued until about 3,000 years ago in
Black. Even if individuals of mixed parentage inherited
some areas. Today we see the physical correlates left by
none of the physical features of blackness, they would still
these dispersions. Much of that variation is continuous
be classi?ed as Black, although they might pass for White
across distances, but with different traits showing different
(Fish, 2002). In areas where Blacks are of higher social
rates and patterns of change. What “race” does is to reify
status, degrees of whiteness may all be seen as departures
these differences as deriving from some imagined natural
from true blackness.
grouping of people that does not in fact exist, except in our
The concept of race serves a social rather than a
biological purpose. Different types of parentage have, at
What we see in terms of skin color correlates very
various times and places, given rise to racial labeling (e.g.,
well with our developed folk taxonomies but only weakly
“Aryan race,” “German race,” and “Jewish race”). In apart-
with genetic differentiations. For example, the amount of
heid South Africa, the races were Bantu (Black African),
genetic variation in Africa is enormous and is much greater
colored (including people of perceived mixed descent),
than that in the rest of the world (e.g., Tishkoff & Kidd,
Indian/Asian, and White. In contemporary North American
2004; Tishkoff & Williams, 2002). In contrast, in terms of
society, we mix together the Black and colored “races,”
the amount of phenotypic variation, or differences in ap-
somehow believing, as noted, that individuals who possess
pearance, Africa is at least comparable to the rest of the
any degree of nonwhiteness should be grouped in the Black
world. The phenotypic differences are nevertheless notable.
category. Hitler designated as a member of the Jewish race
For example, in Africa, one can ?nd very tall Masai and
anyone who had supposed Jewish blood, which could date
very short Pygmies who probably gained an adaptive ad-
back to one’s great-grandparents.
vantage by virtue of their shortness for locomotion through
In parts of Brazil, the supposed races are different
forest vegetation (Fish, 2002). Yet, some may lump to-
again (Fish, 2002). A loura has straight blond hair, blue or
gether all of these Africans as the same, despite the fact that
green eyes, light skin color, and a narrow nose and thin
genetically they differ more from each other, in many
lips. A branca has light skin color, eyes and hair of any
cases, than they do from those who perceive themselves to
color, a nose that is not broad, and nonthick lips. In Brazil,
be of higher social, or even biological, value.
Fish pointed out, a branca is White. In the United States, a
Humans have devised various metaphors for under-
branca individual from Brazil would more likely be clas-
standing why some people are more successful, according
si?ed as “Hispanic.” Then there is a morena, who has
to whatever standards society invents, than others. Usually,
brown or black hair that is wavy or curly but not tightly
comparisons are drawn by those who consider themselves
curly and has tan skin, a nose that is not narrow, and lips
successful for the bene?t of others who consider them-
that are not thin. Morenas in the United States are classi?ed
selves successful or on the road to success (e.g., see
as Black or Hispanic. There are a number of other Brazilian
Herrnstein & Murray’s, 1994, discussion of meritocracy).
terms used to describe socially constructed racial catego-
A curiosity of history is that people come to believe in the
ries, such as mulata and preta, and to the Brazilians these
reality of their own metaphors. For example, some have
terms are every bit as real as the Black, White, and Asian
believed, and some still believe, in “royal blood.” Educated
categories are in the United States. They are real. But as in
people probably realize that the expression is metaphorical;
the United States, they are folk, not biological, taxonomies
others probably believe that the blood of royals differs in
used to socially stratify people, often in the name of sci-
some key respect from the blood of others.
ence. At best, the effects are innocuous. At worst, they
For readers of this journal, a biological concept of
become the bases of genocide.
“royal blood” probably seems silly. At the same time,
People generally use skin color to distinguish races,
however, we know that there are distinguishing blood
but not always. During the genocide in Rwanda, the Hutus
groups. For example, most of us are familiar with the ABO
used other physical attributes, such as height, to distinguish
and Rh blood-typing systems. According to Lewontin
Tutsis. Because there had been so much intermarriage
(1997), there are roughly 35 blood group systems, with 15
between Hutus and Tutsis, the distinctions were generally
serving at least somewhat effectively to distinguish differ-
weak, and many people were killed simply because they
ent human populations. Royal blood, at least within fami-
seemed closer to the imagined Tutsi prototype than the
lies, may well be distinguishable in terms of blood groups,
Hutu one, regardless of their origins. At the time this article
just as the blood of nonroyal families would. So in this
was being written, massacres were going on in parts of
trivial sense royal blood can be said to exist, but differently
Darfur, Sudan, motivated by similar socially constructed
in different royal families. In this same trivial sense, there
can be differences in distributions of blood groups across
The history of the concept of race is inextricably
religious groups, people with different body shapes, or
intertwined with attempts by the winners to explain or
people with different skin colors.
justify why they perceive themselves to be winners. Con-
How mixtures are labeled is a function of social status.
sider, for example, the term Caucasian. It is an odd term,
In the United States, Blacks generally have lower social
in some ways, because although it is used to refer to
status than Whites, so supposed admixtures of blood de-
“Whites,” in Russia people from the Caucuses are consid-
termine degrees of “blackness.” Possessing any blackness
ered dark relative to many other Russians. Especially be-
January 2005 ? American Psychologist

cause of dif?culties in Chechnya and surrounding areas,
that race is a socially constructed, not an evolutionary
these dark Caucasians today are viewed with suspicion and
determined or biologically supported, concept (Smedley,
distrust in much of Russia. So the term that is accepted as
1993). Of course, science does not ?nd truth by majority
“scienti?cally” identifying White people in the United
rule. The problem with the concept of race is not that it is
States, often in preference to the term White to give more
supported by only a minority of anthropologists, but that it
of a feeling of scienti?c classi?cation, is used in a way that
has no scienti?c basis. Moreover, attempts to link intelli-
is largely opposite in contemporary Russia. Where did the
gence, race, and genetics have also lacked an adequate
term come from then? It was coined by Johann Friedrich
scienti?c foundation.
Blumenbach (as cited in Gould, 1994), who chose the name
Intelligence, Race, and Genetics
because he believed that the Georgians, from the Mount
Caucasus region, are the most beautiful race of men (his
The explosion of genetic research within the past 10 –15
words). The term stuck. So people in English-speaking
years has brought the concept of race back to the surface,
countries with white skin have the honor of having a name
with some researchers arguing that new molecular data
they imagine to be the formal label for their race, repre-
have given the concept of race new signi?cance in the
senting what one naturalist in 1795 believed was the most
context of medicine and public health (Risch, Burchard,
attractive “race” and what today largely is believed to have
Ziv, & Tang, 2002). One might think that, because the
rather dark as opposed to white skin, according to Russian
concept of race originated as a social proxy for the descrip-
standards. Thus, the term is scienti?cally unsupportable
tion of biological differences, at least the biologists study-
and part of an old racist typology. The term is just as racist
ing race would agree on its de?nition. However, the reality
as Negroid and Mongoloid, terms the politically sensitive
is different. When variation in genetic markers or allelic
American will not use.
variants is considered, opinions range widely. One view is
that socially de?ned racial differentiation is most pro-
Origins of the Concept of Race
nounced and even discontinuous when it is evaluated on the
Whence emerged the concept of “race”? The concept of
basis of continental residence (Risch et al., 2002). A second
race as a classi?cation scheme representing allegedly nat-
view is that there is continuity in genetic variation across
ural “types” distinguishable on the basis of clear visual
socially de?ned races and that various races are not dis-
attributes such as skin or eye color, hair texture, and certain
tinct; rather, there is a single lineage with a shared evolu-
facial and bodily features was initially introduced in the
tionary fate (Templeton, 1999). According to this view,
17th century (Schiebinger, 1993). However, it took these
there is no biological value in the concept of race (Anon,
ideas almost a century to attract the attention of scienti?c
2001; Schwartz, 2001). However, in considering these po-
“authorities.” According to Gould (1994), Linneaus (in
sitions, it is important to understand that, even within these
1758) ?rst proposed four races: Americanus, Europaeus,
extreme views, researchers agree that although human pop-
Asiaticus, and Afer, or African. He also alluded to two
ulations might differ dramatically in terms of proportions
other categories that did not prove as useful for social
or frequencies of alternative forms of genes (i.e., allelic
purposes as the other categories: wild boys (feral children)
variants), they do not differ in the kinds of genes they
discovered in the forests and monsters, and hairy men with
possess (Snyder, 1951). In fact, both extreme views may
long tails who emerged from tales of travelers. Blumen-
have some merit (Tishkoff & Kidd, 2004).
bach (1775/1969), building on the work of Linneaus, ?rst
A key argument of this article is that race is every bit
proposed a grouping of “races,” namely, Caucasians, Mon-
as real as royal blood. It exists in some trivial sense as a
golians, Ethiopians, and Malays. This early history was no
correlate of various biological groupings stemming from
more scienti?c than the later history was to be. That is, race
migration and breeding patterns, and no more. However,
started out as a not so subtle way of socially classifying
just as royal families are usually interconnected and dif?-
and, ultimately, stratifying people hierarchically, as better
cult to partition off fully, de?ning the boundaries between
or worse. For example, Linneaus viewed the White as
races is impossible. As The American Heritage Dictionary
sanguine and muscular and the Black as phlegmatic and
of the English Language (2000) notes in regard to usage,
“many cultural anthropologists now consider race to be
Historically, the formation of the concepts of race and
more a social or mental construct than an objective biolog-
ethnicity was in?uenced by two main perspectives (Kevles,
ical fact” (p. 1441).
1995). One perspective was formed in the context of the
Although attempts have been made to establish genes
eugenics movement and was used to refer to presumed
for intelligence (Plomin, 1997; Plomin & Spinath, 2004),
biological differences between socially de?ned populations
none have been conclusively identi?ed. A project aimed at
(Huxley, 1951). The other perspective was formed in the
identifying quantitative trait loci (QTL) contributing to
context of physical anthropology and the social sciences
genetic variation in intelligence (Plomin & Spinath, 2004)
and rejected the idea of the biological signi?cance of racial
has attempted to establish QTLs associated with intelli-
classi?cations. It argued that race and ethnicity are primar-
gence. To date, however, whatever positive ?ndings have
ily cultural and historical products of human history (Boas,
emerged have either failed to replicate (Chorney et al.,
1942). Today, whereas some still defend the basis for the
1998; Hill, Chorney, & Plomin, 2002; Hill et al., 1999;
“gene-based evolutionary theory” of race (Rushton, 1995),
Plomin et al., 1995) or produced weak signals that have not
the majority of cultural anthropologists are in agreement
yet been attempted to be replicated with independent sam-
January 2005 ? American Psychologist

ples (Plomin et al., 2001). Of course, the future may bring
For example, being born with two eyes is 100% under
conclusive identi?cations; we simply do not know yet.
genetic control (except in the exceedingly rare case of
As a result, virtually all attempts to study genes re-
severe dismorphologies, with which we do not deal here).
lated to intelligence have been indirect, through studies of
Regardless of the environment into which a human being is
heritability. But heritability is itself a troubled concept. Are
born, he or she will have two eyes. But it is not meaningful
differences in intelligence between so-called races herita-
to speak of the heritability of having two eyes, because
ble? This question is dif?cult to answer in part because it is
there are no individual differences. Heritability is not 1; it
dif?cult even to say what can be concluded from the
is meaningless (because there is a zero in the denominator
heritability statistic commonly used. Consider some facts
of the ratio) and cannot be sensibly calculated.
about heritability (Sternberg & Grigorenko, 1999).
Consider a second complementary example, occupa-
tional status. It is associated with a statistically signi?cant
What Heritability Tells Us
heritability coef?cient (Plomin, DeFries, & McClearn,
1990), but certainly it is not under direct genetic control.
Heritability (also referred to as h2) is the ratio of genetic
Clearly, there is no gene or set of genes for occupational
variation to total variation in an attribute within a popula-
status. How could it be heritable, then? Heredity can affect
tion. Thus, the coef?cient of heritability tells us nothing
certain factors that in turn lead people to occupations of
about sources of between-population variation. Moreover,
higher or lower status. Thus, if factors such as intelligence,
the coef?cient of heritability does not tell us the proportion
personality, and interpersonal attractiveness are under
of a trait that is genetic in absolute terms, but rather the
some degree of genetic control, they may lead in turn to
proportion of variation in a trait that is attributable to
differences in occupational status. The effects of genes are
genetic variation within a speci?c population.
at best indirect (Block, 1995). Other attributes, such as
Trait variation in a population is referred to as phe-
divorce, may run in families (i.e., show familiality), but
notypic variation, whereas genetic variation in a population
again they are not under direct genetic control; in fact, the
is referred to as genotypic variation. Thus, heritability is a
reason for such familiality may be that these attributes are
ratio of variation in the phenotype being considered due to
culturally “inherited.”
relevant genetic variation to phenotypic variation. Herita-
bility has a complementary concept, that of environmen-
Variation in Heritability Within a Given
tality. Environmentality is a ratio of variation in the phe-
notype being considered due to relevant environmental
Heritability is not a ?xed value for a given attribute. Al-
variation to phenotypic variation. Note that both heritabil-
though we may read about “the heritability of IQ” (e.g.,
ity and environmentality apply to populations, not to indi-
Herrnstein & Murray, 1994), there really is no single ?xed
viduals. There is no way of estimating heritability for an
value that represents any true, constant value for the heri-
individual, nor is the concept meaningful for individuals.
tability of IQ or anything else, as recognized by Herrnstein
Consider a trait that has a heritability statistic of 70%; it is
and Murray (1994) and most others in the ?eld (e.g.,
nonsense to say that the development of the trait in an
Bouchard, 1997). Heritability depends on many factors, but
individual is 70% genetic.
the most important one is the range of environments. Be-
Heritability is typically expressed on a 0 to 1 scale,
cause heritability represents a proportion of variation, its
with a value of 0 indicating no heritability whatsoever (i.e.,
value will depend on the amount of variation. As Herrn-
no genetic variation in the trait) and a value of 1 indicating
stein (1973) pointed out, if there were no variation in
complete heritability (i.e., only genetic variation in the
environments, heritability would be perfect, because there
trait). Heritability and environmentality add to unity (as-
would be no other source of variation. If there is wide
suming that the error variance related to measurement of
variation in environments, however, heritability is likely to
the trait is blended into the environmental component).
Heritability tells us the proportion of individual-difference
When one speaks of heritability, one needs to remem-
variation in an attribute that appears to be attributable to
ber that genes always operate within environment contexts.
genetic differences (variation) within a population. Thus, if
All genetic effects occur within a reaction range such that,
IQ has a heritability of .50 within a certain population, then
inevitably, environment will have differential effects on the
50% of the variation in scores on the attribute within that
same genetic structure. The reaction range is the range of
population is due (in theory) to genetic in?uences. This
phenotypes (observable effects of genes) that a given ge-
statement is completely different from the statement that
notype (latent structure of genes) for any particular at-
50% of the attribute is inherited.
tribute can produce, given the interaction of environment
An important implication of these facts is that herita-
with that genotype. For example, genotype sets a reaction
bility is not tantamount to genetic in?uence. An attribute
range for the possible heights a person can attain, but
could be highly genetically in?uenced and have little or no
childhood nutrition, diseases, and many other factors affect
heritability. The reason is that heritability depends on the
the adult height realized. Moreover, if different genotypes
existence of individual differences. If there are no individ-
react differently to environmental variation, heritability
ual differences, there is no heritability (because there is a
will show differences depending on the mean and variance
zero in the denominator of the ratio of genetic to total trait
in relevant environments (Lewontin, 1974). Thus, the sta-
variation in a given population).
tistic is not a ?xed value. There are no pure genetic effects
January 2005 ? American Psychologist

on behavior, as would be shown dramatically if a child
example, they may tell us something about the extent to
were raised in a small closet with no stimulation. Genes
which individual differences in the measured intelligence
express themselves through covariation and interaction
of people in a particular group are associated with genetic
with the environment, as discussed further later.
factors. They say nothing about sources of between-popu-
lation differences in levels of measured intelligence.
Heritability and Modifiability
Lewontin (1972, 1982) provided an illustration of the
Because the value of the heritability statistic is relevant
impossibility of making between-population claims from
only to existing circumstances, it does not and cannot
within-population data. Speci?cally, in a study involving
address a trait’s modi?ability. A trait could have zero,
the use of a set of protein markers (blood groups, serum
moderate, or even total heritability and, in any of these
proteins, and red blood cell enzymes) as indicators of
conditions, be not at all, partially, or fully modi?able. The
genetic differences between populations, Lewontin esti-
heritability statistic deals with correlations, whereas mod-
mated that roughly 85% of genetic variance occurs between
i?ability deals with mean effects. Correlations, however,
any two individuals within any socially identi?ed racial
are independent of score levels. For example, adding a
group; roughly 9% occurs among different populations
constant to a set of scores will not affect the correlation of
within a socially identi?ed race; and only the remaining
that set with another set of scores.
6%–7% occurs between socially identi?ed races. Other
Consider height as an example of the limitation of the
researchers have arrived at the same conclusions using
heritability statistic in addressing modi?ability. Height is
more powerful data sets obtained with more technologi-
highly heritable, with a heritability level above .90. Yet
height also is highly modi?able, as shown by the fact that
Minch, & Cavalli-Sforza, 1997; K. K. Kidd et al., 2004;
average heights have risen dramatically throughout the past
Rosenberg et al., 2002; Tishkoff & Kidd, 2004) or through
several generations.
simulation analyses (Templeton, 1999).
As an even more extreme example, consider phenyl-
Different populations—racial, ethnic, religious, or
ketonuria (PKU). PKU is a genetically determined, reces-
whatever—may encounter quite different environments, on
sive condition that stems from a mutation in a single gene
average. Whatever the heritability of intelligence or other
on chromosome 12 (with a heritability of 1), and yet its
attributes within a given setting, no conclusions can be
effects are highly modi?able. Feeding an infant with PKU
drawn about heritability as a source of differences across
a diet free of phenylalanine prevents the mental retardation
settings. The fact that IQs have increased so much over the
that otherwise would become manifest. Note also that a
years (Neisser, 1998) suggests that environments differ
type of mental retardation that once incorrectly was thought
widely over time. They probably differ substantially as
to be purely genetic is not. Rather, the mental retardation
well for members of different groups at a given time.
associated with PKU is the result of the interaction with an
Nisbett (1995, 1998) reviewed published studies in-
environment (a “normal” diet) in which the infant ingests
vestigating sources of differences in cognitive abilities
phenylalanine. Take away the phenylalanine and you re-
between White and Black individuals. These studies, in-
duce the level of— or, in optimal cases, eliminate—mental
volving designs unlike the behavior-genetic studies de-
retardation. Note that the genetic endowment does not
scribed earlier, have directly sought to investigate genetic
change: The infant still has a mutant gene causing PKU.
and environmental effects on intelligence. For example,
What changes is the manifestation of its associated symp-
one design has been to look at Black children adopted by
toms in the environment. Similarly, we cannot change (at
White parents. Of seven published studies, six supported
least on the basis of our knowledge today) the genetic
primarily environmental interpretations of group differ-
structure underlying manifestations of intelligence (or any
ences, and only one study did not; the results of the non-
other trait); however, we can change those manifestations
supporting study (Scarr & Weinberg, 1976, 1983) were
or expressions of genes in the environment. Thus, knowing
equivocal. What the Scarr and Weinberg study did show is
the heritability of a trait does not tell us anything about its
that IQs of adopted children are more similar to those of
their biological mothers than to those of their adopted
mothers. Less clear are the “racial” implications of their
Within-Population Effects Versus Between-
Populations Effects
Moreover, there is much published evidence indicat-
One of the worst intellectual slips made by investigators of
ing that heritability estimates vary across populations. For
heredity and environment (or rather, most often, by inter-
example, estimates of the heritability of IQ in Russian twin
preters of ?ndings on heredity and environment) is to
studies conducted in the Soviet era tended to be higher than
generalize the effects of within-population studies between
comparable estimates in the United States (Egorova, 1988;
populations. For example, some investigators have made
Grigorenko, 1990; Iskoldsky, 1988). This observation
attributions about effects of racial or ethnic group differ-
made sense: Environmental variation in Russia under the
ences on the basis of behavior-genetic studies (Herrnstein
Soviet regime was constrained; consequently, heritability
& Murray, 1994), even while admitting that such conclu-
estimates were higher. Most of the IQ heritability studies
sions are sometimes ?awed. All of the behavior-genetic
up to today have been carried out in various countries of the
designs used in the studies noted earlier can ascertain
developed world. Relatively little information exists re-
effects of genetic variation only within populations. For
garding the heritability of IQ in the developing world,
January 2005 ? American Psychologist

although some studies suggest that such heritability may be
with a separate expansion into Melanesia and Australia.
substantial, at least outside the Western countries that most
Associated with all of these expansions is accumulating
often have been studied (Bratko, 1996; Lynn & Hattori,
random genetic drift at all polymorphic sites of the ge-
1990; Nathwar & Puri, 1995; Pal, Shyam, & Singh, 1997).
nome. Thus, allele frequencies generally show gradual
Recently, Turkheimer, Haley, Waldron, D’Onofrio, and
changes as one moves around the world. Of course, recent
Gottesman (2003) showed that heritabilities differ radically
migrations (over the past few thousand years) of estab-
across socioeconomic groups. Obviously, without even
lished populations into already-occupied regions can result
knowing much about estimates of the heritability of IQ in
in some adjacent populations having very different allele
different populations, we cannot speculate at this point
frequencies, but that has been rare until historic times.
about differences across these populations.
Today in the United States, for example, we have popula-
In summary, heritability estimates do not explain the
tions from very different parts of that geographically con-
genetic regulation of behavior and do not provide accurate
tinuous spectrum of allele frequencies. These distinct allele
estimates of the strength of this regulation. Heritabilities
frequencies do not mean that different “races” exist, only
are like snapshots of a dancer. They will not tell us either
that different parts of a continuum have been sampled. An
what the dance is about or what is coming next in the
analogy is the distinction among the colors blue, yellow,
dance. The true genetic nature of humans is far from being
and red as samples from a continuous spectrum of light.
de?ned. But what is absolutely clear is that genes do not act
These colors have meaning only because the spectral sen-
in a vacuum; they act in the environment, and their actions
sitivities of the photoreceptors in our eyes and the neuro-
can be altered by the environment.
logical circuits interpreting the signals interact with a label
arbitrarily imposed on some narrow range of wavelengths
Biological and Genetic Data as Related to the
from a continuous spectrum.
Concept of Race
There is no question that populations, de?ned geo-
One would hope that, because the concept of race was
graphically, demonstrate dramatic variability in frequen-
originally, if falsely, conceived as a concept to signify the
cies not only for the several million normal polymorphisms
degree of biological differences between groups of people,
not associated with causing genetic disorders but also for
the strongest support for the concept would originate from
many disease-related genetic alleles (variants). The genetic
biological and genetic data. Does it? Here we review some
alleles (variants) can be readily seen in ALFRED, the
examples of the relevant research.
ALlele FREquency Database (
First, it appears that the global distribution of genetic
The issue is not whether this variation is present or not; the
variation in humans is not easily sorted according to so-
issue is whether explaining this variation should occur at
called races. As reviewed recently (Bamshad et al., 2003;
the levels of populations per se (e.g., Lapps, Chuvash,
Bamshad, Wooding, Salisbury, & Stephens, 2004; K. K.
Nyanja, or Corsicans), continents (e.g., Europe or Africa),
Kidd et al., 2004; Tishkoff & Kidd, 2004), scientists have
or alleged races. According to our review of the literature,
studied diverse populations for many polymorphisms.
variation that seems to be meaningful and transferable into
These studies involve polymorphisms in the nuclear DNA,
helpful public health or educational policies is at the level
including variation in the nonrecombining Y chromosome
of speci?c populations. Global socially constructed catego-
(Underhill et al., 2000) and autosomal (i.e., located on
ries such as race do not appear to be useful proxies for
chromosomes other than Y and X) markers (e.g., K. K.
genetic features.
Kidd et al., 2004) as well as polymorphisms in the mito-
Second, in considering evidence of a biological basis
chondrial DNA (Quintana-Murci et al., 1999). A clear
for racial classi?cation, it is important to appreciate com-
picture has emerged of the distribution of genetic variation
paratively the amount of genetic variation observed within
around the world, at least in broad strokes. These data
and among speci?c racial categories. In this context, let us
overwhelmingly support the following model for recent
turn for an illustration to the research on genetic bases of
human evolution and diversi?cation of populations.
complex diseases. On the basis of rapidly accumulating
Modern Homo sapiens evolved in Africa about
evidence, a number of geneticists have argued that most
200,000 years ago and then spread throughout the rest of
common complex diseases, such as diabetes, hypertension,
the world and simultaneously diversi?ed starting approxi-
cancer, and so forth, appear to be at least partially governed
mately 50,000 to 100,000 years ago. During that spreading
by genetic mechanisms shared by most, if not all, popula-
out, modern humans supplanted now-archaic humanlike
tions around the world (Chakravarti, 1999; Daly, Rioux,
populations identi?able as having spread outside of Africa,
Schaffner, Hudson, & Lander, 2001). This statement has
such as Neanderthals.
triggered a number of large-scale studies, including
The evidence is that effectively only one population