General
intelligence (g factor) as a function of alleles associated with educational
attainment (Education polygenic score). (Fuerst et al. 2021, p. 165)
Among
non-Hispanic European Americans, cognitive ability shows a positive correlation
with Amerindian admixture. The reason is to be found in the history of European
settlement.
We
know that cognitive ability differs among human populations, but are those differences
innate? Or are they purely cultural? The question is difficult to answer because
a purely cultural difference can, over time, become innate. If you are better
able to meet the demands of your culture, you will probably live longer, have
more offspring, and pass on many of your characteristics. Thus, over succeeding
generations, those heritable characteristics will become more and more
widespread in the gene pool, and they will increasingly determine certain
abilities that were initially created by culture.
This
is a recurring problem when we try to distinguish between cultural and genetic
determination. The two often run parallel to each other, and we can seemingly rule
out the existence of genetic determination by showing that cultural
determination runs in the same direction.
But
there is another recurring problem in our efforts to distinguish between
culture and genetics. We lack the proper tools. For a long time, we could only
infer genetic influences by using twin studies or adoption studies.
Things
have changed with the advent of a new tool: genomic data. Specifically, we can
now:
·
Measure ethnic
ancestry in mixed populations, as opposed to using self-report or inferring
from skin color.
·
Measure the
genetic component of cognitive ability, by using genetic variants associated
with educational attainment. Although these variants explain only 11-13% of the
variance in educational attainment among individuals, they explain a much
higher percentage of the variance among populations (Piffer 2019). This is
because genetic variants within the same population are exposed to the same
pressure of selection and will thus vary in the same direction. They act, so to
speak, as “weathervanes” that tell us the strength and direction of selection
in that population.
·
Measure skin color, by looking at
the relevant genes. We can thus control for the effects of “colorism” in mixed
populations, i.e., discrimination in favor of lighter-skinned individuals.
In
my last post, I described how Bryan Pesta used these tools to understand
differences in mean cognitive ability between African Americans and European
Americans (Lasker et al. 2019). To that end, his research team looked at cognitive
ability among African Americans in relation to European admixture and in
relation to genetic variants associated with educational attainment.
They
made several findings: 1) among African Americans, cognitive ability correlates
with European admixture; 2) the correlation is modestly reduced, but not
eliminated, when controlled for parental education; 3) controlling for skin
color has no effect; and 4) the correlation seems to be largely explained by
genetic variants associated with educational attainment.
The
same data source was then used by Fuerst et al. (2021) to investigate cognitive
ability not only in European Americans and African Americans but also in
Hispanic Americans. The research team thus looked at cognitive ability in
relation to Amerindian admixture, and not just in relation to European and
African admixture.
Most
of their findings are similar to those of the first study:
·
Among
Hispanic Americans, cognitive ability shows a positive correlation with
European admixture and a negative correlation with African admixture and
Amerindian admixture.
·
Among
Hispanic Americans, the correlations are reduced but not eliminated by
controlling for parental education. Controlling for skin color has no effect.
·
The
above correlations are partially explained by variants associated with
educational attainment, but not by skin color.
·
Among
non-Hispanic European Americans, cognitive ability shows a positive correlation
with Amerindian admixture.
The
last correlation may seem curious. Keep in mind that the data came from
residents of Pittsburgh and that the native peoples of the Eastern U.S. intermixed
mostly with early settlers of British, Dutch, or French origin. There is much
less Amerindian admixture among the descendants of later immigrants from
southern and eastern Europe. The correlation may thus be due not to Amerindian
admixture per se but rather to variation
in cognitive ability among Europeans.
Until
the eleventh century, mean IQ was relatively low throughout Europe, perhaps hovering
in the low 90s. It then rose during late medieval and post-medieval times
through the expansion of the middle class. There was in fact a broad mental and
behavioral change: "Thrift, prudence, negotiation, and hard work were
becoming values for communities that previously had been spendthrift,
impulsive, violent, and leisure loving" (Clark 2007, p. 166; see also Clark
2007, 2009a, 2009b). More people could better understand probability, cause and
effect, and another person’s perspective, whether real or hypothetical (Rinderman
2018, pp. 49, 86-87; Oesterdiekhoff 2012). As the "smart fraction"
grew in size, a point was reached when intellectuals were no longer voices
crying in the wilderness. They were now numerous enough to form learned
societies and collaborate in projects of various sorts (Frost 2019b, pp.
175-176).
Western
Europe was where the middle class began to expand, and that was where the expansion
would have its greatest impact, not only demographically but also behaviorally
and cognitively. Gregory Clark (2009a) has shown that the English, even in the
lower classes, are largely descended from people who were middle-class several
generations earlier. The same is likely true elsewhere in Western Europe. We should
therefore see a cognitive gradient between the Western European core and its periphery,
as can indeed be seen between northern and southern Italy. When Piffer and Lynn
(2022) looked at genomic data from that country, they found a north-south
gradient in alleles associated with educational attainment. That difference
corresponds to historical differences in economic development. By the 18th
century, the South had already fallen behind the North; its middle class had remained
small and economic relations were still structured by paternalism and
familialism (De Rosa 1979).
All
of that leads to an interesting corollary: the IQ gap used to be smaller
between Europeans and sub-Saharan Africans. On the one hand, European mean IQ
had probably remained in the low 90s until late medieval times. On the other hand,
mean IQ may have been in the upper 80s among those Black African groups that
Europeans had first encountered, particularly the Nubians. By the time of Classical
Antiquity they had reached a high level of material culture, social complexity
and State formation.
A
smaller IQ gap would be in line with an observation by Jason Malloy. He noted
that blacks were often described in the ancient world as having large penises
but not as being less intelligent. Indeed, I have found only two Greco-Roman texts
in which the writer disparaged Black Africans as being unintelligent. One of
them is of doubtful authenticity, and both come from Late Antiquity (Frost 2019b).
By then, blacks in the Roman world were increasingly slaves who came from
farther within the African interior. Thereafter, a stereotype of low
intelligence is regularly attested in Middle Eastern and European sources.
References
Clark,
G. (2007). A Farewell to Alms. A
Brief Economic History of the World. Princeton University Press: Princeton
and Oxford.
Clark,
G. (2009a). The indicted and the wealthy: surnames, reproductive success,
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