If
we look at alleles associated with higher educational attainment, we find more
of them among the Yoruba of Nigeria than among the Mende of Sierra Leone. The
reason may be differences in social evolution over the past 1,000 years,
particularly in trade, urban settlement, State formation, and other forms of
social complexity.
Ife
king's head (14th or early 15th century) (Wikicommons - Vassil)
How
can we measure the genetic component of cognitive ability? We have long used IQ
tests to get a rough idea, but they are not an ideal yardstick. Twin studies
have shown that genetic factors explain about two thirds of the variance in IQ
results, perhaps even less for comparisons between people of different cultural
backgrounds.
In
recent years we've found a new yardstick: the polygenic score. It's a more
direct genetic measurement, being a summation of alleles that have been linked
to higher educational attainment. As a method for estimating the mean cognitive
ability of a population, it seems to be as good as IQ tests. Piffer (2019)
found a 90% correlation between the two methods. In his latest study, he has
again found the same correlation (Piffer 2021, see Figure 8).
Interestingly,
that study shows differences in mean cognitive ability within West Africa: the
Mende of Sierra Leone score much lower than the Yoruba of Nigeria. In fact, the
Yoruba have almost the same polygenic score as do African Americans, even
though the latter have about 20% European admixture. Unfortunately, we have no
data on the Igbo of Nigeria, who are known to be high achievers at school and
in other areas of life (Frost 2015).
These
differences within West Africa support the argument that mean cognitive ability
has continued to increase in some human populations, even in relatively recent
times. With respect to the Yoruba, their cognitive ability may have increased
in tandem with their advances in trade, urban settlement, and State formation
from the tenth century onward (Akintoye 2014; McIntosh and McIntosh 1988).
Meanwhile, the Mende remained at a lower level of social complexity.
There
is one problem with using polygenic scores for West Africans, or for any
non-European population. To identify alleles associated with higher educational
attainment, researchers have used genomes of European origin. There is
evidence, however, that the architecture of cognitive ability may differ in
different human populations. The same alleles might not explain high cognitive
ability in West Africans and Europeans. Indeed, Lasker et al. (2019) found a
lower correlation between polygenic scores and cognitive ability in African
Americans than in European Americans.
References
Akintoye,
S.A. (2014). A History of the Yoruba
People. Dakar: Amalion.
Frost,
P. (2015). The Jews of West Africa. The
Unz Review, July 4
https://www.unz.com/pfrost/the-jews-of-west-africa/
Lasker,
J., B.J. Pesta, J.G.R. Fuerst, and E.O.W. Kirkegaard. (2019). Global ancestry
and cognitive ability. Psych 1(1)
https://www.mdpi.com/2624-8611/1/1/34
McIntosh,
S.K., and McIntosh, R.J. (1988). From stone to metal: New perspectives on the
later prehistory of West Africa. Journal
of World Prehistory 2: 89-133. https://doi.org/10.1007/BF00975123
Piffer,
D. (2019). Evidence for Recent Polygenic Selection on Educational Attainment
and Intelligence Inferred from Gwas Hits: A Replication of Previous Findings
Using Recent Data. Psych 1(1): 55-75.
https://doi.org/10.3390/psych1010005
Piffer,
D. (2021). Divergent selection on height and cognitive ability: evidence from
Fst and polygenic scores. OpenPsych
3 comments:
I think your last paragraph is very true.
It is possible, if not probable, different gene code for similar effects in different populations.
Like with lactose tolerance in adult developed independently in Africa and in Europe, because the populations were separated for a long time and under different selective pressures.
The interaction between intelligence and personality is important, because being abstractly good at solving complex problems is not useful if you are not conscientious enough to exploit this capability.
Their ironwork which I saw at the British Museum a few years ago struck me as quite impressive.
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