Polygenic
scores for alleles associated with educational attainment - Europeans of
different time periods (Kuijpers et al. 2022)
According
to a new study of ancient European DNA, cognitive evolution stagnated after the
last ice age and then speeded up with the rise of farming. It stagnated again
during Antiquity and then speeded up again sometime between then and now.
In
my last post, I mentioned an ancient DNA study of 99 genomes from sites across
Europe and Central Asia. It showed an apparent increase in mean cognitive
ability between 4,560 and 1,210 years ago, as measured by alleles associated
with educational attainment (Woodley et al. 2017).
That
finding has been partially replicated by a new study of 827 genomes from
ancient European remains and 250 genomes from modern Europeans. It looks like
cognitive evolution stagnated after the last ice age and then speeded up with
the rise of farming. It stagnated again during Antiquity and then speeded up
again sometime between then and now:
Interestingly, while the period between
the Early Upper Paleolithic and the Neolithic is characterized by stagnation or
slight decrease in PRS related to intelligence, the genetic data show a clear
increase in the scores for educational attainment, intelligence, and fluid intelligence
from the Neolithic onwards, while the traits related with unipolar depression
tend to decrease from that era on. The most significant differences can be
observed comparing the pre-Neolithic and Neolithic groups, as well as the
post-Neolithic and modern groups, whereas the period between the Neolithic and
post-Neolithic shows a very constant distribution of PRS scores. (Kuijpers et
al. 2022).
The
authors define the time periods as follows:
Early
Upper Paleolithic era – before 28,000 years BC
Late
Upper Paleolithic era – 28,000 to 11,000 BC
Mesolithic
- 11,000 to 5500 BC
Neolithic
- 8,500 to 3900 BC
Post-Neolithic
- 5000 BC and more recent ages (no end date given)
Modern
– circa 1950 AD
The
Mesolithic, the Neolithic, and the Post-Neolithic overlap a lot with each other.
This is because their boundaries are defined by cultural changes that came to
different parts of Europe at different times. The Neolithic began when hunting
and gathering gave way to farming, which came later to northern Europe.
Similarly, the post-Neolithic began with the advent of metallurgy, which
likewise came later to northern Europe.
Such
overlap is problematic for three reasons:
·
In
some cases, there is uncertainty as to whether the ancient DNA came from the
remains of hunter-gatherers or those of farmers.
·
“Hunter-gatherer”
is not a homogeneous category. It includes not only small nomadic groups but
also the hunter-fisher-gatherers of the Baltic and North Sea, who attained a
degree of sedentism, population growth, and social complexity that we normally
associate with farmers (Price 1991).
·
The
Post-Neolithic is too long to be meaningful. It covers all of recorded history,
and then some.
The
study’s authors could have divided the Post-Neolithic into smaller time periods
to give us a better look at changes during historical times. In particular, did
cognitive evolution regress during Classical Antiquity? That was the
preliminary finding of a team led by Michael Woodley of Menie (2019) in a study
of ancient DNA from Greece. They found that mean cognitive ability increased
from the Neolithic to the Mycenaean period and then decreased sometime between the
latter and the present day. That study was never published, perhaps because the
geographic area and the time periods were too small to provide robust results.
To
get more robust results, we could look at ancient DNA from the entire
Greco-Roman world, perhaps divided into three time periods: 5000 to 1000 BC;
1000 to 0 BC; and 0 to 500 AD. Was there a large increase in mean cognitive
ability followed by an equally large decrease? Or was there simply a long
period of stagnant evolution?
In
a previous post, I argued that the culture of Classical Antiquity, particularly
in its later stages, caused cognitive evolution to regress (Frost 2022). There
were several reasons:
·
A
decline in fertility and family formation, particularly among the upper
classes;
·
A
corresponding increase in female hypergamy, often by freed slaves, which
reduced the reproductive importance of upper-class women;
·
An
increase in the foreign slave population, which disrupted cognitive evolution
within the local population. Even if there had been demographic overflow from
the upper classes, that overflow could not have replaced the lower classes,
since those classes were being replaced from external sources.
We
need a clearer picture. According to the current data, it looks like cognitive
evolution simply stagnated during the Post-Neolithic, but I suspect that time period
is so broadly defined that it conceals a regression during the centuries before
the fifth century collapse and the centuries immediately after.
References
Frost, P. (2022). When did Europe pull ahead? Evo and Proud, May 16. http://evoandproud.blogspot.com/2022/05/when-did-europe-pull-ahead.html
Kuijpers,
Y., J. Domínguez-Andrés, O.B. Bakker, M.K. Gupta, M. Grasshoff, C.J. Xu,
Joosten LAB, J. Bertranpetit, M.G. Netea, and Y. Li. (2022). Evolutionary
Trajectories of Complex Traits in European Populations of Modern Humans. Frontiers in Genetics 13: 833190. https://doi.org/10.3389/fgene.2022.833190
Price,
T.D. (1991). The Mesolithic of Northern Europe. Annual Review of Anthropology,
20, 211-233. Price,
T. D. (1983). The European Mesolithic. American
Antiquity 48(4), 761–778. https://doi.org/10.2307/279775
Woodley,
M.A., S. Younuskunju, B. Balan, and D. Piffer. (2017). Holocene selection for
variants associated with general cognitive ability: comparing ancient and
modern genomes. Twin Research and Human
Genetics 20: 271-280. https://doi.org/10.1017/thg.2017.37
Woodley
of Menie, M.A., J. Delhez, M. Peñaherrera-Aguirre, and E.O.W. Kirkegaard.
(2019). Cognitive archeogenetics of ancient and modern Greeks. London Conference on Intelligence
