Farm at Duivendrecht, Piet Mondrian, 1905. The shift from hunting and gathering to farming led to a new cultural environment that selected against sensation seeking and monotony avoidance
Europeans became a high-IQ population through an evolutionary trajectory that began with the adoption of farming and continued because of the cognitive demands of social complexity. Much of the upward trend in cognitive ability has occurred since medieval times.
Human evolution did not end in the Paleolithic. It continued and even accelerated along different trajectories in different populations and for different traits (Cochran and Harpending, 2009; Hawks et al., 2007; Rinaldi, 2017).
One trait is cognitive ability — the ability to process information, recognize patterns, and solve problems. Among those humans who entered Europe, mean cognitive ability would increase to such a degree that the continent is today one of the world’s two “IQ plateaus.” When did that increase happen? During the last ice age? Or more recently?
A recent increase is postulated by Gregory Clark (2007; 2009; 2023), who has studied the demographic history of England. As the English middle class grew in size from the twelfth century onward, its lineages contributed more and more to the country’s gene pool. The result was a mental and behavioral shift toward “middle class” qualities of mind and behavior — not only higher cognitive ability but also lower time preference, greater impulse control, and less willingness to settle disputes through violence.
Georg Oesterdiekhoff (2023) has argued for a similar evolution across Western Europe during the same period. He interprets this evolution in terms of Jean Piaget’s stages of cognitive development, i.e., a growing proportion of the population could go beyond preoperational thinking (egocentrism, anthropomorphism, finalism, animism) and achieve operational thinking (ability to understand probability, cause and effect, and another person’s perspective).
First study of European cognitive evolution - Kuijpers et al. (2022)
To test the hypothesis of recent cognitive evolution, a team led by Yunus Kuijpers compared the DNA of 250 present-day Europeans with the DNA of 827 Europeans from different stages of cultural development: the Upper Paleolithic (before 11,000 years ago), the Mesolithic (11,000 to 5,500 years ago), the Neolithic (8,500 to 3,900 years ago), and the post-Neolithic (5,000 to “more recent ages”). The researchers looked at changes over time in mean cognitive ability, as measured by alleles associated with intelligence, fluid intelligence, and educational attainment.
All three measures of cognitive ability showed the same pattern of cognitive evolution:
no change during the long period of hunting and gathering
with the emergence of farming, a sustained upward trend until the dawn of history
stagnation during the classical era of civilization
a renewed upward trend during the last few centuries (Kuijpers et al., 2022).
These results are in line with Clark’s hypothesis of an increase in mean cognitive ability from the twelfth century onward. They may also be in line with the findings of a team led by Davide Piffer on the genetic history of central Italy. That sub-region seems to have gone through three stages of cognitive evolution:
an upward trend in mean cognitive ability from the Neolithic to the time of the Roman Republic
a downward trend during the Imperial Era
a renewed upward trend from Late Antiquity to the Middle Ages (Piffer et al., 2023; see also Frost, 2023).
These ups and downs are absent from the Kuijpers et al. study because they are subsumed within a broader temporal frame (“post-Neolithic”) and a broader spatial frame (Europe).
All three measures of cognitive ability show the same pattern over time (Kuijpers et al., 2022).
Second study of European cognitive evolution - Piffer and Kirkegaard (2024)
The above findings prompted Davide Piffer and Emil Kirkegaard to do the same kind of study with a larger number of European genomes (n=2625) and with measures of cognitive ability based on larger samples. In particular, the alleles associated with educational attainment were identified by other research teams from two large samples, one having over a million individuals (EA3) and the other three million individuals (EA4).
The two researchers found essentially two stages of cognitive evolution:
no change between approximately 35,000 and 15,000 years ago.
an upward trend beginning near the end of the last ice age and lasting to the present (Piffer and Kirkegaard, 2024)
In this study, the upward trend is more continuous and consequently less steep, perhaps because more of the samples came from non-Romanized regions that were less affected by the cognitive decline of the Imperial Era.
As with the other study, we see a close alignment of all three measures of cognitive ability. The evolutionary change has clearly been in that trait, and not in some non-cognitive aspect of educational attainment.
All three measures of cognitive ability show the same pattern over time. In this study, the upward trend is more continuous and consequently less steep (Piffer and Kirkegaard, 2024).
Regional trends
Because the regional subsamples were often too small, it was difficult to analyze shorter-term trends within any one European region, such as the cognitive decline of Imperial Rome or the cognitive takeoff of late-medieval/post-medieval Western Europe. Among the subsamples, Bronze Age Greeks showed the highest level of cognitive ability as measured by alleles associated with IQ, but this result was not replicated by alleles associated with EA.
The English subsample had enough individuals to test Clark’s hypothesis of an upward trend in mean cognitive ability from the twelfth century onward. When medieval genomes were compared with those of contemporary England, all three cognitive measures showed a significant increase.
This increase may, in fact, be understated. First, mean cognitive ability seems to have fallen in England, and more generally within the Western world, since the turn of the twentieth century (Frost, 2022). Second, the “cognitive takeoff” hypothesized by Clark began in late medieval times. The comparison should therefore be made between the start and end points of this cognitive evolution, i.e., between the early medieval period and the Victorian Age, and not between the medieval period as a whole and the present.
Finally, a comparison was also made between England and the rest of Europe with respect to this recent upward trend in mean cognitive ability. No significant difference was found. Clark’s hypothesis seems to apply not only to England but also to other parts of Europe, certainly Western Europe. For future research, a more appropriate model would be one where this cognitive increase is seen as beginning initially in Western Europe and then spreading outward in line with the growth of the middle class.
Alleles associated with socioeconomic status
The researchers also looked at changes over time in alleles associated with socioeconomic status, as ascertained in contemporary British individuals. Alleles associated with higher status became more frequent from the end of the ice age to around 2500 years ago, after which there was no further change. There was likewise no change between medieval and contemporary English genomes.
This is not what Clark would predict. He argued that the late-medieval/post-medieval growth of the middle class favored not only alleles associated with higher cognitive ability but also those associated with “middle class values,” like lower time preference and greater impulse control. Perhaps higher socioeconomic status is today determined by a different package of mental and behavioral traits.
Alleles associated with autism, schizophrenia, and depression
In addition to alleles for cognitive ability, the two authors also looked at alleles for certain mental illnesses. Autism has become more common since the last ice age. Is this upward trend a side-effect of selection for cognitive ability? Or has it been directly favored by something in our cultural environment?
Meanwhile, schizophrenia has become less common. Schizophrenics have lower cognitive ability, (i.e.., a reduction from 100 to 70-85 IQ), particularly a reduced ability to attach meaning to words, to see through visual illusions, and to understand the self in relation to others. This finding may support Oesterdiekhoff’s argument for a shift away from pre-operational thinking in modern European adults.
Finally, depression has become less common. Perhaps sedentism has selected against sensation seeking and monotony avoidance. These traits are highly heritable and key to the behavioral repertoire of hunters and gatherers (Zuckerman, 2008). In the case of farmers, the same traits would be maladaptive and selected out of the gene pool. One consequence may thus be a higher threshold for depression.
Remaining questions
Cognitive evolution and the transition to farming
Were native Europeans selected for higher cognitive ability when hunting and gathering gave way to farming? Or were they simply replaced by Middle Eastern farmers moving into Europe from Anatolia? Piffer and Kirkegaard argue for the latter scenario:
Hunter-gatherer ancestry (particularly V2 or WHG) was negatively associated with EA3, EA4 and IQ in the regression models (Supplementary Tables S1-S3) even after accounting for Years BP (β=-0.314, -0.4, -0.249), suggesting that the increase in cognitive capacity was not solely driven by the Neolithic revolution but was partly mediated by admixture with the immigrants that accompanied it. Anatolian Neolithic farmers who intermixed with native HGs contributed between approximately 40% and 98% of Neolithic European ancestry (Piffer and Kirkegaard, 2024)
The estimate of 40 to 98% replacement of European hunter-gatherers by Anatolian farmers should be viewed with caution. It is based on the assumption that demographic replacement explains all of the genetic change across the time boundary between hunter-gatherers and farmers. In reality, some of it was due to:
Founder effects - Hunter-gatherers who adopted farming were a tiny percentage of all hunter-gatherers, hence the founder effects were considerable. These genetic changes were random, but a certain percentage of them would have matched the genetic profile of Anatolian farmers.
Selection effects - Hunter-gatherers who adopted farming were now adapting to the same regime of natural selection as that of Anatolian farmers. Hence there was some convergent evolution. Such evolution may, for instance, explain why Europeans lost haplogroup U, which is associated with greater production of body heat — a useful cold adaptation for hunter-gatherers, who slept in makeshift shelters and pursued game in all kinds of weather. In contrast, farmers slept in a warmer environment and could more easily plan their outdoor activities (Balloux et al., 2009; Montiel-Sosa et al., 2006). Farmers likewise had less need for odor recognition, monotony avoidance, and sensation seeking. In sum, even if there were no population replacement at all, we would still expect to see genetic change across the time boundary between hunter-gatherers and farmers.
There is thus an inevitable confound between farmer ancestry and natural selection due to farming. If we look at alleles that seem to indicate native hunter-gatherer ancestry, we are excluding the alleles of hunter-gatherers who successfully adapted to farming and who thus acquired a genetic profile that converges, to some extent, on that of Anatolian farmers. A certain amount of “Anatolian admixture” is actually pseudo-admixture.
We cannot avoid this methodological problem by using only noncoding loci, as is often done, since such loci can still regulate how alleles at other loci behave. Noncoding loci have, in fact, contributed disproportionately to recent evolution. Comparison of our genome with other primate genomes has shown that almost all human-specific deletions are in noncoding regions. Furthermore, DNA is mostly noncoding in human accelerated regions (HARs), which have been well conserved throughout vertebrate evolution but are strikingly different in humans (Bae et al., 2015).
Reduction in brain size after the last ice age
Cranial capacity, and hence brain size, decreased among Europeans after the last ice age (see Hawks, 2011 for a review of the literature). Yet, during the same period, mean cognitive ability held steady or increased among Europeans. How do we explain this apparent contradiction?
Perhaps the brain was starting to do more with less, specifically be relying more on recursive thinking (Corballis, 2014; Cutler, 2024). Alternatively, the decrease in brain size may simply reflect a decrease in mental storage of spatiotemporal data, due to the abandonment of hunting over large expanses of territory. This decrease is much less apparent in tropical humans, who hunted over smaller expanses (Frost, 2019b; Hawks, 2011).
Cold winter theory
Neither of the above two studies supports the theory that higher cognitive ability was favored by Europe’s cold climate — especially during the last ice age. The theory is that the harshness of a cold climate, specifically its occurrence over a predictable yearly cycle, selects for the ability to plan ahead and prepare accordingly (Frost, 2019a). Perhaps cognitive ability did increase when modern humans initially entered Europe, but this increase does not show up in the genetic data because the Upper Paleolithic timeframe is too broad and has too few data points, especially from northern Europe. For later periods, selection for cognitive ability would be determined much more by other factors, particularly the increase in social complexity from the late Mesolithic onward.
References
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> Alternatively, the decrease in brain size may simply reflect a decrease in mental storage of spatiotemporal data, due to the abandonment of hunting over large expanses of territory.
Worth noting that the modern peoples with the largest brain sizes are Siberian indigenous peoples followed by Inuit. Their visuospatial skills are anecdotally prodigious whereas their overall IQs are modest (low 90s).
I've wondered about this. Wolves and coyotes are smarter than domestic dogs, but dogs appear smarter to us because they behave in ways we associate with intelligence in canines. We look at those tiny brained farmers and say, "smarter". But maybe they just had better conflict avoidance? Now, hunter gatherers are the losers. They were the guys that never could learn to do anything else and were pushed into the worst land, (except in the Americas). My thought is that the only place we can really compare intelligence between hunter gatherers and farmers is in the Americas. Yet here we have barriers at every level to test, compare, even to be certain of a group's historical activities.