Cognitive evolution in eastern Eurasia

A steady rise and then stagnation

Kong Qiu (Confucius), c. 551- c. 479 BCE (Wikicommons)

Beginning some 10,000 years ago, hunting and gathering gave way to farming. This in turn gave way to ever more cultural change: population growth, year-round living in villages and towns, trade and specialization of labor, numeracy and literacy, the formation of states, the development of religion, the standardization of law and so on.

Humans were thus entering an ever-wider range of cultural environments, which, to varying degrees, placed new demands on the capacity to process information, recognize patterns and solve problems — in other words, cognitive ability.

The new demands varied from one region to another and from one time period to another, with the result that cognitive ability followed different trajectories of evolution in different populations. We can now chart this evolution by looking at DNA from human remains, specifically the various alleles associated with educational attainment (EA) and how their population frequencies have changed over time.

Several recent studies have charted this evolution in Europeans:

• No change during the long period of hunting and gathering, although this finding is uncertain because of small sample sizes.

• A steep rise between 9,000 and 7,000 years ago with the emergence of farming, in line with the cognitive demands of farming and also admixture from northern hunter-gatherers.

• A slower rise during the Neolithic and into recorded history, in line with the cognitive demands of increasing social complexity. With the stratification of society into classes, cognitive evolution became driven primarily by the higher fertility of upper-class families.

• A decline during the Imperial Era of Rome, in line with a decline in family formation and fertility among the upper classes.

• A renewed upward trend beginning in Late Antiquity, in line with the rise of Christianity and an increase in family formation among the upper classes.

• An especially rapid rise in Western Europe during late medieval and post-medieval times, in line with the demographic expansion of the middle class through higher fertility and lower mortality (Akbari et al., 2024; Frost, 2024; Kuijpers et al., 2022; Piffer et al., 2023; Piffer & Kirkegaard, 2024).

The other end of Eurasia

Europe is one of two large regions where mean cognitive ability has risen the most. The other is East Asia. How has cognitive ability evolved at the other end of Eurasia?

This question has been addressed by Davide Piffer in his recent study of 1,245 ancient genomes from eastern Eurasia over the last 12,000 years. For earlier periods, we have too few samples to draw worthwhile conclusions, as is also true for Europe.

He found an increase in mean cognitive ability over time. It was largest in southern China, followed by Mongolia and Southeast Asia. The size of the increase in southern China probably reflects not only cognitive evolution in situ but also the replacement of hunter-gatherers and simple farming societies by Han immigrants from northern China (Yang et al., 2020). Similarly, the increase in Mongolia may partly reflect gene flow from Han Chinese (10-51% of current Mongolian ancestry) and Europeans (6-40%) (Zhao et al., 2020). Southeast Asia has likewise seen extensive replacement of hunter-gatherers by Austronesian or Sino-Tibetan farmers (Lipson et al., 2018).

Mean cognitive ability did not rise as much elsewhere in eastern Eurasia. These smaller increases may reflect persistence of low social complexity (Arctic, North Siberia), failure to develop beyond a certain level (Central Asia and Tibet), or a complicated trajectory of positive and negative evolution (northeast China).

Increase in mean cognitive ability, as measured by alleles associated with educational attainment (EA), for each region of eastern Eurasia (Piffer, 2025a, Figure 4, p. 7)

A closer look

By pooling these regional results, Davide Piffer was able to track the cognitive evolution of eastern Eurasia in greater detail. His second analysis shows stagnation during the hunter-gatherer period, followed by a sustained upward trend beginning around 9,000 to 8,000 years ago, apparently with the advent of farming. This upward trend ended a little less than 1,500 years ago, near the beginning of the Tang Dynasty (618-907 CE).

The last finding may seem surprising because the Tang Dynasty saw great advances in art, literature and technology. Did this golden age have a darker side? Did the upper classes suffer a decline in fertility as they did in Imperial Rome?

This explanation has some support from historical sources. During the Tang Dynasty, the poet Wang Fanzhi affirmed that having one son was enough. The subsequent Song Dynasty (960–1279 CE) was a time when parents wanted to have only two sons or just one, according to a number of scholars. (Zhao, 2002, p. 756). Abortive drugs were sold during the Tang Dynasty and became even more available during the Song and Yuan (1206–1368 CE) dynasties. Such drugs were produced on a large scale in certain areas during the reign of Kang Xi (1662–1722 CE) and were widely used by the population — from members of the imperial family to ordinary citizens (Zhao, 2006, p. 17). When describing certain places in one of his poems, Wang Fan Zhi (c. 590–c. 660 CE) noted that the rich had few children while the poor had many (Zhao, 2006, p. 22).

Increase in mean cognitive ability, as measured by alleles associated with educational attainment (EA), over the last 12,000 years in eastern Eurasia. (Piffer, 2025, Figure 3, p. 6)

To confirm the stagnation of the Tang Dynasty and onwards, as shown by alleles associated with EA, Davide Piffer repeated his analysis but now used alleles associated with IQ. This method has the advantage of homing in on cognitive ability itself, rather than other traits that may assist success at school. But it also has the disadvantage of being based on much fewer alleles (only 434 independent SNPs, as compared to almost 4,000 for EA).

These results differ from the previous ones in two ways:

• Instead of remaining unchanged during the hunter-gatherer period, mean cognitive ability fell and continued to fall into the farming period, bottoming out only 6,000 years ago. The decline seems to mirror a decline in brain size that began in Eurasian populations after the last ice age, perhaps because their brains no longer had to store, process, and manipulate huge amounts of spatiotemporal data for hunting over large expanses of territory (Frost, 2019; Hawks, 2011). This loss of spatiotemporal ability may therefore show up more in IQ than in EA.

• Instead of remaining unchanged during the last 1,500 years, mean cognitive ability fell somewhat. This decline may show up more in IQ because EA captures not only cognitive ability but also certain propensities — rule following, submissiveness, resistance to boredom — that are less related to cognitive ability and more to classroom performance.

Increase in mean cognitive ability, as measured by alleles associated with IQ, over the last 12,000 years in eastern Eurasia (Piffer, 2025a, Figure 6, p. 8)

Conclusion

The “archeology of the mind” is shedding new light on the historical process. In particular, we’re learning that history is a reciprocal relationship between the human mind and the culture it creates. We make culture, and it remakes us — by favoring those who better fit in and exploit its possibilities. Humans and culture have thus been remaking each other along trajectories that differ from one population to another.

Culture especially favors those individuals who have certain properties of mind and behavior, notably cognitive ability. “Cultural selection” has gone farther in some parts of the world than in others, and has gone especially far in Europe and East Asia.

These two trajectories of cognitive evolution share certain similarities:

• An upward trend that began with the emergence of farming and continued as social complexity progressively increased.

• A halt and even reversal at a fairly high level of social complexity — during the periods of Imperial Rome and Tang China — perhaps due to a fertility decline among the upper classes.

But this reversal would play out differently in the two regions. In the Roman Empire, mean cognitive ability fell and then rose again a few centuries later. This “reboot” was associated with an ideological change: the rise of Christianity and its preeminent role in enforcing morality, particularly in the areas of sexual behavior and family formation. The new ideology would survive the collapse of Rome and define what would be called “Christendom” (Frost, 2024).

In China, the ensuing trajectory is less clear-cut. Whereas alleles associated with EA suggest a flat-lining of cognitive evolution, those associated with IQ suggest a decline. Perhaps the decline in upper-class fertility was partially offset by the growing importance of the Imperial Examination for social and economic advancement (Frost, 2011; Wen et al., 2024). This examination favored not only high cognitive ability but also certain other mental traits: rule following, submissiveness, and resistance to boredom — in short, the ability to sit still at a desk and do tedious assignments.

Like Imperial Rome, Tang China experienced a movement for social and moral reform. This movement was based on the teachings of Kong Qiu (Confucius) and gained ground during the Tang Dynasty through the work of pronatalist scholars who condemned abortion and advocated control of sexual desires (Hsiung, 2011). Their work led to the emergence of neo-Confucianism, which resembled Christianity in some respects, particularly in its efforts to regulate sexual behavior and family formation. But, unlike Christianity, it did not create an organizational network to impose its norms on the population.

In sum, East Asia failed to develop a regulator of public morality that could act independently of the elites and make them conform to certain sexual and reproductive norms. This point is broadly made by Francis Fukuyama in his work The Origins of Political Order.

Hopefully, we will see more studies of this kind, especially on the last 1,500 years of cognitive evolution. In particular, three points need to be cleared up:

• The higher values for Mongolians in relation to those for northeast Chinese. The apparently high cognitive ability of Mongolians may seem surprising, given the evidence that IQ is 5 points lower among them than among Han Chinese (Lynn, 2007).

• The apparent contradiction between Davide Piffer’s findings and Ron Unz’s. The latter has argued that mean cognitive ability continued to rise in China until the 20th century through higher fertility among the wealthy (Unz, 2013).

• The point in time when East Asians surpassed Europeans in mean cognitive ability. The crossover point seems to be just before the time of Christ, according to Piffer’s comparison of ancient DNA from those two regions (see below). This is a rough estimate because the data are aggregated into 2,000 year “bins.” In fact, Europeans may have surpassed East Asians c. 1900, given that the last bin includes both the peak of the Tang Dynasty (thus overstating recent East Asian evolution) and the nadir of Rome’s Imperial Era (thus understating recent European evolution).

Increase in mean cognitive ability, as measured by alleles associated with educational attainment, over the last 12,000 years in eastern Eurasia and Europe. (Piffer, 2025b)

References

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