Recent evolution in human brain size

 

Human brain size remained stable from 300,000 to 60,000 years ago. It then diversified, becoming larger in some populations and smaller in others. This was when modern humans were spreading out of Africa and into new environments in Eurasia.

 

 

With the end of the last ice age, some 10,000 years ago, northern hunting peoples found themselves in a new environment. Men could no longer pursue herds of wandering reindeer over the vast steppe-tundra. They now had to hunt over shorter distances, and the game would be smaller and more varied. Meanwhile, women now had opportunities for gathering fruits, berries, roots, and other small food items. They thus turned toward food gathering, while men moved into the formerly female domain of crafts, kiln operation, and shelter construction. Cognitive demands were thus changing. Men no longer had to store huge amounts of spatiotemporal data when tracking prey, and women were losing their dominance of artisanal work (Frost 2019).

 

The post-glacial period also brought an apparent decrease in brain size. Henneberg (1988) found that male brains shrank by 9.9% and female brains by 17.4% between the ice age and modern times. He attributed the decrease to a reduction in body size. In a reanalysis of Henneberg's data, Hawks (2011) showed that the reduction in body size explains only one-fifth to one-seventh of the decrease in brain size. He also showed that the declining ratio of brain size to body size did not affect all populations equally. In fact, it can be securely demonstrated only for Europeans and Chinese. No decline is discernable for Nubians, the only non-Eurasian population for which we have a large cranial sample.

 

In a recent analysis of cranial data, DeSilva et al. (2021) argue that brain size began to decrease with farming and the rise of larger, more complex societies. They argue more specifically that the decrease was due to an increasing ability to store knowledge externally either in written form (on tablets, paper, or parchment) or in the brains of scribes, skilled tradesmen, and other knowledge workers. People no longer had to rely solely on their own brains to store the knowledge they needed:

 

 […] the recent decrease in brain size may instead result from the externalization of knowledge and advantages of group-level decision-making due in part to the advent of social systems of distributed cognition and the storage and sharing of information. (DeSilva et al. 2021, p. 1)

 

That hypothesis has been challenged by Villmoare and Grabowski (2022). Because farming was adopted at different times in different populations, they argue that DeSilva et al. (2021) should have analyzed the cranial data on a regional basis. But this was not done:

 

Since this transition [to farming] occurred at different times across the globe, rather than over a single 3–5 ka year period, under the hypothesis of DeSilva et al. (2021) we should detect the change in different modern human populations at different times. However, the dataset of DeSilva et al. (2021) is not organized to test the hypothesis in this fashion. Populations from around the globe are lumped together, with only 23 crania sampled over what we would argue to be a critical window with regards to their hypothesis, 5–1 ka, and coming from Algeria, England, Mali, China, and Kenya, among other locations. Later modern human samples are focused on Zimbabwe (at 1.06 ka), the Pecos Pueblo sample from the United States (1 ka), and finally, 165 crania (28% of the total sample) are from Australian pre-Neolithic hunter-gatherer populations and dated in DeSilva et al. (2021) to 100 years ago. (Villmoare and Grabowski 2022, p. 2)

 

The cranial dataset suffers from other problems:

 

In that same dating category [100 years ago], 307 (53% of the total sample) are from unspecified Morton Collection crania, where we have no way of knowing how many may be from pre-Neolithic and post-Neolithic populations. We also observe that the sample of DeSilva et al. (2021) generates a modern human mean of 1,297 cc in the final 100-year category, which is well below other published estimates of contemporary world-wide modern mean human cranial capacity that range from ?1,340 cc up to ?1,460 cc. (Villmoare and Grabowski 2022, p. 2)

 

When Villmoare and Grabowski (2022) reanalyzed the cranial data for the last 300,000 years, they found a very different picture:

 

[…] our analyses showed no changes in brain size associated with the transition to agriculture during the Holocene. Overall, our conclusion is that, given a dataset more appropriate to the research question, human brain size has been remarkably stable over the last 300 ka. (Villmoare and Grabowski 2022, p. 4).

 

Actually, their reanalysis shows that brain size remained stable from 300,000 to 60,000 years ago. It then diversified, becoming larger in some populations and smaller in others. This was when modern humans were spreading out of Africa and into new environments in Eurasia (see chart at top of post).

When the authors looked more narrowly at the last 30,000 years, they found no discernable change in mean brain size or in variation around the mean. They did not attempt a regional analysis. That’s a pity because DeSilva et al. (2021) may have been right within a more limited context, specifically that of complex Eurasian societies. We still have John Hawks’ finding that brain size decreased in Eurasians after the last ice age. But when exactly? Immediately after the ice age? Or during the much later increase in social complexity?

 

Today, more than a decade later, John Hawks has still not published that paper in a journal. When I asked him why, he replied: "I did not feel it was necessary to pursue formal journal publication for this, because I did not think it fit well into the journals at the time." Yet, at that time, the paper was exciting a lot of interest. This is what he wrote on his blog:

 

I've had a dozen requests from colleagues to cite the paper (which anyone is welcome to do by using the arXiv number). I also had two great interactions with colleagues who had comments and suggestions on the preprint, which I am now incorporating into a revision. (Hawks 2012)

 

He might have had trouble publishing the paper in a top-tier journal. But the main problem lay elsewhere. Once it got published, some academics might have viewed him the wrong way. Perhaps not, but why take the risk? Why risk opportunities for getting funding and invitations to work on big projects with big names?

 

Those are questions that many anthropologists end up asking themselves. I have no easy answer, other than to say that you can never control what other people think of you. You only get to own your own thoughts, not those of others.

 

References

 

DeSilva, J. M., Traniello, J. F. A., Claxton, A. G., and Fannin, L. D. (2021). When and why did human brains decrease in size? A new change-point analysis and insights from brain evolution in ants. Frontiers in Ecology and Evolution 9: 742639. https://doi.org/10.3389/fevo.2021.742639

 

Frost, P. (2019). The Original Industrial Revolution. Did Cold Winters Select for Cognitive Ability? Psych 1(1): 166-181. https://doi.org/10.3390/psych1010012

 

Hawks, J. (2011). Selection for smaller brains in Holocene human evolution. arXiv:1102.5604 [q-bio.PE] https://arxiv.org/abs/1102.5604  

 

Hawks, J. (2012). Spreading preprints in population biology. John Hawks Weblog, August 1. https://johnhawks.net/weblog/topics/meta/population-biology-arxiv-callaway-2012.html

 

Henneberg, M. (1988). Decrease of human skull size in the Holocene. Human Biology 60: 395-405. https://www.jstor.org/stable/41464021

 

Villmoare, B. and M. Grabowski. (2022). Did the transition to complex societies in the Holocene drive a reduction in brain size? A reassessment of the DeSilva et al. (2021) hypothesis. Frontiers in Ecology and Evolution 10: 963568. https://doi.org/10.3389/fevo.2022.963568

Giorgia Meloni: The hard work is just starting

 

Giorgia Meloni, October 21, 2022

 

In the space of four years, Giorgia Meloni has gone from being the leader of a minor party to being the leader of Italy, with an absolute majority in both houses of parliament. But she will not find it easy to put her electoral platform into practice.

 

 

Four years ago, when I last wrote about Italy’s political situation, Giorgia Meloni was leading a party that had won only 2% of the popular vote. Her party was, in fact, the smallest member of a coalition dominated by Silvio Berlusconi’s Forza Italia and Matteo Salvini’s Lega Nord. All of that changed with this year’s election. Her party took 26% of the vote, and the coalition 43%. She is now Prime Minister.

 

Meloni rose to power because she lacked the weaknesses of her two coalition rivals. She wasn’t an establishment conservative like Berlusconi, and she wasn’t a northern regionalist like Salvini. She was thus seen as the one who could best represent the entire country and deal with its problems, especially the existential crisis of rising immigration and falling fertility. Will Italians continue to have a homeland for themselves and their descendants? Or will they go the way of other nations that are now footnotes in history?

 

That may sound like hyperbole. With a population of sixty million, Italians will surely enjoy a supermajority in their country for years to come. Keep in mind, however, that their mean age is 47; therefore, more than half are past the age of reproduction. With a fertility rate of 1.3 children per woman, the smaller "procreative fraction" of the population will fall by almost 50% with each generation. Meanwhile, the foreign citizen population has risen from 1.3 million in 2002 to 5.2 million in 2021. The total number of immigrants is actually larger:

 

In 2021, Istat estimated that 5,171,894 foreign citizens lived in Italy, representing about 8.7% of the total population. These figures do not include naturalized foreign-born residents (about 1,620,000 foreigners acquired Italian citizenship from 1999 to 2020, of whom 130,000 did so in 2020) as well as illegal immigrants, the so-called clandestini, whose numbers, difficult to determine, are thought to be at least 670,000. (Wikipedia 2022)

 

The demographic crisis is key to understanding Meloni’s electoral platform:

 

·         taxation that takes the size of the nuclear family into account

·         a lower sales tax of 4% on goods for young children

·         public funding of housing for Italian families who do not own a home. Eligible families must have at least one gainfully employed member

·         no birthright citizenship and no decriminalization of illegal immigration

·         a naval blockade to halt illegal immigration across the Mediterranean

 

Although her coalition enjoys an absolute majority in both houses of parliament, she will not find it easy to put her platform into practice:

 

She will very soon have to deal with the European Court of Human Rights, the Court of Justice of the European Union and the United States, if she does not respect the treaties on the management of immigration, Islam, free and undistorted competition and the European Union's defence policy.

 

If she is really very brave, she will carry on regardless and continue her policy. That is when the European Central Bank will deal with her. Indeed, Italy has become, thanks to Berlusconi, a beggar. It owes its survival only to the accommodative policy of the ECB, which massively buys its abysmal debt, and protects it from hedge funds. Remember that the ECB holds 780 billion [euros] of Italian public debt (30% of total debt), and that this is only growing. Italy's 10-year borrowing rates have already exceeded 4%, which is completely unbearable for the country's budget. Then it would be enough for the ECB to stop its purchases, or even to sell part of its stock on the market at a low price, to immediately raise this rate to stratospheric levels, and make Italy look like Zimbabwe. And the same people who were yesterday in the street with signs of support will throw stones at her while insulting her. (Falento 2022)

 

Looking to the future

 

To date, nationalist victories have been on the periphery of Western Europe, and not in its core. The periphery is home to people who have not fully assimilated into the Western world-system, largely because they are less proficient in English—the main conduit of neo-Western culture. So it is difficult to make them understand ideas and social norms that emanate from the core, let alone comply with them. As a general rule, the periphery is where a world-system has the most trouble imposing its will, not only politically and economically but also culturally and ideologically.

 

The next decade will see rising tensions between the core and the periphery, and it’s difficult to say which will prevail. The periphery is being taken over by nationalists, like Giorgia Meloni, while the core remains dominated by elites who are pushing the globalist project: on the one hand, they want to export high-wage jobs to countries where labor is cheaper; on the other, they want to import low-wage labor for jobs that cannot be exported, i.e., jobs in construction, agriculture, and services.

 

That is why median wages in the West have scarcely risen over the past half-century. High-wage “breadwinner” jobs in manufacturing are largely gone, and the jobs that remain are increasingly low-paying ones in services. During the 2020s, wage stagnation will give way to a leveling downward of wages throughout the West. Elsewhere, the leveling upward will be modest and uneven. The inner periphery will get the worst of both worlds: they’re not poor enough to attract low-wage industries, but not rich enough to attract the financial industry jobs that are concentrated in London, New York, and other world centres.

 

It is doubtful whether globalization will be a net benefit for the average person in the world.  Wealth is created most efficiently in high-trust societies, and those societies are the ones most affected by “replacement migration.” We may simply end up with a world where most workers are equally poor and equally mistrustful of each other.

 

 

References

 

Falento, A. (2022). Giorgia Meloni ne pourra rien faire si elle ne sort pas de l’Union européene. Riposte laïque. September 26. https://ripostelaique.com/giorgia-meloni-ne-pourra-rien-faire-si-elle-ne-sort-pas-de-lunion-europeene.html  

 

Frost, P. (2017). Terra Nostra, for how long? Evo and Proud, November 23. https://evoandproud.blogspot.com/2017/11/terra-nostra-for-how-long.html  

 

Wikipedia (2022). Immigration to Italy. https://en.wikipedia.org/wiki/Immigration_to_Italy

Looking beyond the data

 

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, genetic selection and social class in pre-industrial England.  http://www.econ.ucdavis.edu/faculty/gclark/Farewell%20to%20Alms/Clark%20-Surnames.pdf     

 

Clark, G. (2009b). The domestication of man: The social implications of Darwin. ArtefaCTos 2: 64-80. https://www.researchgate.net/publication/277275046_The_Domestication_of_Man_The_Social_Implications_of_Darwin

 

De Rosa, L. (1979). Property Rights, Institutional Change, and Economic Growth in Southern Italy in the XVIIIth and XIXth Centuries. Journal of European Economic History 8(3): 531-551.

 

Frost, P. (2019a). The Original Industrial Revolution. Did Cold Winters Select for Cognitive Ability? Psych 1(1): 166-181. https://doi.org/10.3390/psych1010012   

 

Frost, P. (2019b). Why that stereotype and not the other? Evo and Proud, July 28. https://evoandproud.blogspot.com/2019/07/why-that-stereotype-and-not-other.html

 

Frost, P. (2021). Commentary on Fuerst et al: Do Human Populations Differ in Their Mental Characteristics? Mankind Quarterly 62(2). http://doi.org/10.46469/mq.2021.62.2.9   

 

Fuerst, J., E.O.W. Kirkegaard and D. Piffer. (2021). More research needed: There is a robust causal vs. confounding problem for intelligence-associated polygenic scores in context to admixed American populations. Mankind Quarterly 62(1): 151-185. https://www.researchgate.net/profile/John-Fuerst/publication/354767141_More_Research_Needed_There_is_a_Robust_Causal_vs_Confounding_Problem_for_Intelligence-associated_Polygenic_Scores_in_Context_to_Admixed_American_Populations/links/614bc1dfa595d06017e4c017/More-Research-Needed-There-is-a-Robust-Causal-vs-Confounding-Problem-for-Intelligence-associated-Polygenic-Scores-in-Context-to-Admixed-American-Populations.pdf

 

Lasker, J., B.J. Pesta, J.G.R. Fuerst, and E.O.W. Kirkegaard. (2019). Global Ancestry and Cognitive Ability. Psych 1(1):431-459. https://doi.org/10.3390/psych1010034  

 

Oesterdiekhoff, G.W. (2012). Was pre-modern man a child? The quintessence of the psychometric and developmental approaches. Intelligence 40, 470–478. https://doi.org/10.1016/j.intell.2012.05.005

 

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., and R. Lynn. (2022). In Italy, North-South Differences in Student Performance Are Mirrored by Differences in Polygenic Scores for Educational Attainment. Mankind Quarterly 62(4), Article 2. https://doi.org/10.46469/mq.2022.62.4.2   

 

Rindermann, H. (2018). Cognitive Capitalism. Human Capital and the Wellbeing of Nations, 1st ed.; Cambridge University Press.