Why that stereotype and not the other?

Nubian Pyramids (Wikicommons - Petr Adam Dohnalek). In classical antiquity, contacts with black Africans were largely with Nubians, a people who already enjoyed a high level of material culture. 



A decade ago, Jason Malloy noted a curious fact: the ancient world did not see sub-Saharan Africans as less intelligent, despite the existence of other stereotypes, like macrophallia (Frost 2009, see comments; Thompson 1989). A stereotype of low intelligence is recorded in only two Greco-Roman texts, to the best of my knowledge. One is a reference by Ibn Khaldun (1332-1406 AD) to the Greek physician Galen (129-210 AD). The statement attributed to Galen does not appear in any of his works, at least not in those that have survived, and may be a false attribution.

We have seen that Negroes are in general characterized by levity, excitability, and great emotionalism. They are found to dance wherever they hear a melody. They are everywhere described as stupid. ... Al-Masfiüdi undertook to investigate the reason [for this]. However, he did no better than to report on the authority of ... al-Kindi and Jalinus [Galen] that the reason is a weakness of their brains which results in a weakness of their intellects. This is an inconclusive and unproven statement. ... The real reason is that ... joy and gladness are due to the expansion and diffusion of the animal spirit. Sadness is due to the opposite. (Hunwick 2005)

The other is the Christian parable of the Ethiopian woodcutter. The desert monk Arsenius (350-445 AD) recounted how an Ethiopian went out to gather wood. When the burden became too heavy, he put it down and continued to gather, but now his load was even heavier. So he put it down and gathered even more (Wallis Budge 1907). This parable is from late antiquity and may reflect the growing influx of black slaves into the Middle East during that period.

It seems, then, that low intelligence was not attributed to sub-Saharan Africans during classical antiquity, at least not often enough to become a stereotype. This stereotype would emerge later, during late antiquity and even more so during the Islamic period (Lewis 1990, pp. 46-47, 92-97).

I suspect there were two reasons:

- mean intelligence was probably lower in the Mediterranean world during classical antiquity, perhaps in the low 90s. This would be consistent with the apparently smaller size of its "smart fraction," in contrast not only to Western societies in later times but also to ancient Greece in earlier times (see July 13 post). In Roman society, intellectuals seem to have largely been isolated individuals. They did not come together to hold regular conferences or publish journals. While there were elementary schools, the ludus litterarius, there were no institutions of higher learning, only private tutors. The difference in mean intelligence with sub-Saharan Africa would have thus seemed smaller.

- contacts with dark-skinned Africans were initially most frequent with Nubians, who under Egyptian influence already enjoyed a high level of material culture and were thus already being selected for cognitive ability. Contacts with peoples farther south developed later, with development of the African slave trade. This trade seems to have slowly but steadily increased in volume during late antiquity and, subsequently, the Islamic period (Frost 2008).


Civilization and intelligence

So, beyond a certain point, does civilization actually select against intelligence? The short answer: yes, in some cases. 

Now for the long answer. First, increased intelligence comes at a cost:

The brain requires about 22 times as much energy to run as the equivalent in muscle tissue. The energy required to run every bodily process comes from the food we eat. Human brains are three times larger than our closest living relative, the chimpanzee, and use up to three times the energy, but the two species have the same metabolic rate. (Welsh 2011)

Because of that high energy cost, any excess intelligence is under strong negative selection and will decline noticeably—even over a few generations. Positive selection becomes confined to a minority of the population as a civilization develops and moves toward specialization of labor, i.e., the most difficult intellectual work is done by a minority while the majority performs menial tasks. 

Nonetheless, we have examples of advanced civilizations, notably in East Asia from ancient times and, later on, in Western Europe, where mean intelligence was and still is quite high. Those civilizations likewise had specialization of labor. So what made them different?

It seems to have been a process of internal demographic replacement that Gregory Clark described with respect to England and Ron Unz with respect to China. The mean intelligence of an entire population will steadily rise if two conditions are met:

1. Fertility is higher in higher social classes.

2. Class boundaries are sufficiently porous that the resulting demographic surplus of these classes can move downward and replace the lower classes.

Historically and cross-culturally, these two conditions were far from universal. In many societies, surplus members of the upper class preferred to remain unmarried and wait for a suitable high-status niche to open up. It was shameful to "lose caste" and enter a niche lower on the social ladder. Nor was fertility universally higher in higher social classes. In some cases, the rich and powerful had fewer children because they could count on other means of support for their old age. In other cases, they tended to congregate in towns and cities, where infant mortality was higher. Finally, greater sexual access to women often failed to translate into reproductive success because of infertility due to STDs or because of a culture of debauchery and indifference to married life.


Conclusion

With ancient DNA and polygenic cognitive scores, we can now understand history in a new light. Mean intelligence has risen and fallen during the time of recorded history, and not simply because of migrant influxes. The people may have been the same, and yet they really weren't:

Since it looks like there has been significant evolutionary change over historical time, we're going to have to rewrite every history book every written," said Gregory Cochran, a population geneticist at the University of Utah. "The distribution of genes influencing relevant psychological traits must have been different in Rome than it is today," he added. "The past is not just another country but an entirely different kind of people” (Wade 2006).

References

Clark, G. (2007). A Farewell to Alms. A Brief Economic History of the World, 1st ed.; Princeton University Press: Princeton,

Frost, P. (2008). The beginnings of black slavery. Evo and Proud, January 25
http://evoandproud.blogspot.com/2008/01/beginnings-of-black-slavery.html

Frost, P. (2009). Skin color and Egyptian/Nubian encounters. Evo and Proud, April 23
http://evoandproud.blogspot.com/2009/04/skin-color-and-egyptiannubian.html

Hunwick, J.O. (2005). A region of the mind: Medieval Arab views of African geography and ethnography and their legacy. Sudanic Africa 16: 103-136
https://org.uib.no/smi/sa/16/16Hunwick.pdf

Lewis, B. (1990). Race and Slavery in the Middle East. Oxford University Press.

Thompson, L.A.  (1989). Romans and Blacks. Norman: University of Oklahoma Press.

Unz, R. (2013). How Social Darwinism made modern China. The American Conservative, March/April, 16-27.
https://www.theamericanconservative.com/articles/how-social-darwinism-made-modern-china-248/

Wade, N. (2006). The twists and turns of history, and of DNA. The New York Times, March 12, Week in Review 14

Wallis Budge, E.A. (1907). The Paradise of the Holy Fathers. London: Chatto and Windus.
https://books.google.ca/books?id=LX_sCgAAQBAJ&printsec=frontcover&hl=fr&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

Welsh, J. (2011). Still up for debate. LiveScience, November 9
https://www.livescience.com/16953-brain-body-size-expense.html