A question of Chinese graveyards

Are urban Chinese really intelligent because of the mandarin system? Do urban Chinese die earlier? And why are these questions related at all?

Chinese graves in Hsipaw, Myanmar, from Wikimedia Commons. 

Last week I published an article about differences in educational attainment between rural China and urban China. Among other things I presented a very off-the-cuff theory about these differences being due to biological IQ differences stemming from the mandarin system, where predominantly urban mandarins were promoted and allowed to procreate based on cognitive achievements.

This was not a very well-thought through theory. But publishing made me think (publish first, think later, great strategy for a successful blog!). It also forced me to do some research, because Chinese history is not really one of my areas of expertise.

To be honest, I will not have any definitive answers to present at the end of this article. But I learned a few things on my journey to no answers, which I might as well share with you patient readers. 

Let us start at the beginning. With buttons.

London 1662

John Graunt's occupation was that wonderfully British profession of haberdasher. For reasons that are probably historical but not very logical the Swedish school system always teaches British English. Apparently haberdasher means something else in American English, but for me it will always be a long and exquisite word for someone who sells small and simple things like buttons.

Unfortunately this article will not be about haberdashery. John Graunt did not only sell buttons. In his spare time he liked to read bills of mortality, 17th century papers documenting burials in different English parishes. His studies lead him to write a book, Natural and Political Observations Made Upon the Bills of Mortality, in which he more or less single-handedly invented the scientific field of demography. 

Death in the city

John Graunt's book introduced a number of concepts central to demography, like birth rate, death rate and fertility rate. These were all very important concepts. Important enough, in fact, to be noticed in Graunt's own time. He initially presented his book to the Royal Society in 1662 and the reception was so positive that he was immediately taken up as a member, despite his rather modest background.

It is obvious that Natural and Political Observations Made Upon the Bills of Mortality was a very important work and its fame is very well deserved. There are, however, details of it that are less well known. One such detail is the fact that London was a much deadlier place than the countryside which is mentioned, almost in passing, in the seventh chapter:

We come to shew, why although in the Country the Christenings exceed the Burials, yet in London they do not. The general Reason of this must be, that in London the proportion of those subject to die, unto those capable of breeding, is greater than in the Country; That is, let there be an hundred Persons in London, and as many in the Country; we say, that, if there be sixty of them |62| Breeders in London, there are more than sixty in the Country, or else we must say, that London is more unhealthful, or that it inclines Men and Women more to Barrenness, than the Country: which by comparing the Burials and Christenings of Hackney, Newington, and the other Country-Parishes, with the most Smoky and Stinking parts of the City, is scarce discernible in any considerable degree.

The simple fact that London constantly had more deaths than births meant that it would have ceased to exist had there not been so many people moving in from somewhere else. This somewhere else was the surrounding countryside, which had more births than deaths. In biology this is known as a source-sink dynamic where one habitat, the sink, can only continue existing if it is constantly replenished from another habitat, the source. In demography the phenomenon where cities need migration from the countryside to maintain their population level is called the urban graveyard effect.

This urban graveyard was first noted by John Graunt in London in the 17th century when it was very much still a thing. Later scientists have been able to demonstrate the same effect for a number of European countries from the Middle Ages up to the 19th century.

Enter evolution

The argument I made in my last article about China was that urban Chinese might have higher IQ than rural Chinese for biological reasons. I speculated that this biological reason might be the Chinese mandarin system in which cognitively gifted scholars were showered with resources that enabled them to procreate more than their less cognitively gifted peers, in effect creating an evolutionary pressure for higher IQ. Since the scholars were predominantly urban this pressure should only have applied in cities.

As everyone can see this theory does not go very well together with the urban graveyard effect. If cities are population sinks which are dependent on a constant influx of people and genetic material from the surrounding countryside it is very difficult to talk about a specifically urban evolutionary history.

The question here is if the urban graveyard effect is applicable in China as well as in Europe. Historically East Asians were famed for their high hygienic standards, something that can not be said about Europeans. Maybe this led to less mortality in Chinese cities which would neuter the urban graveyard effect. 

What the scientists say

Studies of the urban graveyard effect in China are, perhaps not surprisingly, thin on the ground. I did find one study, however, Urban-Rural Mortality Differentials: An Unresolved Debate by Robert Woods from 2003 (sci-hub link). It discusses the urban graveyard effect in several eras and locations, including East Asia (comprising China and Japan).

Unfortunately, the results are not unambiguous. Demographic sources for China are less well-developed than for Europe. In fact, they are almost non-existent. Professor Woods uses several roundabout ways to make estimations despite the headwinds.

The best one, in my opinion, and the only one that gives results from before the 19th century, is an analysis of Chinese clan annals from the 15th century to the 19th century in which male clan members are listed with birth and death dates. By calculating the age of death and comparing urban and rural clans the study arrives at an estimated life expectancy for rural males of 35.5 years and for urban males of 34.4 years.

This is a significantly smaller difference than Europe at the same time. For example in England at the start of the 19th century the life expectancy in rural Surrey was 45 years while in London it was 37 (and even lower in Manchester and Liverpool). But the comparison is also skewed since in China it only measured males of some status while the English data is for the whole population.

Disappointing conclusion

As so many times before, it will not be possible to solve this problem definitely, at least not until someone publishes more data on the births and deaths of Chinese cities throughout history.

The good thing, if one could call it that, is that the limited data from Robert Woods' study indicates that the urban graveyard effect is probably smaller in China than in Europe. Perhaps even much smaller. This might, but just might, indicate that Chinese cities were in fact able to sustain themselves over long periods of time. Long enough periods to allow some evolutionary selection to take place.

On the other hand, China's turbulent 20th century history makes it rather unlikely that any stable urban population could have been sustained. Even more, according to this study, in China in 1949 only 10.6% of the population had urban hukou, compared to a third today. In other words, China has seen rapid urbanization meaning that most of today's urban Chinese were in fact rural only two or three generations ago.

The difference in cognitive performance between urban and rural Chinese is intriguing. But I find it far-fetched that it should be down to genetic reasons. The urban graveyard effect might not be the party pooper I expected it to be but China is still a unitary state where it is implausible for borders between city and country to be high enough to have permitted the degree of separation necessary for different evolutionary histories.