I want to be saved by a po-tay-toe

potatoes

Between 1700 and about 1950, world populations began to skyrocket. This growth was fastest in Northern Europe, and coincided with both an increase in city population share and Northern European world-dominance. There are clearly many reasons why this happened, but one powerful argument suggests that it was the simple potato that played the largest role.

Population increase can be due to both an increase in fertility and or a decrease in mortality. In Northern Europe, decreases in fertility after 1820 were more than offset by the larger decreases in mortality. Although hygienic advances played a major role, the main contributing factor was likely improved nutrition. Importantly, Fogel showed “an enormous increase in caloric intake after the middle of the eighteenth century, measured both directly, from agricultural output and diary surveys, and indirectly through changes in adult height.”

Although often not thought of as a daily part of your balanced breakfast, potatoes are incredibly nutritious. A medium potato contains 45% of your daily vitamin C, 18% of your potassium, 26% vitamin B6, and significant amounts of thiamin, phosphorous, iron, zinc, and an amount of fiber equivalent to that of other cereals such as wheat. In fact, a diet a of potatos and milk/butter is enough to live “healthily” on. Since potatoes have such a higher density of calories than comparable grains – an acre of land can support roughly 10,000 calories of wheat, barley, or oats versus 32,000 calories of potatoes – that families were able to sustain themselves on much smaller parcels of land. A family needed only an acre of potatoes and a single milk-cow to be self-sufficient.

Other factors drove the adoption of potatoes. They could be easily stored in winter, and concomitantly fed to livestock which implies increased availability of meat. Also, potatoes could be discreetly buried. Advancing armies usually demanded local stores of grains for food, causing mass starvation. Since they were hesitant to start digging everywhere up, burying of potatoes allowed increased survival for local peasants. This helps explain why the proportion of land dedicated to potatoes increased after every major war (up to, and including, World War II).

A recent study analyzed potato growth in order to determine the effects of the introduction of the potato across the Old World (all of the non-Americas). They found that the potato accounts for 12% of the increase in population, 22% of the increase in population growth, 47% of the increase of urbanization, and 50% of the increase in urbanization growth. It is astounding that something as small as the introduction of a potato can be such a large positive shock to the population.


suitability_of_potatoes

They begin with an analysis of the suitability of potatoes for a given piece of land, as determined by geologic and atmospheric factors. In figure 2 above, one can see that the most suitable pieces of land (dark green) are localized almost entirely in Northern Europe. Using a measure of outcome (population growth, urbanization, etc) dependent on the suitability of land for potatoes versus the suitability for all crops, they find that potato suitability had little effect on population before the year 1700. From 1700 onwards, though, they find a significant effect of potato suitability on population, population growth, urbanization, and urbanization growth. Effects on urbanization and urbanization growth were delayed roughly 100 years in comparison to the effects on population.

One caveat here is that they are looking at data every 100 years. They say this is because noisiness makes more detailed estimates unreliable, but it would be much more useful to see smaller time bins. In any case, 1700 is a good year to have potato suitability effect population sizes because this (to within 50 years) is when the potato became a popular crop across the Old World.

There are a lot of variables to control here, and they attempt to do so. For instance, the slave trade reached its peak around 1800; perhaps the movement of these populations is affecting
the estimates. Introducing variables to account for that seems to indicate it is not the case, though a more complicated look at the effects of the trade would have improved my confidence in the model.

They also exclude countries from Western Europe from their estimate. In this case, they see the same effects. Worryingly, they see the same time-course in the US/Canada that they do in the rest of the world. They attribute it to the ‘re-introduction of the potato’. Apparently, it is unclear exactly how widespread the potato was in these territories prior to European settlement? This should have had more attention paid to it, as well.

I would be nervous about accepting the estimate of the effect at face value without a more in-depth look. However, I think the evidence presented that potato-suitability as a proxy for introduction of potatoes shows that it did indeed have a substantial effect on population and urbanization, and was a huge contributing factor in Northern European dominance throughout the last few hundred years.

A couple historical notes. Outside of Europe, the next most suitable place for potatoes is in China, where they were indeed grown. China, let it not be forgotten, was still immensely powerful compared to the European countries up until the industrial revolution where technology was advancing too rapidly for China to catch up with. Also, the introduction of the potato is seen as a key development for population growth and urbanization in Incan history. I suppose this is just history repeating itself.

References
William H. Mcneill “How the Potato Changed the World’s History”. Social Research. FindArticles.com. http://findarticles.com/p/articles/mi_m2267/is_1_66/ai_54668867/

Nathan Nunn, Nancy Qian. “The Potato’s Contribution to Population and Urbanization: Evidence from an Historical Experiment”. NBER Working Paper No. 15157, July 2009. Link.

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One thought on “I want to be saved by a po-tay-toe

  1. Maybe you and your brother should colaborate on a paper. He wrote his history thesis on the change in farming techniques in England as a result of the black death and population change.

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