The Sweet Potato is a versatile, nutritious and if cooked properly, delicious root. Whether it’s in fry form, steamed form, or roasted form, we see this humble tuber across multiple cultures and states across the globe. Although the roots of the sweet potato trace its origins back to Meso and South America, it travelled thousands of kilometres in eras before these distances were easily traversed. This little blog post today will explore the travels of the Sweet Potato, and its role in war, and the curiosities of how it is consumed across different cultures today.

Please be warned that this week’s post includes references to the genetic study of plants and to a certain degree Archaeobiology. In a bid to shift my focus to the non-human aspect of history, we will be treating the humble Sweet Potat as the main analytical unit of inquiry.

Archaeobiology what now?

The Sweet Potato, scientific name (Ipomoea Batatas), is a tuber (underground root) that is closely related to the morning glory. Eaten roasted, chipped, fried, stewed, ice creamed, curried and even in leaf form, the consumption of this plant is seen almost on every continent throughout the world. This curiously transnational tuber is significant across a range of cultures, with some touting its health benefits, and others using it as a staple in times of war. The origins of the sweet potato are murky. Dating back to nearly 5000 years ago, it was thought to have originated in Central or South America and was somehow spread to the Polynesian Islands. Most Archeaobiologist has referred to this gradual process of consumption and cultivation as “domestication”, and noted that Mesoamerica had the greatest diversity of Sweet Potato genomes.

The struggle with investigating this tuber comes in two parts. Firstly, it’s old. Very very old. Secondly, much of its history rests in areas that are grossly understudied in the discipline of history. Although the Mesoamerican and South American civilisations such as the Aztecs or Incans are introduced to elementary or middle school students as a sort of novelty, very little “serious” research has been done in this field. Similarly, the disparate and migratory nature of Polynesian civilisations (a gross oversimplification), makes it difficult for historians to find a suitable analytical standpoint from which to start. As a result, literature on the Sweet Potato is left to the niche of Archaeobiology.

The Travelling Tuber

According to Francisco J. Morales, a specialist in Plant Virology (of all things), wrote in the Agricultural Journal Geneflow. He points to the incongruity between how the Polynesian Islands were thought to be colonised by South-East Asian migrants, and the strong archaeological presence of the Sweet Potato on Palliser, Mangareva and Easter Islands (Rapa Nui). Most notably, the Easter Islands had an entire agricultural civilisation built on the Sweet Potato before its total agro-ecological collapse. The possible linguistic link between the name Polynesian name for Sweet potato, Kumara and the Central American name Kumar, points at the possibility of migration outwards from South America, but even here the evidence is far from concrete.

Once again, Archaeobiology rears its ornate head, and we see overlapping routes of exchange both linguistically, and genetically. The map above explores the possible routes that the sweet potato may have taken in its travels across the pacific. But with these perplexing travels aside. We can look at the cultural differences in how this particular tuber is consumed.

Taken from Historical collections reveal patterns of diffusion of sweet potato in Oceania obscured by modern plant movements and recombination, PNAS 2013

The Tuber in War and Peace

The Cantonese saying “mo faan sik, sik faan shue”, or “If there is no rice, eat sweet potato“, rings true in several East Asian countries in the aftermath of WWII. Conventional historical evidence points to the post-war US-occupied Japan. Where food production had dropped by nearly a quarter. Okumura Ayo, a Japanese food scholar, notes that from 1944 large swathes of rural Japan were turned towards cultivating sweet potato and that every part of the plant was eaten. This academic account is corroborated by accounts of a close Japanese family friend that to this day, remembers the harshness of rationing and the copious amounts of sweet potato as a staple. This was despite living in a relatively rural part of the country, Gifu, which was an agricultural area.

Taiwan, also saw an enormous amount of sweet potato production before, during and after the post-WWII period, producing 3.7% of the worlds total sweet potato crop. On a personal level, my Grandmother to this day avoids eating sweet potatoes. As it reminds her of rationing during WWII in Taiwan as well. It is curious to see the consistencies in the use of sweet potato as a rationing staple across East Asia.

The Modern Tuber

Most people here in the UK would know sweet potatoes in the form of fries, and it is indeed seen as a healthier and sometimes less tasty alternative to the common potato. The connotation of health that the sweet potato belies in most of the Western world resulted in it being consumed amongst athletes and the health-conscious. With a low glycemic index (meaning it is more slowly digested) it is recommended as a healthy carbohydrate. However, the history of sweet potato as a health food is only a recent development.

In modern-day Japan, sweet potato is sold by street vendors and out of trucks in the winter, with a characteristic Yakiiiimoooo, Ishiyakimooo, Yakiiiimooo (焼き芋ー、石焼きも、焼き芋ー) jingle, meaning “Roasted Sweet potato, rock roasted sweet potato!”. Not unlike the twinkling sounds of an ice cream truck in an American neighbourhood. These sweet potatoes are frozen to drive out the moisture from its cells, resulting in concentrated sugar levels. Creating a food as sweet and rich (and more nutritious) as ice cream. It is probably fair to say that the Japanese cultural equivalent of the American Ice cream truck are these Sweet potato trucks that ply their trade in the cold winters.

In Taiwan, we see an even stranger development. The tuber itself is often incorporated in rice porridge, and the leaves are commonplace in Taiwanese cooking. I distinctly recall having to explain to visiting German friends that what they were eating was Süßkartoffelblatt, and them remarking that they didn’t know that the leaf portion was edible. 蕃薯葉 in Taiwan is something of a unique vegetable that thus far, I have not found anywhere else.

This little historical journey the transnational tuber has taken across the globe is a remarkable one, and the variance in consumption across the globe fascinating. Thus, I have decided to have sweet potato for dinner, tomorrow night.

Migratory Sweet Potato: A Transnational Tuber