The Columbian Exchange

The Columbian Exchange: A History of Disease, Food, and Ideas

The Columbian Exchange refers to the exchange of diseases, ideas, food crops, and populations between the New World and the Old World following the voyage to the Americas by Christopher Columbus in 1492. The Old World – by which we mean not just Europe but the entire Eastern Hemisphere – gained from the Columbian Exchange in a number of ways. Discov­eries of new supplies of metals are perhaps the best known.

But the Old World also gained new staple crops, such as potatoes, sweet potatoes, maize, and cassava. Less calorie-intensive foods, such as tomatoes, chili peppers, cacao, peanuts, and pineap­ples were also introduced and are now culinary centerpieces in many Old World countries, namely Italy, Greece, and other Mediterranean countries (tomatoes), India and Korea (chili peppers), Hungary (paprika, made from chili peppers), and Malaysia and Thailand (chili peppers, peanuts, and pineapples).

Tobacco, another New World crop, was so universally adopted that it came to be used as a substitute for currency in many parts of the world. The exchange also drastically increased the availability of many Old World crops, such as sugar and coffee, which were particularly well-suited for the soils of the New World.

Source: Youth Voices, https://www.youthvoices.live/the-columbian-exchange-a-history-of-disease-food-and-ideas/
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Disease

The Spread of Disease from the Old World to the New

The list of infectious diseases that spread from the Old World to the New is long; the major killers include smallpox, measles, whooping cough, chicken pox, bubonic plague, typhus, and malaria. Because native popula­tions had no previous contact with Old World diseases, they were immunologically defenseless.

Dobyns writes that "before the invasion of peoples of the New World by pathogens that evolved among inhabitants of the Old World, Native Americans lived in a relatively disease-free environment. . .. Before Europeans initiated the Columbian Exchange of germs and viruses, the peoples of the Americas suffered no smallpox, no measles, no chickenpox, no influenza, no typhus, no typhoid or parathyroid fever, no diphtheria, no cholera, no bubonic plague, no scarlet fever, no whooping cough, and no malaria".

Although we may never know the exact magnitudes of the depopulation, it is estimated that upwards of 80-95 percent of the Native American population was decimated within the first 100-150 years following 1492. Within 50 years following contact with Columbus and his crew, the native Taino population of the island of Hispaniola, which had an estimated population between 60,000 and 8 million, was virtually extinct. Central Mexico’s population fell from just under 15 million in 1519 to approximately 1.5 million a century later. Historian and demographer Nobel David Cook estimates that, in the end, the regions least affected lost 80 percent of their populations; those most affected lost their full populations; and a typical society lost 90 percent of its population.

The uncertainty surrounding the exact magnitude of the depopulation of the Americas arises because we don’t know the extent to which disease may have depopulated the regions beyond the initial point of contact before literate European observers made physical contact with these populations. If disease traveled faster than the explorers, it would have killed a significant portion of native populations before direct contact, causing first-hand accounts of initial population sizes to be biased downward.

The result is that 1491 population estimates for the Americas have varied wildly, from a lower-bound estimate of approximately 8 million to an upper-bound estimate of over 110 million people. Surprisingly, despite decades of research, the range of the estimates has not narrowed, and no clear consensus has emerged about whether the true figure lies closer to the high or low end of the range. For examples of the opposing views, see Henige and Mann.

Syphilis: A New World Disease?

There are very few examples of disease being spread from the New World to the Old. The most notable exception, and by far the most controversial, is venereal syphilis. Biologist Irwin Sherman lists venereal syphilis as one of the twelve diseases that changed the world. This may seem surprising, given that, today, venereal syphilis is a nonfatal disease that is effectively treated with penicillin. However, this was not always the case.

Early on, in the late 15th and early 16th centuries, the disease was frequently fatal, and its symptoms were much more severe. They included genital ulcers, rashes, large tumors, severe pain, dementia, and eventual death. Over time, as the disease evolved, its symptoms changed, becoming more benign and less fatal. By the 17th century, syphilis had developed into the disease that we know today.

Two theories of the origins of venereal syphilis exist. The first, referred to as the "Columbian hypothesis," asserts that the disease-causing agent Treponema pallidum originated in the New World and was spread in 1493 by Christopher Columbus and his crew, who acquired it from the natives of Hispaniola through sexual contact. Upon return to Spain, some of these men joined the military campaign of Charles VIII of France and laid siege to Naples in 1495. 

Encamped soldiers exposed the local populations of prostitutes, which amplified disease transmission. Infected and disbanded mercenaries then spread the disease throughout Europe when they returned home. Within five years of its arrival, the disease was epidemic in Europe. Syphilis reached Hungary and Russia by 1497; Africa, the Middle East, and India by 1498; China by 1505; Australia by 1515; and Japan by 1569.

The second theory, the "pre-Columbian hypothesis," asserts that the disease had always existed in the Old World, and the fact that there were no accounts of the disease prior to the 1490s is because, prior to this time, it had not been differentiated from other diseases with similar symptoms. Proponents of the pre-Columbian hypothesis cite pre-Exchange accounts of disease symptoms similar to venereal syphilis, as well as skeletal remains with scars that are similar to scars left by syphilis. The debates over the true origins of venereal syphilis have been a direct consequence of the difficulty in distinguishing venereal syphilis from other diseases that had similar symptoms and left similar bone scars.

Recent findings from phylogenetics (the evolutionary study of the genetic relat­edness of different populations of organisms) have added valuable evidence to the mystery of the origins of venereal syphilis. The evidence supports the Columbian hypothesis that venereal syphilis is, in fact, a New World disease. A recent study by Harper et al. found that the bacterium causing venereal syphilis arose relatively recently in humans and is most closely related to a variation of the tropical disease yaws found in a remote region of Guyana, South America. This relationship is most consistent with venereal syphilis or some early ancestor originating in the New World. After decades of debate, this powerful study showed that venereal syphilis was indeed a New World disease.

The Transfer of New World Foods to the Old World

The transfer of foods between the Old and New Worlds during the Columbian Exchange had important consequences for world history. Historian Alfred Crosby describes the significance of the transfer of food crops between the continents, writing: "The coming together of the continents was a prerequisite for the population explosion of the past two centuries and certainly played an important role in the Industrial Revolution. The transfer across the ocean of the staple food crops of the Old and New Worlds made possible the former."

There are two channels through which the Columbian Exchange expanded the global supply of agricultural goods. First, it introduced previously unknown species to the Old World. Many of these species – like potatoes, sweet potatoes, maize, and cassava (also known as manioc) – resulted in caloric and nutritional improvements over previously existing staples.

Other crops such as tomatoes, cacao, and chili peppers were not by themselves especially rich in calories but complemented existing foods by increasing vitamin intake and improving taste. In many instances, the New World foods had an important effect on the evolution of local cuisines. Chili peppers gave rise to spicy curries in India, to paprika in Hungary, and to spicy kimchee in Korea. Tomatoes significantly altered the cuisine of Italy and other Medi­terranean countries.

Second, the discovery of the Americas provided the Old World with vast quantities of relatively unpopulated land well-suited for the cultivation of certain crops that were in high demand in Old World markets. Crops such as sugar, coffee, soybeans, oranges, and bananas were all introduced to the New World, and the Americas quickly became the main suppliers of these crops globally.

Table 1: The World's Most Popular Foods in 2000. All figures are for the year 2000. Bold type indicates a New World food crop. Italics indicate an Old World crop for which more than 26 percent of current world production is in the New World (26 percent is the fraction of arable land that is located in the New World). The table does not report the consumption of oils. Among oils, the fourth most consumed oil, sunflower oil, is derived from sunflowers, a New World crop.

The extent to which foods indigenous to the New World today comprise an important portion of the world's diet is illustrated by Table 1, which reports the world's most popular foods in 2000. The first list reports foods with popularity measured by the average consumption of calories per person per day. Because this measure may overstate the popularity of high-calorie food crops, we also provide rankings based on production and land under cultivation. These are reported in the second and third lists. Foods that are indigenous to the New World are reported in bold text.

From the table, it is clear that today New World foods are an important part of our diets. Although the two most consumed crops (by any of the three measures) are Old World crops (either rice, wheat, or sugar), many of the next most important crops are from the New World. Four New World crops that make it into the top ten by two or more measures are maize, potatoes, cassava, and sweet potatoes; tomatoes rank among the top 15 by two different measures. Also high on the list are a number of additional New World foods, such as chili peppers and cacao, which despite not being consumed in large quantities, are of central importance to the cuisines of many countries.

Staple Crops: Potatoes, Sweet Potatoes, Maize, and Cassava

The exchange introduced a wide range of new calorically rich staple crops to the Old World – namely potatoes, sweet potatoes, maize, and cassava. The primary benefit of the New World staples was that they could be grown in Old World climates that were unsuitable for the cultivation of Old World staples. Crosby writes: "The great advantage of the American food plants is that they make different demands of soils, weather and cultivation than Old World crops, and are different in the growing seasons in which they make these demands. In many cases, the American crops do not compete with Old World crops but complement them. The American plants enable the farmer to produce food from soils that, prior to 1492, were rated as useless because of their sandiness, altitude, aridity, and other factors."

This benefit of New World crops has resulted in their adoption in all parts of the world. This is shown by Table 2, which reports the top consuming countries for different New World foods. The New World crop maize has been widely adopted by a number of Old World countries, including Lesotho, Malawi, and Zambia. The average person in Lesotho consumes an astonishing 1,500 calories per day from maize. Even more widely adopted than maize is cassava. The top ten cassava-consuming countries are all from the Old World.

 Although both foods do have their imperfections – for example, a diet of too much maize causes pellagra, and consumption of insufficiently processed cassava results in konzo – they provide sustenance for millions of people around the world today. The table also shows that sweet potatoes have been widely adopted in the Old World and today are most heavily consumed in the Solomon Islands, Rwanda, Burundi, Uganda, and China.

The New World crop that arguably had the largest impact on the Old World is the potato. Because it provides an abundant supply of calories and nutrients, the potato is able to sustain life better than any other food when consumed as the sole article of the diet. Humans can actually subsist healthily on a diet of potatoes, supplemented with only milk or butter, which contain the two vitamins not provided by potatoes, vitamins A and D. This, in fact, was the typical Irish diet, which, although monotonous, was able to provide sufficient amounts of all vitamins and nutrients. The potato was also adopted as a core staple in many other parts of the World. As shown by Table 2, this nutritious crop has been so widely embraced by Old World populations that today the top consumers of potatoes are all Old World countries.

Recently, two studies have attempted to estimate empirically the benefits that arose from the introduction of the potato. Mokyr (1981) examines variation across counties in Ireland and estimates that the cultivation of the potato did spur population growth. In Nunn and Qian (2009), we also examine the effects of the potato on population growth but do so for the entire Old World. Using a difference-indifferences estimation strategy, we compare the pre-and post-adoption differences in population growth of Old World countries that could adopt the potato with Old World countries that could not.

We find that the potato had a significant positive impact on population growth, explaining 12 percent of the increase in the average population after the adoption of the potato. We also estimate the effect the potato had on urbanization, a measure that is closely correlated with GDP. We find that 47 percent of the post-adoption increase in urbanization is explained by the potato.

Table 2: Top Consuming Countries for Various New World Foods (average calories per capita per day)

We now turn to a discussion of crops that provide fewer calories. Still, we are no less important to Old World cuisines: capsicum peppers, tomatoes, cacao, and vanilla, and two less healthy New World crops, coca and tobacco.

Capsicum Peppers

The capsicum pepper originated in the areas that today are Bolivia and southern Brazil. By the arrival of the Europeans, the plant had migrated to Mesoamerica and the Caribbean. Capsicum annum, which was domesticated in Mesoamerica, is the ancestor to most of the peppers commonly consumed today: the cayenne pepper, bell peppers, and the jalapeno pepper. A second variety, Capsicum frutescens, first cultivated in the Amazon basin, gives us the tabasco pepper.

By 1493, capsicum peppers had arrived in Spain and Africa. They then reached the East Indies by 1540 and India by 1542. In Hungary, paprika, the spice made from grinding dried fruits of the capsicum pepper, was first mentioned in 1569. Paprika has since been widely adopted in a variety of Hungarian dishes, including goulash, and today is the country's national spice. The capsicum has also had a significant impact on the cuisine of many other countries. In South and Southeast Asia, some form of pepper is used in the base of almost every dish (for example, curries). In China, cuisine in the southwest (like Sichuan, Guizhou, and Hunan) is defined by the use of certain chili peppers. In Korea, a side dish of spicy kimchi is consumed with every meal.

Capsicums provide several health advantages. First, they are very nutritious. By weight, they contain more vitamin A than any other food plant, and they are also rich in Vitamin B. If eaten raw, capsicums provide more vitamin C than citrus fruits. Capsicums also contain significant amounts of magnesium and iron. Chilies, of course, are not eaten in vast quantities, but for populations with traditional diets deficient in vitamins and minerals, even a small amount can be important.

Second, capsicums also aid digestion. Capsaicin, an alkaloid uniquely found in capsicums, is an irritant to the oral and gastrointestinal membranes when ingested. This causes an increase in the flow of saliva, which eases the passage of food through the mouth to the stomach and increases gastric acids, which aid in the digestion of food. If ingested in large quantities, this same alkaloid can cause oral burning, which can be removed by casein. (Since casein is most readily available from milk and yogurt, it is not surprising that many spicy diets, such as those from South Asia, pair chilies with milk and yogurt.) Finally, capsaicin is now being utilized in medicine to treat pain, respiratory disorders, shingles, toothache, and arthritis. Research into its various properties is ongoing.

Tomatoes

Tomatoes are a fruit that originated in South America. Botanists believe that approximately 1,000 years before the Spanish arrived in the Americas, an unidentified wild ancestor of the tomato made its way north and came to be cultivated in South and Central America. The tomato was first mentioned in European texts in 1544. Mathiolus described how tomatoes, pond d'oro (golden apple), were eaten in Italy with oil, salt, and pepper, suggesting that the first tomatoes in Europe were yellow and not red.

European cultivation became widespread in the ensuing decades in Spain, Italy, and in France. The first documented authentic recipe in Italy appeared in 1692 in an early Italian cookbook, Lo Scalco Alia Modema, by Antonio Latini. Tomatoes were brought to Asia by Spaniards who visited the Philippines in 1564. However, in China, where they were regarded as foods of the "southern barbarians," they were not cultivated until the 20th century. In North Africa, English travelers reported that Spanish tomatoes were cultivated in fields of North Barbary as early as 1671.

One of the difficulties in consuming tomatoes was that they did not preserve well. Ripe tomatoes can become putrid within days in hot climates. The canning process helped increase the shelf life of the tomato to several months, but prior to 1890, it was a costly manual process. The mechanization of canning at the turn of the 20th century significantly lowered the cost of this process and resulted in a significant increase in tomato consumption.

Tomatoes have truly become a global food. As shown in Table 2, nine of the top ten tomato-consuming countries are Old World countries. Greece consumes the most tomatoes per capita, followed by other Mediterranean and Middle Eastern countries. Italy, known for its use of tomato sauces with pasta and on pizza, ranks sixth on the list. Table 3 lists the top ten producers of some New and Old World foods. The top producers of tomatoes are listed in panel A of the table; eight of the top ten producers are Old World countries, with only two New World countries, Brazil and Mexico, breaking the list of top tomato producers.

Although not particularly rich in calories, tomatoes are an important source of vitamins, particularly vitamins A and C. The tomato has been so thoroughly adopted and integrated into Western diets that today, it provides more nutrients and vitamins than any other fruit or vegetable. Medical researchers have also recently discovered a number of additional health benefits from tomato consumption. Recent research has found that lycopene, a powerful antioxidant contained in cooked or canned tomatoes, has properties that may help reduce cancer. Although research is still in progress, the American Cancer Society has already begun to promote increased consumption of tomatoes as a potential method for cancer prevention.

Cacao

The Codex Mendoza – an Aztec record of administration and description of daily life, written approximately 20 years after the Spanish conquest of Mexico – documents that by the time Cortes arrived, chocolate was being cultivated by farmers in the Yucatan and was traded in large quantities throughout the Empire. Historical records indicate that Columbus first brought back specimens of cacao pods to King Ferdinand I after his second voyage to the New World. Outside of the Americas, cacao was first cultivated in 1590 by the Spanish off the coast of Africa on the island of Fernando Po. At first, it was used in expensive chocolate drinks, mainly confined to aristocratic courts. From Spain, it spread to Italy and then to France via the royal marriage of Philip Ill's daughter, Ana of Austria, with Louis XIII. In England,

Samuel Pepys, the renowned 17th-century diarist, records that chocolate drinks changed from being novelty drinks to a regular luncheon beverage of the middle class during his lifetime.

Improved Cultivation of Old World Foods in the New World

After Columbus' voyages to the Americas, it was soon discovered that certain Old World crops were very well-suited to New World climates. In many cases, the Old World crops were grown much more productively in the New World soils and climates than they were grown back home.

Table 1 indicates in italics Old World crops that today have more than 26 percent of their total production in the New World. We chose a 26 percent cut-off because this is the fraction of arable land located in the Americas. Therefore, the table highlights Old World crops for which a disproportionate share of output (normalized by arable land) is produced in the New World. Because the Americas have 16 percent of the world's population, on a per capita basis as well, these foods are disproportionately produced in the Americas.

The fact that Old World crops flourished in the New World and New World crops flourished in the Old is not just a coincidence. It is, in part, the result of two aspects of the Columbian Exchange. First, both the New World and the Old World contain continents that lie on a North-South orientation and span nearly all degrees of latitude. Because climates change most drastically as one moves North-South rather than East-West, this helped to ensure that New World plants could find an Old World climate similar to their native climate and vice versa. Second, a benefit also arose from the two regions being isolated for thousands of years. The isolation caused separate evolutions of plants, parasites, and pests.

Therefore, transplanted crops often flourished because they were able to escape the pests and parasites that had coevolved with them in their native habitat. Because of the greater preva­lence of pests and parasites in tropical regions, tropical plants benefited most from being transplanted. This benefit partially explains why today, 57 percent of the production of coffee (which originated in the Old World) is produced in the New World and why 98 percent of natural rubber is produced in the Old World from transplanted rubber trees originally from the New World. Numerous other examples of transplanted crops exist. For example, the Americas currently produce 84 percent of the world's soybeans, 65 percent of its oranges, and 35 percent of its bananas.

Sugar Cane

The most striking example of an Old World crop that could be much more effectively cultivated in the New World is sugar cane. Most of the world's land suit­able for sugar cultivation lies in the Americas, particularly in Latin America and the Caribbean. Sugar cane was first carried to the New World (from the Spanish Canary Islands) on Columbus' second voyage in 1493 and was first cultivated in Spanish Santo Domingo (Dominican Republic). By 1509, enslaved Africans were being imported to the island, and by 1516, sugar was being exported to Europe.

Soon after, the Portuguese also brought sugar cane across the Atlantic, and by 1526, sugar was being exported from Brazil to Lisbon. Beginning in the last two decades of the 16th century, the interests of the Dutch, English, and French also turned to sugar production. Between 1630 and 1660, the Dutch, English, and French began to found their own sugar colonies. The climate in the Americas provided such an advantage to New World sugar producers that by 1680, sugar cane production was dominated by the New World.

One consequence of the large-scale production of sugar in the Americas was that, for the first time in human history, there was a large enough supply of the commodity that it could be consumed by the commoner in Europe. In England, the annual per capita consumption of sugar increased by 20-fold between 1663 and 1775, and it increased a further five-fold between 1835 and 1935. Sugar, providing a cheap and easy source of calories for the growing urban working class in Europe, was first consumed in tea and other hot drinks. During the 19th century, sugar consumption further increased as processed foods – such as jams, cakes and biscuits, canned vegetables and fruits, relishes, and white bread – became more common.

It is hard to overstate the importance of sugar for the European masses. Hersh and Voth estimate that the increase in sugar availability between 1600 and 1850 increased English welfare by an amazing eight percent. Anthropologist Sidney Mintz even goes so far as to put forth a hypothesis about the importance of sugar for creating an industrial working class in the United Kingdom. He writes that sugar, "by provisioning, sating – and, indeed, drugging – farm and factory workers, sharply reduced the overall cost of creating and reproducing the metropolitan proletariat."

Today, as shown in Panel B of Table 3, Brazil is the world's largest supplier of sugar cane. Other New World countries that are also top producers include Mexico, Cuba, Colombia, and the United States. Global production of sugar cane in 2000 was 1,252 million tonnes. Of this, 45 percent was produced in the Americas, with Latin America and the Caribbean accounting for 94 percent of the New World production.

Indirect Consequences of the Columbian Exchange

Quinine: The New World's "Gift" to Europe's Old World Colonies

Quinine, an important medicinal "gift" from the New World, had significant consequences for the relationship between Europe and its tropical Old World colonies, particularly its African colonies. Quinine and related anti-malarial alkaloids (quinidine, cinchonine, cinchonidine) are derived from the bark of cinchona trees native to the Andes.

The trees grow in scattered clumps in the eastern moun­tainous forests of Colombia, Ecuador, Peru, and Bolivia between 10 degrees north and 20 degrees south at elevations between 800 to 3,400 meters. Quinine was the first effective treatment of malaria caused by Plasmodium falciparum, the protozoan parasite that is transmitted between mammals by the female Anopheles mosquito. Quinine works by inhibiting plasmodium reproduction.

The use of quinine as a prophylactic was first discovered in 1841 by Dr. Thomas R. H. Thomson; the findings were later published in The Lancet. The British government, amidst the expansion of its empire into many malaria-ridden regions and seeing the potential benefits of quinine, encouraged the Royal Society to research the properties of quinine and explore the possibilities of farming it outside of the Andes.

In 1858, the British Botanical Gardens (headed by Kew Gardens, London) began the "cinchona transfer project" that aimed to ensure a stable, adequate, and cost-effective quinine supply to the colonizers of the British Empire by buying, stealing, bribing, and smuggling cinchona plants and seeds out of the Andes to London and colonial gardens in Ceylon and India. The British were successful in transferring plants to Kew Gardens in London, Calcutta, and the Nilgiri Hills of India. Within decades, production was also expanded to Singapore and Dutch Java. Estimates suggest that by 1880, enough was produced to supply ten million people with a daily dose.

The exact importance of quinine's use as an anti-malarial alkaloid is still being established by historians. Still, the evidence suggests that it was an important "tool of empire" and significantly enhanced Europe's ability to colonize tropical regions of the globe. Although debated, traditional historiography recognizes quinine as having facilitated European survival in malaria-ridden regions during the age of exploration and colonial expansion. The standard view is that Europe's colonization of Africa would have been virtually impossible without quinine.

Curtin notes that "between 1819 to 1836, the average annual death rate per thousand mean strength of European troops on the West African coast was 483 for enlisted men, and 209 for officers. Between 1881 and 1897, the annual average death rate for officials was 76 in the Gold Coast and 53 in Lagos…. since there were no further medical reforms between the 1850s and the 1880s comparable to quinine prophylaxis or the aboli­tion of dangerous treatments, it is fair to assume that the medical reforms of the 1840s reduced European mortality on shore by at least half and perhaps more." Curtin concludes that "the history of tropical Africa would certainly have been very different if European mortality had continued at the old rate."

Rubber in the Heart of Darkness

Natural rubber is made from latex, which is produced when certain plants are cut or punctured. Although rubber can be made from many different plants from around the world, the only commercially viable rubber plants are the Hevea rubber tree from Central and South America and a wild vine that grows in West-Central Africa.

Historically, Africans made little use of rubber except as an adhesive to fasten spearheads and arrowheads to their shafts. Native Americans, on the other hand, had developed methods to prevent the latex from decaying, which was accomplished by smoking the latex over fires to form spools of usable crude rubber. The rubber was used to create a wide range of items that were of central importance in their daily lives: hoods, boots, tents, balls, torches, jars, containers, syringes, toys, breastplates, rubber-headed drum sticks, and adhesives.

Europeans did not recognize the benefits of rubber until 1770 when French naturalist Charles Marie de La Condamine noticed its use by Amazon natives. The first commercial use of rubber was in the production of shoes, primarily from New England, in the early 19th century. However, the real boom for the rubber industry did not occur until the process of "vulcanization" was discovered. This process includes heating the rubber and combining it with other chemicals to produce a more stable product with a wider range of uses.

Between 1851 and 1881, the world's production of rubber increased from 2,500 to 20,000 tons annually. This boom, although significant, was modest compared to what was to come. The following three decades witnessed an explosion in the demand for rubber. Hobhouse describes the rubber boom, which lasted from 1880 to 1910, writing that "rubber became the most important, most market-sensitive, most sought-after new commodity in the world." The rising demand for rubber was first driven by the rise of electricity since rubber was used as an insulator. The demand was also fed by the need for rubber to produce rubber tires for bicycles and later for motorcycles and cars.

During this period, rubber production increased rapidly, doubling every three to five years. This was accomplished, in part, by an increase in supply from tropical regions outside of the Americas. In 1876, 70,000 Hevea rubber tree seeds were taken from Amazonia to Kew Botan­ical Gardens in Ceylon and Singapore by Sir Henry Wickham. This was the genesis of the rubber industry that now exists in all of Asia. (The current domination of the rubber industry by Asian countries is evident in Panel A of Table 3 – the top six producers of natural rubber are all Asian countries.)

A second supplier of rubber during the period, one which became the most notorious example of European exploitation in sub-Saharan Africa, was the Congo region of West Central Africa. Here grew the only other indigenous plants that were able to provide commercially viable sources of natural rubber. Between 1900 and 1908, during the height of the boom, between 4,500 and 6,000 tons of rubber were exported each year from the Congo Free State.

Concluding Thoughts

The aim of this paper has been to provide a historical overview of the Columbian Exchange, with a particular emphasis on aspects of the exchange that have generally been neglected by economists. The New World provided soils that were very suitable for the cultivation of a variety of Old World products, like sugar and coffee. The increased supply lowered the prices of these products significantly, making them affordable to the general population for the first time in history.

The production of these products also resulted in large inflows of profits back to Europe, which some have argued fueled the Industrial Revolu­tion and the rise of Europe. The Old World also gained access to new crops that were widely adopted. Potatoes were embraced by the Irish and Eastern European societies, chili peppers by the cultures of South and Southeast Asia, tomatoes by Italy and other Mediterranean societies, and tobacco by all nations of the world.

Table 4: Origins of New World Populations

The exchange also had some extremely negative impacts. Native American populations were decimated by Old World diseases. This depopulation, along with the production of valuable Old World crops like sugar cane and coffee, then fueled the demand for labor that gave rise to the transatlantic slave trade. The result was the forced movement of over twelve million slaves from Africa to the Americas and devastating political, social, and economic consequences for the African continent.

Following the slave trade, the African continent was divided and brought under European colonial rule, an event that some have argued would have been impossible without the discovery of quinine in the New World. Moreover, the knowledge of how to harvest and process rubber learned from natives of the Andes had particularly regrettable consequences for those in Africa’s Congo region.

Our hope is that this broad overview will spur further research examining the neglected aspects of the exchange. One interesting question that is particularly relevant for the exchange is the effect that diseases have on domestic institutions, social structures, and development generally. The recent book by Mann argues that the New World was much more politically, economically, and technologically developed than scholars have presumed, and one reason for this mischaracterization is the large negative impacts Old World diseases had on New World societies.

The study by Hersh and Voth provides estimates of English welfare gains from the increased supply of sugar and coffee that arose after the discovery of New World virgin soils. Their study makes one wonder about the welfare gains that arose from the introduction of various New World crops. For example, what were the welfare gains from tomatoes in Italy, maize in Lesotho, chili peppers in Asia, or cassava in West-Central Africa? Another interesting avenue of research is to exploit the introduction of new food crops to examine the effects of agri­cultural productivity and health on paths of development.

Our findings in Nunn and Qian suggest that the improvement in agricultural productivity from the introduction of potatoes had significant effects on historic population growth and urbanization. This raises the natural question of whether the adoption of potatoes brought any additional effects.

For example, how did the introduction of the new food crop affect health outcomes? Given the evidence that the introduction of potatoes eased population pressures and increased incomes, it is natural to ask whether the adoption of potatoes had any effect on conflict or warfare. If so, how did this, in turn, affect state formation and subsequent institutional development?

These examples provide a small sample of the many questions that one could investigate to further our understanding of the effects of the Columbian Exchange. These questions lie in virgin soils, waiting to be explored.