The Columbian Exchange

Misha Glenny and guests discuss the exchange of cultures and biology across the Atlantic and Pacific after 1492. That was when Columbus reached the Bahamas, a time when Europe had no potatoes, tomatoes, sunflowers or, arguably, syphilis in its most virulent form; the Americas had no cattle, bananas, sugar cane or smallpox. The lists of what was then exchanged are long and as these flora, fauna and diseases moved between continents, their impact ranged from transformation to devastation. In parts of the Americas, European viruses helped kill over 90 percent of the population. In parts of Europe, Africa and Asia populations boomed on the new American foods. Sheep from Europe grazed fertile land into deserts in some parts of the Americas, while the lowered populations in others led to local reforestation which, arguably, is linked to a particularly cold period in the Little Ice Age. With Rebecca Earle Professor of History at the University of Warwick John Lindo Associate Professor of Anthropology at Emory University And Mark Maslin Professor of Earth System Science at University College London Producer: Simon Tillotson Reading list Steven R. Brechin and Seungyun Lee (ed.), Routledge Handbook of Climate Change and Society (Routledge, 2024), especially the chapter ‘Human Impacts on the Climate Prior to the Industrial Revolution’ by Alexander Koch, Simon Lewis, Chris Brierley and Mark Maslin Judith Carney and Richard Rosomoff, In the Shadow of Slavery: Africa’s Botanical Legacy in the Atlantic World (University of California Press, 2009) EJ Collen, AS Johar, JC Teixeira and B. Llamas, ‘The Immunogenetic Impact of European Colonization in the Americas’ (Front Genet, August 2022) Alfred W. Crosby, The Columbian Exchange: Biological and Cultural Consequences of 1492 (Greenwood Press, 1972) Rebecca Earle, ‘‘‘If You Eat Their Food . . .”: Diets and Bodies in Early Colonial Spanish America’ (American Historical Review 115:3, 2010) Raymond Grew (ed.), Food in Global History (Routledge, 1999), especially ‘The Impact of New World Food Crops on the Diet and Economy of China and India, 1600-1900’ by Sucheta Mazumda Simon L. Lewis and Mark A. Maslin, The Human Planet: How We Created the Anthropocene (Pelican, 2018) Nathan Nunn and Nancy Qian, ‘The Columbian Exchange: A History of Disease, Food, and Ideas’ (Journal of Economic Perspectives 24:2, 2010) Jeffrey Pilcher (ed.), The Oxford Handbook of Food History (Oxford University Press, 2012), especially ‘The Columbian Exchange’ by Rebecca Earle In Our Time is a BBC Studios production Spanning history, religion, culture, science and philosophy, In Our Time from BBC Radio 4 is essential listening for the intellectually curious. In each episode, host Misha Glenny and expert guests explore the characters, events and discoveries that have shaped our world.

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  Hello, Misha Glennie here. Did you know you can get episodes of In Our Time 28 days early with a subscription to the BBC website and app? Just head to bbc.com/subscribe to find out more.

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  This is In Our Time from BBC Radio 4, and this is one of more than 1,000 episodes you can find in the In Our Time archive. A reading list for this edition can be found in the episode description wherever you're listening. I hope you enjoy the programme. Hello. When Columbus reached the Bahamas in 1492, Europe had no potatoes, no tomatoes, no sunflowers, and arguably no syphilis. The Americas had no cattle, no bananas, no sugarcane or smallpox. The lists go on. As these flora, fauna and bacteria then moved between continents, their impact ranged

• 2:08Speaker 03

  from transformation to devastation. In parts of the Americas, European diseases helped kill over ninety percent of the population. In parts of Europe, Africa and Asia, populations boomed on the new American foods. And this Columbian exchange, as it's known, has even been linked to a mini Ice Age and the start of humanity's greatest impact on climate. With me to discuss the Columbian exchange are Rebecca Earl, Professor of History at the University of Warwick, John Lindo, Associate Professor of Anthropology at Emory University

• 2:47Speaker 03

  in the USA, and Mark Maslin, Professor of Earth System Science at University College, London. Mark, let me start with you. The phrase "the Columbian exchange" comes from a book by Alfred W. Crosby from 1972, but you prefer to call it "the Great Dying". Why?

• 3:10Speaker 04

  Well, this is one of the great schisms in human history, and calling it the Columbian exchange feels rather benign. The idea is that people and species were swapped and exchanged between the Americas and Eurasia and Africa by European explorers. But the reality was very different. In 1492, there were sixty million people living in the Americas, which was roughly the same size as the population in Europe and in China. Within a hundred years of first contact with Europeans, fifty-five million out of those sixty million were dead. That's over ninety percent of the population. The only world event that actually killed more human beings was the Second World War.

• 3:55Speaker 04

  So we've called it "the Great Dying", and this was because of the diseases that were brought across the Atlantic by the Europeans, for example measles, typhoid, smallpox, among others. And the impact was so devastating because the indigenous people had very little resistance. And that's Because they first arrived in the Americas about twenty to fifteen thousand years ago. They made the journey from Asia across the Bering Straits into Alaska. Because at the end of the last ice age, the sea level was slightly lower. And there was lots of sea ice, so it made the journey possible. And then, when they were there, they actually then populated down into Central and South America. And apart from occasional visits from Polynesians and Vikings.

• 4:39Speaker 04

  The population was isolated from the rest of humanity for over ten thousand years. And that's why they had no resistance to these diseases which had evolved in Eurasia.

• 4:50Speaker 03

  Just to clarify, how do we know that the populations of the Americas, Asia and Europe were roughly the same in the late fifteenth century?

• 4:59Speaker 04

  Well, this is where the archaeologists come into their own. Because it was about fifteen years ago that they actually started to pull their data together. And even though they've been seeing really high population densities in certain areas, when they started putting it all together. The realisation is that our ancestors were just as good as us. And actually, we're much more adept at spreading. And so therefore, we find out that our ancient populations were much larger than we ever guessed.

• 5:28Speaker 03

  To be clear, there was movement of people within the Americas before fourteen ninety-two. But you don't see it in quite the same way in terms of the exchange.

• 5:40Speaker 04

  The key thing is there was huge exchanges within the Americas. So having started from Alaska, the population went down the West Coast. Some moved over to the East Coast. And then the rest moved into Central and South America. And if you think about it, we know about those empires, you know, the Aztecs in Mexico, the Incas in the Andes and the Mayans in Central America. But you have to remember, these were just the latest empires that the Europeans came in contact. And we have thousands of years of history where they had centralised governments, massive cities, urban planning, advanced agriculture. And extensive trade networks across the whole Americas.

• 6:20Speaker 04

  So what you're seeing is you have the Americas as one supercontinent where everybody was slowly exchanging ideas. And agriculture products and things like that. But they were isolated from Africa, Europe and Asia.

• 6:36Speaker 03

  Thank you. Rebecca Earl. Why did the Europeans bring their own food when they started travelling to the Americas in numbers after 1492?

• 6:46Speaker 05

  Europeans, when they travelled to the Americas, well, Columbus, we could start with Columbus and say, what did he bring with him on his ships when he was sailing on his multiple voyages, looking to try to get to China and Japan? Well, he brought radishes and he brought seedlings to grow cabbages and he brought seedlings for peach trees and pear trees and things like that, along with wine and olive oil and wheat flour. And it's easy to imagine that Europeans were simply behaving in some kind of, you know, stereotypical touristic fashion, thinking, well, the food's going to be terrible, I don't want to eat any of that, I'm going to pack my own cornflakes and definitely my own tea bags, and that they were simply reflecting their cultural preferences. But there was much more to it, which had to do with health and with questions about

• 7:28Speaker 05

  bodily integrity, because the way in which people thought about their bodies and healthful behaviour at the time gave food a really, really important role in keeping you well, which in fact is not so different, I think, from how we think today about travel. So, we now think that if you have very disrupted sleep, if your diet has gone out the window, if you're not taking any exercise, that that's probably going to have an impact, not just on your state of mind, but also on your health. And that's exactly what people thought in the period when Columbus and Europeans were invading the Americas, as you've just described. So, for them, lifestyle was really important to staying healthy, and living in a different

• 8:11Speaker 05

  climate was seen as being particularly challenging. You can't do anything about the climate if you're travelling somewhere else, you can do something about the food. So, food was really, really important to keeping Spaniards well.

• 8:23Speaker 03

  But I'm just interested to know, they would have come across indigenous populations who were also relatively well nourished, and yet they rejected their food, is that right?

• 8:34Speaker 05

  By and large, so there were certain things, I mean, nobody in Europe had a bad word to say about the pineapple. Everybody thought pineapples were absolutely splendid. But other staple components of diets that they encountered in the Americas didn't have such a positive reception by Europeans. And it had to do, I think, with these ideas about health. It wasn't simply that they said, oh, other people eat them, we don't want to touch them. It was they had real doubts about whether those foods would be suitable to their constitutions. So Europeans were quickly interested in the physical differences that they perceived between themselves and the indigenous peoples that they encountered. For example, the Spanish men were really worried about the fact that, by and large, indigenous men didn't have beards.

• 9:19Speaker 05

  Why not? Beards for European men, like, they were like a manifest proof of your masculinity. They were seen to be directly caused by your testosterone production. I mean, not that they use the terms of testosterone, but it was manliness on your face. So why? Why didn't indigenous men have beards, by and large? Well, the explanation was eventually ascribed to their diet. It was too wet a diet, it was too cold a diet, it was the wrong sort of diet to encourage facial hair growth. So if you adopted that diet, where, you know, whence the Spanish beard? And they were, they wrote about this at the time, and they said, don't worry, don't worry, we've got lots of good European food, we're not going to lose our beards.

• 9:59Speaker 03

  But nonetheless, at some point, some remarkable foods were exported from the Americas and conquered the world. What sort of foods were those?

• 10:08Speaker 05

  Well, again, all sorts of foods that we take completely for granted these days. In fact, when Alfred Crosby's The Colombian Exchange was first published in 1972, and he argued that these exchanges, and I take your point completely, it's probably too attractive a picture of what was going on. When Alfred Crosby published The Colombian Exchange in 1972, the story that he was telling about why these movements of foods and animals were important was so novel, it was so unusual, it was so outside of the kind of history that had been told up until that point, by and large, that some people who reviewed his books had real trouble getting their heads

• 10:50Speaker 05

  around the basic facts that he was trying to analyze, such as that potatoes come from the Andes. So one of the early reviews says, well, this is a very interesting book, it explains how potatoes got to South America.

• 11:03Speaker 03

  And tomatoes.

• 11:05Speaker 05

  So all sorts of foods that we now think of as belonging to like us right here. In fact, came from the Americas. They had no presence in the cuisines or the cultures of anywhere else in the world. And it's hard to imagine, let's say, Indian food without tomatoes, without chili peppers, without a potato, you know, no sag alu.

• 11:25Speaker 03

  Mark, you wanted to come in briefly there.

• 11:28Speaker 04

  So if you think about it, maize and cassava, which are the basic diet of a lot of African countries, all come from South America. So again, it's these huge movements of food that we just don't see. You're absolutely right.

• 11:41Speaker 03

  We'll come on to some more foodstuffs later on. But before then, I want to go to John Lindo. John, you've tracked infectious diseases in the Americas. What kinds of diseases were people used to before 1492?

• 11:58Speaker 06

  So that question is a little bit complicated because, well, first of all, I think the idea back in the day, a few decades ago, was basically that there was no disease in the Americas before Europeans arrived, that there was some sort of paradise. But now, given various aspects of evidence from archaeology, as well as skeletal remains that show damage that could be associated with different pathogens, we are starting to piece together that this was not only not true, that there was disease before the arrival of Europeans, but that it varied across North and South America according to ecology and culture, as you would expect. And more recently, we have the advantages of advances in ancient DNA that have actually

• 12:43Speaker 06

  given us the ability to extract actual strains of a particular pathogen from a skeleton to actually identify the pathogen instead of being less specific with ideas of what was causing skeletal damage. So that being said, one of the major aspects that we've noticed is that tuberculosis, a different strain of tuberculosis that was endemic to the Americas was there before European contact, so tuberculosis was not brought over. Well, it was, and the European version was brought over. Tuberculosis was endemic, especially to areas of the Andes for a thousand or 2,000 years plus, we have that evidence, and specifically that that particular strain that we see in the Americas before contact may have come from seals.

• 13:27Speaker 06

  Other types of disease that is somewhat surprising, we see intestinal or rather stomach pathogens like H. pylori, that's associated with stomach cancer, but it's also seen all across the world, but it looks like it was also in the Americas before contact. And then we have other aspects of disease that you would expect that are local to particular ecologies, both in North Meso and South America, like intestinal parasites and a range of insects and soil-borne diseases, as well as various pathogens that are associated with syphilis. Now, at that point, in terms of the lineages that we are extracting before contact, it's unlikely that this is the same type of syphilis that we see today.

• 14:10Speaker 06

  This is not something that would have been sexually transmitted, and it would have varied by ecologies. And so-

• 14:16Speaker 03

  John, if I can interrupt it, if it wasn't transmitted sexually, how was it transmitted?

• 14:22Speaker 06

  It's likely it was transmitted via skin contact, so very different than it would be today in terms of what we know or associate syphilis with.

• 14:30Speaker 03

  So, there was disease, obviously, before 1492, you've proved that, but which European diseases then had the most impact in the Americas after Columbus arrives?

• 14:42Speaker 06

  There are many different diseases that are thought to actually be new to the Americas that were brought over during the exchange, but the top three, I would argue, probably from historical, but now from also genetic evidence, seems to be by far, the number one would be smallpox being the most devastating, then followed by measles and influenza. Historical reports are looking at for, depending on where the epidemic occurred and when, and what type of culture it hit, and how colonization was affecting that culture. The mortality rates for smallpox were 30 to 50%, where some other locales were reporting over 80% mortality rate, so incredibly devastating, but again, these were modified. By colonization itself.

• 15:25Speaker 06

  It wasn't necessarily that these populations had just complete susceptibility, but it was more that their susceptibility was determined by how the effects of colonization disrupted their culture, disrupted their food, there were things like forced labor, as well as pretty much a destruction of cultural buffers that would have, without European interference, would have helped populations deal with disease in general. The next would be in terms of devastation, when they've been followed by measles and influenza, which historically show much less mortality, but still significant, especially among children, reaching around 10 to 30 percent. But again, it would be affected by how colonization was affecting particular populations.

• 16:10Speaker 06

  This was not something that was seen, sort of like a monolith effect throughout North and South America. It's very dependent on the culture, how it was being affected by colonization, as well as whether or not the population was weakened immunologically from previous epidemics that were brought by Europeans.

• 16:29Speaker 03

  Thanks very much for that, John. Mark, there are countless consequences of this exchange, and you make a link, I understand, to low temperatures around the world during what's known as the Little Ice Age. Can you explain what that hypothesis is?

• 16:49Speaker 04

  So this is the really interesting thing about how the Earth system is linked. So the dying of those 50 million people meant that almost all farming in South America and Central America stopped, because they all lived off the land. And so from the archaeological records and modeling, we estimate that about 60 million hectares of land was abandoned. Now, to give you some scale, that's about two and a half times the size of the whole of the United Kingdom. And it was just abandoned, and of course, nature came back. So the forests, the savannas grew back. And as plants grow, of course, they photosynthesize, they suck carbon dioxide out of the atmosphere to build the plants, and that regrowth was

• 17:33Speaker 04

  So large and so great that we've seen in ice cores have been taken from Antarctica. And in those there are little air bubbles that you can extract and you can measure the greenhouse gases in those air bubbles. And what we've seen is around sixteen ten, there's a big dip in CO2. Now, of course, we usually worry about carbon dioxide as a warming, this is all about climate change. But if you remove it, it cools the place down. And so what we were seeing is that this regrowth was removing CO2, cooling the atmosphere. Now, the Little Ice Age is part of these natural cycles that have occurred during the last ten thousand years, during our nice warm interglacial.

• 18:15Speaker 04

  So we had a natural cycle that was slightly cooler, but this extra CO2 made it a lot worse. And if we look at the impact of the Little Ice Age, firstly, there was the Great Famine in Europe in the sixteen hundreds, which caused at least a million deaths. It also contributed to the Thirty Years' War between sixteen eighteen and sixteen forty-eight, because nations were trying to fight for the food-producing areas that were shrinking. And there's also suggestions that it contributed to the collapse of the Ming density in China.

• 18:50Speaker 03

  Well, Rebecca, are you convinced by that hypothesis, that argument?

• 18:54Speaker 05

  Well, I think there's a lot to be said for this set of, this conjunction of events. And it's certainly true that there are close connections between environmental change and the invasion of the Americas by Europeans in this period. I have no reason to dispute ice core samples in any event, but it certainly, what you say certainly meshes with the kind of scholarship that people have produced on, for example, the introduction of European livestock into the Americas.

• 19:22Speaker 03

  I wanted to ask you about that. Tell us about the impact of sheep and cattle when they arrive in the Americas.

• 19:30Speaker 05

  Well, so Europeans, concerned as they were with feeding themselves, and with feeding themselves with food that they thought was wholesome for their constitutions and their corporeal needs, made a point of leaving breeding pairs of animals all over the place in the Americas, with the hope that if they came back in a couple of years' time, there'd be a lot more pigs or whatever it was that they'd left on the particular island where they'd been. So there was a huge increase in the introduction of European livestock all across the Americas. And these animals flourished to a degree that Europeans found nothing short of miraculous. I mean, they thought this was a further sign of God's support for their entire venture, that these animals were multiplied. Because for the same reasons that you were describing,

• 20:14Speaker 05

  the lack of immunity in people of the Americas to European oral diseases, the livestock and the other animals that were being introduced by Europeans had few natural competitors and few predators that were likely to keep the population in check. So populations exploded. And this happened, for example, with sheep, who multiplied in what's referred to as an ungulate eruption, when you have these particular types of herded animals explode in population. And they, huge numbers of them then are born and are tromping around looking for things to eat. And what they found to eat was grass, all sorts of plants that were growing up and down Mexico, for example, which with their little teeth, they gnawed out of the ground,

• 20:58Speaker 05

  effectively removing the ground cover that prevented soil erosion in these areas. And this process proceeded, it's been very beautifully shown by a scholar called Eleanor Melville many years ago, who looked at how the spread of sheep in central Mexico led to desertification and soil erosion, and the land got poorer and poorer and poorer. And people at the time would say, Europeans would say, "Well, you know, look at this lousy land. I mean, it's a really good thing we've got sheep, because what else would we do with it? It's not good for anything other than grazing sheep." But as she shows, it was the sheep that made it so poor, not the other way around.

• 21:33Speaker 03

  Mark.

• 21:34Speaker 04

  So I think this whole idea of the domestic animal is really central to this story. So if you go to the Americas, the actual domesticated animals were guinea pigs, llamas and alpacas. That's about it. Nothing else. If you go to Europe and Asia, you have chickens, you have cattle, you have pigs, you have goats. And that is important because most of these diseases that were in Eurasia were from zoonotic diseases. These were diseases that were in our animals that we domesticated and jumped into humans. So we co-evolved these diseases with them. And so therefore,

• 22:13Speaker 04

  the populations built up some immunity. There were no similar huge domesticated animals in the Americas. So they hadn't got those diseases. Had they had that, then there would have been this disease war swapping between the two sort of like major continents.

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  My first ever in the world show was when I was 10 and I sang at a pub called the Georgian Devonshire. I was so nervous. I was 10. So they let me in only to sing my song and they kicked me out right after. And then I remember I wrote, I've been writing since I was 10. So I, I wrote this song called Lady in the Mirror, made this little track with it. But I just like pressed it. And I remember I sang this song and there was like five people in there. And I remember how myself I felt. And I felt like I understood myself and understood what I needed to do.

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• 24:36Speaker 03

  Hello, Misha Glennie here. Did you know you can get episodes of In Our Time 28 days early with a subscription to the BBC website and app? Just head to bbc.com/subscribe to find out more.

• 24:54Speaker 03

  John, coming to you. Still on the diseases. You've noticed, I think, through your research that some areas of the Americas were affected differently from others in terms of the impact of these European pathogens.

• 25:09Speaker 06

  Right. So at first, the ones that get hit the most are the ones that are, well, first contacted, but also are where the trading happens. So the Caribbean and the coast, those happen first, but also start disseminating diseases across trade networks that were established in the Americas before European contact and actually start hitting populations before Europeans even made contact with those populations. But I've also noticed that in terms of the mortality rates and the effect of these particular pathogens, it seems to be different that could be also have an evolutionary explanation. What I've noticed is that the impact on the Andes and populations in the Andes, they

• 25:49Speaker 06

  seem to have not only suffered far less of a mortality rate for things like smallpox than coastal or even populations in British Columbia that I've worked with. I've also noticed that it seems that populations in the Andes, especially in Peru, as well as Ecuador that I have worked with, that They actually had some immunological response and adaptation to that could be associated with smallpox. So it wasn't so much that perhaps they were more isolated and that certainly like the Spanish did not like being at high altitude, which certainly helped reduce transmission. But there are other factors that could be associated with genetic variation that may have been present in certain populations that may have helped them actually fight off these European born diseases.

• 26:33Speaker 06

  Instead of this idea that every single population, both in North and South America, were just immunologically naive.

• 26:39Speaker 03

  Mark Maslin, tobacco, of course, existed in the Americas. But what happened when this and sugarcane and cotton became cash crops?

• 26:49Speaker 04

  Well, the global trade exploded when the Americas were colonized by the Europeans because it was a perfect place to grow crops such as tobacco, sugarcane, cotton and food. I mean, as Rebecca has already said, all of that food stuff coming to Europe meant there was this huge population expansion there despite the great famine. But the long term was increasing population. There was also a source of mineral wealth such as silver, which the Spanish exploited to make sure that they grew their empire. But there was a problem. And this is where there weren't very many people left in the Americas to actually be put onto the sort of farms or to mine.

• 27:33Speaker 04

  And so this is where the transatlantic slave trade originated. So over 350 years, something like 12 and a half million people from West Africa were transported across the Atlantic to work in the Americas in the mines and on the actual fields, creating wealth and food for Europeans. I also want to stress that only 10.7 million made it across the Atlantic. That means 1.8 million people died on that crossing. So the mass movement of peoples from Africa to the Americas was a result of the great dying. And you could see that the transatlantic slave trade was part of this whole Columbian exchange.

• 28:16Speaker 03

  And as I understand, almost half of those actually went to Brazil, not to what later became the United States.

• 28:23Speaker 04

  Oh, absolutely. If you look at the distribution, a lot went to the Caribbean, a lot went to South America. Yes, through the fields of Virginia and places in America. But no, you're absolutely right. The vast majority went to Central and South America.

• 28:36Speaker 05

  Absolutely. I mean, if you look at a map of where it was that enslaved people were taken from West Africa to, and superimpose that with a map of particularly where sugarcane was grown, you see an almost complete identity, that it was sugar and tobacco, but fundamentally sugar that was driving the transatlantic slave trade.

• 28:56Speaker 04

  And also, you have to remember that these aren't real foods. I mean, I think it was Cosby who also coined the phrase "drug foods". These are things that add value and are highly sought after, you know, such as sugarcane and tobacco, but they don't really give you nutrition, okay? So hence why they became incredibly valuable like coffee and tea, but they don't actually provide anything in terms of substance.

• 29:21Speaker 03

  But there were some foods, Rebecca, which did change the world's diet in a positive way that came out of the Americas.

• 29:29Speaker 05

  That's true. And I suppose, well, I don't know if I want to say that sugar changed people's diets in a positive way, but sugar was also an important source of calories. And we may, we may think of calorificness as a bad thing, but in the early modern period...

• 29:43Speaker 03

  I certainly do.

• 29:44Speaker 05

  Food was the fuel that enabled labour, right? You know, there was no petrochemical-driven engine. So scholars have been really interested in looking for the connections between diets and, for example, the Industrial Revolution, and have tried to make connections between the population growth that Mark just mentioned, the possible improvement in nutrition possibly connected to some of these new foods coming in from the Americas, and perhaps industrialisation.

• 30:15Speaker 03

  But also, I mean, it changed people's diets entirely, if you think of the chili pepper, for example.

• 30:22Speaker 05

  Absolutely. So there are all sorts of ways in which people's diets change. To finish off on the question that you were asking about, about improving people's diets, and you might say a chili pepper improves everyone's diet, anyway, we could end the discussion there. But certainly, there's, I think, a very plausible case to be made for people's diets becoming better in terms of their, their overall level of nutrition and their greater caloric intake. As a result of some of these starchy new foods from the Americas, it used to be argued that European peasants were hopeless culinary troglodytes who threw up their hands in horror at anything that their great-grandparents hadn't grown, and that they only started adopting some of these unfamiliar starchy foods from the Americas, such as maize or

• 31:06Speaker 05

  potatoes, when they were gently led by the hand by far-sighted aristocrats who encouraged them to grow potatoes or to eat maize, et cetera. I think that is completely untrue. I think it was peasants who were the first adopters of many of these foods. They had the agricultural expertise that allowed them to adapt these foods to the new places that they might want to grow, to the new day lengths, et cetera. They valued foods that they could grow on marginal land that wasn't good for wheat, you know, you could grow on hilly zones or areas that were less likely to be owned by wealthy people. They tended to fly under the radar in terms of tax because nobody was paying much attention to them for quite a long time, and that led to better nutrition.

• 31:51Speaker 03

  And is it true that India, East Asia, Indonesia weren't spicing their food with chilies until the Americas happened?

• 32:03Speaker 05

  Yes.

• 32:04Speaker 03

  So curry, spicy curry is a relatively recent development.

• 32:08Speaker 05

  Well, spiced with chili peppers. So there are other things that can make a food hot. In fact, the reason they're called peppers, right, is because Europeans, the first non-Americans to encounter them, quickly perceived that they could substitute for expensive black pepper cords, which is what Columbus had been looking for. Anyway, that's why they're called peppers.

• 32:28Speaker 03

  John Lindo, your research into diseases is incredibly illuminating, but how do you go about understanding what pathogens existed before 1492? I'm just baffled by the research.

• 32:48Speaker 06

  Well, one way that we can do that is by looking at archaeological sites that predate the arrival. Usually, we like to have Those are radiocarbon dates at least several hundred years before European contact or before 1492, just to be sure. And what we do is, when we extract the DNA, the majority of that DNA actually isn't human DNA, say from, if we're extracting it from a tooth, it's actually from bacteria that was either in the tooth originally, or was actually decomposing the tooth. So what we do is, we scan all of that genetic data to see if we can identify pathogens

• 33:29Speaker 06

  within that data to a reliable extent, and then examine which pathogens make sense in terms of what we can know, or what we should know about the Americas pre-contact in terms of diseases that were affecting humans.

• 33:44Speaker 03

  And do you work with indigenous communities? Is that an important part of your work?

• 33:51Speaker 06

  Yeah, absolutely. A, a lot of times you can only do that type of work by working with indigenous communities whose skeletons from the archaeological site are literally their ancestors. So that, that has to be a collaboration from the beginning, instead of us going to the archaeological site and taking remains, human remains. But also, it's important because their oral histories can also inform us about potentially what type of diseases were in their particular communities for thousands of years before the arrival of humans. And we can put what we're seeing in terms of extracting particular strains of pathogens into a environmental context by using their oral histories.

• 34:30Speaker 03

  Rebecca, did the Americas get anything out of this? Because we've heard about the benefit to the rest of the world, but the Americas seem to have picked up the worst of it.

• 34:39Speaker 05

  Well, in terms of blended cuisines, those blended cuisines played a really important role in the construction of a type of national identity in the early 20th century. So for much of the first hundred years after Latin America became independent from European rule, the people who were in charge were skeptical at best about the potential of the indigenous populations to contribute meaningfully to creating a modern state. So there was a lot of... Hand wringing and really horrendous commentary made over the 19th century about how is our nation ever going to progress because we've got this dead weight of this, you know, indigenous peoples.

• 35:22Speaker 05

  That discourse changed in the early 20th century and new visions of these Latin American nations began to be articulated, which stressed the uniquely modern character of the populations, precisely because they were able to draw on the strengths of three different populations of indigenous peoples, of Europeans and of West Africans, and that this was creating, as one Mexican writer put it, a cosmic race, unlike what you saw anywhere else in the world. And food often became a place where this blended nation was seen to be exemplified. Most countries in Latin America have some national dish, which is said in some way to reflect this blended population on a plate.

• 36:07Speaker 03

  Mark Maslin, you see this period as highly significant in terms of humanity's relationship with climate. What's that beyond what you described about the Little Ice Age?

• 36:19Speaker 04

  Well, I think there's this growing awareness that humans have had a much longer history of impacting both local, regional and global climate than we expected. And we refer to this period of time very loosely as the Anthropocene. It's the time when humans have had a global impact. And there was a brilliant colleague of mine, Bill Rutterman from the States, who many years ago noticed that our current warm period, our interglacial, was a little bit strange. So it starts off right, it has high CO2, high methane, and during most warm periods, those slowly descend down, and then you get to a point that you then go into the next ice age. What he noticed was about 5,000 years ago, something weird happens.

• 37:04Speaker 04

  CO2 starts to rise again and methane starts to rise. And when he pointed this out, then people were scratching their heads, but it was then the archaeologists that started to look at their data and went, hang on, that's when farming really expanded. And so lots of forests were being cut down. It's also when wet rice agriculture was invented and exploded in Southeast Asia, which of course releases lots of methane. And also the spread of cattle that we've already talked about, that also produces a lot of methane. And so this was then an idea. And what is interesting is the great dying provides us with proof

• 37:43Speaker 04

  that it was humans. Because when we stopped farming, and as I said, when fifty five million people died and stopped farming, CO2 dropped out of the atmosphere. Of course, humans recover very fast. So the population of South America expanded rapidly, so did the Europeans. So that small dip in CO2 was then overtaken both by agriculture and then later by the Industrial Revolution.

• 38:09Speaker 03

  Are we still talking about our hypothesis here, or are you convinced that this is actually what happened? And the Anthropocene begins sometime in the early seventeenth century?

• 38:20Speaker 04

  At the moment, what geologists have decided is that because of this long history, because we've started working with archaeologists and we look at the long history, the impacts of humans are progressive, they build on each other, and they're heterogeneous. So instead of having a start date, here's a line in the sand or line in the rock, this is where it all went wrong. No, what we do is we're talking about the Anthropocene event. We are in the Anthropocene, and it started off gradually, and now it's accelerating into the future.

• 38:51Speaker 05

  Can I come in on that?

• 38:52Speaker 03

  Absolutely, Rebecca.

• 38:53Speaker 05

  So I want to put in a word for historical evidence as something that further supports the the argument that something really distinctive happened around this time. And that's to say that Europeans also noticed what was happening in the sixteenth and seventeenth centuries. And there are writings by European chroniclers based in the Americas saying, well, you know, one of the many miraculous things that we noticed since we Europeans have arrived in these Indies is that God himself has tempered the climate to make it more suitable to our constitutions. It is less hot than it used to be. And this is again further proof of the providential nature of the enterprise on which we've embarked.

• 39:34Speaker 05

  So you can look at comments from the time to support the points that you're finding through science.

• 39:40Speaker 04

  I also think it's important to realise that this colonisation of the Americas

• 39:46Speaker 04

  Drove European expansionism, but it also drove wealth and huge inputs of money into science. And you see this sort of like huge renaissance that occurs because there was the wealth to actually put into science. And so we rediscovered all the science from the Persians and from Arabia. This was brought into Europe and then it was then mechanized. It was like put into a system of capitalism and then drove all the way to the Industrial Revolution.

• 40:19Speaker 03

  I'd like to go to John. What are you researching now? Where is your research taking you next?

• 40:25Speaker 06

  Well, one aspect of European colonization that I think hasn't been as well regarded is the impact on dogs. So there are all types of dogs and domestic companions that various cultures had before European contact and colonizers, colonizing powers like the Spanish, especially in Mesoamerica, would actually target dogs and their particular breeds that were associated with indigenous populations and either decimated them or would actually bring in European breeds to make them less indigenous, make them more European. And supposedly that was to help deculturate the indigenous populations to help them acclimate to the Spanish.

• 41:10Speaker 06

  And so my, my, one of my new directions is actually to utilize ancient DNA to look at these dog lineages that existed before European contact, but also what remains in the few so-called indigenous dog breeds that are around today.

• 41:27Speaker 03

  That's fascinating. Mark, you've also come across changes that probably couldn't have been predicted. Can you tell us, moving on from dogs to earthworms, can you tell us about earthworms and the Colombian exchange?

• 41:42Speaker 04

  The earthworms are a real symbol of what the Colombian exchange has done. So if you go to North America now and you dig up soil, the majority of earthworms will be European. They were brought over with plants and soils and they have a little trick, which is the European earthworms, they will go up into the leaf litter, they'll grab it and pull it down and munch away. Whereas the American earthworms, they'll just wait for it to rot. So they get completely outcompeted. What has happened is humans have made the world into an artificial supercontinent, where species are being moved around by us. So of course, we have black rats everywhere.

• 42:23Speaker 04

  We had smallpox everywhere until we were able to eradicate it. So it has some really interesting consequences. So if you go to a place, then what you'll find is the plants and animals will have higher diversity than it did before these exchanges, but overall, the world has a lower diversity.

• 42:43Speaker 03

  And is there any way of mitigating this? Or would that be entirely quixotic?

• 42:51Speaker 04

  So there are huge conventions to actually prevent invasive species, because some of them are incredibly destructive. Think about the gray squirrel and the poor red squirrel in this country. And there are some really nasty things like Japanese knotweed, which you really don't want anywhere in your garden or in your farm. So there are lots of trade deals and barriers. And this is why, when you go to the airport, they actually turn around and say, you cannot take plants and animals or meat with you between the different airports.

• 43:25Speaker 03

  Rebecca, where do you see the impact of the Colombian exchange today in everyday life?

• 43:32Speaker 05

  Well, it's all around us. I doubt anybody listening to this programme has had a meal that was untouched by the Colombian exchange in the last 24 hours. And so I think we've talked in a way that I think has conveyed the damage that this movement of pathogens and living creatures around the world has caused. And normally, I think that's the thing that it's really important to stress, because the phrase the Colombian exchange, as Mark was pointing out, summons to mind a sort of, you know, a happy, well, a recipe exchange of people saying, oh, let me show you how to make cornbread and, you know, and I'll show you how to make cheese. But actually, possibly because we focused, I thought, I think, very appropriately on the damage that this process has done, maybe we should have a little spot to think about

• 44:17Speaker 05

  some of the changes that aren't so negative that have come out of this. I mean, beyond possibly population growth, which we might also not think is such a great thing these days.

• 44:25Speaker 03

  So do tell us.

• 44:26Speaker 05

  It's transformed global diets. It's really hard to think of anything that we eat these days which doesn't reflect it. I mean, there was, you know, we've come out of the Christmas season and the Christmas table in Britain is a testimony to the blendedness of our cuisines these days as a result of the Colombian exchange. The turkey is native to the Americas. Possibly you had cranberry sauce with it, also native to the Americas. You possibly had roast potatoes, or maybe in some part of the country you might have mashed potatoes. So debate there, I understand, with your Christmas dinner. That's from the Andes. Maybe you had a chocolate log, which would probably have been flavoured with vanilla as well as chocolate. It's really hard to think about anything that we eat.

• 45:10Speaker 05

  Perhaps you washed it down with some coffee, which is not a crop from the Americas, but which became popular because it was introduced into the Americas as a commercial crop and it was grown particularly in Brazil on such a scale that it became a global staple as a result of the introduction of plantation agriculture. Again, I could go on and on and on.

• 45:33Speaker 03

  My thanks to John Lindo, Rebecca Earl and Mark Maslin. Next week, it's the unbreakable Margaret Beaufort, who towards the end of the Wars of the Roses ensured her son Henry would become King Henry VII, the first of the Tudor dynasty. Thanks for listening.

• 45:52Speaker 05

  And the In Our Time podcast gets some extra time now with a few minutes of bonus material from Misha and his guests.

• 46:01Speaker 03

  Is there anything that we missed out? And John, let me start with you.

• 46:05Speaker 06

  Whether or not syphilis was brought over to Europe, is that, am I getting that wrong? Did we actually cover that?

• 46:11Speaker 03

  No, I think you're probably right. I remember from history that in 1494, when the French invaded Italy at the start of the Italian wars, Italy was devastated by the spread of syphilis, two years after 1492, of course. Do you think that there was a connection between that outbreak and what happened and the Colombian exchange?

• 46:37Speaker 06

  There's a perspective that it was because it was brought over from the Americas, or the Pacific strain was brought over and then turned into this venereal disease that we know today. But recent, modern DNA, looking at various strains related to syphilis across the world, have actually established that this is a very old pathogen that has different strains across the world, including in America and including Europe, and that the European version that is now associated with the sexually transmitted disease is actually, was very much European in origin and was not brought over from the Americas. Now, that isn't to say that the American strain and the European strains didn't intermingle,

• 47:19Speaker 06

  but it looks, at least from the genetic analyses that have been done, it looks like that particular strain was very much European.

• 47:27Speaker 05

  It's really interesting, because people at the time, who were of course materially interested in this new disease, Europeans thought it was new. They wrote extensively about this as a completely novel illness, never before seen, that it didn't appear in the ancient Greek writings. They were persuaded that this was something new. And they, again, to go back to the point about the climate becoming colder and Europeans saying, well, this is providential, it makes it better suited to our bodies. They also found evidence for God's providential hand in the fact that a particular wood from the guayacum tree, which is native to the Americas, was thought to provide a remedy for syphilis and for the French disease, or for the pox, as it was called at the time.

• 48:12Speaker 05

  And so people at the time commented, again, this was sign of God's mercy, that from where the disease comes, there comes the remedy.

• 48:19Speaker 04

  You can also add to that malaria because of quinine, which was discovered in the Americas, was brought over and seemed to actually help. And hence why we have the G and T. Because of course, quinine is rather bitter. So let's create a drink which has tonic water and gin. And therefore, this was the way of empire, you know, sort of G and T to keep the malaria away.

• 48:42Speaker 03

  Yes, and it's worked very well in my case.

• 48:45Speaker 05

  Long may that continue.

• 48:48Speaker 03

  Um, I, Mark, I wanted to ask you about, there's also this thing about, we think people arrived in the Americas in about 13,000 years ago, but there's new evidence that suggests they may have been there a lot earlier. Is that right?

• 49:04Speaker 04

  So absolutely. So this is a ongoing debate that's been raging for decades, which is every so often some new archaeological evidence is thrown up that shows that there were people in the Americas before. So about 30,000 years, 35,000 years ago. The problem is always techniques. The dating, is the dating correct? Because you're not actually dating the skeletons or the remains, you're dating the sediment that they're in. So there's controversy around that. But I don't see any reason why people could not have made it across through the Polynesian islands to the Americas. But what we know is the big

• 49:44Speaker 04

  population explosion with the Clovis archaeological system, which is in North America, is really post 12,000 years.

• 49:54Speaker 03

  Can you just explain what the Clovis?

• 49:56Speaker 04

  So the Clovis is a type of technology. So it is very clearly of a particular group of people. And you can track that all across North America and into South America. And so that group of people seem to be highly successful, and they seem to move through into South America. So I would never rule out that there were people there before 15,000 years. I have no problem with that. But the big population and the big spread of people across America seem to occur after the end of the last ice. Age with the genetics following from the north down through to the south. Of course, they were also mixing with some of the Polynesians that were making it to South America.

• 50:40Speaker 04

  And we also know that from the Viking literature that they also made it to North America.

• 50:45Speaker 03

  And they've made it to North America and then decided, thanks, but no thanks, and apparently returned.

• 50:52Speaker 04

  Well, the thing is, if you think about it, it was the Vikings that said, oh, we're Iceland, let's go to Greenland, which was the biggest PR campaign ever because it's not green at all. And then they made it to North America, which, if you think about it, is still incredibly cold. They didn't make it further down the coast where, say, the pilgrims did, where you go, oh, okay, it's a bit nicer here in New England.

• 51:15Speaker 03

  John, have you come across anything using the ancient DNAs to suggest that there was definitely human populations before 13,000 years ago?

• 51:26Speaker 06

  Absolutely. Utilizing ancient DNA and like whole genomes, I think the consensus is, at least from the genetic point of the argument, is that peoples in the Americas started differentiating from people in Siberia over 25,000 years ago. So seeing these dates getting pushed back beyond Clovis is not surprising to me. However, there is one thing that is a problem in terms of migration is that pre 13,000 years ago, the Ice Age pretty much had a gigantic ice sheet over most of North America and in part into the United States. So the coastal route is likely how those first migrants pre 13,000 made it down

• 52:07Speaker 06

  and seemingly made it down very quickly, not just to below those ice sheets in the United States, what is now in the United States, but also very rapidly to South America.

• 52:15Speaker 03

  Doubtless eating seals on the way and picking up TB.

• 52:19Speaker 05

  People, again, Europeans again, at the time, thought about this. There's a wonderful account by a Jesuit writer from the late 1500s, somebody called Jose Le Acosta, who wrote about how people got to the Americas. And he said, well, how did they get here? I mean, everybody's the son of Adam and Eve. You know, we must have started from a common point of origin and spread out all. Over the world, how do they get there? And he says, well, you know, they could have come in boats. They could have come across maybe from Europe in boats. And he says, OK, that might explain how the people got there. But how does that explain Jaguars? He said, nobody would bring a Jaguar in a boat with them or a fox. He said, you just wouldn't do it. He said, the very idea is laughable. So he continued thinking about it and he said, they must have come from some sort of connection

• 53:02Speaker 05

  far up in the north, way, way up in Siberia. They must have walked. That's the only way they could have got here. So he figured this out in the fifteen nineties.

• 53:11Speaker 03

  But also a critical difference is is that other civilizations and communities, the Chinese, for example, would go and explore places. And then they'd leave them and go go back home to China. It's only the Europeans that have stayed in places and expanded their territory beyond their familiar familiar landmass.

• 53:34Speaker 04

  Well, I think that's because there's a unique geography and political systems that came in Europe. Because if you look at fourteen hundreds, China and Europe, about the same size, have the same population. China, if you think about the geography, is fairly simple. OK, it's a big landmass. It has deserts to the north. It has mountains to the sort of west and it has a simple coastline. You look at Europe, it has a central mountain system, which then has radial rivers. It's got these annoying islands like ours. You've got this incredibly complicated coastline around the Mediterranean. And what happened is you had lots of principalities and kingdoms that fragmented.

• 54:18Speaker 04

  And literally, we were at war with each other constantly. And this is what we think drove that technology. You suddenly lose a war and you go, oh, you know, I lost all these peasants. Right, I need to get a load of money to build up my army so I can beat my cousin who's in the country next to me. And this is why colonialisation was brilliant, because you got to other places, you could take all their resources, you could then put it back into your own country, build up to continue this European constant war. And if you think about it, eighty per cent of the time, from fourteen hundreds to the Second World War, the great powers in Europe were actually at war with each other. And it's that technology that drove everything

• 55:02Speaker 04

  that then led to the Industrial Revolution.

• 55:04Speaker 03

  Wow, we've reached the Industrial Revolution. I think that's the point where I ask Simon to come in and offer us teas or coffee.

• 55:14Speaker 04

  South Asian tea.

• 55:15Speaker 03

  South Asian tea. We've got one South Asian tea order, Simon, and I'm just going to have a builder's tea, which probably is a South Asian tea. Rebecca, do you want anything?

• 55:24Speaker 05

  I'll have the same.

• 55:25Speaker 03

  Thank you.

• 55:27Speaker 05

  In Our Time with Misha Glenny is produced by Simon Tillotson, and it's a BBC Studios production.

• 55:35Speaker 01

  Hello, I'm Alan Davis, and on BBC Radio 4, we're off into alternate realities mapped out by science. This is Life Without, where I pull one thread from the magnificent fabric of life and watch what unravels.

• 55:50Speaker 05

  Scientists around the world would be crying themselves to sleep. A bunch of mammals would be worrying about where their favourite snack was.

• 55:57Speaker 01

  And we bring it down to earth.

• 55:59Speaker 05

  David Beckham, I can imagine him putting that on the socials, my bees, my girls have all disappeared.

• 56:05Speaker 01

  Sometimes we patch it up and crack on. We will survive. We will survive. Humans are ingenious. That is our hallmark writing. We should prize above everything else. But sometimes it's bigger than us. Join me to find out just how far the unravelling can go. Subscribe to Life Without on BBC Sounds.

• 56:31Speaker 03

  Hello, Misha Glenny here. Before you listen to this episode, I wanted to share some exciting news. You can now watch this episode and all future episodes of In Our Time in full video. Just search for In Our Time on YouTube or watch episodes 28 days early by subscribing to the streaming service, BBC Select, in the US and Canada.