World Views
12:18 pm
Fri October 25, 2013

Germ Theory: How Disease And Climate Change Toppled The Roman Empire

The Roman Colosseum - September 26, 2009.
The Roman Colosseum - September 26, 2009.
Credit Yellow.Cat / Flickr Creative Commons

University of Oklahoma historian Kyle Harper says there have been thousands of answers to what caused the fall of the Roman Empire. Overexpansion, economics, and the rise of Christianity are all valid explanations, but he’s exploring the role of disease and climate change.

“When we look back at the Roman Empire now, we can see that changes in the Romans' environment, both the climate, but also the kind of species that live in and around humans, especially pathogens, play an enormous role in the collapse,” Harper says.

The last Western emperor abdicated in 476 CE, and Harper says two of the first great pandemics in human history frame that date. Roman troops brought a plague of smallpox back from the Near East in the second century, and 400 years later bubonic plague spread across the Eastern Empire during the reign of Justinian I.

“These diseases had existed before, but there’s something that happens in this period in the early first millennium when all of a sudden you start having really global disease events,” Harper says. “Once you start to think about it, it seems almost impossible to believe that this kind of event wouldn’t have had just a fundamental effect on the stability of the empire as a whole.”

Harper says different kinds of pathogens flourish or flounder based on temperature, moisture, and the nutritional level of the population. As modern scientists and historians gain a better understand of climactic fluctuation over time, they’re learning more about how it affects human history.

“There are a lot of smart people around the world trying to use ice cores, trying to use tree rings, trying to use speleothems, cave deposits, trying to use other kinds of proxy evidence to understand the history of climate variability,” Harper says. “It’s giving us an almost unimaginably rich picture of climate and climate change in a period like the Roman Empire.”

Harper says while the post-industrial, information age makes direct comparisons to the Roman Empire facile, there are lessons to draw from a world superpower that once seemed unconquerable.

“The Romans are quite arrogant about proclaiming themselves to be eternal, but at the same time, they knew that all things change and that empires rise and empires fall,” Harper says. “They have no germ theory. They have no sense of why people are dying in such huge proportions. They have no idea that the climate is changing because of small variations and the orbits of the earth and its relationship to the sun, but the Romans don’t know necessarily what caused their own fall, but it’s exciting to think that we can have some understanding of what cause the fate of their empire.”

INTERVIEW HIGHLIGHTS

On the similarities and differences between Roman and Atlantic slavery

There’s always a tendency to view slaves as outsiders, and as inferiors, but, it’s only in the modern world that slavery becomes fully racialized and that racism becomes a fundamental prop of the slave system, and so, when you look at Roman slavery, you’re studying a slave system that, ironically or paradoxically, for those of us who are only are familiar with, say, modern slavery, doesn’t have a kind of skin color at the root of its ideology, and so, it helps us understand what slavery is and how it can be transformed in different contexts. At the same time, you can see really important similarities. Most large scale slave systems in history have been driven by the circulation of consumer products, and so in the modern world, it’s cotton. It’s really the last of the major commodities in new world slave systems, but, before that, it’s tobacco, it’s rice, it’s coffee, and above all, it’s sugar and in the Roman world, it’s wine, and so, when you see this huge global history of slavery, it becomes apparent in ways that you might not have otherwise seen, how dependent the growth of really intense slave systems has been on kind of consumer products that people want, and especially addictive ones throughout history.

On how advances in science can lead to a better understanding of history

Even the Romans, which are quite successful, and have quite a prosperous economic system, they’re, by our standards, almost unimaginably poor and huge parts of the population struggle, just to get the basic calories they need on a day to day basis, and so they’re extremely vulnerable to some kinds of pathogens, which disproportionately affect people who lack stable nutrition. So, what we’re coming to understand about this period is changing and one of the ways it is changing is that we have increasing DNA evidence, and so we can, we’re starting to be able to identify the actual pathogens that killed actual individual peoples that are recovered archeologically, and one of the things that is changing about our understanding of this period is our understanding of climate change, and this is why viewing the past through the present isn’t even subtle, because we’re concerned about climate change and we’re trying to understand the history of the climate.

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FULL TRANSCRIPT

SUZETTE GRILLOT, HOST: Kyle Harper, welcome to World Views.

KYLE HARPER: Thanks for having me.

GRILLOT: So you’ve got this really interesting background, trained as an ancient historian. You’ve written a lot about ancient Rome, issues like slavery in that part of the world at that time, sexual ethics. What is interesting about these topics to you? Why should they be interesting to us? And what is it about ancient history that matters to us, today?

HARPER: Well I think the Roman Empire is a topic of perennial fascination because it’s one of the great empires in the history of the world. What the Romans achieve is comparable in some ways only to some of the, kind of, Central Asian empires, or, in more recent times, the British Empire, but what’s so different about the Romans is that this is not a kind of step empire, this is not a naval empire, they build a tri-continental, Iron Age empire, that’s grounded on land, transportation, military organization, in ways that no other people were able to do, and to unify the Mediterranean has been the dream of many imperialists, but only one people’s were able to achieve it, and so we perennially look back to this civilization which flourished some two thousand years ago, and always ask, “How did they do it?”

GRILLOT: So, historically speaking, the many empires have been trying to learn lessons, I think, from the Roman Empire, but the specifics of their interactions and, in particular along these lines of religious history, and slavery practices, ethics within that period of time, law, justice, I mean, are these some of the things that we can also take from the Roman Empire that transcend generations and millennia?

HARPER: I think there are lessons to be learned there, and certainly we can deepen and enrich our own understanding of our place in the world in world history by having a depth of perspective that goes back through thousands of years of the human experience, and so you take a topic like slavery, which was something that I worked on for many years, and it’s a subject that Americans, generally, know at least a little bit about because it’s a part of our national history and part of the world that we have inherited and what we need to understand is that the American experience of slavery is a very unique in particular experience and there’s an entire global history of slavery. Slavery is older than the oldest human records. Humans have been enslaving each other for, probably, tens of thousands of years, and there enormous slave systems before the rise of modern Atlantic slavery and the Roman slave system is one of those. The large scale slave systems are rare in the pre-modern period, but the Romans create an enormous slave system and slavery is just an integral part of Roman culture, Roman society, entire Roman way of life, and so when you have that perspective then you recognize some of the things that are unique about modern slavery, for instance, its racialization. There’s always a tendency to view slaves as outsiders, and as inferiors, but, it’s only in the modern world that slavery becomes fully racialized and that racism becomes a fundamental prop of the slave system, and so, when you look at Roman slavery, you’re studying a slave system that, ironically or paradoxically, for those of us who are only are familiar with, say, modern slavery, doesn’t have a kind of skin color at the root of its ideology, and so, it helps us understand what slavery is and how it can be transformed in different contexts. At the same time, you can see really important similarities. Most large scale slave systems in history have been driven by the circulation of consumer products, and so in the modern world, it’s cotton. It’s really the last of the major commodities in new world slave systems, but, before that, it’s tobacco, it’s rice, it’s coffee, and above all, it’s sugar and in the Roman world, it’s wine, and so, when you see this huge global history of slavery, it becomes apparent in ways that you might not have otherwise seen, how dependent the growth of really intense slave systems has been on kind of consumer products that people want, and especially addictive ones throughout history.

GRILLOT: So how are we to feel about that, then, noting that slaves have been largely responsible for producing these kinds of goods that we want and that we consume regularly?

HARPER: Well I think it makes you stop and think twice, maybe, about some of the kind of ways that consumer goods are produced today, hopefully. You know, it’s easy to say, ‘Well in that past that was slavery, and today, we have wage labor, which is different,’ and it is different because the rise of free labor and the rise of abolitionism is one of the greatest changes in the history of the human experience. But at the same time, I hope it alerts us to keep our own eyes open for the kinds of things that people don’t want to see, or don’t want to look at.

GRILLOT: So, your most current project also focuses on the Roman Empire, but the fall of the Roman Empire, and you’re looking at it from a bio-historical perspective, focusing on disease and climate change. What is it about disease and climate change that lead to the fall of the Roman Empire?

HARPER: Great question, and I will tell you the answer in a year or two when I…

GRILLOT: As soon as you finish your research.

HARPER: As soon as I finish my research project, but I can share with you…

GRILLOT: What do you expect to find?

HARPER: Some of my hypothesis that I’m testing now…the fall of the Roman Empire is one of the great questions in history, and there have been, literally, over a thousand answers offered to this question as to what caused the fall of the Roman Empire, and the sheer number of answers that people have given shows you that there isn’t a single answer. You’re talking about an enormous civilizational change, from the high Roman Empire, the classical world of the Mediterranean, to the Christian Middle Ages, to the Dark Ages of the 6th and 7th Century, and it really is a collapse, it’s a civilizational catastrophe, in a sense, because you go from a fairly complex, prosperous, integrated society to a fragmented, in many ways, poor, certainly simpler kind of society, culturally, much simpler than the kind of high Roman Empire, and so it is a real question. What causes this great imperial power to collapse and become the successor of Germanic kingdoms? The barbarian kingdoms of the Dark Ages. It’s a legitimate historical question, and I think every generation of historians tends to see the past, to some extent, through the eyes of the present, that’s inevitable, but in this case, it’s not even subtle. I think we live in a world where we are recognizing that human societies are sensitive to their environment and to changes in their environment, and when we look back at the Roman Empire now, we can see that changes in the Roman’s environment, both the climate, but also the kind of species that live in and around humans, especially pathogens, play an enormous role in the collapse of the Roman Empire, the period of the fall of the Roman Empire, what we call late antiquity, sees the first two great pandemics in all of human history. The, what’s called the Antonine Plague, the smallpox pandemic in the second century, and then the Justinianic Plague, which is the bubonic plague, the first real plague, in the 6th century, and these diseases had existed before, but these diseases have their own history, but there’s something that happens in this period in the early first millennium when all of a sudden you start having really global disease events. Pandemics that wipe out, not just on an urban or city scale, but on a continental scale, Huge portions of the population, and so, once you start to think about it, it seems almost impossible to believe that this kind of event, the two major plagues, the two pandemics, wouldn’t have had just a fundamental effect on the stability of the empire as a whole.

GRILLOT: And how does that relate to the issue of climate change? The disease is an outcome of change in one’s environment is what you’re suggesting. These two things related together.

HARPER:  Right...

GRILLOT: And to bring that to current day, is there anything different then, than there is now about this connection between health and our environment?

HARPER: Well, diseases are sensitive to the environment, and there are many different dimensions of that. Diseases are different, infectious diseases in particular, are very sensitive to human population structure, and so most people in the Roman Empire die of infectious diseases. We, in the modern world, after a kind of major transition in the early 20th century, we mostly die of chronic diseases. Our heart gives out, some other part of our body goes wrong, but in the ancient world, most people die of infectious diseases, and these kinds of diseases are very sensitive to variables in population structure, like population size and density, and in some ways, the arrival of these kinds of new diseases and new pandemics in the Roman Empire is an artifact of their very success. They build an enormous population, but that population is so big that it puts itself on the brink of, kind of, ecological disaster, and so in a sense, the Romans are victims of their own success. They advance so far that it leaves them vulnerable to these kinds of new disease events, but at the same time, there is probably a direct climatic element in the disease history of the delayed empire. Different kinds of pathogens flourish even on a year to year basis, based on the kind of weather, really, and so, some kinds of diseases are particularly acute when there are warm or cold conditions, or when there are wet or dry conditions, and then another kind of major variable is nutritional level, and so these ancient societies, even the Romans, which are quite successful, and have quite a prosperous economic system, they’re, by our standards, almost unimaginably poor and huge parts of the population struggle, just to get the basic calories they need on a day to day basis, and so they’re extremely vulnerable to some kinds of pathogens, which disproportionately affect people who lack stable nutrition. So, what we’re coming to understand about this period is changing and one of the ways it is changing is that we have increasing DNA evidence, and so we can, we’re starting to be able to identify the actual pathogens that killed actual individual peoples that are recovered archeologically, and one of the things that is changing about our understanding of this period is our understanding of climate change, and this is why viewing the past through the present isn’t even subtle, because we’re concerned about climate change and we’re trying to understand the history of the climate. Climatatic fluctuation has been one of the major drivers of all global history, of the history of life on earth, and of human history, in particular, and coming to understand the massive fluctuations that have affected the human species upwards history is very much a part of the kind of present agenda to understand the history of the climate and the dynamics of the climate, and climate fluctuation in a richer sense, and so, we as historians, of a period like the Roman Empire, have been great beneficiaries of this because there are a lot of smart people around the world trying to use ice cores, trying to use tree rings, trying to use speleothems, cave deposits, trying to use other kinds of proxy evidence to understand the history of climate variability, and it’s giving us an almost unimaginably rich picture of climate and climate change in a period like the Roman Empire.

GRILLOT: Well I think that’s a wonderful answer to my next question, actually, because as we were talking about the specific connection between something that happened in the ancient worlds, such as disease and its connection to the climate, I really wanted to kind of end with this discussion of how ancient history or how a study, studying, you classical history, or the classics, I mean, you’re a professor of classics and letters, and so how is it that studying those things help us understand today, but it sounds very much like we know what will be able to do now is go back and scientifically study things that took place thousands of years ago and that helps us understand, you know, our world, today. I mean, that’s one example, but, you know, if  you were to make an argument as to why it is we really need to understand the Roman Empire, or, you know, early ancient history, what is the main reason? How is it that that helps us understand anything about life today?

HARPER: Well, the great Roman, Cicero, said, ‘To know only your own generation is to remain forever a child,’ and it’s true. The fact that we can cite that shows the kind of wisdom of knowing the classics that there’s a certain kind of timeless knowledge that humans have achieved and preserved over thousands of years, and more importantly, the substance of what he says is that if you only know your own time and what’s around you, then you have a kind of facile or even juvenile understanding of the human experience, and to think that anything is new is just not to know the past. The only new thing in the world is the history you don’t know, and the Romans are very different from us. They live in a very different world. It’s a pre-industrial world. It’s a world of extremely high mortality and high fertility. It’s a world that’s very different from our own, which is an industrial and now post-industrial world, an information age, a post-fertility, transition world, where people live in small families and have long life expectancies, so direct comparisons are facile as well, that we’re not the Romans, we’re very different from the Romans, but at the same time, there is something to be learned from the experience of an empire that is a world super power, that seems almost unconquerable. It seems unimaginable that it could face threats to its existence, internal or external. In fact, the Romans are quite arrogant about proclaiming themselves to be eternal, but at the same time, they knew that they, that all things change and that empires rise and empires fall, and so I think having a sense of the history of that, and why they’ve risen and why they’ve fallen and for the Romans, it was things that they couldn’t see or couldn’t understand. They have no germ theory. They have no sense of why people are dying in such huge proportions. They have no idea that the climate is changing because of small variations and the orbits of the earth and its relationship to the sun, but the Romans don’t know, necessarily, what caused their own fall, but it’s exciting to think that we can have some understanding of what caused the fate of their empire, both its rise and its fall.

GRILLOT: Well, Kyle Harper, thank you so much for joining us today to make these very important historical connections, and hopefully we’ll do better about understanding our history, thank you.

HARPER: Thanks for having me.

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