 Thanks, Alayama. We've had two wonderful papers, and now one time for one flaky paper. One apology I need to make is that everything I need to do at the conference is happening today. And so I'm going to give my paper, grab my bag, and run out. This is not an attempt to avoid discussion. I'll be here for the final end of the day, but I'm jumping between sessions a lot. It's not because I don't want to hear over in the paper. So my apologies. So what I want to talk about today has only the most tenuous relationship with care in the sense I'm thinking about, if you were trying to assess what are the big health problems medieval people face? And as skeletal people, it's easy to get fixated on, things that leave traces on bones. And if you follow historical sources, it's easy to get fixated on the big headlines as it were. So in that sense, if you were to say, what is the biggest single catastrophe of the Middle Ages, what most people would probably say is the Black Death, the second pandemic starting in 1347, I have the regulatory picture from Monty Python. Bring out your dead. But it was a major serious cultural trauma. In that sense, I'm sure everyone here is familiar with it, but just to go through the facts, this was a so-called second pandemic. It was an epidemic of Yersinia pestis throughout Eurasia, spreading from the east to the northwest. It's a bacterial infection with a complex life cycle involving animals and humans. And the actual number of people it killed varied from country to country. For England, the best guess is on the order of 40% to 50%. So one period of a couple of years, wiping out almost half the population, this is a big health problem. I'm not sure how much archeology of care caused because generally, if you got it, there's a good chance you would die. And the survivors would need it. The native view of the Black Death, there are two main theories about the causes of it. There was a medical theory that this was contagion by miasma. This was a useful theory in the sense that the therapy appropriate to it was isolation, which is a good thing to do to prevent the spread of infectious disease. There was a spiritual theory which was that this was punishment by God for human sin, very generalized because obviously the innocent were dying in droves as well. And commentators at the time were struck by the world turned upside down, the social effects of plague. So effectively, and what mainly upset them, as far as you can tell, aside from the psychological trauma of waking up in the morning and being dead by nightfall, which is not a minor matter, was the social order being reversed. And people who should know their place being uppity and asking for higher wages and so on. There's a lot of historical debates about the Black Death. There was a long historical debate about the actual pathogen. Fortunately, ancient DNA has nailed down that it really was your synopsis. There are different models for the cause. I think the traditional line is simply what you might think of as the pathogen as protagonist. It was an act of God in the story. There's a more complicated model which contextualizes it socio-ecologically. This is Bruce Campbell's perfect storm model, where the reason the epidemic was so devastating depended on a whole combination of social and ecological circumstances. If you look for the archaeology of the Black Death, it's actually surprisingly hard to find sometimes. There are plague pits, such as mass burials in London and other places. There are deserted villages. But aside from that, the archaeology before 1346 does not look amazingly different from the archaeology of the later 14th century, for example. So it's surprisingly elusive in some ways. And we might raise the question, how important was the Black Death really? Now, assessing health problems in the past is a nightmare. The point about it is there is no single source that will tell us everything. It's a mosaic of sources, all of which have biases. So we know about the biases of skeletal records. Everyone here is probably into this. Bones tell you some things and not others, fine. If you think about historical records, this is an example of a so-called bill of mortality from 18th century London. It lists what people died from. And you can see some things we might more or less figure out, apoplexy and suddenly is probably strokes, mostly consumption is probably mostly tuberculosis. There are things we don't know, like inflammation could be due to lots of different causes, fever, malignant fever, et cetera. That's a whole series of infectious diseases put together by symptoms. When it says teeth, what it means is not people who died from bad teeth, but infants who died in the stage of teething, from the sorts of things infants died from. So some idea about the relative scale of problems, but not a lot of hard guidance. So at this point I decided I would try a thought experiment. This is where things become flaky. And for those of you who are not into English television, this is a famous time machine from Dr. Hurley. This is hard as. The World Health Organization has a concept called the burden of disease. This is an estimate of the human, socially economic cost of ill health. So you see it in news reports when they say that X billion euros is cost to the economy by lower back pain every year or something like that. It's used for health policy planning. As far as I know, no one's ever tried applying it to historical problems. There may be good reasons for this, but I'll try it anyway. Fools, Russian, were angels through the train. The way you calculate the burden of disease is the unit of analysis is a disease adjusted life year. And this measures both the amount of time you lose by dying young due to a health problem and the activity and life quality lost due to a health problem. So in the top arrow there, you can see if you would live to 60 based on life expectancy in the population, but a disease kills you at the age of 30, then you've lost 30 years of life due to that disease. Okay, if you're going to live to 60 and at the age of 30 you catch a disease which impairs you and removes 50% of your ability to experience life, then you've lost 50 years lost to disability. You'll see right away that there's a lot of made up parameters even when working with modern data. For example, who is to say that becoming blind reduces your ability to experience life by X percent? The World Health Organization doesn't necessarily know better than the sufferer does. It depends on cultural context and all sorts of things. So it's a notional measure good for rough comparison. And since I have to make up a lot of parameters to use it, I'm happy to point out that people using it on modern populations also have to make up a lot of parameters. One of the key parameters is demography. This is one of the relatively easy ones because you can look for comparative life tables and get pre-modern or non-modern or developing world life tables. So here I've used one from Colin Demity's Western Model. And this is one where there's a lot of child mortality and a sort of sloping off people die in young adulthood as well. It's what you might think of as a pre-modern mortality curve. Okay, you also need to estimate the prevalence of different diseases and how they affect people at different ages and what the consequences are. I won't go through this all in detail, but I'll just give you an idea of the way that I've made up my parameters. And the idea here is not to try and nail it exactly because you can, but simply to come up with some relative estimate. So for example, if you assume all of the epidemic, all the plague years in the Middle Ages might have an average prevalence of 25%. And if you get it, you die. But there's a lot of years when there isn't plague around. So you have to figure out an average prevalence over all of the Middle Ages, not just the plague years. If you think about tuberculosis, you might say, let's say it affects 10% of the people in the population. Let's assume it doesn't have an age bias. Let's assume it gives you a 40% in capacity. Obviously you can argue about every single one of these, but I just want you to get an idea of how I'm modeling it. If you think about gout, perhaps it affects 10% of older males. It's not likely to kill you, although it might make you wish it had. But it might give you some incapacity. If you think about death and childbirth, if there's a certain percentage of, a certain probability of dying in childbirth every time a woman has a child and the average fertile medieval woman might have had six pregnancies in her fertile years, this adds up to a considerable probability of death and childhood affecting half the population in the middle part of their lives. So you make up a lot of parameters like this. You feed it into the World Health Organization model and you see what happens. You'll see I've put in a few things like dental disease, which is age progressive, affects almost everyone, results in some form of incapacity. You can estimate it how much you like. We know philosophers cannot put up with toothache, Shakespeare tells us that. But it might say, it might reduce your capacity for living by 10 or 20%, let's say. I've put in, as a sort of experiment in making up things even more, famine, you can track famine years and if you average these over the whole villages, you can get some idea. So for example, the great famine of the 13, 15 through 13, 20, might have killed 10 to 20% of the people in Britain, but most years were not famine years and so if you average that you can come up with a much lower estimate. War, here I've calculated in not disruption to society as a whole, but specifically the males who may have been involved in fighting forces, which is a relatively low percentage. The most controversial one probably is social inequality. If you assume that 25% of the medieval population are seriously poor, and if you assume that being seriously poor adds to the probability of malnutrition, accident having a compromised immune system and therefore things like tuberculosis, you can say that actually may have some serious consequences. Okay, as I say, we can argue about all of these, but you get the idea of the logic as if it's a thought experiment. So if you run all these through a relatively simple spreadsheet, you can see some of the primary results here. The big one as a killer is diseases of infancy and childhood and if you think about it, the way that they calculate these disease-adjusted life years, this is absolutely obvious because if you think about years of life lost, if you killed every single medieval 50-year-old male, well, goodbye, here I go, you're likely not to lose that many years of life given medieval life expectancy. If you kill half of the children born before they reach adulthood, that's a huge amount of life potential lost. So that's a real killer. Other important ones, death and childbirth, tuberculosis, social inequality, and so on. What happens if you put plague in here? Well, this is simply some comments, sorry, before we go on to play. Tuberculosis is very common, it both kills and disables people. Social inequality affects a large amount of the population and adds incrementally to all sorts of things that kill you. Diseases of infancy and childhood kill a lot of people early in life. Childbirth accumulates over a woman's life, the risk of death. So that's why these are major killers. Some things we're familiar with archeologically really are not that serious health problems, I hate to say. Leprosy is rarely lethal, it affects a minority of people and it may be progressive as you go on in life so it doesn't affect young people to the same extent. Things like cancers affect relatively few people late in life. So if you're going to prioritize your health resources then, probably not those. Your syniapestis is devastating when it strikes, particularly in 1347, 48, 49, 50, but it's only in sporadic years, perhaps one year in every couple of decades. The average mortality of the epidemics might be between 10 and 20%. So in that sense it's devastating but it's not omnipresent and you can see it comes in sort of about fifth or sixth in my list. So it may not have been the biggest health problem of the Middle Ages. If I were really going to put my money on something, I'd probably choose something else. At this point, just to wrap up with some thoughts, let's get beyond the question of the highest body count and think about patterns of disease and in some ways a metaphor is useful here. Plague is like wildfire. If you've ever been in a fire in a forest that's been burned, it's devastating, it's very fast, it leaves ruins, it looks horrible, but recovery can be very highly, recovery can be quick under the right circumstances. Tuberculosis is much more like climate change. It's gradual, it's chronic, you may not actually realize the cost of it but it's omnipresent and it may have greater historical effects. So in that sense, you have to think not only about the visible effects or the body count but also how things may have affected history. I'll just close with a few thoughts about catastrophes and their effects. If you killed 40 to 50% of the people in the world, what might you expect to change? Well, a major trauma like this, you might have psychological trauma, you might have cultural trauma worked through literature, philosophy of art, it would structure memory, people would say before the war, before the plague. You might expect new or reoriented religions, loss of culture, traditions, knowledge, regime change, perhaps we could use it now but internal political restructuring, international political realignment and you see a lot of these with things that are even much less lethal. So for example, World War II had great transformative social effects with a body count of perhaps three to 4% of people in the world. The closest thing to the plague would be something for a body count would be something like the European colonization of the Americas. So that's our expectations. In this case, there are various known historical effects of the Black Death, obviously psychological trauma in the short term. Economically in the longer term, increased wages for the working class by basically readjusting the balance of people in land, decreasing income for landowners, increasing prosperity for the working classes, increasing mobility, a shift in land use and one long-term effect of cutting the population of Europe down to about half its earlier size in a way that remained more or less demographically flat for a couple hundred years. So it did have effects. But what I find equally striking is what didn't change. We seem to be having a Chaucer day so we can talk about Chaucer. Chaucer is the 14th century writer. He talks a lot about topical things. He mentions the peasants revolt a number of times. He doesn't mention the plague at all. He lived through it as a small child. People in his family died. It's not part of his working history. There was no regime change, talking mostly here about England, but for other countries as well. There were no major political shifts. There was no change in the basic structure of medieval society. It didn't result in a social revolution. There was relatively little obvious change in religion, art, or literature. Not much in the way. And when people talk about things like the triumph of death, one argument is that actually a lot of these things were starting before the plague and were accelerated by the plague. So there are actually surprisingly a few things historically, which can be defined as pre-plague and post-plague. A lot of trends, such as liberating surfs from the land, become, were accelerated by it, but not necessarily caused by it. So in this sense, it's worth thinking just upon opposing thought about if there's any lessons for us about resilience. And I've been wondering why there was so little visible effect. A few ideas. One is that it killed both rich and poor. And it killed people in different countries. So there wasn't sort of major change in the balance of power in Europe as a whole. No vacuum in England that France could have made or vice versa. Institutions for conserving knowledge were preserved even when individual people died. So the major repositories of knowledge and tradition managed to carry on. Religious narratives channeled psychological responses into stability rather than into overturning things. It was generally used to reinforce the religious and social order rather than the other way around. And the other thing I think is quite important is that medieval society had a very cellular structure. So for example, the basic productive economy was locally based. And therefore, if you wiped out a lot of people, disruption didn't necessarily spread. Whereas if you wiped out 1% of the modern population now, you can imagine the effect on supply chains, the organization of work, the organization of the economy were so much more integrated that any disruption affects the system much better. So I don't know if there are lessons in this for us. Let me finish up very quickly with one question. If you are God or the World Health Organization visiting the Middle Ages, what would you cure? Plague has always been the poster child for health disasters. It's sort of like elephants for wildlife conservation. But to really improve human life for medieval people and change the course of history, perhaps we should go back and think about childhood infectious diseases, clean water tuberculosis, death in childbirth and social inequality. Thank you.