Science Friday - Galileo, Home COVID Monitoring Tech, Origin Of The Feces. May 15, 2020, Part 2

Episode Date: May 15, 2020

Galileo’s Battle Against Science Denial Galileo Galilei is known as the father of observational astronomy. His theories about the movement of the Earth around the sun and his experiments testing principles of physics are the basis of modern astronomy. But he’s just as well known for his battles against science skeptics, having to defend his evidence against the political and religious critics and institutions of his time. In his new book Galileo and the Science Deniers, astrophysicist Mario Livio talks about the parallels of Galileo’s story to present-day climate change discussions, and other public scientific debates today. Monitoring Your Pandemic Health, From Your Home In recent weeks, the FDA has given the go-ahead to several tests for COVID-19 that can be performed remotely, from your own home. Such tests could help greatly expand testing capacity, an essential part of plans for recovery—but only if the tests are sensitive and reliable. Researchers are also working to develop other ways of using tech to monitor the outbreak, from heart rate monitors in smartwatches to sampling community sewage plants for evidence of the virus.   Eric Topol, the founder and director of the Scripps Research Translational Institute, joins Ira to talk about some of the technology that could be brought to bear to get a better picture of the COVID-19 pandemic. The Origin Of The Feces For some researchers, nothing is more exciting than finding fossilized feces. These ancient poops are called coprolites, and they’re quite rare. Despite their less-than-glamorous-origins, each one is a gold mine of information about who left it behind. That’s because fecal fossils are a snapshot of the microbiome from which they came. Some researchers say studying these ancient records of diet and bacteria could help us learn about modern problems such as lactose intolerance and gut inflammation.  Christina Warinner, assistant professor of anthropology at Harvard University in Cambridge, Massachusetts, joins Science Friday producer Kathleen Davis to talk coprolites, and what ancient feces can tell us about our ancestors, and ourselves.  Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Plato. A bit later in the hour, I look back at Galileo with Mario Livio and also the power of fossilized feces. Yeah. But first, one of the keys to managing the COVID-19 epidemic is data, accurate data from lots of people and lots of communities. Who's sick? Who's not? Where are the hotspots? And can we learn anything from the patterns of who gets sick and who gets better. But how to collect that reliable data? Maybe it's a better test available to more people. Maybe it's tracking your own health on a smartwatch or other device. Maybe some answers already exist in our medical data and we just need to sort through them and find out. Joining me now to talk about how technology can help us get and manage all that data and what we might be able to learn from it is Dr. Eric Topol. He's the founder and

director of the Scripps Research Translational Institute, the professor of molecular medicine, and the executive vice president of Scripps Research in La Jolla, California. Welcome back to Science Friday, Eric. Oh, great to be with you again, Ira. One of the things that keeps coming up during this pandemic is testing, and recently the FDA has given the okay to a couple of at-home tests. Can you tell us a little about them, what you think of them, how reliable they're turning out to be?

Well, I think the at-home path is probably the best of all, just because you can then get to the massive scale that we need to. In working with the Rockefeller Foundation, our action plan called for 30 million tests a week. And it's going to be hard to achieve that level without being able to use the home, at least a large part of the testing path. Now, the tests that have been approved to date for the home are not as accurate as we'd like. for the test that we'd like to see, it would get to very high levels of sensitivity to try to get that false negative rate for the virus or the antigen. They're both two different ways that you can detect an infection. Get that rate as low as possible. Right now are false negative rates and the tests that are available are 10 to 30 percent.

So a lot of people are getting the sense that they don't have an infection when they actually do. Another big question that people have is, did I already have the disease? Do I maybe have the antibodies that might protect me? And there are what? 50 some tests out there for that, but how many of them are really good? Right. Well, there's, I guess, over 100 these days, but there aren't any that are yet really good. The one from Mount Sinai from Florian Kramer just got reported in Nature Medicine. and maybe one of the best. The problem is just the opposite as what we've been talking about with the virus infection. This is the problem of false positives.

So that people get this reassurance that, oh, well, you have the antibody when they actually have never even seen the infection. It's just a false test. The reason, the primary reason for these false positive tests is that there are four coronaviruses that cause common colds. And many people develop antibiotics.

to those coronaviruses, and they cross-react to give this false sense that you have COVID-19 antibodies when you actually don't. So the test need to get more specific for antibodies, and we're moving in that direction, and I think it's pretty clear that, you know, we're going to have good serology tests in the short term. What could we be testing more? People talk about we're not doing enough testing. Is there a kind of testing or a kind of monitoring we should be doing that we in the U.S. are not doing? Well, I think the problem, frankly, is that because we went two to months or more with essentially no testing, we got into this horrendous situation. So testing our way out of it right now is going to be much more difficult. It's potentially achievable.

But, you know, if we think about it, while we're all were in lockdown, what was done to fix this testing infrastructure, you know, almost nothing. So the testing is going to get better. It's another reason why we need to be patient. We're obviously seeing, you know, drugs and neutralizing antibodies and convalescent plasma, all these things that could help us in the short term, even before potential vaccines. They're kicking in, too. So we just need to bide time and not be impatient. think that's really something that's missed out there is that this rush to reopen when there's a lot of good indicators right now. There's a lot of things like, you know, we didn't talk about sewage

surveillance where that could be a great way. It's cheap. It's easy. It's accurate. And all you got to do is look for signs of COVID-19 in poop and in a community. And you can anticipate an outbreak. So there are a lot of things we're not doing that we should be doing. And it's really unfortunate. We asked our listeners on Twitter what types of tech they have been using to monitor their own health. And the answers basically came down to three camps. One, people were using some sort of digital thermometer regularly. Others were relying on the old-fashioned liquid thermometer. And some people were using an oxygen measuring device, which I have, which my doctor said,

that was the first thing he wanted me to get out of anything besides a thermometer, was this little thing that you slip your finger in. and it measures your oxygen level in your blood. Why is that so important? Well, it's important if you have either a known infection and you're feeling okay, but you want to know whether or not your oxygen levels are starting to drop in the saturation of oxygen in your blood. So it could be helpful to detect before you've got more problems with breathing that you're starting to have a lung issue. it's a really interesting thing because it also could engender a lot of anxiety.

The numbers for these oxymetry devices are not so perfect in terms of accuracy. So if you take it one minute and minutes later, even though the real oxygen saturation hasn't changed, you could see some fluctuations that could be concerning. But no, I think it's a useful tool. What's interesting, Ira, is that many, of the smartwatches actually can detect oxygen saturation. So, in fact, they've been in the watch, but haven't been activated until recently, things like Fitbit and the Apple Watch and Samsung and Withings and many others.

So what's going to be nice is when you don't have to buy another device, but it's actually in a watch. And that should be available for continuous monitoring rather than having to take it at certain time. Are you saying they're already in these watches and they're just not activated? Right. It's amazing. So for years now, the same light sensing that's used for heart rate, which we need to talk about because heart rate is really an exciting way to follow this condition. That same optical sensing is capable of getting the oxygen in your blood.

But for whatever reason, the companies that have had this in their watches have only realized recently that this is extremely useful. And possibly the whole COVID-19 helped precipitate that. But now already Fitbit has released theirs. And we're expecting Apple and the others to do that in the very near future. Tell me about why monitoring your heart rate is so important. Yeah, I think that's one of the biggest things of all, because, Because we have shown our group at scripts that if you try to anticipate flu or flu-like illness, we could do that better among 50,000 people with Fitbit.

Then the CDC, in terms of picking up particular areas within five states where flu illnesses were occurring. So now we've launched an app called Detect Study. And that app basically is donating heart rate data. We have about 22,000 people in it now. We hope to get hundreds of thousands. And when we have that, we should be able to pick up COVID-19 clusters before they become significant outbreaks. Because heart rate is so important that it comes before you have a fever. A lot of people never have fever.

We know that at least 30% of people who are. get infections never have any symptoms, but we anticipate that their resting heart rate would go up because they are fighting the virus, even though they don't know it. So we think the heart rate is an ideal way because it doesn't take any work. It's passively being collected through a fitness ban on the wrist or a smart watch. And the other thing is that in two other countries that read our work and attribute their programs to our effort. Germany has over 500,000 people, smartwatch heart rate monitoring, and China, 1.3 million people. So we're lacking in the countries, even though we did the initial work. We think heart rate is going to be a winner, especially as

we're waiting for the testing infrastructure to develop, which is going to take time. If you would like to take part in this new study that Eric is talking about, you can do that If you have a smart watch or smart device on your wrist that can monitor your heartbeat, go to their website at Detectstudy.org and sign up. Your last book looked at the role of artificial intelligence and what it could play in medicine. Is there an AI role in the coronavirus pandemic? Oh, I think we're seeing that in many different dimensions. The problem is that I don't know that any of them have.

made a big difference yet. But for example, we've seen it for repurposing drugs and data mining of, you know, massive amounts of what we know about every drug molecule that's ever been considered. We've seen it for triage of patients for who should go in the hospital, who should go in the intensive care in it, but it really hasn't been validated there. It could ultimately be useful for monitoring people at home with continuous vital signs, but it's in the early stages. So there are lots of different ways that AI could help here, but most of it is really theory. It hasn't been proven or validated. Eric, I've run out of time.

I know there's so much to talk about, and it's always great having you to come on and talk about this with us. So I want to thank you very much for taking time to be with us today. Oh, it's always great to have a conversation with you. Thanks, Ira. You're welcome. Eric Topal is the founder and director of the Scripps Research Translational Institute, Professor of Molecular Medicine and the Executive Vice President of Scripps Research in La Jolla, California. When we come back, a trip back to the days of Galileo. Stay with us. We'll be right back after this short break. This is Science Friday. I'm Ira Flato. Galileo Galileo is known as the father of observational astronomy.

His theories about the movement of the Earth around the sun and his experiments testing physics principles is the basis of modern astronomy. He's just as well known for his battles against science skeptics, having to defend his scientific evidence against the political and religious-based critics and institutions of his time. Sound familiar? My next guest is here to talk about how Galileo's story is relevant today. Mario Livio is an astrophysicist and author of the new book called Galileo and the Science Deniers.

Welcome back, Mario. Always good to have you here. Thank you very much for having me again. Why did you decide to write this book at this time? Well, there were several reasons. One is that I've always been fascinated by Galileo. I'm an astrophysicist and he founded modern astronomy in astrophysics. Another is that most of the books about Galileo have been written by science writer, science historians.

Not many, if any, have been written by a research astronomer. So I thought, you know, I can bring some perhaps fresh perspective to this side of things. And finally, most importantly, you know, Galileo fought against science denial. And unfortunately, we are facing blatant science denial today. Is there a real parallel between what he was doing and what is happening in science denial today? There are many parallels. I mean, the motivation is not always the same. You see, in his case, it was a clash, not as he's often said between science and religion, but between science and literal interpretations of scripture. That was the clash.

Today, the motivation is somewhat different. For example, let's say in the case of climate change denial, It is usually political conservatism and adherence to certain economical ideas and things like that. When you talk about the initial reaction to the COVID-19 pandemic, it may have to do with the fact that we are in an election year, and so the motivation is completely political. In some cases, religiosity plays a role, like, you know, in the idea to teach creationist idea in science classes, in schools. It's interesting to say about the parallels, because he was at his time. Wasn't he sort of a rock star of science in his time? He was. At some point, he became the best known scientist in Europe.

But, you know, maybe rock stars have lots of followers. I'm not sure how many followers that Lileo actually had, but it is true that, for example, his first book about his discoveries with a telescope, did some. sell out very quickly. There were only 550 copies, but still, it was a best seller of the time. There are many myths about Galileo that you go through in your book. Like, well, folks, he never dropped those balls off the Leaning Tower of Pisa. No, he did not. He did drop balls, though, from, you know, certain heights. And, yeah, measured how they arrived to Earth. But most probably never did that from the leading tower of Pisa,

because no documents at the time record that, and Kalile was very, very fierce about, you know, people not giving him the proper credit. So he did draw balls, and he achieved some important discoveries that way, but not from the leading tower. There are other things. I mean, I recently wrote an article about whether he ever said,

and yet it moves about the earth. most probably I conclude he did not. That was added by later historians. But there is no doubt that he fought that. That was his defiant thing against being convicted by the Inquisition. He certainly thought that in spite of what you think these are the facts, but he probably never actually uttered those words. Interesting.

Let's talk about some of the very clever and imaginative of ways he had to test ideas about things. He's credited with modern laws and rules of experimentation, but he doesn't always get them right? Correct. I mean, he started doing experiments. You see, the ancient Greeks, in particular, Aristotle, for example, they didn't do experiments. They thought that the way to understand the nature is to sit down and think about it. But Galileo said, no, you have to do experiments, you have to do observations, and then do the reasoning based on what. what you get from those. He did fantastic things, you know, in particular, by wanting to study, for example, a free fall. He didn't have good enough devices to measure short periods of time. So instead, he devised this thing where he used inclined planes

and rolled balls down inclined planes, thereby slowing down the motion by a lot and enabling him to actually measure these things. But his theories were not always correct. I mean, for example, he had a theory of tides, of ocean tides, which was completely wrong. I mean, he thought that it had to do with the motion of the earth around the sun and the motion of the earth spinning around its axis. And we know that that was not true.

It's actually the influence of the moon. And he didn't believe in that. But to his great credit, as you're right, he created the system of experimentation and re-experimentation. and re-experimentation, sort of the modern basis of how science is done so that things could be disproven. Exactly. He was one of the founders of what today we call the scientific method, which means, you know, you want to explain something. First do experiments and observations. Then, you know, create a model or a theory that tries to explain all the observed facts. if the theory doesn't explain all the observed facts, it's not good.

Now, it has to do something more. It has to be able to make some predictions that can be falsified by new experiments or observations. Unless it does that, it's not really a theory. This is the greatness of science, that it can make predictions that you can then test and see if they are actually correct or not. And Galileo was really the person to do that.

There was one other thing that he did. And that was the mathematics of science. He said that the universe is written in the language of mathematics. This was an incredible statement. Because, you know, today, okay, we know that all the laws of nature are written as mathematical expression. But at his time, this wasn't the case. And yet he had this incredible intuition that it has to be like that. Let's talk a bit about Galileo becoming and battled with the Catholic Church.

We touched on it a little bit before when he came out siding with the Copernican ideas about the Earth revolving around its sun and his own theories. What was the main issue that Galileo had with the church? So the issue really was it was not against religion. Galileo himself was a religious person. It was against literal interpretations of the texts. He argued, look, the Bible is not a science book, and it was written for the common people to understand. He also had this very strong statement which said that he never believed that God, who has given us intelligence and our senses and reasoning, wished us to abandon their use.

So he said, whenever there is a conflict between what observations and experiments tell you, And a literal interpretation of what's in the Bible, you have to change the interpretation because he said the Bible doesn't do errors. It's just that we interpret it incorrectly. That's the point. So as a result, however, he didn't convince everybody, especially not the Inquisition, and he was put on private. You compare Galileo to Einstein's views on religion and science.

How did they differ? Yeah, they did differ. I mean, they were both great scientists, of course, but their views on religion were rather different, almost, I would say, orthogonar in some sense. You see, Galileo thought, well, he advocated that the Bible is not a science book. It was never written as a science book. So it was written for our salvation, you say. So the language in terms of science was certainly not precise. The planets are not mentioned. in the Bible and things like that. But he did see it as a guide to moral behavior, to ethics and things like that. Einstein, on the other hand, when asked

whether he believed in God and how religious he was, he answered that he believed in the God of Spinoza, the great philosopher, in the sense that he was in awe in front of the beauty, wonders of the universe.

But he did not believe in a personal God, a God that interferes with the actions of humans and punishes or rewards and things like that. That is the moment. And so what happened to his career after that? What did you discover about the rest of his life? Well, you know, he was found guilty, vehemently suspected of percy. He was condemned to house arrest, which he did for eight and a half years. For the rest of his life, He was on house arrest. You know, if you think that today, you know, being shut in place for two, three months, he was in his house on house arrest for eight and a half years.

And all his books were put on the index of prohibited books, and they stayed there until the middle of the 19th century. Even reprints of his books that had already been printed were not allowed. This effectively, it didn't think. his career because at house, in his house, he actually wrote his last book, which was his great book on the campus. That's interesting. The idea of truth comes up in conversations that we're having today with the idea of fake news.

What are your opinions about that? Yeah, well, you know, that's where exactly his statement, you know, apocryphal or not of and yet it moves becomes so important. Because what that statement says, you know, in spite of what you may believe, these are the facts. And he established the ways to determine truths. And the only ways, in this particular case about nature, was through experiments, observations,

and reasoning based on the data that you get from that. The data are there. and you cannot deny the data. Today, unfortunately, we live in a situation where there's not just fake news, there are alternative facts, there are all kinds of words like that. It's almost the death of facts, if you like.

It's a very sad situation. And this sad situation is leading to, unfortunately, very dire consequences. I mean, you know, if you look at statements such as that were at the initial stages of this, pandemic. Oh, we only have 15 cases and so we will have not. This is a total dismissal of the actual facts and of scientific reasoning. You know, we pay a dear price for them. Do you think it is the duty of scientists to stand up for beliefs that are outside of science

and the way that Galileo did? I actually do, yes. I honestly think very strong. about that. But, you know, intimidation works today as well as it works in Galileost. Okay, today people are not burnt at the stake and they are not tortured, but, you know, careers are affected, lives are affected, but we absolutely have to, especially when you deal with topics that are so important for life on earth. I mean, to bet against science, it is never with it. But to do so when you have a case like climate change or when you have a case like a pandemic, where literally the future of life is at stake, I mean, it's really unconcernable. I'm Ira Plato, and this is Science Friday from WNYC Studios.

Do you think that more scientists today should be speaking up? Are there not enough scientists who are voicing their condemnation? I believe that most scientists are voicing their condemnation. I think that what is lacking is people who are also non-scientists and are influences or are in the political system who actually know that these are the facts and they are not speaking out enough. And I'm not talking about those who are convinced otherwise. I mean, there are many studies that show that if there are people who already have strong opinion about something, it's extremely difficult to change their opinion, even if there are shown facts that are contradictory.

But I'm convinced that in our political system, there are people who actually know what the facts are and know what the right path should be, and they still don't speak up enough. That's interesting because that was the parallel up to a point, as you say, with Galileo, was that he was trying to present the facts. He had the evidence. He had the experimentation and still could not convince people of the way the world works. Well, there are people that were convinced, even at this time. We had some friends.

He had some supporters. He had other scientists. You know, Johannes Kepler was a great astronomer, was completely convinced of. of Galileo's findings and all that. So there were people, even at his time, science is not always right. We know that. All scientists know that science is provisional.

It always can be improved, but it corrects itself. Sometimes this takes a year, sometimes it can take decades to correct itself. In Galileo's case, of course, the science corrected itself relatively fast, already by new people, but it took, you know,

of John Paul II until 1992 to declare that Galileo's right. There is always this, you know, somewhat of a tension between who do you convince first and who gets convinced first. I think that the main lesson from Galileo is believe in science. And this is true today and more true than perhaps today in the middle of a pandemic than it ever was. because like I said, science isn't always right, but science understands that it's not always right. And it always tries to do, you know, to behave according to the facts and the data. And that's a good place to end because we have run out of time.

A great conversation, Mario, a fantastic book. It's something, you know, it's a great history and it's a great lesson there. Thank you for writing it and sharing with us today. Thank you very much. Mario Libio is an astrophysicist, and his new book is called Galileo and the Science Deniers. Great reading, relevant today as, well, relevant forever. After the break, we're going to talk about what fossilized feces can tell us about our ancestors and ourselves. Stay with us. We'll be right back after the short break.

This is Science Friday. Iro Plato. The fossil record is littered with countless interesting things. Ancient bones of giant beasts, the remains of long extinct plant life, to name a couple. For some researchers, though, nothing is more exciting than finding fossilized feces. Yes, you heard me right. Dr. Christina Warrner is in this camp. She's an assistant professor of anthropology at Harvard University, sci-fi producer Kathleen Davis spoke to Dr. Warriner about her recent research with fossilized species. These ancient poops are called coprolites, and they're pretty rare. The origins might be less than glamorous, but each one is a gold mine of information about who left it behind.

And that's because coprolites are a snapshot of the microbiome from which they came. Some researchers say studying these ancient records of diet and bacteria could help us learn about modern problems like lactose intolerance and inflammation. Dr. Christina Warner, thanks so much for joining us on Science Friday. Thank you for having me. I want to start with a technical question. People and animals make waste constantly. And at the same time, we're not drowning in coprolites.

What makes them so uncommon? Well, fortunately, most feces does break down and compost really, really quickly. Otherwise, we'd be swimming in it at this point. But no, they do preserve archaeologically under very specific conditions. So, and generally, we only find preserved feces when you have something that immobilizes water. So that could be a very, very dry environment that desiccates the material or really salty soils or freezing, for example. So does that mean that the coprolites that we do have are often found in the same places? Exactly. They almost always come from some sort of context that's extremely dry or frozen.

So places like dry caves in the American Southwest or in northern Mexico or salty deposits in mountainous areas, those are typically where we find copperlates. And so say you have a copper late in front of you that you want to study. What kind of information can you actually learn from it? Well, although we tend to just flush it away without thinking about it, they're actually incredibly rich sources of information about ourselves, about our lives, and about our activities. So, for example, our feces contain our own DNA. So you can reconstruct a person's genome from a fecal sample. They also are a great snapshot of our gut microbiome, where we can understand the structure of the microbiome, the types of bacteria that are present.

We can look for evidence of infections, so pathogens, either bacterial pathogens or potentially viral pathogens. We can also look for things like parasites, which were very common in the past. And then, of course, we also have dietary DNA that's present. and this can provide a real important window into what people ate in the past. And remind us again what the microbiome is. So the microbiome is this community of bacteria that lives in and on the human body. And they're very important.

For a long time, they were very difficult to study, and so we really underestimated their importance. But we now realize they're a fundamental part of our biology, and we actually rely on many of their activities for our basic biological functions, everything ranging from digestion to even producing some of the, the vitamins that we require. So I would assume that to be fossilized, these coprolites would have to be pretty old. I mean, how much detail is actually retained inside of them? Well, it really depends on the preservation. So sometimes they actually resemble turds and they're very visibly recognizable.

Other times, they've been really kind of squashed and flattened by the sediments around them. And so you can look at them visually and often identify them as copperlights. They have a different texture and consistency than the soil around them. But it doesn't necessarily mean that they're preserved at a molecular level. So many of them, although they retain some aspects of their morphology or shape, have actually essentially composted in place and have been replaced by soil bacteria. But rarely, we do find these extraordinarily well-preserved copperlites, these particular cases where they dried out very, very fast. And in those cases, they still retain the original bacteria, the original human DNA, and the original dietary DNA. Those are the ones we're trying to focus on.

You recently studied a problem that apparently plagues coprolite researchers. Human coprolites can be confused with those from other species. How does that happen? So, yeah, so to some degree, I was aware that this could happen, but I wasn't aware of the scale of it until we started digging into this problem a little bit more closely. So feces turned up at archelaal. sites in different contexts. Actually, toilets are really rare in the archaeological record. Most people either deposited fecal material into what we call middens or garbage deposits or practice open defecation. So any kind of like systematic sewage treatment or collection is actually not that common archaeologically. We do find then these feces kind of mixed in with different, usually

garbage at different sites in dry caves in particular. And we had assumed, and many people had assumed for a long time that the vast majority of this was human. However, over time, there have been a number of cases that really raised suspicion as to whether or not some of this truly was human or not. Now, some types of feces are really easy to distinguish. So a cow pie is very obvious. It's huge, and it contains very fibrous material and grasses that cows eat, for example. But dogs are a bit different. Dogs have lived with humans for tens of thousands of years, they poop in the same places. And so you could mix these up. Now, from fresh feces, you can often distinguish human and dog feces just in the basis of size or shape. But

archaeologically, those features often get very distorted just through the formation of the archaeological site, so the compression of sediments around them, the color changes as the pigments inside the feces break down. And so many of those visual cues you might use to identify dog feces just aren't present in the archaeological record. Because they co-occur and because dogs are often fed by humans, so they ate the same food and so microscopically they contain the same food material, they can be really hard to distinguish. I think anyone listening to this who has a dog or has cleaned up after a dog before is going to have a very visceral reaction to this conversation. So how do you actually distinguish the human coprolites from the dog ones?

So there are some techniques that can be used microscopically. Dogs do get infected with different types of parasites, for example. And dogs who are feral dogs will often hunt rodents, for example, and so you'll find little rodent bones in their feces. However, for dogs that are really associated with humans and being fed by humans, we have to take another approach. And so here we used genomics to solve this problem. But we had to use two different approaches, because one of the big problems we face in the archaeological record is that, For many ancient people, dogs were a major and important food. So dogs were consumed as food. So you might expect to find dog DNA in human feces. And also dogs very frequently will scavenge either human latrines or open defecation sites for human feces. And so you might expect to find some human DNA in dog feces. So as a first pass, we did look at the abundance of either dog DNA or human DNA within the feces, but we didn't feel that was sufficient to really distinguish them. So we took at a second level and we looked at the microbial communities as well. And the microbial communities within the human gut microbiome and the dog gut microbiome,

although similar in many ways, are distinct. And so we were able to use these two different lines of evidence to distinguish them. And what was the age range of the coprolites that you were looking at in this study? So the oldest ones we looked at date to around 7,000 years ago and come from Neolithic China. The youngest ones that we looked at are actually just a few centuries old and come from Surrey, England where we had a really unusual case where there was a house that was constructed in the 18th century and someone had taken a chamber pot that had a turd in it and walled it up into the house. And that was only discovered in the 1990s when the homeowners were renovating. And so when they took down the

walls and opened up the attic, they found this chamber pot. And so we thought this must be a clear case of human feces, because what else would you find in a chamber pot, although it is very odd that it's in a wall. But that turned out to be a dog, actually. So it's an enduring mystery as to what the story is behind that case. That is very strange. Did you learn anything about the humans that were the source of the coprolites during this study? Yeah. So we didn't actually set out to find dog feces, the ancient dog poop. We started the study really because we were interested in the humans themselves and then discovered that we had dogs mixed in. But what we're really after with this study is we're trying to understand the evolution of the gut microbiome.

We know that the communities of bacteria that live in our gut are highly responsive to the diets that we eat. We know that industrialized diets have really changed the way that our microbial communities are structured. And in many ways, these changes are associated with health consequences and chronic inflammation. So the big question we wanted to ask was historically or prehistoricly, when did these changes start to happen? Is it really associated with industrialization or might it begin earlier with more intensive agriculture or maybe with the beginnings of agriculture? So part of what we were trying to do was to look for human feces from different points in time and try to understand how it had changed in response to different and new human social behaviors. What we found along the way was also all the dog poop mixed in. So part of this study was coming up with a systematic way of separating those so that we could focus on the human feces and understand this evolutionary process.

But then it also gave us a new window into dogs, which are some of our oldest friends and how they have adapted and lived alongside us over the same period of time. And what did you find that might shed more light on that? So that is the focus of a study that we're still doing. I mean, we found some basic information. So, for example, from the human feces, we are able to reconstruct aspects of information about those individuals. We could tell if they were male or female. We could reconstruct their ancestry profile and show that it matched the reasons. of the world that they came from. We also were able to identify some of the dietary components.

So, for example, from the individuals from northern Mexico, we recovered a lot of maize DNA and also some other DNA of plants that are very common in traditional rural diets. And so we were able to reconstruct some of that information. Our next step now is trying to understand how these microbial communities have systematically shifted in response to things like social complexity, new forms of agriculture, state-level societies. These are some of our interests. I'm curious, do you have a favorite coprolite that you've studied? Of course I do. So I work at both ends of the gastrointestinal tract. So I work on coprolites, which is paleofeces, and I also work on dental calculus, which is calcified dental plaque.

So all the things that people spend money trying to get rid of, I'm so interested in. And I definitely have favorites. There's some that we've found that we've just found really fascinating information from. So I have to admit the dog coprolite from the chamber pot was quite the puzzle for our whole group. It took us a lot of time kind of working out what might have happened there. And so that was a really fun project to work on. We also have looked at other individuals that are not included in this study who just had a really wide variety of foods and are giving us a tremendous insight into whole meals that people consumed thousands of years ago. So those are some of the really exciting samples to work on. I'm Kathleen Davis, and this is Science Friday from WNYC Studios.

We're talking to Dr. Christina Warriner, an assistant professor of anthropology at Harvard University in Cambridge, Massachusetts. So you mentioned that you work at both ends of the gastrointestinal tract. Tell us a little bit about studying fossilized plaque. What can you learn from that? That might be a little bit different than studying coprolite. Yeah, so copper lights are fantastic in terms of the range of information you can get from them, but they're rare. So we can only really access particular places and times in the past. What's really exciting about looking at calcified dental plaque or calculus is that nearly every skeleton has it. And so this really opens up the entire archaeological record for us to investigate the past.

One thing that, you know, people go to their dental hygienists, to the dentist, and they have all of their calculus or their tartar is another. term for it, scraped away. But it's a really amazing material. It's the only part of your body that actually fossilizes while you're still alive. And it's this sticky substance that slowly calcifies, and during that process traps all sorts of debris related to your daily lives. So we find everything from seasonal pollen that gets trapped in was probably an allergen. We find little bits of tiny fragments of food. So plant, microfossils get entrapped in calculus. We find, of course, bacteria that are present. We find human DNA. Also, we find a lot of dietary proteins. And so this is a technique that we've been really exploring lately in reconstructing the food histories of different

places by looking at the food proteins. They get left behind and entrapped in this calcifying dental plaque. And in particular, we've really focused on using this to track the origins and spread of dairying around the world, which originates in the Near East about maybe 9,000 years ago, and then spreads from there to Europe, Africa, and throughout Asia. Speaking of dairy, food allergies and intolerances are pretty common these days. Can we learn about things like lactose intolerance from studying these fossilized feces and plaque? Yes, and I think this is something that is really exciting. This is something my group is working on right now.

Lactose intolerance is actually a really interesting phenomenon. on the one hand, all mammals produce lactase, which is the enzyme we use to break down the milk sugar lactose. And we produce this in our small intestine, and it helps us to digest milk when we're young, when we're infants. But all mammals are actually genetically programmed to lose the ability to produce this enzyme, effectively becoming lactose intolerant. And this is part of the weaning process of mammals. And what's really interesting in humans is that a subset of humans have developed mutations in this system such that They just produce lactase all the time and for their entire lives. These mutations are in Europe, parts of the Near East and parts of East Africa.

And so these populations are called lactase persistent. And they're milk tolerant. But what's really interesting is that we see that while these societies and these areas have long practiced dairy production, we also see that other populations, for example, in Mongolia, also have very long histories of dairying. And this is something we've shown through some of our work looking at preserved proteins and dental calculators. we can trace back the origins of daring in Mongolia more than 5,000 years. What's really amazing about Mongolia today is that they milk seven different species of animals. So they milk cattle, sheep, goats, yaks, horses, camels, and reindeer.

And yet they don't have any of these mutations that are associated with producing lactase. So this has long been a puzzle that these mutations don't actually explain all of the daring behavior that we see in populations around the world. So we've been working really closely with herders in Mongolia trying to understand this. And we're starting to gather evidence that we think that the microbiome is really strongly involved in this process. That's so interesting. Dr. Christina Warner, that's all the time we have for today. Thank you so much for joining us on Science Friday. Thank you. That was sci-fi producer Kathleen Davis speaking with Dr. Christina Warner, assistant professor of anthropology at Harvard University. If you missed any part of this program or you would like to hear it again, subscribe to our podcasts, or ask your smart speaker to play Science Friday.

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