Science Friday - COVID Fact Check, Ocean Circulation and Climate, Bread Culture. Sept 3, 2021, Part 2

Episode Date: September 3, 2021

Fact Check My Feed: Why Are People Taking Discredited Horse Medicine For COVID-19? If you’ve been online at all in the past few weeks, you’ve probably seen discussion about the drug ivermectin. It was originally developed as an antiparasitic treatment for livestock, and in 2015, the Nobel Prize in Medicine went to scientists who found that it helped control parasitic diseases in humans as well. But recently, non-medical groups have been incorrectly promoting the drug as a treatment for COVID-19—even though the coronavirus is a virus, not a parasite. Virologist Angela Rasmussen of the University of Saskatchewan joins Ira to look at the data behind sometimes hyperbolic COVID-19 claims, from the latest on booster shots to the emergence of a new coronavirus variant in South Africa.     What Happens If Atlantic Ocean Currents Cease To Churn? Early last month, the Intergovernmental Panel on Climate Change released its latest report. It was a grim document, concluding that global warming had already set in motion irreversible levels of sea level rise, along with other changes that are threatening lives and health around the globe. The report focused in part on climate tipping points, or phenomena that, if they occur, could lead to a long term re-setting of our global climate and cascades of dangerous changes. Included among tipping points like the loss of the Amazon rainforest and melting of the permafrost, was the potential shutdown of the Atlantic meridional overturning circulation—the AMOC, for short. That circulation, a set of currents that includes the Gulf Stream, ferries cold water from the poles toward the equator, and distributes heat from the equator to northern latitudes. And it’s powered by two things that are both changing as the climate warms: the temperature of ocean water, and the varying concentrations of salt in that water.  Climate models that use data from thousands of years ago can help us predict what might happen if the AMOC shuts down. Because the currents are a huge source of heat redistribution globally, a shutdown could have a complex array of consequences, from rainfall disruptions in the southern hemisphere, to even greater sea level rise on North America’s east coast. And if it shuts down completely, it may not come back on again in any of our lifetimes. Unfortunately, researchers have been finding evidence that the circulation is, in fact weakening, including a study published in the journal Nature Climate Change in early August. Ira talks to Levke Caesar, a researcher at Maynooth University’s ICARUS Climate Research Center. While not affiliated with the latest research, her work has helped map the ongoing pattern of weakening in the AMOC.       A Sourdough Saga, From Starter To Slice What makes sourdough taste sour? Was the first bread invented, or discovered? How did scientists eventually figure out that yeast and bacteria were the true master bakers? Will commercial bread ever be as good as that hand-baked loaf? Ira releases his inner breadmaking nerd in this conversation with Eric Pallant, author of the forthcoming book Sourdough Culture: A History of Breadmaking From Ancient to Modern Bakers.   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 Flato. Later in the hour, a look at how global change is upsetting vital ocean currents in the Atlantic, and a trip to the bakery for some sourdough bread geekery. But first, if you've been online at all in the past few weeks, you've probably seen discussions about the drug Ivermectin. It was originally developed as an anti-parasitic treatment for livestock. And in 2015, the Nobel Prize went to scientists who found that it helped control paracetting. parasitic diseases in humans as well. But now some groups have been promoting the drug as a treatment for COVID-19, even though the coronavirus is a virus, not a parasite. Joining me now to help unpack that and other news from your COVID news feed is Dr. Angela Rasmussen, research scientist at Vito InterVAC, the University of Saskatchewan's Vaccine Research Institute in Saskatoon, Saskatchewan, up there in our friends in the north in Canada.

Welcome back, Angela. Thanks for having me back, Ira. Okay, so what's the deal with this horse medication story? Ivermectin, in some ways, is really the new hydroxychloroquine. I'm not entirely sure how Ivermectin came on the scene as a possible treatment for COVID-19, but multiple clinical trials have been conducted to look at Ivermectin for treating COVID-19 or preventing COVID-19, and it doesn't appear to do either one of those things. the FDA, as well as the one of the manufacturers of ivermectin Merck have both release statements saying

that that ivermectin cannot be used for treating COVID-19 and that people should not use it, especially as a substitute for vaccination. And, you know, for me, like months ago when Merck said don't take ivermectin for COVID, I mean, that's not usually the kind of thing that a pharmaceutical company says about a product that they make. Please don't take our product. You know, all of that, along with the data is really a strong indication that ivermectin doesn't do much in the way of treating COVID-19, and it certainly doesn't prevent it. And it certainly is not a good alternative to vaccination. Now, some people who are promoting ivermectin for this purpose have said, well, ivermectin is on the WHO's list of essential medicines. It's a crucial medicine. And you mentioned

that the discovers of ivermectin won the Nobel Prize, because it is used for treating some some really horrific parasitic diseases. One of those onchocirchiasis, African river blindness, is a disease caused by worms that can ultimately result, as the name implies, in loss of vision. Most of the listeners probably are most familiar with ivermectin as an ingredient in heart guard or any of the other types of deworming medications that they give pets. It's very effective for treating parasitic worm infections. It is not effective, however, for treating COVID-19. and this is what really concerns me, are people who are promoting ivermectin as a valid alternative to vaccination for preventing COVID-19, and this is just simply not the case. If you're taking

ivermectin every day, not only if you are taking an off-label, can you suffer the consequences of taking too much ivermectin? Because if you're buying ivermectin in a dose that's meant for horses or cows or large animals that have considerably more body mass, than we do, you could overdose on it, but also you are going to continue to be vulnerable to COVID-19. And if you think that that ivermectin is providing the same protection that a vaccine would, you're going to potentially put yourself at a greater risk. Let's move on to something that has a bit more evidence behind it, and that is boosters. There's been a lot of talk about boosters, what Israel is doing, what other countries are doing.

will there be a third shot, who will get it, and when? Yeah, this is really kind of one of the hot topics of the hour. And really, a lot of this is based on evidence that I was pretty skeptical of at first, but I'm starting to be more and more persuaded. We're starting to see more evidence at really the population level that over time, the mRNA vaccines and particularly the Pfizer vaccine appears to be decreasing in effectiveness at preventing symptomatic COVID-19. Now, this has been a really confusing topic, I think, because we are also hearing all the time about

breakthrough infections and how they're more common with the Delta variant. And that's not necessarily due to this decrease in effectiveness. And that's not always talking about cases as cases of symptomatic COVID-19. Sometimes it conflates symptomatic disease with PCR positivity. But overall, this is really important. A decrease in effectiveness is something to be on the lookout for because, the clinical trials to evaluate these vaccines, they were expedited because this was an emergency situation. So we weren't able to look at durability. We don't know how long these vaccines are going

to have a long-term protective effect. And it is entirely possible that a third dose would always be needed because oftentimes one of the reasons why vaccine clinical trials take such a long time is they try multiple configurations of the dosing regimen to determine the optimal one for establishing durability. We have many vaccines that are three-dose regimens, usually with the third dose being given after a longer time interval from the second dose, which is really what's being discussed now. The reason why this is important is not just to prevent asymptomatic breakthrough cases. And I think this is one of the things that has really confused people because there has been some talk of, well, you're moving the goalpost. First, it was just to prevent COVID. And now it's to

prevent all these infections and why do I care if I get infected if I'm just positive on a test and you know I don't have symptomatic COVID but for people who are already high risk of developing severe COVID-19 an increase in the number of symptomatic COVID-19 cases and healthy low-risk vaccinated people probably means that there could be an increase in the number of severe COVID-19 cases in high-risk people who are more likely to end up in the hospital more likely to die from having COVID. So it does make sense to say, well, we do have a surplus in many parts of the country of vaccines right now. We do have increasing evidence that a third vaccine or even a mix and match vaccine regimen with a third dose is safe, if you can increase vaccine

effectiveness to take it from, you know, 50 to 70 percent back up to 90 percent in terms of preventing disease, that's something that we would want to have. And then finally, As I mentioned before, many vaccine regimens are three-dose regimens. And the reason for that third dose, and we are getting data to support this too for the COVID vaccines, is that if you have an increased interval between your second and third doses, your immune system basically says, you know what, this is something that I might continue to see this pathogen. So I'm really going to exert the resources needed to really make that long-term.

memory protective immune responses. And I hope that that's what we will get from the third vaccine. Now, of course, we don't know for these vaccines because we weren't able to look at durability. But knowing what we know from other vaccines and other types of vaccines, this usually applies that sometimes booster doses are needed, but they're not needed at frequent intervals. And they do result in immunity that lasts for years in most cases. Can we learn anything from the Israeli experience on this? They've already been using third doses. Well, absolutely. And unfortunately, what we can only learn is about the Pfizer vaccine in Israel, because that's predominantly the one that they're using. But Israel has really been a wealth of

information because they have had such a successful vaccine campaign and they've been collecting so much data on it. So I think that probably we will be able to learn a lot more, at least about what the benefit is to a third dose for the Pfizer vaccine at the population level. I hear you saying or implying that the Moderna vaccine may be longer lasting than the Pfizer vaccine. Well, a study came out this week in the Journal of the American Medical Association that suggested just that. Now, there aren't very many studies that are directly comparing these two vaccines. And I think people have assumed that they're basically the same vaccine as far as what the MRNA is encoding. But there are a couple differences. The Pfizer vaccine is given in a lower

dose, 30 micrograms compared to the 100 microgram dose of Moderna. And they have a different interval, three weeks for Pfizer, four weeks for Moderna. And they also use a different lipid nanoparticle to deliver the vaccine that ends up going into your cells where the spike protein gets made. All three of those things could make a difference potentially. And that's really what this study in Jama showed, it showed that the Pfizer vaccine was reduced in terms of its effectiveness in people who'd received that compared to Moderna and also that they had lower levels of neutralizing antibodies. So that may explain, you know, any of those things, the lipid nanoparticle, the interval and the dose might explain why the Pfizer vaccine doesn't seem to hold up for as

long or be as durable as Moderna, but we still, of course, need to do more research. Let's talk in the few moments we have left about news this week about a new variant called Mew. And now in 48 states, should we be concerned about that and other variants that we're hearing about? Yeah. So there's been a lot of news about variants this week and it's been more along the lines of scuriant kind of news where, oh my God, there's a new variant. It's also got a Greek letter, which is now how the WHO has recommended naming the variants. It's called mu, and that's just really because they've now gotten to M in the Greek alphabet. There's another cluster of variants called C1-2. That's a sub-lineage that was discovered in South Africa.

This is a group of variants that has a lot of mutations that have accumulated in the spike protein, and there have been rumors going around that it's, you know, it mutates faster or that it's, you know, the most mutagenic virus ever. none of those things are really true. And that's not to say that these variants aren't something we should be concerned about, something we should watch. I think that's why Mew is classified now as a variant of interest by the WHO. It's not yet a variant of concern. And the reason why none of these are variants of concern yet is that we don't actually know that we should be most concerned about them. What we are really going to have to see in the coming days and weeks is whether or not these variants start to out-compete

Delta. And that to me is really going to be the thing that we need to be most concerned about. Because we already know that Delta is pretty bad. It's more transmissible. It may be more virulent. It's causing more breakthrough infections. It's spreading like wildfire in places where people are unvaccinated. If either Mew or one of these viruses shows that it has the potential to do that even better than Delta, that's what we really should be worried about. So we should be vigilant, but we shouldn't freak out just because there's, you know, a new variant on the block or a couple new variants on the block, it really does remain to be seen whether they're going to be a big bad or not.

Okay. Advice for not freaking out is a good place to end our discussion. We've run out of time. Thank you, Angela. It's always a pleasure, Ira. Thanks for having me. You're quite welcome. Dr. Angela Rasmussen is a research scientist at Vito Intervac, the University of Saskatchewan's

Vaccine Research Institute in Sassad. Saskatoon, Saskatchewan, Canada. We're going to take a break, and when we come back, the research on one potential climate change tipping point isn't looking great. Stay with us. This is Science Friday. I'm Ira Flato.

The current depends upon a delicate balance of salt and fresh water. No one has taken into account how much fresh water has been dumped into the ocean because of melting polar ice. I think we've hit a critical desalimization point. I think we're on the verge of a major climate change. shift. When Dennis Quaid back in the 2004 film the day after tomorrow gave the bad news about melting glaciers stopping the flow of warm ocean currents like the Gulf Stream, not a lot of

people had heard about such a possibility. And while the movie may have over-dramatized the effects, a UN report released last month, though less dramatic, was no less cautionary. The IPCC report focused on the current weakening of this crucial ocean circulation. and the potentially irreversible changes resulting from a shutdown of what is formerly known as the Atlantic meridional overturning circulation, AMAC for short. Joining me now is Dr. Leifka-Cesar, a postdoctoral researcher at the Icarus Climate Research Center at Maynooth University in Ireland. Her research has helped identify the current weakening of this crucial circulation and some of the historic trends that might help us understand what could

happen next. Welcome to Science Friday. Thank you. Yeah, it's great to talk to you. Please introduce us to this system of currents in the Atlantic Ocean, this so-called conveyor belt for heat. Yes, so the system is called AMOC, which is short for Atlantic meridional overturning circulation. And basically, it's a large system of different ocean currents that connect the Southern Ocean with the North Atlantic. So the simple picture is that we have warm and salty water that is flowing near or just below the surface from the South Atlantic through the tropics towards the subpoly North Atlantic. And there in the north, the water releases heat to the way colder atmosphere. And as cold water is denser than warm water, this leads to a sinking of the water masses to deeper ocean layers. and there in the deeper ocean, this waters form the southward return flow of the conveyor belt,

where water is flowing from the North Atlantic back to the South Atlantic. This flow of warm surface waters in and of cold, deep water out of the North Atlantic, basically leads to a redistribution of heat, and we're talking about a lot of heat energy here, basically that the maximum northward heat transport by this ocean circulation system, system sums up to about 1.3 peta watts, a peta that is basically a one with 15 zeros. And to give you an idea, 1.3 peta watts that's basically or approximately the energy produced by a million medium-sized nuclear power stations.

So that's a lot of heat that's being released. And where does it go and what effect does it have? Yes, it is. And while it's released over the North Atlantic, and due to the prevailing wind systems with mainly westerly winds, a lot of this heat is actually transported towards the European continent. And it's one of the reasons why when we look at average winter temperatures for cities like Stockholm or Dublin, they are about 10 degrees warmer than cities in Canada, like Montreal, for example, or Quebec, even though the latter are. at the same latitude. And so as the globe continues to warm, and especially as the ice and the Arctic continues to melt, the idea here is that we might lose the difference in salinity that drives the circulation,

and that's why researchers are worried about it getting weaker or even stopping entirely? Yes, one of the main driver of this circulation system is this sinking of water masses in the Sapul and North Atlantic. and for the sinking to happen, the surface waters have to be denser than the waters below. And helping in that is a high salinity value because more saline water is denser than freshwater. And for the water being cold would also help because colder water is denser than warm water. And as you said, under global warming, we are seeing so much freshwater input into the subpoena North Atlantic because of the melting of the green and ice sheet, because of the melting of the arseous,

of the Arctic sea ice, also because we see enhanced precipitation over the North Atlantic under global warming. And all this freshwater is basically diluting the surface waters and therefore weakening the sinking of water masses that are driving the overturning circulation. So we're seeing then actual evidence of the circulation weakening. Dr. Caesar, how do you assess an entire ocean climate system? Where do you get your data? How do you collect it. I mean, you have this flow of water, but it's exact location, it's exact width, the depth. They vary over time. So if you really want to get the full picture, you basically need to cover the whole width of the Atlantic, and that's a few thousand kilometers.

And we actually have gone a good way in doing that. And in 2004, such an array spanning the whole width of the Atlantic was installed approximately at the height of Florida, that is 26 degrees North, and this is now, with all its instruments and monitoring system, is giving us a lot of information about how the AMOC evolved from 2004 onward. For any information about the overturning circulation before 2004, we have to rely on so-called proxy data. That is, climate variables that are directly affected by the overturning circulation and can therefore be an indicator for its strength by the changes that we see in those climate variables. And for the overturning circulation, there are basically a variety of proxy data. So for example, one thing is that

we look at the surface temperatures in the sub-polar North Atlantic, because that is a region where the AMOct transfers most of its heat into, and when we see a cooling there, this is an indicator of the overturning circulation slowing down. And other proxies that we can add, and we actually did this, is, for example, that we looked at the grain size found in ocean sediments, because when you look at the right place, then these can give you an idea of the strength of the bottom current of the overturning circulation, just by the fact that a faster current can actually carry larger grain sizes with it.

Then what we see is that for the main part of this time period of the last 1,600 years, the overturning circulation was fairly stable, but it did start to slow down, probably at the end of the 19th century, already by a little bit, but mainly since the mid part of the 20th century. Since then, we've seen approximately a decline between 10 and 20% of the overturning circulation, and this is likely going to continue in the future, as this is what climate models predict. That's very interesting.

What about the possibility of the circulation stopping entirely? Is this a real risk, as the IPC... climate change report has assessed in recent years. If the current stops, cold water stays at the poles, warm water stays at the equator. Is that a real possibility? It is. Basically, and we have several lines of evidence why we think it is a real possibility. On the one hand side, we know from paleo-climate data that this has very likely happened already in the past. When we look at temperature records, for example, from the Greenland Ice course, we see that there are pronounced, in the temperature where they were way below the previous value,

and think this is linked to a shutdown of the overturning circulation in these time periods. We also see this in climate models, that when we drive these models with a lot of warming, with a lot of freshwater input into the North Atlantic, that the overturning circulation can shut down in these models. So while there is this evidence that this can happen, we are not that close to actually really estimating when this will happen in terms of how much global warming is still okay for the overturning circulation to keep going and where is the critical value or threshold when the overturning circulation might actually shut down.

We are, and this is what the IPCC at least states, is that it's unlikely to happen when we stay below two degrees of warming. It is not impossible to happen below two degrees of warming. below two degrees of global warming, but the risk definitely increases when we see more warming. We're really not that close to really giving you the exact number here. I get it. But what are the consequences of if this happens? What happens to people in Europe that are depending on this warm water to keep them a milder climate?

This is really a huge question, and it's a vast question in the sense. It really depends on how much of a slowdown do we? see and also how much global warming did happen until that moment. Because in some aspects, global warming in a shut of overturning circulation work in different directions. Because if the overturning circulation shuts down, then we would expect a cooling in the North Atlantic region. And if the two effects happen at about the same time, then they superimpose. And it really kind of depends on how strong each factor is. But what we do, we do. And it's a lot of the fact that do know is that even just a weaker overturning circulation has strong impacts on both natural and

human systems. So there are studies showing that a weaker circulation will lead to a decrease in marine productivity in the North Atlantic, basically because the ecosystem is just accustomed to the overturning circulation being there and running. So that will definitely affect all life in the North Atlantic. There are studies showing that because of the changes in the sea surface temperature patterns that will happen when the overturning circulation continues to slow down, that this will lead to more and severe winter storms in Europe, especially the northwestern part. We also see effects for the United States, mainly an increase in the regional sea level around the Atlantic, so that is the east part of the United States. That's actually a simple physical

mechanism to understand. Normally, the northward surface flow of the overturning circulation leads to a deflection of water masses to the right away from the U.S. East Coast. That's basically just due to the Earth rotation, that is the Coriolis Force, which moves objects such as currents that are flowing northward in the northern hemisphere to the right. And as this current slows down, this effect will weaken and then more water can pile up at the U.S. East Coast, which leads to an enhanced sea level-wise. And we do believe that we already see a little bit of that right now due to the already weaker overturning circulation, but that's just in the range of a few centimeters at the moment. You know, there was that movie from 2004,

the day after tomorrow, that dramatizes this phenomenon. In the Hollywood version, the current stops so fast that you have a wall of winter descending in a matter of days. That's not a correct image that you're predicting, is it? No, luckily not. Well, for a movie, for a Hollywood blockbuster to work, everything has to happen fast. But when we as a scientist talk about an abrupt climate change that will still take a few decades before the overturning circulation has weakened so much that we would basically say it's now in a collapsed or a shutdown state. I said, okay, luckily, and this maybe does not seem that fast. But of course, just a few decades, or if such a huge change in the climate system happens within a few decades,

that actually is still fast for even as humans, but of course also for other ecosystems, because the question is, will we be able to adapt within the few decades? And I'm a little bit doubtful of that, actually. This is Science Friday from WNYC Studios. Talking with Dr. Levka-C-Cesar about the weakening of the circulating current in the Atlantic Ocean. I would imagine once you reached that tipping point

and you flipped, there's no flipping back any time real soon. That's true. I mean, again, it depends on the timescales we're looking at. It is possible. We also see that from paleo-climate data for the overturning circulation to recover, but that would take much longer than it takes word to shut down.

So we're then talking about hundreds or even thousands of years. And I guess from our human perspectives, we can say it's kind of irreversible at that moment. There are, I guess, ideas of people thinking, or maybe we can just pour a lot of salt into the North Atlantic or even kind of try to drag the water masses ourselves. But you have to keep in mind, this system is huge. The overturning circulation transports about 20 million cubic meters of water per second.

That's about 100 times the size of the Amazon River which is the world's largest river. And yeah, I'd say it's numbers or water masses that you can't really picture in your head. And it will be extremely difficult for us humans to really interfere with this system on a local scale and trying to keep it running. So what has to be done to keep it running, that is something that has the climate system basically has to provide for. The density differences that drive the system have to remain in place for it to keep going. So general climate protection basically, trying to stop. global warming would be our best chance.

Yeah. You said we can't know yet how soon a shutdown would be. We have gaps in our knowledge. What are the gaps in the data? What would you like to know? What more research and where should that be focused? So basically, we should always start with what we do know, and we do know that it can potentially collapse,

and we do know what the driver is, which is the freshwater input into the, North Atlantic, or at least simplified, we can say that this is the case. And now what we're missing is the link of how much freshwater will lead to a collapse or a shutdown of the overturning circulation. We can look at climate models, but those really give you just a certainty range. So kind of a vast range of numbers of how much freshwater could disrupt the system. And we have to specify that a little bit better. And then even more importantly, we have to know what is the link between how much global warming will lead to how much freshwater input. And I'd say we probably have to look

at climate models there a little bit more, just because it's probably difficult to just look at paleo data to try to estimate this range, because the states that the climate was in when the overturning circulation like the collared before was so different to what it is now. That's not perfectly comparable. And while we do that, I think we should also take a mind that even though we right now think that at least for the next few decades, it's unlikely for the overturning circulation to shut down, it is still, there is still a low risk. And while it's just a low risk, it is a low risk, a low risk high impact scenario in the sense that if it really does shut down, there would be a lot of disruptions all over the globe, especially in the North Atlantic region.

So while we try to estimate this better, we should probably try to just prevent it from happening anyway. Does this kind of keep you awake at night? If I think about it, yeah. But honestly, if I would think about it too much, then I would probably hardly ever sleep at all. I know that there is a huge problem. And I know we have to do something to stop it.

But I also think that I'm trying to do something. in the sense that I am a climate researcher, but I can't think about it every time I'm awake because that would drive me crazy. So basically, I just hope that humanity as a whole kind of, I don't know, gets themselves together and tries to stop global warming. But it actually does worry me a lot.

So sometimes I just try to push it from my mind. Yeah, I think we all do at times. I want to thank you very much, Dr. Caesar, for taking to have to be with us today. Yes, you're welcome. That was a really interesting talk. Thank you. You're welcome.

Dr. Lefka-Cesar is a postdoctoral researcher at the Icarus Climate Research Center at Menuth University in Ireland. We're going to take a break and when we come back, the history of our relationship with yeast bacteria and baking. Stay with us. This is Science Friday.

I'm Ira Plato. What new hobby did you take up during the long COVID isolation period last year. For me, it was baking sourdough bread. I must have watched hundreds of videos on how to make sourdough, spend countless hours waiting for the bread to rise and proof. In fact, COVID has been the perfect time to practice waiting. It takes two or three days to make sourdough bread, and as one instructor said, it's 15 minutes of work, three days of watching. But you know what? It's all worth it. There is nothing quite like that.

crunch, the smell of the flavor of homemade sourdough. And the geek in me, and there is a lot of that, enjoys understanding the chemistry and biology, the ongoing battle between yeast and bacteria in the ferment. That's why I want to heard about a new book called Sourdough Culture, a history of breadmaking from ancient to modern bakers. That book spoke to me. So I invited the author to break bread, so to speak, on the radio. Dr. Eric Palant is a professor. of Environmental Science and Sustainability at Allegheny College in Meadville, Pennsylvania. Welcome, Eric. Hey, great to be here, Ira. Nice to have you. So why this book? Well, let's geek out. Okay, so it comes from curiosity about living with a batch of glop in my home for a couple of decades and then

realizing this is older than anything else I own. And it's alive. And it's not just one thing. It's this whole ecosystem of bacteria and yeast. And I got it from somebody who I met once. And like, where did it come from originally? And that started a search to see how far back I could push the origins of my sourdough starter, which turned out to be the Cripple Creek Gold Rush of Colorado from 1893, is as far back as I think I could push it. But then the question is, how did it get there?

How did it get to Colorado? and then I had to start at the very beginning. Who invented bread? Who invented sourdough? So sourdough starter, just for people who don't know what that is, that's something you need to have, make, beg, or borrow to get your sourdough bread started. Sure. But anybody can do it, and you can do it by accident.

All you need is some flour and some water. And as you said at the beginning, about three days. If you put it out on your countertop, and it doesn't matter if you're in Arizona or Seattle or Stanford, Connecticut, it will, after three or four days, wild bacteria and wild yeast will start to consume, essentially, predigest that yeast, and you'll get little bubbles of carbon dioxide, and off you go. Now, people who bake bread, just regular bread, they go to the store, they buy that yeast in that flat package, but you're saying the yeast in sourdough does not come from that package.

Oh, no. So it's actually the other way around, right? the yeast in the package came from a wild variety of yeast, and it was selected to put in the package, whereas wild bacteria and wild yeast, which are surround all of us, are what's going to land and grow in your mash that you've just put out on your cantorotop or your window cell. But that's going to be a whole suite of organisms. It's going to be a little ecosystem, as opposed to think of it as a monoculture is what you're buying. You know, you're buying monocultural agriculture when you buy that single package from the store.

So why is wild yeast better than the store bought? Why is that? Is that what gives it its unique flavor? It's better because you have multiple species of yeast at work, and even more importantly, you have multiple species of bacteria in the microbial competition to consume the food. essentially in dough, those bacteria are competing like pigs in a trough, but they're doing it by exuding acids and microscopic compounds that are toxic to other bacteria and other yeast. It has its benefit, which is a sourdough bread, won't mold because it's got this acidity in it.

But they are also, to us humans, they provide flavor and variety and aroma and so forth. Whereas if you go out and buy Red Star or Fleischman's yeast, you've just bought a single species of yeast, completely absent of all other microorganisms, no bacteria, and you will get a single flavor, which is pretty flat, pretty boring, my opinion. Where does the sour flavor in sour dough come from? So that's the bacteria, right? So bacteria excrete either lactic acid, which is the same. acid you would find in yogurt. And so some breads that are made with sourdough will have kind of a

creamy yogurt kind of acidity. And then there are others that are using acetic acid to, again, their purpose is not to make bread taste good, but is to keep all those other microorganisms from getting into the bread. And they're excreating acetic acid, which is vinegar. And there are sour dough breads that taste sort of vinegory and have a little bit more bite. to them and the great bakers are the ones who can reliably manipulate their starters, their sourdough cultures, to end the flavor in one direction or the other or get some combination of creaminess and tanginess and acidity that are partly a function of low pH. You can make a sourdough bread and watch the pH drop as those bacteria do their work. But it's the bacteria that give most of the

flavor and the wild yeast that give most of the leaven, which caused the bread to rise. Let's talk about the history of bread, and you spend so much time in your book talking about it. It's very fascinating because I was never quite sure whether bread was invented or discovered. Which one was it? Yeah, well, so there's a problem there. I hand it to archaeologists for the work that they are doing and sort of pushing back the date for when the first breads were made. But the problem is that when the first bread was either discovered or invented, there wasn't Instagram. So we don't really know for sure who did the work.

You know, we can speculate and the archaeologists do so by finding remnants of the grain and the flower and finding that next to a stone, that a flat stone that has been fired. You know, it's next to a big campfire from which you can fairly safely assume that at least a flat brick. was made here, and if that bread had wheat in it, which is really rich with gluten, then chances are that there was some leavening agent there. And then it's speculation, right, which is somebody made this thing probably by accident. They had a porridge. We know they were eating parage probably. But, okay, now we have to figure somebody forgets about that porridge for a day or two or three, and they're in the fertile crescent. It's really warm. And that thing starts to bubble away, and they say, heck with it. I'm going to cook it anyway.

and it rises and then it springs in the oven. And then all the kids say, whoa, mom, that's great. Can you do that again? We can only speculate that that probably happens across the fertile crescent between six and eight thousand years ago. Discovery or intentional or an accident, some combination of all the above. But it's really a function of the human brain to recognize it's this particular grain, wheat, which is really good for making bread.

And it's this process of waiting a few days for the thing to bubble. And then, okay, let's do this intentionally. Let's plant these seeds of wheat. Let's harvest them. Let's mash them into a flour. Let's soak them in water, maybe need them a little bit, add a little bit salt because that really makes it taste great. Now we have bread.

Let's talk about bread and culture, because you make a good point. showing how it's involved in so many cultures. For example, in Christianity. You say that there are many references to Jesus' symbolism with bread. Yeah. So Jesus at the Last Supper says to his 12 disciples, among the last things he says, is my body is bread and my blood is wine.

And what are those both? They're products of fermentation. Nobody knows that at the time. but there's something spiritual about both bread and wine that they're transformed in some ways magically, spiritually, and now we know scientifically exactly what's happening. From the time that they're dough or a mash of grape juice to the time they become something rather sublime, which is baked bread and wine. And for 2,000 years, the sacrament is to take both bread and wine.

And so I don't know that it starts there, but you can't help. but notice that connection between all Western religions and bread. When did we begin to understand that it's the microbes in the bread, the starter, the yeast, that it is necessary for bread to rise? You mentioned in the book it was the invention of the microscope that made this possible, and then it went on from there. Yes, so Anton von Lüvenhawk is the first guided to actually see things that are invisible to the naked eye. that are tiny, right? We have Galileo looking up into the heavens. And at the same time, we're taking those same lenses in some race and reversing them. And Bon Lovinoff sees these little tiny, tiny things that he calls cells, but he has no idea what he's looking at. He calls them

anemalkules, part animal, part molecule, and at that point, nobody knows what molecule is. It takes 200 years of really interesting experimentation before they can sort of, sort of, you know, wrestled those cells back and forth between chemistry. Are they just molecules that cause grape juice to turn into wine and barley malt and water to turn into beer and bread to leaven? Back to biology, are they cells that are living? And if they're living, do they reproduce and do they actually consume nourishment? It doesn't really end until, you know, we start in the 1650s until the 1850s, more or less, when Louis Pasteur finally puts the whole puzzle together. and says, you know what, yeast are living organisms.

They consume sugars. They excrete carbon dioxide and alcohol. They reproduce. They're the organisms responsible for fermentation. If bread is so simple, why fundamentally do we see so much variation culturally with different kinds of breads? And you talk about going around the world and tasting all these different breads in these different cultures.

I wish I had been along on that trip with you. Yeah. I think that has been a wonderful part of this journey is that to make bread really only takes four, I would argue, five ingredients. You need flour, preferably wheat flour if you want the bread to rise, but it doesn't have to be wheat flour. You need water, salt is absolutely essential, but it tastes better. And then the hidden ingredient you alluded to at the very beginning is time.

I hope you had this experience. Anybody who starts making bread can't help but do a little experimentation, which is like, what if I added in a little bit of rye flour? What if I added in some sesame seeds? Yeah, yeah, I did that. Guilty as charge. Exactly. What are the local products? And some of these you think, oh, this is a nice combination, a little bit of cocoa powder and dried cherries.

Now we're talking, right? And that becomes part of the local culture. And then it's further advanced by local geography. So wheat is a really finicky crop. It needs a lot of attention. It needs the right climate and so forth. It's fairly limited where it will grow. And so by the time you're, for example, in Northern Europe,

if you're in Germany or Scandinavia or Scotland, wheat doesn't grow, but you still like bread. And so what do you do? The local crop there are oats and rye. So if you go buy a bread in Denmark, it's going to be a dense, heavy rye bread. And if you buy bread in Scotland where wheat won't grow well because it's just too wet and damp, you're going to get an oat cake. They're all breads. This is Science Friday from WNYC Studios.

We're talking to Eric Palant about the history and culture of sourdough bread. until 150 years ago, you said that all bread was sourdough, and then we got little loaves you get in the packages in the store, right? Yeah, yeah, yeah. How did that happen? So that's not so complicated. That's an American, well, it's not American per se, but we did it better than anybody else. If sourdough, as you said at the outset, it is a three-day process, and commercial yeast that you buy in the store is so vigorous. and reliable that you can make a recipe that says after one hour of putting in your yeast to your dough,

that bread is so inflated, you have to punch it down. Sow dough bakers don't usually have to, their wild yeast aren't that strong, so they don't have to punch their bread. But a bread that can be given enough yeast that it will inflate like a balloon is a really reliable product. If you want to make a profit as a baker, you've got a choice. Am I going to spend three days fencing with this bread every few hours trying to add a little bit, turning it, all that? Or can I make a lot of breads very quickly and reliably every couple of hours with commercial yeast? So it's about profit.

Do you have any vision for making good bread and maybe sourdough more widely accessible? Most of us who are living, even in urban areas, most of us can now in an urban area walk to a handful of artisanal bakeries. They're making really good, good quality bread, a large portion of which is sourdough. And what makes it so good is the time and the attention they're giving to it. The big manufacturers are paying attention. And so the big manufacturers are thinking, okay, the market growth in sourdough is just exploding. we've got to get in on that. And they're doing everything they can to try and figure out how to do that quickly, including,

and you and I can debate whether this is legit or not, they're growing like Olympic swimming pool size vats of sourdough, just huge quantities, drying it, autoclaving it. There's nothing alive in that, turning it into powder, and adding that to their bread, marketing it as sourdough bread. It does have sourdough in it, but it is not leavened by sourdough by any stretch of the imagination. But it doesn't take a lot of imagination to picture in the next couple of years how many loaves of bread are going to say sourdough on them, that also say yeast on them, and the sourdough is just dead dry powder. And so there is a kind of competition going on there over which way bread is going to go.

the part I wish would happen, sort of the next thing I'm starting to think about and think about how to work on, is that really good bread is expensive. And there's a justice issue. If only wealthy people can afford good bread. Yeah, because you're talking 10 bucks a loaf when I look for it. Yeah, that's crazy. Yeah. And if you make it yourself, it's about time poverty. And who has the time to be at home, you know, the average working stuff doesn't have the time to put into just making all of their own bread. And so there is still a problem among the artisanal community, I think, in trying to figure out how to make good bread, like all good food, accessible. Well, Eric, we bread geeks could go on talking forever. It's a great book, Eric. I want to thank you

for taking time to be with us today. Thank you, Ira. Eric Palant, author of Sourdough Culture, a history of breadmaking from ancient to modern bakers. And if we have wedded your appetite for sourdough culture, we've posted an excerpt from the book on our website at ScienceFriday.com slash culture. One more thing before we go. Next Wednesday at 6 p.m. Eastern,

we're holding a live Zoom recording for our first ever charismatic creature carnival. Come join us as we celebrate two weeks. wet and wild creatures, the Hellbender's salamander and mantis shrimp. Experts will tell you all about them, and you can ask questions about these two spectacular creatures. Sign up at ScienceFriday.com slash live stream. Have a great weekend. We'll see you next week. I'm Ira Flato.