From the Vault: The Interior World

environment that we have created for ourselves. I remember enjoying this one. I think I recall it made me look at the door frames inside my house in a different way. Yeah, I have not looked at my door frames the same way since. Let's jump right in Welcome to Stuff to Blow Your Mind production of My Heart Radio. Hey, welcome to Stuff to Blow your Mind. My name is Robert Lamb and I'm Joe McCormick. And today we're gonna be taking a look at interior spaces. Yeah. Year certainly brings

to mind the old curse. May you live in interesting times? And one of the factors here has of course been the coronavirus COVID nineteen pandemic, and in an effort to fight the spread of the illness, save lives, and prevent overwhelming our hospitals, we've made a lot of changes to our lives, and these range from the simple such as just wearing a mask when you're out in public and you can't social distance from people, to the harder choices

about employment and UH. In life choices, we've all been social distancing and stay at home orders, teleworking and quarantine have meant that we've all been spending a lot more time at home. Now. Depending on your home, this could mean a lot of things, but we wanted to explore what this means from a biological UH standpoint. For the most part here now now. Make no mistakes, spending more

time at home has absolutely been the right move. But just as it's forced you to focus more on, say that weird staying on your ceiling, we wanted to focus on the other often unseen aspects of life in the home right much the same way that being, say, on a Spanish galleon out in the middle of the ocean might have made you pay much more attention to the biology and behavior of of ship rats than you ever

would have otherwise. I think being at home more and more is forcing all of us to turn our eyes and maybe our microscopes and magnifying glasses to the corners and the cornices, and the shower heads and the drain traps and all of the wonderful places in our house

where life dwells. Yeah, we're gonna really get into the difference really between the natural world outside of our homes and the unnatural world inside, and get into some ideas about how how we could perhaps enable our interior world to be a little more on the natural side of things. But before we get into all that, I wanted to take a moment here just to discuss the history of houses in general, you know, just to get into the concept of what a house is our our first and

still most important interior artificial environment. So you can certainly look at a home as an artificial cave to a certain extent. And indeed we have lots of early evidence that early hominants sought out shelter in caves in the same way that many other animals do. Uh. These can shelter one against the elements and against predators, and as recently as a hundred and thirty thousand years ago, cave dwellers were already augmenting these natural interior environments with things

like rough stone walls. They were using timbers so um. So you know, even a hundred thirty thousand years ago, we were taking naturally occurring interior spaces and making them a little less natural. Um. And of course, on top of just the shelter that caves can provide, it also seems that caves had a strong sacred meaning to many of these uh phistoric people's. Those might be important, but

ultimately proximity to water is far more important. Thus, as Kate Spence and Brian and Fagan point out in UH in the a section of the seventy Grade Inventions of the Ancient World about homes, most early hominids lived out

in the open, near streams and lakes. They built temporary structures, and most of this has been lost to time, but some of the earliest evidence of potential structures for homes goes back one point seven two point seven million years ago with homo erective sites in southern Africa, and these were potentially contemporary with the domestication of fire um and these would have been temporary tents, but but they still

would have been artificial interior environments. Now more secure evidence comes from the Ukraine roughly forty four thousand years ago, the mammoth bone structures from Maladova, which we recently discussed on the show. Actually, yeah, we did uh talking about

these uh. That would have been structures in one of the northernmost habitable regions of the Earth at the time, because this was during a time of glacial advance where the polar ice caps from the north were coming deep down into Europe and Asia and uh, and so this would have been far far north, way up among the ice and for some reason humans were building these structures out of the bones of mammoth And we don't know that.

There's still things we don't know about those structures, like how how consistently they were inhabited and for how long and so forth. Right now, beyond this, the history of human homes is is largely dictated by local resources and a local climate. A long process of trial and air ends up leading to the development of regional and cultural

building forms construction methods. But before nine thousand b C. We see evidence of clay houses in Palestine, what is today Palestine, and before seven thousand BC we see rectangular dwellings in Anatolia. But but home is far more than just a shelter. As the authors here point out, houses became key to social structure as well. They point out that ethnographic studies in West Africa reveal complex and layered

symbolic associations and rituals in the context of dwelling. And this is a you know, it shows a clear role of physically structuring and expressing the relationship between different members of the household. And we see this of course in um and cultures, you know, throughout history and throughout the world. There's this physical shape of the place. Uh, and then that ends up defining or influencing like that, there's this

this feedback between the two. It goes both ways, right, It's kind of like pouring a liquid into a container. Oh of course. And this actually got me thinking about how having permanent, constructed dwellings must have changed the way that power and hierarchy are expressed in social groups. And of course this is true with normal social status. You know, it's it's stake out through displays of wealth. There certain kinds of taste or aesthetics in your house, your apartment,

you're you know, you're living space. But this also made me think about the way that for many leadership positions, there is a special house, there's a special dwelling place that comes with the job, rather than belonging to an individual. So here in Georgia we have the Governor's mansion, there is the White House there, you know, the palace that the king stays at in many cultures, and there's a

there's a strange metonomy that derives from this. Often the house identified with the position of power is used as a metaphorical stand in for the person. You know, like today the White House said such that, like the permanent dwelling place is actually almost the source of the power, and there just happens to be a particular person living there right now. Yeah, it's weird. We get so used to it because it's just part of our daily, um

daily you know, linguistic world. You know, you can you read the news, you read about these very as locations, these houses, and it's almost as if they have some sort of intrinsic power to them, right, I mean, if you weren't familiar with their cultures, you would read this then, and people might think, oh, well, they they clearly thought that this big white house had some sort of magical powers, and whoever was allowed to go inside it became the

ruler of a country and got to do whatever they want. Yeah, and it's funny that it's so normalized for us, like we've forgotten to notice that that's weird that like the power is somehow linked to the house itself. Um. But it also makes me wonder, you know, did we think about power differently before living in artificially built environments? Yeah? To what extent did we? Um? Did we end up yet changing the way we live our lives by altering

this physical environment which we live. I mean, it makes sense, right because so much of what we do, you know, it's dictated by the environments that we evolved to thrive in. Right. So anyway, I don't think we need to remind everyone about the value of a home. Housing tends to be one of, if not the most expensive parts of your life. But it's it's interesting to think about them not simply as this valuable thing in your life, for a valuable

location where your life takes place. The basic idea of the house may be as old as our mastery of fire, and it forms out of and forms ideas of who and what we are, and of course it may do so in more and more powerful ways every year, as humanity slowly transitions to become a more indoors e on

average species. All the time, I was reading some interesting figures about this trend in a book by the science writer Emily and thus Uh And the book is called The Great Indoors The Surprising Science of How Buildings shape our behavior, health, and happiness. This is a really interesting book and I'm going to refer to it throughout this episode because she has an early chapter that's very good

about the microbial ecology of indoor spaces. But she also gets into some interesting territory about the trends in how much built environment ment and floor space we're actually creating. Obviously, this currently varies a lot by culture and climate, but in some parts of the world human kind is transitioned to an almost entirely indoor existence. And this really shows in the way we've transformed our environments to convert to

this largely indoor existence. Anti writes, quote, the island of Manhattan is only twenty three square miles in size, but has three times that much indoor floor space. And furthermore, she refers to a report put together by a United Nations commission in which concluded that over the next forty years, humankind is going to roughly double the amount of indoor

floor space that exists currently. And the way this works out is quote those additions are equivalent to building the current floor area of Japan every single year from now until that much floor is going to take a lot of pin sall. Yeah, I mean it is crazy to think about how certainly during pre pandemic times, you know, you would you had this home, this interior space that you live in, you sleep in, you bathe in, you spend time in, and then uh, and it is, you know,

very much like the center of your life. And then you're getting into another interior space which happens to be motorized and on wheels, and use that to travel then a certain distance to another interior space that you'll go into to work either set at a desk or you know, work with some sort of machinery or what have you. Uh, and then at the end of the day back into this motorized interior space and then return to the one in which you live it's worth remembering yet again, biologically speaking,

this is not normal. This is not like what our bodies are naturally adapted to. Spending this much time indoors is still fairly historically novel, and it is very weird. Yes. But the other big thing this is going to be a recurring theme throughout the rest of the episode, is that these artificial spaces that we made, they are they're not completely alien, you know, they're they're constructed all of the natural world. They're not the natural environment, but they

are made out of it. And uh and and much of the natural world is still present, just in um rebalanced and unbalanced ways. Uh So that that is going to be what we're going to really get into, Like what in creating these interior spaces, what sort of environments have we created? Right? Indoor spaces are not unnatural, and that they're completely separate from the rest of the world, but they're also not just like outdoor spaces. They're kind of like a special niche environment, like a like a

cliff face or an island. You know, it's a place where you have to investigate. Okay, what kinds of life from around and other places are going to colonize this space. Yeah, and and who are your roommates? Who are your inhuman roommates in this space where you've been trapped uh these past several months. Well, maybe we should take a break and then when we come back we can start talking

about those in human roommates. Than alright, we're back, so U. Rob Donne, a professor of applied ecology at North Carolina State University and Raleigh, wrote an excellent book titled Never Home Alone. From Microbes to Millipedes, camel, crickets and honey bees, then natural History of where we Live. That's a nice long title. I know you'll be like those those long colond titles. I want like a whole paragraph after the colon. But it's it's as hard as I go. It's pretty

good title. Anyway. It came out last October and it's currently available in all four mats. So however, you read your books. But I remember hearing an interview with the author around the time that came out, and I picked it up for this episode because it's a yeah, it's it's it's just a very well written book and it really gets into some just crazy mind bending facts about these artificial environments, most of which we won't even really be able to get into in this episode, but we

wanted to touch on it. So if you look around it's science papers, you'll find Dunn's name um all over the place when it comes to this area of microbial life. For instance, he's the co author on a two thousand eighteen paper that found that chimpanzee treetop beds, which are like a daily affair, contained fewer microbes and arthropods than human beds, which is not shocking given again the the idea,

there are beds that are kind of like set in place. Um, you know, we will change the sheets, but it's not every night probably, whereas the chimps are going to be refreshing things a bit more. Also, of the bacteria in human beds stem from our own bodies and includes fecal, oral, and skin bacteria. Yeah. The way I heard it put, because this is covered in anthesis book too, is that with the with the human bed basic you're just gonna

find tons of human type stuff in it. But for a chimpanzees bed, you will find you know, bugs, arthur pods and microbes in in this bed, but they're almost all from the surrounding environment. Uh, The way it was put was that you might not be able to tell that a chimpanzee had ever been there. Right, very strange.

But from anthesis book, there's uh So, there's a chapter that discusses a lot of the work of the same researcher, robbed On, the the ecologist at North Carolina State, but also a researcher that he's collaborated with a lot named Noah Fierre, who's a microbiologist at u C Boulder, And there's a part where it talks about a survey that they tried to conduct called the Wildlife of Our Homes Project.

There was a pilot study they started in North Carolina, and so what they would do was they would get a bunch of families to take cotton swab samples of seven different surfaces from inside their homes. And this would include a countertop, a cutting board, a refrigerator or shelf, a pillow case, a toilet seat, a TV screen, and then the trim around an interior doorway. And the results

were interesting. They found more than two thousand types of microbes in these samples, and there were distinct microbial habitats within the house. So perhaps on surprisingly kitchens would have a lot of bacteria that are naturally associated with food that might be you know, found on food or aid in the decomposition of food. Meanwhile, doorways would have a lot of environmental species stuff you might find outside the house, you know, things you would find on plant leaves and

in the soil. But then this was the quote that really stuck with me. And this writes quote from a microbiological perspective, toilet seats and pillow cases looked strikingly similar. Both were dominated by bacteria that typically live on our skin and in our mouths. All right, So that's that's kind of a shocking sounding statement. They might make you want to instantly go and wash your pillow case and

maybe your toilet seat too. But but but hold on, wait till we get through the whole episode, because I think one of the big take comes here is like, if you think that your pillow is going to be a microbial sterile um experience, you know you should think again, likewise with the toilet seat, likewise with anything in the house.

So in Dunn's book, one of one of the things he drives home is that again our our house environments are again not natural environments, but they are made out of the natural environment, and they are not cut off

from the natural environment. So what we end up with is an artificial environment that kind of mashes up all of these various environmental parameters, sometimes in surprising ways, especially when it comes to microbes, because if we as we've discussed on the show plenty of times before, there is no microbe free living. Our bodies, independent of anything else,

are home to multitudes of microbes. To come back to a quote that we've pulled up on the show in discussion in the past, in a Life in a World without Microbes by Gilbert and Newfeld bushed in Plist biology, the authors contend that quote it would be false to claim that macroscopic life cannot exist without microbes. However, although life would persist in the absence of microbes, both the

quantity and quality of life would be reduced drastically. So Done points out that even the outer layer of our skin is just this rich microbial environment. Our armpit bacteria are essentially fed by glands, nurturing what has likely been an historically important microbe passenger, and we can we can look at this as an example of the sort of

microbe that then thrives in our creative environments. We tend to find the same bacteria that that that thrives in our under arms living in our homes, especially homes where males live. If there's like a predominantly male population of a household, you will find this particular bacterium. I believe

it's uh corn a bacterium, just thriving Coriina bacterium, Corina bacterium. Yes. Yeah, So this thing about the sex composition of the household versus the household microbiome was also mentioned in anthesis book, and it's very interesting. So, just as you say, homes with more male residents tend to have higher counts of bacteria such as Rosa burria and this is commonly a gut bacteria, as well as Karina bacterium and Derma bacter and uh at. This points out that these are most

common on the skin. Now, Coarina Bacterium is often found in the armpit. As you say, it is a contributor to body odor. But also it's been found that just on average, men tend to have more Coarina bacteria on their skin than women do, and men tend to shed more skin microbes into the environment than women do. And then on the other hand, households that have more women living in them tend to have higher counts of Lactobacillus,

which is our old friend from the fermentation episode. I don't know if this translates to a workable difference, maybe not, but it makes me wonder if it's possible that houses occupied by high a numbers of women might be a better place to make sauerkraut. Interesting to some to think about, but sort of what this suggests is that humans are walking fountains of microbes. We we shed our microbial passengers everywhere we go, and it turns out this can be

kind of quantified to creepy levels. So consider this. No two people's microbiomes are exactly the same. Each person is a unique ecosystem. So if everybody has their own unique profile of microbiota, and everybody is shedding microbial life all the time, are we essentially leaving identifiable microbial evidence of our presence everywhere we go, you know, kind of the slug trail of our microbiome all over the place. And

the answer appears to be kind of yeah. And this reports one study led by Jack Gilbert at the University of Chicago. I think that might be the Gilbert of the Gilbert and Neufeld study that you mentioned a minute ago. But it follows three families that were in the process of moving into new homes. And what Gilbert and colleagues found was that each family began to colonize the new

house with their microbes within just hours of arriving there. Uh. And that the researchers quote could even detect the individual microbial contributions of each family member. Uh. And then Gilbert says, people who spent more time in the kitchen, their microbiome dominated that space. People who spent more time in the bedroom, their microbiome dominated there. You could start to forensically identify their movement. Oh wow, So this makes one try to

imagine like lawne order microbiology. Yes, surveillance biotech. But to come back to to Rob Dunn's example about Corina bacteria in homes, especially where males live. You you had an interesting thing about that. Yeah, he brings up a very curious case of an interior environment intier home that had a predominantly certainly at the time of the study, had a predominantly male um population. And that is the international

Space Station. So this was basically there was a study of the micro buyouta one finds inside the I S S. This was conducted in two thousand thirteen by Jonathan I. Sen, a microbiologist at U C. Davis. So the the I S S, done rights, is very much like a house on Earth. Quote, in nearly every way, the bacteria of the I S S are the sorts of bacteria we would expect in a house on Earth if all the

environmental influences were removed. I S S is what you get when you scrub and scrub and close the windows, doors and hatches. So the I S S might be kind of like a very well scrub department in a high rise in a big city. Yeah, I mean there's there's no outside to get inside, right, UM mean immediately, so obviously, um stuff can be brought up. But anyway, Done also points out that in this study of ISS microbes, quote, everything was everywhere, the interior was just coded in human

bacteria and nothing from outside was getting in. Obviously. He points out that in a small traditional home made out of mud and leaves, which would have been you know, the normal for the vast uh, you know, the vast majority of human existence. Everything would be everywhere as well, but environmental microbes would be everywhere. What's outside would be inside.

But for the I s s there there is no outside. Really, it is a you know, this sterile environment that is then inhabited by human beings, certainly, but then inhabited populated by human microbes. Right, So, so environmentally sterile, but heavily colonized by what the humans bring with them, right, He writes, quote, if you scrub and scrub your home, this is what you may achieve too. It is not unlike what we

see in some apartment in Manhattan. And as we and others have begun to study such apartments, we have found a problem. The problem is not what is present, but instead what is absent. The problem has to do with what happens when we create homes devoid of nearly all biodiversity except that which falls from us, and then for twenty three hours of the day we don't go outside. So they're kind of getting high on our own supply here. Yeah, I mean, that's that's exactly. I mean, it's we're in

these interior worlds. We're not we're actually going to great pains and many times or just by the virtue of the shape of our cities, in the shape of our lives. We're not bringing anything in or're ringing in as little as as possible, and except for everything that just sheds off of us. This kind of like constant um um, you know, fog of detritus that we're leaving in our wake. Now, this isn't to say there aren't some really interesting things

living in the average human home. In his book, Done discusses, for instance, the thermophilic bacteria thermo aquaticus, which normally thrives in hot springs and geyser's uh, you know, kind of a you know, a specialist in that regard, but you can pretty much rely on the fact that you can find it in your hot water heat a part of your artificial environment that recreates environmental conditions that it finds favorable. Yeah, Anthes discusses the research on shower heads. Apparently there tends

to be a lot of bacteria living in biofilms. And biofilms are you know, these mats that microbes make when they gather in big concentrations. For example, the dental plaque on your teeth is a biofilm. These tend to form on shower heads in our showers. We don't know exactly why, but maybe because you know, hey, it's the shower, doesn't it just get cleaned by itself? Like, do I really need to clean it? Uh? It is clean, it's water

coming out of it, exactly. It's kind of the logic that's like, why would I ever need to wash my bath towel holes? You know, they only canter you when I'm at my cleanest um. But Anthus quotes Noah Noah Fear, explaining that when hot water suddenly starts shooting out of the shower head where these films are perched, it creates this kind of mist and spray that carries bacteria with it, and then of course, standing there under the spray in the shower, we ingest that spray, We breathe it right in.

And Fierra says, quote, I think it's a really important mechanism by which we're exposed to bacteria. Which, okay, so you might be thinking again like, oh my god, my shower head. You're filled with horror, But it's not necessarily a bad thing. Again, like a lot of our exposure to microbes is either neutral or beneficial, though of course not all of it. Yeah, the biofilms in your shower

head contain mostly harmless bacteria, but it but it. Interestingly enough, it includes non tuberculosis micro bacteria, which are relatives of leprosy into bercua losis um. The interesting thing here is that their chlorine tolerant. So while the chlorine in them, like a major metropolitan water system, kills a lot of the micro organisms that it might otherwise be found there, it doesn't hurt these guys and actually creates room for

them to grow and to thrive. So there are otherwise quite rare and say, well water, Uh, these are I think I read that these biofilms are typically found in general, are found in swamps, totally adapted to altering between wet and dry conditions, much like your shower head. Um. But yeah, in the natural world, they're just gonna have their their niche to occupy. But we've created an artificial environment where they have room to just really grow and thrive and

then of course rain down upon us. And there could be health implications about those microbacterial films. We don't know for sure, but there's a there's a possibility. Anthis talks about she writes quote. In fact, Fear and Done discovered that showerheads harboring potentially dangerous strains of micro bacteria clustered in the same regions mentioning Hawaii, southern California, Florida in the mid Atlantic that are known to be hot spots

for micro bacterial related respiratory infections. So the question is, are people getting these infections from their shower heads. Fear suspects that might be the case, but that doesn't necessarily mean your shower head is making you six. Some micro bacteria, when inhaled, are are not harmful. They might even strengthen your immune system. Now Done points out that that we've been studying microbiota in our homes actually since the earliest

days of microbiology. Uh. You have this individual by the name of Anthony van Lewenhoek who lived sixty two through seventeen twenty three, and he's often called just the father of microbiology and and weirdly enough, he's possibly the model for two different Vermeer paintings. I don't know if you've read about this. I haven't. Yeah, um, but courage listeners

to look it up. It's pretty fascinating. Like basically he knew Vermeer and may have posed for these paintings, but he's the first individual known to have engaged in this sort of study. He charted the microbial populations of his own house, of his own body, and also some neighbors homes and bodies. Um with permission, I believe. But but after his death, no one really bothered with the sort of study again until we realized later that some of

the microbes we encountered could make us sick. And so it's really it's it's really getting into modern times here where we're finally uh, taking a close look at our household microbial environment, with researchers like done playing a key role. Um. Here's another great quote where he's just talking about, you know, undertaking this this project and what they expected to find. He says, quote, we expected to find hundreds of species. Instead, we discovered, depending on just how you do the math,

upward of two hundred thousand species. Many of these species are microscopic, but others are larger and yet nonetheless overlooked. Breathe in inhale deeply. With each breath, you bring in oxygen deep into the alveoli of your lungs along with hundreds or thousands of species. Sit down. Each place you sit, you are surrounded by a floating, leaping, crawling circus of thousands of species. We are never home alone WOA. And this is on top of tins and perhaps hundreds of

different types of vertebrates as well as various plants. And then there are the arthropods and the fun guys. Something like forty thousand species of fungi that can be found in the home um. But the bacteria are just really the crazy Party points out that more species of bacteria have been found in human homes than there are species

of birds and mammals on Earth. Yeah. This type of research is also explored in in Anthesis book, where there's a section where she talks about how Done and Fear followed up on their initial research who you know, asking people to take the swabs from the different parts of their home to find out what was there. They decided to do with like a bigger, deeper study of the

microbes found specifically along the trim of interior doorways. And they picked this area because nobody ever cleans it, so dusty, you know, collects for years maybe without being sterilized. Then this would give you potentially a fuller inventory, and they just found enormous numbers of bacteria. In anthesis book, the number is over a hundred and sixteen thousand species of bacteria,

more than sixty three thousand species of fungi. And the count of fungi species was especially interesting to them because they found more numbers of species of fungi in these samples around doorway trims than there are named species of fungi in all of North America, So it means that inside our houses, it's it's very likely that there are species of fungus that have not yet been discovered or

cataloged by science. And they also found that that for some of these samples, there was more uh fungi diversity inside the house than outside the house, which which reminds me of the scene in Primer where they don't realize they've created a time machine yet and they think that that the box that they put together as an incubator for mold oh I forgot about that detail that a while since have seen that one and fungi in our homes are somewhat different than bacteria in our homes, so

that they have a different different vectors in different ways of living Anthests discusses how the bacteria in our houses they mostly come from us and from the other creatures that live with us, like dogs, and we'll get into more on that in a bit, but the fun guy are not as populous on and in our own bodies.

They tend to come more from the environment outside. And what kind of fungi are found within a home is largely determined by where the home is regionally, in the climate around the home, what kind of fungi are prevalent in the exterior environment. But there are other factors that have an effect as well. And there's one that I found very interesting. It was what the house is made of. And she quotes from Done saying it's kind of a

three pigs thing. A stone house feeds different fungi from a woodhouse from a mudhouse, because unlike the bacteria, they're eating the house. So it's like, what have you put out on the buffet for them? Yeah, I mean again, it comes down to the fact that our home is not this um, this alien thing, you know, it is made out of the natural world, and therefore there are things that want to eat it, to eat those materials

that made up your home. Uh, so yeah, it's it's easy to overlook that, but yeah, it makes perfect sense. So obviously, I'm sure some people, despite our our warnings early on, are like, Okay, I'm just getting the bleach. I'm gonna sterilize my entire living space. Maybe now we should explain why that that might not be a good idea. Yeah, that might be your inclination. And and really it kind of falls in line with what advertising has has been

has been telling us for years. You know, the sort of world that we grew up in, where it's like we got to disinfect the house, you gotta keep the house clean, as if there is this absolute cleanliness, this nobiotic um aspect of our homes. But but this way of thinking is essentially treats our homes again like some sort of lifeless, nobiotic box, hermetically sealed from the outside, an impervious to occupation by anything but the presumably nobiotic

creatures living inside it. But all of this, you know, nothing could be further from the truth, because nature of horrors of vacuum and your home will come to harbor a robust ecosystem. But our actions and our choices have an effect on that ecosystem as we saw with the shower head and the and the water heater or example above. You may keep certain things out, but that just means there's more room for other things to make themselves at home. All right, well we need to take a second break,

but we will be right back with more. Alright, we're back. So raining anti microbial death down on your apartment or house is is also crazy, given that, as Done and Sebastian Tilch discussed in a two thousand nineteen study published in Nature Ecology and Evolution, only a relatively small proportion of the micro organisms in our environment actually cause disease.

It's also worth noting that insects and other arthur pods, especially spiders that live in in the home, are important actors in the ecosystem, as they can exterminate mosquitoes, bedbugs, cockroaches, and house flies, all of which actually can transmit diseases. And it's not a universal thing around the world that people see a spider in their house and say, oh, we've got to kill that. Like, some cultures are much more tolerant of spiders with the knowledge that they're performing

this important cleaning service. Yeah, I I personally like seeing the spider in the bathroom every day. You know it's it's a friend. You know that it's it's he or she is working to to to help make this bathroom a better environment. In that paper by Done and Tilt Uh, the authors agree that there there's simply no need to weigh devastating war against all of these organisms. But more to the point, a lot more work is needed to determine just what sorts of environments are more susceptible to

the bad stuff. Another interesting wrinkle in all of this is that and and this is one Done discusses in his book, is exactly what household dogs reveal about the contrast between the exterior ecosystem and our interior worlds. Dogs are amazing at bringing you filth that I think about this with my dog every day. It's like every single day he's like, let me nourish your microbiome. Well, I think ultimately the way to look at it is the dog is not just bringing filth in. The dog is

nurturing your filth. Like there's going to be filth. If you wish to categorize the microbial world as filth. Uh, there's no escaping it. Um. So the dog is ultimately just bringing something to the equation. So for a lot of us, we tend to leave our our artificial interial world, you know, again, hop into another one that happens to have wheels, travel doors, to work, come back, etcetera. A lot of us do get out into the natural world, but there are plenty of us that don't do it

on a regular basis. If you have pets, indoor only varieties contribute to the microbial stew that is your home. But there's no beating a dog for a bridge between inner and outer ecosystems. There's also no beating a dog. Just I don't want to encourage anybody, but for starters, your dog is likely drawing you out into the outside environment. Uh. You know, you're gonna probably hopefully you're gonna take your dog on walks, You're gonna, you know, go out into

the world with it. But at the very least, that dog is going out to get all up in the natural world and then bring some of it back home. This,

this has been your experience with his a dog owner. Correct, absolutely, Now, Now, they're certainly harmful possibilities here, such as if your dog were to bring back fleas or ticks, And this has always been an issue with ancient Egyptian dog remains showing signs of brown dog ticks, which certainly do carry pathogens, but there's also a plethora of harmless effects and a

seemingly beneficial um impact as well. Done points out that by looking at household microbes alone, first of all, one can tell if there's a dog in the house at all of the time. Uh. The dog just leaves a microbial footprint that's hard to miss. But be honest, it's hard to tell at this point what specific effects dogs and cats have on the inner and microbial environment, because

there's a lot of complexity there. But Done says that we certainly see, especially in urban environments with dogs, that the children in those households are less prone to allergy and asthma. So the dogs might actually be a vehicle connecting the children to nature, and just the dirt on their paws, for instance, might be enough uh to essentially provide some sort of UH replacement for spending time in

nature and in the natural microbial environment. Yeah. This is the connection to what used to be known as the hygiene hypothesis, though Anthes notes that some researchers have pointed out that this name can be kind of misleading because the point of the hygiene hypothesis is not that you like,

shouldn't wash your hands. Uh, It's more about having an exposure to a diverse array of microbiota early in life can, if this hypothesis is correct, help help strengthen your immune system in various ways and make you less prone to say,

allergies and asthma and things like that. More recently, people have tried to to recoin this thing not as the hygiene hypothesis, but as the old friends hypothesis, like the the natural microbial world is an old friend, right, that we should reacquaint ourselves with, and that it's good to get acquainted with early in life. Uh, not necessarily that you like, shouldn't wash your hands or shouldn't wipe down the counter after you've been slicing chicken or something. Yeah.

Now this is primarily with dogs. With with cats there seems to be far less of a connection. Uh. And also it's noted that in rural environments, uh, we see less evidence of this, and the ideas that individuals in a rural environment are probably getting more exposure to the outside of the natural world in general. So the dog isn't going to make that much of a difference. The dog is less of a tap of hot and cold

running exterior microbes. And I think all of that helps to underline, you know, our desire and our and indeed our need to get out of the house and interact with nature on a regular basis. Uh Done says that that one day we might be able to manage our interior microbiota in a way that will help ensure that we're healthy and uh and that you know, everything's in balance,

But for now that's just not the case. We just we don't understand and enough if we haven't explored uh the interior world enough to know exactly what we're dealing with. And again like what kind of environments are are more prone to be occupied by the bad stuff versus the the the beneficial stuff or the stuff that is just uh there and part of the world we live in.

Though I think it is clear that built environments do make a difference, that we we don't fully understand exactly what all the causal relationships are yet, but there have definitely been measured differences that show, for example, where rooms are placed and what their relationships to other rooms, where different things happen. Uh, that that does affect what kinds

of microbiota we find in those rooms. Just the example of having open windows that open to the outside world as opposed to having a room that's all closed off to the outside world and just ventilated by you know, HVAC systems. That makes a difference to what the microbiome of the room looks like. Yeah, I mean, I mean even if the windows don't open. You know, we've looked at studies before, they've looked on the psychological impact of just being able to see the outside world, especially in

hospital environment. Uh. And we do know a few other things too, Like one of the things that Anti mentions it seems to be a pretty straightforward finding is that one good way to encourage healthy ecosystems of microbes within the house is basically to keep the house dry. Moisture seems to activate a lot of unwanted fungal activity, but you can still have a lot of healthy microbes with

the house that's that's relatively dry. Uh. You know that She says that a lot of these experts who are looking at this do not recommend using anti microbial agents in the house. As you've been talking about. So there are a few things we know, but yeah, there's still a whole lot more to learn about the interactions between our our living space architecture and our home cleaning regimes and all that stuff. With the microscopic invisible world. Yeah,

and it's interesting. I mean, obviously it's going to be more of a challenge and damper environments, say like, um, you know, a rainforest environment. But I guess there, I guess one is tempted to ask the question, well, what are the traditional modes of housing? You know, what were the were the were the the trial and air developments in housing there versus the um that the modern solutions that have been brought in from other environments without perhaps

without really taking full account of the local conditions. Yeah, that's an interesting question. I haven't considered that. Yeah, I mean, I don't know. You walk around any given neighborhood, right and you you you see these trends and homes and occasionally you'll see at home that is that it's clearly out of place. But it makes you wonder, like, just

how out of place is it is? The design like not suited for the you know, the the energy consumption rates or the or or just the like the the the level of the amount of sun you get in a given part of the world, that sort of thing. Uh, you know, I think one of the things we can take from this episode is that homes are are far more complicated. They're not just the the space we in which we live, you know, a container for our lives.

Like they they're going to shape who we are on a microbial level, on a symbolic level, Um, it's uh, you know, it's it's it's mind blowing stuff, definitely. And then sometimes you find yourself, you know, during a pandemic, spending a lot of time in your closet recording podcasts in your laundry room. Yeah, rooms that were never designed or intended for this kind of lengthy habitation. Luckily, my my closet here does have an air event in it um,

which has been a lifesaver. I don't think my laundry room does sing around for it. I have. I've had a few sweaty times in here. Well, it's this good news for when the winter sets in, right for both of us, because I think this is gonna be pretty cozy in here. And if you get cold in the laundry room, you can always just turn on the dryer, right, I'm really trying to get it's set up so that

I can record from a different room. I'm trying to make a different room in the house less echoy, so I can get good sound and not have to hunch over next to the washing machine. I am digging an earthen pit in my backyard, which I am told will have a really good uh sound installation. So we'll see how that goes. Mammoth Bones Studio. All right, Well, there

you have it. Hopefully this provides some some food for thought. Again, we're not trying to encourage anybody to go on a h any kind of a killing spree in their house concerning microbes or Arthur pods or anything like that. Uh, just we thought that as we're spending more time looking at our homes and thinking about getting out of nature, we should really look at what the in the relationship

between those two environments actually is. In the meantime, if you like to check out other episodes of Stuff to Blow your mind, well you can find us wherever you get your podcast and wherever that happens to be. Just make sure you rate, review and subscribe, and if you get in touch with us. I mean, clearly, we'd love to hear your thoughts on this episode. How do you relate to the content here, How does it change or back up your own thoughts and observations concerning your interior

environment or the external world. Huge thanks as always to our excellent audio producer Seth Nicholas Johnson. If you would like to get in touch with us with feedback on this episode or any other, to suggest a topic for the future, just to say hi, you can email us at contact that Stuff to Blow your Mind dot com. Stuff to Blow Your Mind is production of I Heart Radio.

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