Science Friday - Ant Traffic Flow, Natural Reactors, David Quammen. August 17, 2018, Part 2

Episode Date: August 17, 2018

Worker ants keep the nest alive. They look for food, take care of the eggs, and dig all the tunnels. Fire ant colonies, for example, have hundreds of thousands of worker ants. You’d think traffic jams happen all the time. But they don’t! The majority of the ants aren’t working, according to a study published in Science this week from the Georgia Institute of Technology. They remain idle to stay out of the way, leaving only 30% of the ants to dig a new hole. The researchers also believe the dynamic between idle and active ants could be applied to teaching small robots to dig together at an earthquake site or find shelter underground during a natural disaster. Long before humans enriched uranium to create nuclear fission, the Earth was doing it on its own. Two billion years ago, some natural deposits of uranium contained enough Uranium-235 to undergo spontaneous fission reactions. Those deposits are no longer undergoing fission. But, new research of the Oklo natural nuclear reactor in Gabon has found something curious. Not all the cesium (a toxic waste product of fission reactions both natural and man-made) was released into the environment. Rather, some remained bound in the reactor, with the help of other molecules. How could this finding help lead to safer nuclear waste storage? In The Tangled Tree: A Radical New History of Life, science writer David Quammen tells the tale of the microbiologist Carl Woese, who discovered in 1977 that a certain methane-belching microbe was not a bacterium, but instead belonged to another, altogether new branch of the evolutionary tree, the Archaea. The news shook up scientists’ understanding of the tree of life, Quammen writes—and our human place in it. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Plato. Worker ants keep the nest going. They look for food, take care of the eggs, and also dig an intricate tunnel system for the nest. In fire ant colonies, there can be thousands of ants moving around trying to do their job. Well, all these ants coming in and out of the tunnels. Now, traffic jams should be happening all the time, right? But they don't. This is because more than half of the ants aren't actually working.

Well, it might sound like they are just lazy. They're really just staying out of the way. My next guest was curious about the perfect ratio of worker ants to idol ants ants and whether it could help swarm robots work in close quarters. Dr. Daniel Goldman is Professor of Physics at Georgia Institute of Technology, and his study appears in the journal Science this week. Welcome to Science Friday. Thank you for having me.

So you're a physicist, but you're curious about how ants build time. Yes. Correct. All my life I've been interested in animals, in particular when I was a kid, I liked lizards and snakes and even played with ants to some extent. But when I was training, I decided that it was more serious to become a physicist and study dynamical systems and pattern-forming systems. But in my later training, I learned that there were people who actually were interested in understanding the mechanics of organisms. And so for the last 12 years, I've combined those trainings to be a professor of physics at Georgia Tech, whose group largely focuses on problems of organisms, including lizards, snakes, and more recently ants, with complex environments. So you had to actually learn how an ant builds a tunnel? How does it do that? Correct. Well, I should say right off the bat that we didn't study tunnel nest formation in natural environments. If you go out into the fields of Georgia or along the side of the road,

You see these mounds, which basically howls or cover the colony's nest, which is a structure which can extend a meter deep into the ground, filled with ants and tunnels and brood and queens. And we couldn't study that in the laboratory in the way their physicist likes to study things, which is to make careful, controlled situations. So basically, we would go and dig up nests in the ground and bring them back to the laboratory and flood them out. These ants have a very interesting behavior, which features in kind of the behaviors I'll discuss, in which if they are subject to flood, which happens where they evolved in the Pantanelles of South America, the whole colony will pick up and raft down the river, forming a hydrophobic, basically, structure out of ant bodies. My colleague David Hu at Georgia Tech has studied this extensively. And when they hit dry land, then they have to get into the ground quickly because the nest is basically their,

their shell of the superorganism. So how did you discover that some of the ants are sort of lazy? And they weren't really lazy. They were, there was a natural course they had to take. Yeah, well, we decided to do careful controlled experiments. We would take about 30 ants. And we chose 30 because we had to tag the ants to see who was doing what, where, and when. and we had tried a number of techniques, including little paper barcodes glued to their abdomens,

and the glues would just kill them. So postdoc in my group, Dr. Dariy Monankova, figured out a clever technique to paint the ants with about 30 different color combinations using oil-based markers. And she then put the ants into a little container filled with soil and made sure they dug a little tunnel near a clear sidewalk. and then basically we tracked for hours and hours of video which ants were coming to the tunnel, whether they had excavated soil, scraped it away from the tunnel face, and whether they were transporting that soil up to the surface. And so they figured out in their own way, because that's what they do,

how to then delegate the work, which ones are going to hang back so they don't clog up the tunnel? Yes, and I should say right off the bat that we don't know how they make those decisions. So the origin of decisions by which the ants say, well, you know, the one we painted purple-blue is going to dig the most, we don't know. Simply recording the activity or the number of visitations from different ants resulted in sort of a funny distribution where you had basically three to five out of the 30 doing the bulk of the labor over 12 or 24 hours, and the rest doing little bits, although about 50 percent, as you alluded to, we never saw a visit at all. Wow. So why don't they just make the tunnel wider? So more ants can get. That is a terrific question, and we don't know why. We have some evidence that the narrow tunnels allow them actually to climb up and down quite quickly while missing footsteps, because when they pitch back, which they do frequently, they encounter another tunnel wall with their antennae or heads, and they just get a little bump and go right along their way. So there seems to be some locomotion benefits to it. We also think that making a narrow tunnel allows you to get deep into the ground quickly.

So that's basically what we know about that. But once you do make a narrow tunnel, and by the way, you can try to force the ants to make larger tunnels. You can start a hole with a larger diameter, and they always make it more narrow. Or if you start the hole with a narrow diameter, they always widen it. So they like to dig these tunnels of this diameter, and that is independent of whether it's Georgia Clay or Sandy stuff. Yeah. But you're trying to apply this research to test to a bunch of swarm robots.

Robots, you're going to teach the robots what you learned about the ant. Well, in some sense, yeah. So I'm a physicist, and so the kind of studies we like to do are careful biological studies coupled to modeling studies. And so in our paper, we had computational models called cellular automata models, which allow us to get some insight in silico as to what's. the ants might be thinking and why. But it's more satisfying to conduct what we call physical modeling studies where we actually build robots, autonomous robots. And because we were physicists,

we couldn't build thousands of robots like the ants. We could build a few. But that turned out to be okay because the real story happens to be in these narrow tunnels, the kind of clogging and clustering that occurs when few numbers of ants or ant robots all get in each other's way. So you can apply this to swarming robots and teach them not to get in each other's way or how to just, if you don't know how the ants decide what to do, how do you get the robots to know what to decide what to do? Well, it's an excellent question. And what we did was, in fact, we programmed the ants to model what the ants were doing. We programmed the robots to model what the ants were doing in the sense that when we first started this project, we were curious as to whether we could make groups of robots excavate. model system well. And the student who was working on it, a guy named Vadim Linovich, had the idea,

well, I'll make a couple autonomous robots, and I'll just send them in to the tunnel, and they'll start to excavate. And indeed, one robot did pretty well. Two robots did better, three even better. But by the time he got to four, the whole excavation came crashing to a halt. And he tried all sorts of clever things like rules, which said if a robot's in a jam, it should wiggle a little bit or back up, and nothing was robust. And then we realized what the ants were doing, and we tried these strategies in the robots. And very broadly speaking, combinations of the strategies, including staying out and giving up when the tunnel was too clogged, produced real benefits in the robot excavation performance in the laboratory. Did you ever bring in E.O. Wilson as a consultant

on this? No, we did not, although I would love to know what he thinks. You can give him a call, I think we have his number. So where do you go from here with this? What have you learned, and how do you apply that to what you want to do? Well, you know, so I'm a scientist, a physicist, and so for me, it's the joy of discovering how, you know, secrets of nature and these answers are just so incredible at what they do that I feel like we've understood a little bit about how, a group which has no leader and has limited information about what everyone else is doing can accomplish a complex task that no individual can. We are presently trying to understand how the ants develop this optimal digging strategy. We have evidence in our computer models and robot models that, in fact, such a strategy can evolve pretty quickly.

One of the interesting experiments we did was take in a bucket of 30 ants the top five excavators out and let the remaining 25 excavators. a fresh batch, and we found that the remaining 25, Doug, just as effectively, but five more stepped up. So how that happens, we're very interested to know, and how we can teach the robots to quickly converge on this distribution is interesting to know as well. These were fire ants you were using? Correct. Were you a little careful about that?

We're very careful about that. We wear gloves, and the sides of the containers that we house them in are coated and baby powder because they can't walk across it very well, climb across it. But if you don't bother them, like most animals, they don't tend to bother you, and they're just great study subjects because they see soil and they dig. Is this because you're in Georgia? Could you do with this with other kinds of ants that might be found around the country? Yeah, we could do this.

There are a lot of ant species that dig subterranean structures, and they're quite beautiful. In fact, you can buy casts of these things. Moulton casts are made, particularly by a professor. Walter Chinkle, Florida State, and you can buy these casts and see the different structures, but fire ants turn out to be very convenient in Georgia because they've taken over everywhere. Do you think termites build the same way? That's a great question. I don't know. They build those great tunnels and, you know, mounds.

Correct. Correct. They build structures and tunnels, and I think that it's well worth looking into. What about applying your bots to taking them to Mars or another planet to do, you know, to work on their own digging stuff? Yeah, well, I think this brings up an interesting point in that, you know, we presently have now robots that are pretty good flying robots, you know, the little drones that you can buy for a couple hundred bucks. And you can actually get swarms of those to do pretty interesting things, like if you remember the Olympics where there were swarms fine. But we don't have and not even close to having comparable robots in terrestrial environments, like rubble, like rock piles, like, you know, the material after a building collapses or an earthquake. And so we need to get robots that are actually capable of moving in those terrain. And once you have robots that are capable of moving in those terrain, you could imagine putting many of those robots into a nasty terrain. and once you have many, then you have a swarm,

and then we think some of the principles we've discovered will be useful for such swarms. Well, we wish you great luck, Dr. Goldman. Thank you. Yeah, I saw that movie, The Swarm. Read the book. Ditto. Daniel Goldman's professor physics at Georgia State Institute of Technology.

Thanks again. We're going to take a break, and if you think nuclear reactors are a modern invention, there is a natural nuclear reactor. The Earth has had natural ones. below the ground two billion years ago. I mean, well, we'll talk about it. Where they are?

What happened to them? Are they still running? We'll talk about it after the break. Stay with us. This is Science Friday. I'm Ira Flato. You know, once we figured out how to do with generating energy with nuclear efficient

is actually something simple to do. You just chuck some neutrons with enough energy at the right kind of uranium or even plutonium. And you've created a chain reaction that can power a city or a bomb. Sounds easy now. It took a lot of time for people to figure that out, but you know who figured it out a long time ago?

Mother Earth did. There are deposits of uranium in the Earth's crust where nuclear efficient has happened naturally billions of years ago when uranium deposits had more uranium 235 than they do now. These natural reactors even cycled on and off over hundreds of thousands of years and they might be able to teach us something about safely storing waste for millennia to come.

My next guest is the author of a new research published in the proceedings of the National Academy of Sciences looking at waste. Evan Grupman is a research physicist at the U.S. Naval Research Laboratory in Washington. Welcome to Science Friday. Thank you, Ira. Glad to be here. I'm going to have to start off with the obvious question.

How to heck this? Did the Earth do this? Right. I mean, this is a, you had an incredible confluence of conditions that happened in Gabon, Central Africa, two billion years ago. And so what you had was, you know, these natural nuclear reactors that were able to cycle on and off, as you mentioned, underground. And this happened for tens of thousands and hundreds of thousands of years. So like you mentioned, reactors today need an isotope of uranium, uranium 235. to be enriched over its natural abundance.

And so its natural abundance right now is about 0.72%. And most of uranium, uranium 238, so 99% of it, can't sustain these nuclear reactions. And so it turns out that 2 billion years ago, because uranium 235 decays six times faster than uranium 238, you actually had more uranium 235, 2 billion years ago is about 3% or a little more. And this is about the same amount that you have in light-enriched uranium or low-enriched uranium reactors today, and it allowed these reactions to occur. So why didn't one go critical and explode? Right. So there's a couple of other conditions that you need. First, you need enough of this uranium packed together.

And then you also generally need a neutron moderator. And so groundwater around these reactors actually moderated the neutrons. So uranium 235 likes to fission when it has slow or low kinetic energy neutrons. Normally during a fission event, you split an atom into two roughly equal mass halves, and you also have some neutrons. These neutrons are very energetic. And so collisions with the water that was coursing through this reactor actually allowed, it slowed down the neutrons enough to split the uranium and keep this fission process going. And so this water also ended up moderating the reactors and preventing the reactors and prevent.

a runaway because when the reactors are running, they heated up a bit and they turned the water into steam. And this prevented the reaction from continuing. And so after about 30 minutes, the reactor turned off and stopped this nuclear chain reaction until it cooled down enough for the water to seat back in and the reaction started up again. So it had this self-control mechanism that allowed it to cycle. It's really. And so how do you find, what is left behind so you know that something like that has happened? How do you search for it? So these things were discovered by a French worker who in the 1970s was looking at these uranium

ore deposits that were being mined. And it's really a triumph of mass spectrometry that they were looking at the ratio of the two isotopes of uranium, 235 to 238, and he noticed that this ratio was slightly lower than it should be. So he measured a ratio of 0.717, and it should have been 0.72 or thereabouts. And it sounds like a very small amount, but it turns out that this is actually a larger variation that you see across the entire Earth and the whole solar system. So they knew that something was up, and they went looking for the specific places where this uranium 235 was even more depleted. And when they picked up this ore from these regions, they then were able to fingerprint that nuclear fission had occurred by looking at the fission products.

So these are these, you know, two halves that split apart from a uranium atom. And you look at different elements of these, such as neodymium. And the distribution of the isotopes of these elements that formed from fission are very different than you find elsewhere on Earth. And so this provided the fingerprint. So you knew, okay, it had to be nuclear fission. Interesting. You know, we all know that the nuclear reactors produce waste, and that's really a major problem we have now with them is what to do with the waste. So what happened to the waste from these reactors?

And can we learn anything from that? Well, these reactors are very interesting because they're really our only natural analog, and the best analog we have, for studying the retention of waste long term. And because there was water coursing through these reactors, and there's about 17 reactor sites in this region, so you had a different level of processing and different types of processing that were going on to these reactors in their 2 billion-year history since they stopped working. So there was groundwater, there was local volcanism that heated up rocks.

And so when you go in and look at the different elements and isotopes that are in these different regions, you can tell how much of each element was lost or retained in the reactors. And so that was some of the work that we did. We started looking around and we found that cesium, which is one of the elements produced in these fission events, and there's several different fissionogenic isotopes that are produced. reduced of cesium. It was actually retained in certain minerals within these reactors. So these were lithium metal that formed inside the reactors, and it captured this cesium while it was still radioactive, and then retained it for two billion years after

the reactor stopped. And this is really remarkable because cesium is a very mobile element. It's volatile, which means when you heat it up and moves around a lot. And it's also incompatible with the uranium fuel crystal structure. So it's lost very easily from the reactor. And so it was incredible to actually see that it had been captured in these new minerals. So it's locked up, so to speak. Right, exactly. Interesting.

So you don't think because it's now been 2 billion years and all this uranium has decayed, that there are any active natural reactors still around? That's correct. There aren't. And it's because the uranium 235 isn't enriched enough anymore. So where do you go from here? Let me just say these were these found in mines, right? People were in mines looking for, were they mining or looking for them?

So they were mining uranium. They knew the uranium was there. And some of these mines were on the surface, open pit mines and others are about 200 meters below the surface. Wow. So what's next for you with this project? So now that we know that ruthenium, for instance, and some of these minerals capture cesium and other fission products, one avenue of research is to figure out if we can create new materials that hold these fission products better. Or when you're thinking of long-term storage, one thing that's done today is you try to vitrify or turn uranium waste into glass, or you add it to glass so it's retained.

And now that we know that ruthenium actually captures the cesium, and ruthenium is present, it's made in the nuclear fuel by these reactions. perhaps we can modify the chemistry a bit to force that cesium to be better retained in these long-term waste structures. Wow, that's very, very interesting. Thank you for taking down to talking with us today. Thank you. Evan Gruppin is a research physicist at the U.S. Naval Research Laboratory in Washington. The world of biology was upended in 1977 with the announcement of the classification of a new form of life, tiny single-celled archaea. Archaea looked like bacteria in size and shape. They originally thought they might be, but it turns out they weren't,

and they didn't fit anywhere into the plant or animal kingdoms. Archaia were classified as a third domain, classified by Carl Wows and George Fox in research they published 41 years ago. As George Fox told me on NPR's All Things Considered, in November of 1977, he believed these archaea may be signposts toward discovering the earliest forms of life on Earth. And then you can extrapolate backwards to see how early it started. Right. We would like to try to determine...

Dr. George Fox at the University of Houston in 1977. I bring all of this up now because the discovery of archaea, as well as the trials and tribulations of biologists trying to decipher early life on Earth, is a story wonderfully told in the new book, The Tangled Tree, a radical new history of life, written by science writer David Quaman. David, welcome back to Science Friday. Thanks, Ira.

It's great to be back with you, and it's dizzying and wonderful to hear you talking to George Fox back then. Yeah, he's still around, isn't he? Oh, he is. I interviewed him for the book. I get emails from him a couple times a week. Yep, he's in Houston still. And I want to tell our audience that we have an excerpt of your book at ScienceFriady.com slash tangled tree. And I remember when I was talking to George Fox, I remember how excited and how shocking that discovery was back in 1977.

It was shocking enough to get Carl Woes on the front page of the New York Times on November 3rd of that year, including a picture of him, typical Carl Woz, what tousled white hair, sports shirt, and his feet up on his desk wearing Adidas. And so what was so shocking about that? Well, there were supposedly only two major forms of life, as you were saying. The tree of life, and by that I mean the sort of the classic Darwinian picture of the shape of the history of life, had two major limbs at that point. Fancy names for those were prokaryotes and eukaryotes. Less fancy names were bacteria constituting the one limb and everything else, including animals, plants, people, fungi, constituting the other. And then Woz and George Fox came along and said, wait a minute,

there's this third group. They look like bacteria. But if you look at their DNA and their RNA, they are not bacteria. They're not only very different from bacteria. They're more similar to us. They're more similar to eukaryotes. And that was the big news. So what exactly makes them different from bacteria? Well, what Woz and Fox detected was differences in one particular very fundamental molecule that they were looking at, using as essentially the Rosetta Stone, for comparing different forms of life, as George said, back at the earliest stages of the history of life. And those molecules differed drastically between the bacteria and the archaea. But then the biochemist came in, and they started particularly germany. and biochemists, and they said, yeah, well, we've been noticing weird things about those

so-called bacteria, too. They have different kinds of cell walls. There's no peptidoglycan, fancy name for a fancy molecule, in their cell walls. They have different kinds of membranes, different kinds of linkages in the lipids, the fatty molecules in their membranes. They're really different at the biochemical level, too. And eventually they were classified, as you said, as a separate domain of life. Our number 844724-8255 is our number.

We're talking with David Kwanman on Science Friday from WNYC Studios. And when they were first discovered, and as I said in my report, there was sort of the biological weirdos. They preferred these really extreme environments, right? Exactly, yeah. They called them extremophiles, extremity lovers. They preferred really salty environments or acidic environments or hot spring. Some of them were found in the hot springs of Yellowstone Park. Some of them more recently have been found around thermal vents at the bottom of the North Atlantic between Greenland and Norway.

Not all of them, we know now, prefer extreme environments, but that's how they were first detected. Also, some of them in environments with little or no oxygen, so they metabolize carbon dioxide and produce methane. Now, as you mentioned, it was big news at the time, front page. of the New York Times, but it was sort of that the newspapers were getting it a bit wrong, weren't they? Oh, yeah, they were saying, you know, Martian-like bugs, the bugs that predate the earliest forms of, earliest known forms of life. The newspapers, the New York Times did a pretty good job. The Chicago Tribune did not do so well, and a lot of other papers got it very confused. and the fact that Carl Woz had allowed this discovery to be announced in a press release.

His funding came from NASA, and NASA issued a press release, and the newspapers got a hold of it. And so people, including scientists, respected scientists like Salvador Luria, heard about it, read about it from newspaper, garbled newspaper accounts before they saw the journal article. And that was one of the causes of... it being largely rejected by the scientific community at the time. There was a lot of resistance. People thought this was junk science because it had been announced in the newspapers confusedly before they saw the scientific paper. It saw the Woes in Fox, 1977, and saw that it was very solid science.

Let me go to the phones to Walter and West Columbia, North Carolina. Hi, Walter. South Carolina, but that's all right. Fascinating topic, and a very fine speaker. I'm honored to participate in your show. My question is, among the archaea, are there to date any known pathogens of humans or animals or plants? That's a great question, Walter. Yeah.

And as far as I know, the latest answer to that question is no, but nobody knows exactly why. We have all these bacteria that are pathogens of humans, and now we know these other things that look like bacteria. and have the same sort of appearance and do not infect humans, do not cause disease, as far as we know, at least as far as I've heard so far. But the question remains, why not? When I was talking to Dr. Fox on that little cut, he said, you know, there might be three, four, or five more of these undiscovered branches out there. Could there still be? Well, I don't think so, because woes' work, the woes and fox work, the methodology

of it became, in a sense, even more important than the discovery of the archaea. And a lot of other scientists started using that methodology, using this one Rosetta Stone molecule, to compare different forms of life, to sketch new versions of the tree of life, but also a wonderful scientist named Norman Pace, and now at the University of Colorado in Boulder, who was essentially Carl Woz's scientific son, his protege. Norm Pace pioneered the use of that methodology for identifying and characterizing creatures that couldn't be grown in the laboratory, that couldn't be cultured and grown in a lab. And they call that sort of environmental discovery of organisms. So there has been a lot of that done.

You don't have to grow a bug in the lab anymore to identify it. And if there were completely different non-archaia, non-bacterial microbes out there, the norm-paced methodology probably would have detected it by now. Talking with David Klaman, author of The Tangle Tree, we'll get into that tree a little bit more in great detail after the break. 844-8255 is our number. You can also tweet us at SciFri. We'll be right back. Stay with us. This is Science Friday.

I'm Ira Flato. We're talking about the origins of life and how we divide and classify the. The Living World with science writer David Quaman, author of the new book, The Tangled Tree, A Radical New History of Life, our number 844-724-8255, if you would like to comment. We also have an excerpt up on our website, Science Friday.com slash tangled tree. Let's go to the phones. A lot of interesting calls on this. Let's go to Cleveland.

Renee, hi, welcome to Science Friday. Hi. Hi, thank you so much for taking my call. I'm a biology teacher, high school biology, and when you say tree of life to students, they immediately get an image of a straight stalk with a bunch of branches, and obviously that's not exactly how it works. So I was wondering if you have a better analogy that you use to describe that. Thank you.

Yeah. Good question. That's what your book is all about. That's what it's about, yeah. And let me introduce a new term, a new idea here. Horizontal gene transfer. These discoveries by woes and others led to the awareness that genes move sideways across species boundaries sometimes, even across kingdom boundaries. Genes move horizontally.

It's supposed to be impossible, and it was astonishing to me when I first read about it in 2013. But that is what complicates the tree of life. The tree image that goes back to Darwin is all about divergence, limbs diverging into branches, branches diverging into twigs, eventually leaves making the canopy of the tree representing the abundance of life's diversity on earth. But now we know, thanks to these molecular researches, that there are convergences as well as divergences of limbs. There are channels that go from one major limb to another. There are branches that go sideways from one to another representing this horizontal gene transfer effect. So if it's not a tree, then what is it? Well, some people say it's a web.

You should talk about the web of life or it's a network. One researcher talked about the circle of life. None of those really get it either. It's a very complicated, somewhat but not entirely tree-like history. and that's why I ended up with the title that I did, The Tangled Tree. At one point I was thinking about calling this book, The Tree of Life is not a tree.

It's interesting because this sidewood movement is fascinating to me also. Also is the idea that we carry in our genes a great history of our genetic background, right? Much simpler forms of life. We do. We do. We carry it in our genomes. We carry this record.

And in our bodies, we carry this record. There are a couple different instances of that, but one of them that I discussed toward the end of the book is the fact that scientists now recognize that 8% of the human genome consists of viral DNA that has arrived by the capture of retroviruses in our genomes. You know, a retrovirus is retro because it moves backwards, inserts its genome into the genome of the cell that it infects. And if it's HIV infecting immune cells, it inserts that genome. into immune cells. But if a retrovirus infects reproductive cells, if it infects ovaries, testes, eggs, or sperm, then that viral DNA gets inserted into those cells and it becomes hereditary. And over the millions, tens of millions of years of mammalian evolution, we now know there have been viruses captured by our genomes that way amounting to 8% of our genome,

some of which are now still functioning genes that allow us to be what we are, that allow us to be mammals. So what kinds of viruses might we have? Do we have other species in our genome? Are there some animals that do that? Well, yes, there are other animals that have acquired DNA from other creatures, in some cases acquired it from bacteria. There are some fascinating studies showing that certain insect genomes have acquired bacterial DNA from a kind of bacteria called Wolbachia that infects. It's a cellular parasite that infects many, many, many species of insects, and it gets inside the cells. And when it gets inside reproductive cells, sometimes it inserts its DNA into the DNA of the insect.

Let's go to Judith in Chico, California. Hi, Judith. Well, let's go to Frank first in Columbia, Missouri. Sorry, Frank. Hi there. Hi there. I haven't read the book, but I'm looking forward to it. I was lucky enough to hear Carl Woz's seminar when he and are very close to the time that he announced the archaea. And there are a couple things that I think, I hope your book brings out. First of all, both horizontal gene transfer and the archaea, they were just known as funky bacteria, time existed and were known and had been studied before the Fox and Woes paper. And the other one in a time when people kind of say, well, evolution is kind of maybe not so important to biology that I remember distinctly Carl Woz is going on at great length and emphasizing very strongly

that he was trying to put the bacteria into the evolutionary framework. And his first work actually he did come up with a tree. It was much later that he emphasized the horizontal gene transfer. But it's a fascinating history, and I knew a couple of the players, and I think it's just a wonderful story of how science works. So congratulations for writing it. Thank you, Frank. And yes, those aspects that you mentioned are in the book. What did you find that you studied this carefully? What was the most surprising thing that you discovered? I think the most surprising thing was one particular instance of that viral DNA getting into the human genome. I read about a scientist named Tiri Heidman in Paris, who with his group had done a series of papers, made a series of discoveries about one of these viral stretches of DNA acquired by the human genome that is still a functioning gene.

It's called Sinsitin 2. Sinsettin is not spelled like Cincinnati in my hometown, but like synonym. And this gene, Sincetin 2, was originally in the retrovirus an envelope gene, meaning it made sort of an envelope, a membrane around the viral particle. It got into the mammalian line, and now in humans, our version of this gene, Sinsatin 2, is absolutely essential for creating a different kind of envelope, but different kind of membrane. It's a membrane between the placenta

and the fetus in humans. And without that membrane, which has a really fancy name, without that membrane between the placenta and the fetus, fetus, human pregnancy is impossible. So I read about that, and I emailed this fellow,

Tiri Heideman, and said, if I come to Paris from Bozeman, Montana, will you talk to me for an hour? And he said, sure. So I went, and we talked for seven hours about this, and it's in the book. Let's go to Liz and Waco. Hi, Liz. Welcome to Science Friday. Hi, I'm so excited to ask this question. I've always wondered that if Archaia have no pathogenic significance for humans or no agricultural significance, where the research dollars are coming from.

And possibly if biotech companies are really looking toward Archaia to mine them for genes, especially since they're thermophiles. So I'm just curious about research dollars and the biotech aspect of that. That's an interesting question. In terms of the second point, are biotech firms looking to mine these for particular genes that adapt to extreme environments? My answer is probably so. I don't know the specifics, but I would guess that you've put your finger on it there and that there are some that are doing that. Earlier on, I mentioned Woz's funding. Some of it came from NASA.

That was why they issued a press release. and they were funding him as part of their exobiology program, which had been, I don't know if it had been founded by Carl Sagan, but he was certainly part of it. So they were funding this because they thought, well, this stuff might tell us something about the conditions that are necessary for the arising and the evolving of life on other planets.

A more general answer to your question is that this gets funded mostly because it's pure science. It tells us something about the history of life on this planet going back maybe four billion years, and we should want to know that. Well, isn't it more, though, another reason also or might should be? I mean, this is part of our lives. These archa are living with us. Aren't they living in our gut? They're living in sheep.

They're all over the place. They're part of the microbiome, part of the soil microbiome. That's right. How do we know what we don't know about them? I mean, they just seems to be, for example, do they have a crisper tool of their own that they use to battle one another or the other bacteria? That's a good question. Do they leave fossils behind when they die like bacteria do, you know? All these good questions.

So why are we? We used to think that there was just, most of us were made out of junk DNA until we always thought that was a silly concept, until we always thought that was a silly concept, until we knew, hey, there's a lot of stuff that DNA is used for. Maybe we consider our kid to be too much junk DNA? Yeah, yeah. It's just surprising. You know, the listener has a great question. Why don't we study it, them more?

Well, I think we do study them more, but you don't hear that much about them. All of these things that we've been discussing today, the scientific literature is full of it, but it hasn't penetrated much to the general public. I mean, some of my colleagues and people you know have written about it. this. Carl Zimmer has written about some of this in short form. Ed Yong has written about some of this. I'm not the first person who wrote about this for the general public, but I don't know. I may be the first person who has written a book about it for the general public, about this particular constellation of discoveries. Let's go to Grand Junction, Colorado. Michael, welcome.

Okay, go ahead. So I was just wondering, I've read quite a bit about Extreme Files, not that I'm a I just always found them interesting. But I've never seen any answer this question. I was wondering if extremophiles from our own planet could live on planets besides ours. Okay, good question. Well, I don't know the answer to that question. It is an interesting question.

And I certainly am not going to rattle off three reasons why they couldn't. I mean, who knows? Maybe. Maybe if there's, you know, if there are, if there's liquid water, and forms of mud, maybe acidic mud, and just the right absence of oxygen, carbon dioxide. I'm not going to say it's impossible. And that man is David Kwan, author of the new book,

The Tangle Tree, Irradical New History of Life on Science Friday from WNYC Studios. You know, it's sort of a little bit of hubris to say, hey, none of this could ever happen. Yeah, nobody wants to be. I'm not going to say that. I mean, when you think of the history of science where none of anything could happen, that eventually happens. Right, right, right. And the other thing, I mean, unexpected IRA, and another good reason for studying these creatures, these archaea, that don't infect us, is that because is that the latest thinking on them, the latest research suggests that they, in fact, are our deepest ancestors, that when complex cells came to be with the acquisition of cell nucleus and cell organelles,

internal structures and things, the host cell from which our complex cell lineage was assembled was not a bacterium but an archaean, that they are probably our deepest ancestors. And that's a little headspinning, too. Let's go to the phones because you have ignited it's some interest. Judith in Chico, now let's see if I can get to Judith and Chico. Hi, welcome to Science Friday. Studying microbiology and infectious diseases, I learned about jumping genes that could be transferred from one species to another, like the chigella toxin to e coli causing that horrible kidney-killing disease.

So how is this different than horizontal transfer? Well, I am talking about horizontal transfer, and as you say, and as someone else said, I think it was Frank, it had been known in bacteria going back before Carl Woos. Joshua Letterberg in the 1950s coined the phrase infective heredity because he saw this happening among bacteria, passage of genes from one bacterium to another, and even from one kind of bacterium to another. And in a 1963, a Japanese scientist named Tsutomu Watanabe and his group showed that this problem that we now face of antibiotic-resistant bacteria, that it is transferred around the world from one kind of bacterium to another by horizontal gene transfer. That's why we have multi-antibiotic-resistant bacteria turning up everywhere. It's not because they're evolving independently evolving resistance to all these different antibiotics. It's because one kind of bacterium can evolve resistance, the slow way, and then a gene for that, or a package of genes, for multiple drug resistance, can pass in an instant from Shigella to Salmonella, from Salmonella to Streptococcus, from Streptococcus to Staphylococcus. And it's horizontal gene transfer.

Last question on the phone from Thomas from Los Altos, California about horizontal gene transfer. Hi, welcome. Thank you. As you were talking about head spinning theories, is it possible that our human genomes is getting mixed in with maybe lower level species as we speak as the journey of evolution continues? Well, is it possible? Yes, but it happens very slowly, very infrequently. I mentioned the Sinsitin genes acquired from retroviruses. Those have happened over the course of the last 80 million years in the course of mammal evolution.

Horizontal gene transfer, I mean, there are a lot of reasons why it shouldn't happen at all. And it doesn't happen very often, but it has happened enough over the long stretches of time to have been really consequential in terms of shaping us and in terms of showing us. shaping the tangled tree of life. So, yes, it's probably still going on, but we're not going to see it, you know, popping like popcorn in a popper in terms of its frequency. I'm constantly reminded of Jeff Goldblum's line,

Life will find a way. He didn't write it, but he said it. Thank you, David. Thank you, Ira. Great to talk with you. Great to have you on. It's a great book. David Kwanman is author of The Tangled Tree,

a radical new history of life, and you can find an excerpt of it on our website at ScienceFriiday.com slash tangled tree. One last thing before we go. SciFri is headed to Salt Lake City. Oh, we love to go to Salt Lake. Join us next month, Saturday, September 15th, circle the calendar at September 15th

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