Modern Wisdom - #394 - Carl Zimmer - What Are The Weirdest Types Of Life?

Episode Date: November 6, 2021

Carl Zimmer is a science writer, journalist and an author who specialises in evolution, parasites, and heredity. Life is the thing which illuminates our corner of the universe. It gives colour to an otherwise cold, brutal void. But what is life? How is it defined? Despite seeming obvious at first glance, this question is one of the most contested in science. Expect to learn what are the most extreme forms of life which can live in the vacuum of space, how life might have begun in rock pools, why aliens might be so different to us that we don't even recognise them, how a slimemould that looks like dog vomit can learn its way through a maze and much more... Sponsors: Join the Modern Wisdom Community to connect with me & other listeners - https://modernwisdom.locals.com/ Get 20% discount on the highest quality CBD Products from Pure Sport at https://puresportcbd.com/modernwisdom (use code: MW20) Get perfect teeth 70% cheaper than other invisible aligners from DW Aligners at http://dwaligners.co.uk/modernwisdom Extra Stuff: Buy Life's Edge - https://amzn.to/3pZZLZx  Follow Carl on Twitter - https://twitter.com/carlzimmer Get my free Reading List of 100 books to read before you die → https://chriswillx.com/books/ To support me on Patreon (thank you): https://www.patreon.com/modernwisdom - Get in touch. Instagram: https://www.instagram.com/chriswillx Twitter: https://www.twitter.com/chriswillx YouTube: https://www.youtube.com/modernwisdompodcast Email: https://chriswillx.com/contact/  Learn more about your ad choices. Visit megaphone.fm/adchoices

Hello friends, welcome back to the show. My guest today is Karl Zimmer. He's a science writer, journalist and an author who specialises in evolution, parasites, and heredity. Life is the thing which illuminates our corner of the universe. It gives color to an otherwise cold, brutal void. But what is life? How is it defined? Despite seeming obvious at first glance, this question is one of the most contested in science. Expect to learn what are the most extreme forms of life which can live in the vacuum of space. How life might have begun in rock pools

rather than at the bottom of the ocean, why aliens might be so different to us that we don't even recognize them. How a slime mold that looks like dog vomit can learn its way through a maze and much more. Don't forget to join the modern wisdom community on locals if you want to connect with me and everyone else who listens to the show, 1,500 members and counting so far. So you'll be in good company, lots of people that like interesting things. But now, please welcome Karl Zimmer. It's an interesting thing talking about life and what it constitutes, right?

Because I think a lot of people have heard about discussions to do with euthanasia and assisted suicide and is this person really alive? What does it mean? Philosophical arguments to do with is somebody in a coma, discussions around abortion, what constitutes life during childbirth and beforehand, yet it's an interesting and interesting area. It seems like it's sort of coalesce is a lot of big questions that people have. It really does, but at the same time, as important as it is, there hasn't been really all that much thinking among scientists about life with a big capital L. I mean, when we talk about life, what do

we really mean? And so what's really astonishing is that you can find plenty of definitions of life in the scientific literature, but they're different definitions. And I find if I start talking about life with a scientist, they might very well have a definition, and it's different from the one I heard from the last person. So you have a situation which is really strange. I mean, imagine like in chemistry, people didn't agree on what an atom is.

I mean, that would be kind of problematic. And yet we're in this situation where scientists who study life, life in different forms, they just, they really don't agree on what it is they're talking about. Why is it so messy? You know, that's a good question. I think part of the problem is that sometimes they're trying to get at different things when

we use the same word. So there are these issues about end of life. So is someone who's on a ventilator? Are they alive? And so we start to talk about brain death as being sort of the definition of the end of life. That's really the end of one person's life. They're state of being alive. Whereas other people want to say, okay, you know, a snake and a tree and me, we all have something in common that's different than a rock. What am I going to call that? And people will say, well, that's life. And so it can be a way of trying to pull things together and try to figure out what they have

in common. But even then you get yourself into trouble because then you think you have a nice little category of things that are alive and then someone comes along with something else like a virus and then everyone starts yelling all over again. So it's marvelously prone to lead to big arguments. Whose job is it to work out what life is? Is it biologists, chemists, philosophers? It's funny. I mean, if you talk to a typical biologist, I talk to biologists all the time for my work.

And if you kind of stop the conversation and you say, by the way, I'm kind of curious, like what's your definition of life? I mean, what does it mean to be alive? A lot of them actually don't want to really talk about that at all. Well, because you might be a scientist who, let's say, you're a scientist who studies tigers and you really like tigers. You don't know a whole lot about fungi. They're fine. You know that your tiger and the fungi have some things in common,

but like it's not really your job to get to into that. Like there's enough to do with the tigers. So for a lot of scientists, like life is so big and so complicated and so overwhelming that they really just want to kind of zero in. You know, I mean, somebody, there's some people who just want to study,

you know, one protein. So that's even smaller. And you can get a lot out of that as a scientist. You can learn a lot, but it is a little awkward when, as a biologist, you are studying life, and yet it can be really hard to get a straight answer out of scientists about that. But, you know, so it's so it so it so it then it's fun to find the the people who really are thinking about life. And and to get and who are even trying to do research on, on, you know, life itself. And to it, to learn what they're trying to do and how

they're grappling with it. But it's definitely a minority. Would you say that humans are the only animals that are aware of life and death? No, actually not. Let's put it this way. There are other species that can recognize things that are alive and are not alive. That doesn't mean that they have a deep conceptual understanding of life, but you could argue that we don't really either. For example, a fish swimming along can tell that there's something dead nearby and will avoid it. You know, that

you can see different behaviors that animals have in response to living in dead things. You can see that some animals are very good at sort of recognizing biological motion. That is the movement of living things and can distinguish that from the movement of things, you know, like rocks or something that are moving, but are not alive. And that's really important for a lot of species, you know. You want to avoid cadavers that could make you sick. If want to, if something's moving, that could be a predator that's going to kill you or it could be a rock that's tumbling down and, you know, that could kill you too, but you need to respond in different ways. You know, the rock isn't going

to come after you, the predator might. So, so there are good evolutionary benefits to being able to recognize life and death. And we can probably, our own sense of life, that we ourselves are alive, that probably has these deep evolutionary roots too, just sort of monitoring our own bodies and that kind of sense of being alive. It's not like a rational deduction. We don't say like, ah, from these certain things I deduce that I'm alive, it's just you feel alive. And what's fascinating is that the flip side is that there is actually a syndrome, a psychological syndrome where people are convinced that they are dead. And

they will tell you that they're dead. And they'll explain how they died and how it is that they are still able to talk to you after death. It's called Katar D'Sindrome, named after a doctor who first recognized it in a patient in the 1800s. So I actually think that like this sort of deep ability to recognize life and death, actually kind of gets in the way of our trying

to understand life scientifically because we sort of we sort of assume that it's going to be easy, you know, because it feels easy but it's really if you're trying to understand life as scientists it's not easy at all. What are some of the stories that the patients that have that catard syndrome will tell the doctors? that the patients that have that catard syndrome will tell the doctors? Well, they'll say, well, I drown in a lake last year and I've been a zombie ever since. They're breathing. They're talking, they're telling this to them. What can I tell you? These are the things that you see in these accounts. I'm sure that the psychiatrists or the doctors

were trying to get that out of them. Really? One lady that was worried about being washed down the drain or something, wasn't that? Yeah, so it's pretty common in these reports of catarge syndrome. It's very rare, but there are enough reports that you can kind of see some patterns.

And there is this feeling that people have that they're just a husk. They're sure empty inside. There's just nothing there. And, uh, yeah. And so one woman was saying that that's why she never bathed because she would just wash away down the drain. Um, and, uh, it's, it's, it's astonishing. Um, and, you know, what there, there is just one report that I've seen

where some scientists tried to actually look at the brain of someone with cathardis syndrome. And what was interesting was that there did seem to be some damage to a part of the brain that's involved in monitoring the bodies, sort of taking in information from different parts of the body and kind of integrating that into a feeling. And so if you're not getting those signals, then you just feel, well, there's nothing there. I don't feel alive. Therefore, I must be dead.

What are some of the current working definitions of what constitutes life and death? definitions of what constitutes life and death? There are literally hundreds, but I think the perhaps the one that you see most often came about a meeting of scientists the 1990s brought together by NASA. NASA wanted them to come up with a plan for looking for life elsewhere in the universe. And they pretty quickly realized, you know, we need to like agree on what we're talking about. You know, what are we exactly looking for? And so, you know, because like you don't want to say like, we're going to look for human beings, you know, like no matter what you see on Star Trek where everybody seems to look just like

us on other planets, you need a broader definition, so, or at least a working definition. And so they settled on something, it was basically that, you know, that life is a chemically self-sustained system capable of Darwinian evolution. So that's what they settled on. And so you can find other ones where people emphasize other things, you know, that they really emphasize metabolism or, you know, anything, anything capable of evolving is alive or what have you. But, you know, I'd say that the NASA definition is perhaps the most common one you'll see, maybe because it's one of the shortest. All right, so that's life. What about death? Just that stopping in its system that used to have it? Well, you know, NASA did not ask scientists to define death and

You know really like they were just more interested in like the presence of life versus the absence so like you know The moon is not alive the moon is not life, you know because the moon is a rock is it dead? Well the moon is not life, you know, because the moon is a rock. Is it dead? Well, I mean, okay, no scientists would like use the language of death to describe the moon, you know, they would might say it's abiotic, you know, in other words, not having anything to do with life. It was never alive. But yeah, defining death becomes a big challenge. And just in medicine, it's been very challenging for centuries, really. Physicians had this problem where some other patients didn't seem very alive, but were they dead yet? Was it time to dig a grave for them? There was a great terror actually in the 1700s and the 1800s that people would be buried

prematurely. You could actually request to be buried in a coffin that would have a little hole in it with a wire that could run out of it. It was a little bell, wasn't it? Exactly, exactly. Yeah. In Germany in the 1800s, in the late 1800s, actually, there would be these sort of kind of like funeral parlors, but really what they were, they were just like people would be taken to these very large buildings.

And they just be put there just for a few days just laid out just and again they would have a little bell there just in case they came back. They didn't but but there was this anxiety because no one could really say like boom this person is dead you know. The stethoscope obviously helped things a lot because you know if you waited for a while and there was no heartbeat, then maybe we could agree on that. On the other hand, if someone had been suffered from hypothermia, that might be kind of ambiguous. The big problem for us came about through the invention of ventilators.

So you would have these situations in which someone had massive brain damage and would be unable to even breathe on their own because they lacked the connections to the brain required for breathing. So you would put these people on ventilators. And some of them might be able to recover somewhat. Most of them just lived for a couple of days at most and then died. And in the 1960s, this is actually at the time when organ transplantation

was becoming a reality. And of these transplant surgeons were saying, like, here are all these people who are really they're effectively dead. They're going to be dying very shortly and we need organs, you know, and if we wait for people to die and then go about taking organs. Those organs are degraded. So they're worse for the people receiving them. So what if we were to say brain death is death? Or what if we just say like,

there's no hope that this person is coming back? That's it. And so they wanna donate their organs. Now's the time we do it. This is more, a lot of this is like a social agreement, you know, you can't say it's pure science, it's us as people making a decision about these very difficult situations, not just the difficult situation of the person who's on the ventilator, but the difficult situation of the person who's going gonna die if they don't get an organ. And, you know, there have been, you know,

sometimes there have been conflicts over that. Yeah, you can see how perverse incentives could arise here. Sure, sure. And, but also you can see how if people don't agree with this particular definition of life and death that they might say, like, no, we don't want you to declare our daughter dead.

And this actually is a case that happened. I write about in the book where a girl in California, you know, she went on a ventilator, suffered massive brain damage and went on a ventilator after a surgery that had gone bad, and her family didn't want her declared dead. And so she was actually flown from California where a death certificate had been issued to New Jersey where there were these religious exceptions made. And she actually was taken off the ventilator. She was able to live for several years in this state.

She went through puberty. I should say she was still on the ventilator, but her body was continuing to grow and to mature. And then she died of internal bleeding and then got a second death certificate. So it's an extreme demonstration of how hard it can be for us to agree on what it means to be alive and then what it means to be dead. What about cryptobiotic species? Yeah, cryptobiotic species are amazing. And they are these animals and other species that just totally make fun of us in terms of our notion that there's a clear dividing line between life and death.

So one example are these little animals called tardigrades. They're barely visible to the naked eye. They're in the soil. They're in the ocean, they're all over the place. And there's sometimes called water bears because they have this cute kind of bear-like appearance. And what's amazing is that if they're in a situation where they're in a drought, where their environment is drying out, this is a situation where we would just die. I mean, if you lost a substantial amount of water from your body, your biochemistry falls apart, you're dead.

They don't die, however. They can actually survive for decades, maybe over a century, completely desiccated. They have been sent out into space and then brought back. And if you just put them back in water, they're back to the way they were before. And so scientists are trying to understand, well, what do the water bears do? What are these tardigrades do? And what they seem to do is they do these amazing chemical tricks to go into this state, that sometimes people call it a third state,

cryptobiosis. And one of the key things that they do, is they start making a special kind of protein that encases all of their essential molecules in their cells, kind of like glass. So that you can imagine that these animals are basically turning themselves into a kind of a protein glass. Nothing's moving. And if nothing's moving on a molecular level, you can't say that you're alive by most definitions of life. I mean, there's no chemical activity,

there's no metabolism. That's just not happening. But they're not dead. In other words, they're not falling apart, they're not disintegrating. They're just on pause and can stay on pause for decades, maybe centuries. And it turns out there are more and more of these species, plants, fungi that may be able to do the same thing. Yeah, so that defeats my previous definition of death, being an absence of a thing that used to be alive. Right, I mean, I think you are thinking about, you're thinking about death, you know, human death, you know, the death we know best, you know.

And, you know, for the most part, you know, if there's an absence of certain key things, you know, if you, if you can't breathe, if your heart stops, if your brain's not working like, boom, everything's going to fall apart, and you're, and you're not coming back. But that's just, that's not a universal rule. It doesn't have to be that way. Life doesn't really care about our absolutes that way. What about some other animals, some of the interesting creatures that you found in your research for the book of weird ideas about life and death? Yeah, well, you know, there are certainly things that features of living things that people

talk about a lot, you know, hallmarks of life, sometimes they're called. And so one of the hallmarks is metabolism, the ability to take stuff in to use it to generate energy and to produce biomass. And, you know, metabolism is chemically speaking. It's really similar in some fundamental ways from species to species to species. I mean, anywhere you look, metabolism involves this one molecule, our basic fuel ATP.

involves this one molecule, our basic fuel ATP. So bacteria, they make an ATP, we're making ATP, snakes are making ATP. But there are just some species that are just really amazing, metabolically speaking, and really stand out. They're exemplars. And so one example is certain kinds of snakes, like bow constrictors or pythons.

And so I went to visit a scientist to studies them and hung out with some of these massive snakes, these amazing animals. And they can go for weeks without eating anything. And they're fine. And then they can suddenly leap into action, attack something, whether it's someone feeding the marath or if there's a python on the wild might kill a deer.

And then they will suddenly swallow something, they can be their own weight, and then break that down. So over the next few days, they completely digest it all. It's after a little pot of fur coming out the other end. And so there are some scientists who have been studying this amazing feat of metabolism. It's not easy to do this. It actually, you know, they're eating these things to get energy out, but they have to put a lot of energy in, you know, they have to, they have to make an investment to get all that return. And so, you know, part of what is involved is that they have to basically something, all sorts of things start to happen in their bodies. Their intestinal walls double in thickness. Their hearts increase, I think, is about 50% in size.

Their livers get bigger. I mean, again, we're talking about this happening in a matter of hours. And so, that way, they're ready to handle this incredible challenge of breaking down this whole animal and extracting as many nutrients as possible, moving them around the body as fast as possible. And then once that praise digested, you know, the intestine goes back to its normal thickness, the heart shrinks back down, everything goes back to its normal thickness, the heart shrinks back down. Everything goes back to the way it was. So scientists would love to understand this better because this could have all sorts

of important implications for human health. Snakes are able to go through these remarkable changes in organ size or chemistry and the blood and so on. They might have implications for diabetes, for maybe even growing organs, just all sorts of potential clues might be there in how these particular species just use this particular strategy to stay alive. It's like being two animals in one. It really is, yeah, because, yeah, you just, you snap into this sort of eating mode. And then you go back to, you know, not eating for weeks.

And then, hopefully, a few weeks later, you go snap back into eating mode again. And what's interesting is we think of snakes as being cold-blooded, but the fact is that they're effectively warm-blooded when they are digesting something because they're using so much fuel, they're burning fuel, they're giving off heat as a byproduct of the work they're putting into digesting things so that you can, you can search, if you use one of these sort of, you know, heat imaging cameras, you can see them glowing because of that. They're effectively warm blooded just for that period of time.

The metabolic rate is roughly on par with that of a galloping horse. Now, you know, a race horse might run for a couple of minutes and then we give them a big prize and say congratulations, but these snakes, they're keeping up that metabolic rate for several days when they're just lying there. It's astonishing.

What about fungi and mushrooms and stuff? They must be an interesting case study for life. Absolutely, absolutely. We, animals are fascinating and bizarre. So I just talked about snakes. interesting case study for life. Absolutely, absolutely. Animals are fascinating and bizarre. So I just talked about snakes. I talked about tardigrades. But they're very close to us on the tree of life. And if you look further afield,

you get to see like weirder things, things that don't even have bodies as we think of them. So in the book I write about slime molds, which are, they're not fungi, although they go kind of like fungi. There's sort of these giant single-celled blobby organisms that you can see in the summer when you're walking around in the forest.

They have very evocative names. There's one species that's called dog's vomit because that's exactly what it looks like. You're walking along, you're like, wow, who puked here. It's an organism, it's alive. And that pool of vomit is actually one giant cell that is spreading out. It's tentacles across the forest floor and feeding on bacteria that it finds. So scientists love to study slime molds because you can take a little bit of it and dry it out, take it to your lab, and then splash some water on it. And it starts to grow.

And those tentacles start to grow across a peatry dish. And scientists have found that you just need to give them a little oatmeal and they're very happy because oatmeal flakes have bacteria going on them. So they'll smell, essentially smell or taste the oatmeal and they'll just send their tentacles out across a petri dish until they find it. Now, what happens when you've got like three or four different clumps of oatmeal on a petri dish? Well, you know, the slime all wants it all, but you know, it doesn't want to like build

like a whole sheet of tentacles. That's a big waste of effort. So what it'll end up doing is it'll create this beautiful network of tentacles that's the shortest distance between those little clumps of oatmeal. It's solving a mathematical problem in order to eat. So scientists have all sorts of fun running experience with them. They put them in mazes, the slime molds, send their tentacles to the mazes and solve them.

But they do all sorts of these things. And again, this is something fundamental about life. That in other words, that a slime mold is like us, and that it takes in information about surroundings, and then it does something to sort of improve its chances of survival. thing. It does something to sort of improve its chances of survival. It respawn, it behaves in a way that's better than random. And so, you know, the scientists who study slime molds, they like to call this capacity intelligence. So you could say that intelligence is one of the hallmarks of life because everything from us to a slime mold has it. And it's just easier to study an slime mold in a petri dish because you can run experiment over experiment over experiment. And they, you know, clearly you don't

need a brain to be intelligent because these slime molds are literally solving math problems with no need of a brain. Yeah, it seems like they've got intelligence. And if they do a maze, they must have memory and if they're able to detect things around them they must have some sort of senses of some kind. Yeah, they seem to have all of that. And it's not clear, it's not really clear how they've got it. I mean, so for example, it could be that you just need some very simple strategies to tap into these kinds of intelligence. So for example, slime molds, they can detect where they've been. In other words, if they've extended out a tentacle and they retracted back and then they're

extending another tentacle and that crosses to where they were, they can kind of they can kind of taste their own trail and they don't like it. So they'll sort of move away from that place where they've been. So that is a way for them to not basically just keep going back to the same place over and over again. just keep going back to the same place over and over again. If there's like a bad, if there's some sort of toxin or a bright sunlight, which they hate in a certain area, and they retract their tentacle, they're not going to make that same mistake again, because they're like, okay, that direction is bad. I've been there, didn't work out. I'm going to go over here. So that helps them to get around barriers to go through mazes and so on. That's kind of like a rudimentary memory, but it's not sort of symbolic.

It's not phenomenological. It's just leaving little trails here and there, and then you detect the trails again. What about... Yeah, you're sort of... You're making... Yeah, it's like an external memory. So you don't need a hippocampus tucked away in your brain. You're just like, okay, I'm going to leave a little trail there. And I know that when I... If I reach that again, that reminds me, I don't want a hippocampus tucked away in your brain. You're just like, okay, I'm gonna leave a little trail there. And I know that when I, if I reach that again, that reminds me, I don't want to be here. Don't come back here, yeah, exactly.

What about phanotology? Yeah, so phanotology is this wonderful name for basically the science of death. And it's, there's a small but dedicated group of scientists who study the science of death. Particularly, there are scientists who are interested in how animals respond to death, recognize that other animals are dead. There's a particular sort of specialty of thanatology called primate thanatology, which is particularly important for us in terms of understanding where our own concepts of life and death came from.

So for example, Jane Goodall, the famous primatologist, she spent years just sitting with chimpanzees observing them day in, day out. And she would just see things that you wouldn't see if you just came to visit them quickly. In one case, there was a female chimpanzee with a baby and the baby wasn't looking well, and then the next day was obvious to good all

that the baby was dead. And she could see that the mother was treating it differently now, was sort of just carrying it around, but sort of in a sort of strange way, just sort of holding it by a foot and things like that. And then after a few days, eventually let it go, just left it behind. And there, that's just like one observation,

but since then, in the decade since the 1960s, there have been more, more observations of primates and how they respond to the death of their fellow members of their species. And that is sort of leading to theories about, well, what are evolution routes of our concept of death? It's probably a chimpanzee recognized, chimpanzee doesn't say to itself, oh, this other chimpanzee is dead, but there's a confusion because, you know,

they're looking at something that the biological part of their brain, there's biological sensing part of their brain would say, well, this is something that's alive, it's got a face, it's, you know, and so on. But it's not moving, or it's, but arms are at a strange angle that living chimpanzees don't have, and it may be that they're takes a while to overcome that, to override that. So we can, you know, it's not, it takes quite a while in the fossil record for humans to really show how modern examples of recognizing

death, a funeral, for example. That's probably just in the past maybe 100,000 years that there are these rituals that humans performed in conjunction with death. So in the millions of years before that, they were probably behaving a lot more like the chimpanzees. Have you thought about what other types of life forms that might be out there in the universe? I watched a series on Netflix not long ago where they were talking about silicon-based life and also it's other exotic things.

Do you look into this? Yeah, there's actually a small but really fascinating little thread of scientific research that goes back 100 years of people trying to think of alternate life. Sometimes they like to call it weird life. Because they call it weird because you know, life as we know it on earth is kind of boring. Just in the sense that, familiar. Well, boring in the sense that it's like, oh, here's another species.

Like if you find a new species of bird, I can guarantee that it uses ATP. I can guarantee that it has its genes and code in DNA. Either all these things I can guarantee that it has its genes and code in DNA. Either all these things I can guarantee it, I can even get down to what is the genetic code that it uses to translate its genes into proteins. Just down to that level, there's not a lot of variety. So all the wonderful variation that we see

and all these weird things I've been talking about, that's in a way kind of external. Like at the core, life on Earth is very similar. Now that could be because, that could be because there's just one way to do it. There's just one way to do life. And that's what we see around us. And there's no other way to do it. The rules of matter and energy don't allow anything else.

Or that's just what happened to start here on Earth. Or maybe there were two different kinds of life on Earth and our form won out, the other ones extinct. We have no idea. And so until we start to go to planets and moons and see whether they have life at all, and if they do, what form it takes, will we be able to say, you know, is silicon life possible? You know, chemically speaking, maybe it could be, you know, because some people have said,

well, you know, what is it about DNA that's so important? Well, it's important because it's a way to store information that you can then use to build other molecules. Well, there could be ways of using silicon or some other materials, essentially, to work as genes. And while we wait to finally get to other planets and moons to really, really look hard for life, some scientists are saying, well, okay, let's get to work. And they're trying to build the systems in their labs.

And so you actually are seeing kind of alternatives to DNA that scientists are building and trying to figure out if they can make them work. Was there anything else other than silicon? Silicon is one of the main ones. There's also an issue about the matter of water. So that's another boring thing about life is that on earth is that it needs water. Is that because of the ATP? Well, that's because the chemical reactions that make ATP possible and and lots of other chemical reactions, they need water to act as a solvent. And so, you know, water interacts with proteins in all sorts of important ways with our DNA as well. And so we need water as a solvent in There are other solvents, you know, caracene.

We would not want to drink caracene, but maybe caracene or liquid ethane or something like that, maybe that could be a solvent for some alternate form of life. And, you know, this is this actually is not like a totally pure thought experiment because, you know, there are some parts of the solar system, some moons where there isn't liquid water, but there might be liquid ethane. And so, you know, it's it's actually really interesting to say like, well, could there be life there? You know, is it impossible for there to be life there? Or would there be some bizarre, super cold, ethane-based life out in our own solar system? Who knows?

One of the coolest things that I looked at, I'll try and find, I can't remember the name of the documentary. It was something like different alien worlds, a museum. It was just on YouTube. It was so good. And it sort of moved through all of these different pretend exhibits within a museum and it explained how they all might come about.

One of the things that that video said was the likelihood of finding really, really intelligent advanced civilizations that are water-based is essentially zero. And the reason is that in order to become technologically advanced, you need smithing, you need to be able to heat stuff up, you need to be able to create things in ways that allows you to get outside of your, and when you're underwater, that's really, really hard. So that was something that I hadn't considered as well, that you kind of have a cap on technological development for a civilization if it's water-based. And children of ruin by Adrian Chakowski, he's got these huge orbs that have got super-intelligent octopuses in, octopi.

And they're flying these massive orbs of water around. And it's such a funny idea. Well what about, given that we've talked about alien life origins, what about origins of life on Earth? So there again, you know, the definition of life is really important because if you want to talk about when life began on Earth, you have to say like, well, this is the kind of thing that we would say was the original form of threshold we have crossed that now is defined as, yes.

Yeah. And so clearly like a pool that's just full of loose bits of peptides and nuclear tides and ATP, that's not alive. That's a primordial soup. That is just a mixture of molecules that, you know, if they were to come together in a certain way and could sustain themselves and reproduce, we might call them alive. So then the big question is, how do you get from one to the other? And so in the book, I talk about how scientists are trying to do experiments and going to extreme environments on earth to address this question. What's fascinating to me is that there are two really well thought out fleshed out scenarios

for how life might have started on earth and they're completely mutually exclusive. So on the one hand, you have some people who are saying that life started on the surface. So like four billion years ago, there may have just been a few volcanic islands popping up through above the ocean's surface. And you might have little ponds there. And in those ponds, as they filled up with water and dried out, you would have a series of chemical reactions that might have actually produced RNA and then might have been able to encapsulate the RNA into protocells. So you there you got some people who say, that's where life started.

You have other people who say, nope, life started at the bottom of the ocean at these vents in the sea floor where you have these magnificent sort of mineral towers that form as hot mineral-laced water shoots up from the earth's interior. And as that water and those chemicals get pushed through these chimneys, all sorts of interesting chemistry happens. And then you could actually start to, it could start to build up on itself, and you start to produce the molecules that will eventually become our genes. You start to produce membranes and might eventually become our cell walls and so on. So, you know, they might both be right. Maybe one of them is right for earth and one of them is right for a moon in orbit around Saturn. It's hard to say. But along the way,

these lines of research, they lead to amazing discoveries, very practical ones in some cases. For example, right now in the pandemic, a really important way that scientists figure out whether SARS-CoV-2 is infecting someone in a way that scientists figure out whether, you know, SARS-CoV-2 is infecting someone or what kind of SARS-CoV-2

would variant it is. They use a special kind of DNA sequencing called nanopore sequencing. It's a pretty new technology. It's like the sequencer is smaller than your iPhone. You plug it into your computer. That was actually developed by people who were

trying to understand the origin of life because the fundamental way that it works is that DNA gets run through a little poor. And that was something that people were thinking about when they were thinking well, okay, when you have these proto-cells, they're going to need to get stuff in and out. these proto-cells, they're gonna need to get stuff in and out. We have very elaborate channels and various portals in our cells, but how would this all begin? It couldn't be a perfectly sealed bubble. Stuff is gonna get in and out.

And someone was like, well, maybe they just have a simple poor. Maybe you could get a genetic molecule in and out. And then he said, there's someone named David Deemer, University of California at Santa Cruz. he said, is someone named David Deemer, University of California at Santa Cruz, he said, wait a minute, like if I'm pulling DNA in and out through a poor, it's going to generate an electric current, a tiny, tiny current. And we might be able to measure that. And 30 years later, that's how we are, one of the tools we're using in the pandemic.

That's sick. What about viruses viruses then? A virus is alive? Again, it really depends on who you ask. I mean, I, one morning, I had a virologist email me and tell me, of course, viruses are not alive. And any expert will tell you that. And then that afternoon, another one said, well, of course, viruses are alive. And any expert will tell you that. So, you know, as a science writer, as a sort of a chronicler of science, it's kind of an awkward position to be in because people ask me questions as if there's some sort of clear-cut answers that I can refer to.

Who's science to go with. Yeah. Well, you know, I mean, science is, you know, debate and conflict is at the heart of science. There's nothing wrong with debates, you know, just as long as that they're, you know, meaningful ones. And this is a very meaningful one because it really forces us to think about, well, what are viruses in themselves?

How do they work? And, you know, what does it take for something to be alive? And, you know, what do we even mean when we're using these terms? The thing about viruses is that if you line them up next to a cell, they're very different. They're not just much smaller than a cell, but a cell is full of ATP. Like I mentioned, our fuel, there's just constant metabolism going on. Molecules are being built. Other ones are being torn apart. They're pulling in things from their environment. It's just this buzzing, high of activity. Look at a virus. just what scientists call it, virion, just a little thing floating around on its own.

It's just a little protein shell with some genes inside, just wrapped up nice and tight. That's it. It's not doing anything to keep itself going. What has to happen for a virus to replicate is that it has to fuse with a cell and it goes in and now the cell basically just starts treating the viruses genes like its own genes. It starts making those viral proteins, those viral proteins then take over the cell and make the

cell make new viruses which then leave the cell to go and affect other ones. viruses, which then leave the cell to go, in fact, other ones. So one of the architects of that NASA working definition of life was asked, well, if life is this chemically self-sustaining system, capable of Darwinian evolution, our viruses alive. And he said, you know, according to this definition, no, they don't make the cut. They can't sustain themselves. Other people say, well, you can't understand viruses without looking at them as being part of life. Viruses evolve. Just look at the variants that are making our lives miserable. The Delta variant didn't exist before October of last year.

It evolved from earlier forms of the virus. And so, and it follows all the same rules of evolution that animals are plants do. It's a classic evolving thing. So, so, so, so so people make a number of arguments about how viruses really are alive based on a number of different ways of looking at it. And it could be that there may actually be viruses that really blur the line and could make this even more interesting because there are certain viruses that they have genes for things that are not just for making new viruses. They have genes for building proteins. They have genes for things that are not just for making new viruses. They have genes for building proteins. They have genes for photosynthesis.

They just carry those genes along, and then once they get inside the cell, they basically tell the cell like, okay, here's what you're going to be doing now. You're going to be photosynthesizing in a different way. You're going to be capturing some like in turning that into molecules that are better for making viruses than for making more cells.

So let's get to work. And, you know, it's, so there are ways in which, you know, viruses themselves may make this question even harder to answer. I had a geneticist on a while ago talking about how we could engineer life to reach other space systems. And he was saying that one of the things Dr David Sinclair is talking about some of this stuff in his longevity research lab in Harvard, where you have particular types of viruses that are turned on and turned off with antibiotics or with particular types of bacteria, I think.

And then you could have, he had created this idea of a human who had Fathersynthetic skin and you'd need I think he worked out in order to survive you'd need about two tennis Courts worth of skin just laid out But he kind of imagined these green humans that wouldn't need food You wouldn't need to carry all the food with you because you can just have your your tennis court of wings stuck out to the sides and then you can just get all of your sunlight and you could exist like that. So yeah, it's um it's funny how all of this stuff comes together. So

it seems like there's quite a bit of chaos trying to work out what's going on here. Did you arrive or discover a better definition of life? I think the most radical proposal that I came across was from a philosopher named Carol Cleeland, the University of Colorado, who said, don't try to define life, definitions are pointless. You're wasting your time. And this really bothers a lot of scientists

because they think that definitions are just part of what they do. But in fact, you know, if you're not careful, you can get into sort of language traps. So for example, you think about water. Think about an alchemist trying to define water for you in 1500. And alchemists did. And what they would do is they would like list off some characteristics it had. Well, water is something that's transparent, something that's wet, something that dissolves certain things.

That's my definition of water. But then there were certain things that looked a lot like water, but we're dissolving other things like it's dissolving in kinds of metal. So were they water? Well, they would actually say like, oh, we're going to call this royal water. And then you'd have a problem when it got cold. And this liquid water froze and became something called ice. Is ice water?

Well, strictly speaking by the division, no. And so, you know, even Leonardo da Vinci writes in his journal about how frustrating it is that water just seems to be whatever you want it to be. It's just maddening. So the definitions did not help in understanding. What was necessary was a few more centuries of research and the invention of chemistry as a science. The way to talk about water is to talk about it in terms of, in a theory, a theory of atoms and elements of molecules. And then you can talk about molecules of two hydrogen atoms and one oxygen atom. And now you're really having a meaningful understanding of it. So, so what Carol Clulein argues is that what we really need is a theory of life, which we do not have yet. There are people working on it, but until we have that, if we just try, if

we waste time coming up with hundreds more definitions of life and yelling at each other about it, that's time we could have spent moving towards a real theory of life. Yeah, it's interesting thinking about that. I think it was you that said, it's like trying to describe red or effort. It's always described in terms of analogies, and then we have this sort of imperfect language, so you just end up playing lexical Brazilian Jiu-Jitsu in an effort to try and work out the closest approximation of the thing that you mean, and then as soon as you make an analogy,

the analogy is always slightly imperfect, because by definition, it isn't the thing you're talking about. It's a thing like the thing that you're talking about. And I'm glad I don't work in the theory of life business, frankly. Well, it's not for the faint of heart. That's for sure. And in the book, I actually write about some figures in history who really tried to go out there to life's edge, the title of the book. And that edge where you're trying to figure out what divides life from non-life,

and they've flamed out. They've made terrible mistakes, and they've gone down into obscurity for coming up with crazy ideas that really just were completely off base. We tend to think of science as just nothing but a series of triumphs and a linear progression from one deep insight to the next. That's not how science works. Science is full of branches in different directions, many of which just lead to complete

failure. Who is one of those failures. Well, I talked in the beginning of the book about a physicist named John Butler Burke, who he was at Cambridge, and he was working at this lab where in the early 1900s where the electron had just been discovered. Quantum physics was being uncovered for the first time in places like this lab. Radioactivity was another thing that was fascinating people there because it could tell you about how atoms worked

in this very strange way. And people were fascinated by the element radium, for example, and they would be dance performances where the dancers were dressed in radium clothing that glowed in the dark. And so in this context, Burke thought, well, maybe radioactivity is at the, maybe that's what life's about.

Maybe radioactivity is the organizing principle behind life. And so he ran an experiment where he took some sterilized beef broth and he dropped some radium into it and then let it stay there overnight. And then he went into the lab the next day and he saw that a layer had formed on top of the broth. And so he scooped some of that output in a slide, looked at it under

a microscope, and he convinced himself that he was seeing microbes, teeny tiny structures that grew and became more complex over time that seemed to divide. And these are much smaller than microbes, but they seemed to be alive to him or at least to be right on the border And so he named them radios after radio activity Published a paper about them wrote a book about them was just the the talk of the town I mean people were saying that Burke was important as Darwin and this glory lasted for maybe a year Until some other scientists reran the experiments

and showed that it was all a fluke from bad chemistry. You know, if he used distilled water, this just didn't happen. And that was it. And he, for the rest of his life, insisted that he had been right and that radiobs really were there at that life's edge. And nobody knows who Burke is now. In a way, he was a real pioneer. He actually used the term artificial life for the first time for what he had done. trying to make life in a lab, he was trying to do it. But

we don't remember him because he was playing this very, very dangerous game. Dangerous state of job being a scientist. Life's edge, the search for what it means to be alive will be linked in the show notes below. If people want to keep up to date with what you do, where should they go? My website is Karlzimmer.com and I'm Karlzimmer on Twitter. I love it. Thanks, Karl. Thank you. you