บทถอดความฉบับเต็มของ How Mars Could Split Humanity Into Two Species - Prof. Scott Solomon - #69

had my thoughts and opinions about it, but I wanted to dive into the science, meet the people who are actively working on trying to answer those questions and then share those stories with my readers. Yeah. And you actually also wrote a book about that specific topic, right? Whether humans are are actually evolving. And it's a different episode and it's an super long Well you could wrote a book ab write a book about it. You did in fact write a book about it. Yeah. Just to to set the ground, to set the stage there. Are we in fact still evolving even if we don't move to another planet? Yeah. Spoiler alert for for so the first book was called Future Humans, right? It came out ten years ago now. so I guess there's been enough time for people that are interested to get their hands on it. But yeah, I I very clearly make the argument that or I should say I I make the argument that I think it's clear that humans are still evolving. and there's a bunch of evidence to try to to support that conclusion. And that's really the bulk of the book is trying to to sort of show the ways that we know that humans are still evolving today. the the slightly longer, I won't go too too long on this, but the slightly longer answer is like we're we're evolving, but the nature of our evolution, the ways that we're evolving today, not surprisingly, I think, have changed a lot from how our ancestors evolved. But evolution is not something you can just switch off, right? Like any species is gonna always be evolving. Yeah, no, that's that that's true. And what fascinated me w as I was reading the book is that we often think when we talk about evolution as this very slow, tedious process that takes millions of years and goes goes, yeah, it's inc very incremental. However, given the right circumstances, it can actually go pretty fast. And I I want to get into that. And I think if we talk about how living in space will change our bodies and minds, I think it would make sense from a chronological perspective to start at the beginning because we have to get there, right? And of course, as some people may know, there's different windows when we could go to Mars. I think in the best case scenario, it only only takes eight months to get there. if we miss our window of opportunity, it can take up to two, almost three years if we're not careful. But in the most positive scenario with the current technology, it will take us eight months to get there. So what does that do? To our human bodies and what kind of challenges will we face on our way to Mars? Yeah, there's actually a lot to talk about, just in that simple question, because yes, you're right. The two planets being kind of on different orbits around the sun, right? Earth being closer and Mars being a little a little farther away from the sun, that means that they are sometimes closer together and sometimes farther apart. So if we're on the path, hopefully the shortest Possible path from Earth to Mars, you're still talking about, yeah, something like eight months of travel time. So, you know, people have spent more than eight months in space. So on the one hand, that might not seem like something so radically different from what some humans have experienced, right? you know, people have spent about a year on the International Space Station. there was the the NASA twins study where Scott Kelly and his Russian counterpart spent about a year on the International Space Station while Scott Kelly's twin brother, Mark Kelly, was back on Earth. And there's some really interesting results from that study that I describe in the book. But yeah, the record actually for the most amount of time that any one person has spent continuously in space is is a little longer than a year. and so you know, I I'm not sure I remember the exact number of days. it's something like like four hundred and thirty-seven days or something like that. So, you know, a little shy of a year and a half. so part of the answer is like, well, okay, we can look at what those people experienced when they were in space for that amount of time. And we know that they start to become physically weaker, right? When you're not having to fight against gravity. Just to stand up and and move around, your muscles weaken, and some muscles more than others. So especially the muscles of the lower lower body, the legs, your back, your your core muscles that are normally just engaged in keeping you upright, they're gonna weaken. And also the bones that are supporting those muscles, they also will become actually more brittle. We they'll they'll become weaker as well because bone is. always responding to what muscle is doing. so, you know, those are some of the challenges. But there's another thing that is is important to talk about, which is radiation. And we know that you know, there's radiation out in space. Some of it's coming from the sun. Some of it is coming from other galaxies, what we call galactic cosmic radiation. And here on Earth, we are Not completely, but largely protected from a lot of that space radiation by two things. One is Earth's atmosphere, and the other thing is Earth's magnetic field or magnetosphere. Both of those things help to make you know the radiation exposure on the surface of Earth much, much lower than than out in space. So you know, the the ways that we have studied that in the past involve looking at People on space stations like the International Space Station and trying to understand how that radiation is affecting them. And we've seen things like Scott Kelly in that year in space, he had some changes to his DNA, right? So he actually had mutations that were caused by being exposed to that radiation. So we know it, it we we know it plays a role. But here's the really important thing: the International Space Station's close enough to Earth that it's, even though it's above the atmosphere, it's inside or within the magnetic field. So they're not actually, the people on the International Space

Station are not actually exposed to as much radiation as a person traveling further. So going to Mars means you're going to be exposed to substantially more radiation on the journey there. And the you know bottom line here is we've never been able to study the effects of of that type of radiation for that amount of time on a person. I describe in the book ways in which researchers are trying to simulate it using, for example, a particle accelerator that can create simulated galactic cosmic radiation and then expose rats to that radiation. and so we're getting some idea of some of the effects. There's some you know suggestions that the the brain is actually affected by that. There's some cognitive effects where those rats are a little bit slower in their response times after being exposed to that simulated. Galactic cosmic radiation. But we won't really know until somebody actually goes and and does it. Yeah, and this is what's so interesting to me, right? When we're talking about space exploration and specifically going to Mars, it's often about the technology. What kind of rocket do we have to build? And of course people take into consideration, you hear you have to go through the Van Allen radiation belts, et cetera, and we have to shield ourselves from the radiation once we arrive on on Mars. But often the discussions are mostly about the technology and and not so much focused about the people who are actually going to have to live there, which is why it's so important to dive deep into the science. And I just want to say also, I was I had surgery back in January, ACL surgery, and I had to walk on crutches for two months. And it was terrifying how fast my my right leg, the muscle, it was gone. It was completely deteriorated. My knee was the thickest part of my entire leg. And it just looked like a stick. And luckily when I started Doing training and physical therapy, it came back to normal. But just in those two months, not putting any pressure on the leg, like my muscles just disintegrated. And it makes sense, right? From a evolutionary perspective, maintaining muscle costs a lot of energy. It costs a lot of calories. So if the body notices, right, hey, this muscle isn't being used as much. We will just delete it because that will save us calories and therefore increase our likelihood of surviving. However, our our evolutionary biology yeah didn't really keep space travel in mind when designing that system. No, that was not ever a consideration in the three and a half billion years of evolution of life on Earth. that's that which is an important point, right? Like I try to really emphasize that. We are well adapted to life on this planet, right? With with all of the things that come with it. Some things have changed on in the environment over time, the climate and temperature and things like that. But gravity is one thing that has not changed. So we are well adapted to 1G, Earth's Earth's gravity. And actually, what you point out is really insightful because you know, one of the ways that researchers try to study the effects of exposure to to lower gravity for long amounts of time is by having people just lay in bed. So bed rest studies where they're they're not it's not quite the same as you know what you were experiencing with you know being on on crutches and not being able to use your leg. But it's the same idea, right? If you just don't engage those muscles at all for a long amount of time, they will start to atrophy, they will start to weaken. Yeah. they had to cancel the study, right? Because the the the patients were showing too much deterioration in such a short amount of time, they had to cut it short. In the very first ever. That's right. So one of the stories I share, which was just to me like this i it well, was actually kind of a remarkable coincidence because I happened to meet this this person, this amazing woman who turned out to be one of the people involved in the first ever NASA bed rest study where they were trying to look at okay, what's gonna happen when we send people to the moon because nobody had ever spent that amount of time in microgravity before. And they planned to do this for I forget what I think maybe four or six weeks, something like that was the initial plan. And they cut it off after two weeks because they were concerned that it was unethical to continue because the the deterioration was so rapid. And so yeah, that put an upper limit on how long those moon missions could be back in back in the Apollo days. Yeah, that's it's so scary to to think about. And you mentioned radiation there and and the study that was performed on rats, which is kind of simulates what we might encounter when we go through those vanillan radiation belts. But what what were some of the effects that were seen in those rats that were exposed to this type of radiation? Yeah, so there's a whole bunch of studies that that kind of d are are doing various types of of experiments to try to look at these effects. When I was visiting, and this is a facility, a NASA facility that is part of Brookhaven National Lab in in New York and and it's basically taking advantage of the fact that they have a particle accelerator. Well, they have several particle accelerators at Brookhaven, but but one in particular where they've created kind of an offshoot that goes towards this facility that NASA runs. and that's the NASA Space Radiation Lab. So basically they can take an element and zip it around at very high speeds around this giant loop, right, and then point it at a target. And that target could be, for example, the these rats. And so that is similar to the way that there are you know, elements up in space floating around. You've got, you know, little iron atoms that are zipping at you know, incredibly high speeds through space. And if one of them happens to pass through your body when you're up there, it's like a little microscopic bullet. Like you it is physically damaging. the the

whatever it is impacting in your body and it passes right through any kind of material because it's it's so small and going at such high speed. So this is the risk. So what are they actually studying? Well when I was visiting the researchers there were looking at rats, as I said, and what they were doing is exposing these rats every day to just a s a a small amount, meaning like a a short duration of this simulated galactic cosmic radiation. And then asking those rats to perform a task. And by asking them, what I mean is they are basically s giving they're they've been trained to I forget exactly how it works, but it's something like it, you know, you see a flash of light or something like that, and then you know they know that when they see that, they press a little lever and they get a food reward. They get a piece of cheese or whatever it is, or a pellet or something. And and what they're measuring is the amount of time it takes them to see the the light and react and press the the button. And so what they have found is that after exposure for many, many days and and and weeks to this simulated galactic cosmic radiation, the rats become slower in their response time. And this is interesting because this is the same type of study that is done with with humans who are doing stressful types of things. So actually I don't describe this in the book, but because I ran out of space basically. But the the manuscript I initially submitted to my editor was like twice as long as I had had you know initially promised. So we had to cut some things. But I did get to actually go and watch some astronauts training in the Neutral Buoyancy Lab. This is this giant swimming pool inside of which they have like a mock-up of the International Space Station and they can do all different type types of things. And the day that I visited they were doing a simulated moon landing and moon mission. And so these astronauts were down on the bottom of the pool in spacesuits that are weighted down to simulate the effect of being in the, you know, moon's gravity. And they were doing a bunch of different things. But one of the things they did was basically the same thing the rats do. They weren't getting a food reward, but they were basically they were able to, because they were communicating back and forth with the, you know, kind of mission control. And they would a mission control would play a a tone, like a sound. And every time they heard that sound, they were supposed to do something, either say something or raise their hand, or I forgot exactly what it was, but they're supposed to react in some way. And so the question is after you know, doing this stressful, physically demanding thing for several hours they were in there, is your response time slower? So this is a standard way that researchers look at the effect of any sort of physically or psychologically demanding or stressful. Activity. So the rats, by being just exposed to the simulated galactic cosmic radiation, they appear to be slower in their response time. So that suggests perhaps that people exposed to that type of space radiation might be impaired in some way. So think about the impact of a long mission to Mars. You've now arrived and now you have to do all these important tasks. You've landed, you've got to set up your habitat, right? We don't want those people to be impaired or or in any way impeded in their ability to do all those important things. so it's really important to understand these effects. Yeah, it seems like no small small feat. And you wanna be at your your best capabilities when undergoing something that is so dangerous to to everyone involved. And the the radio the last thing I wanna touch on before we move on to actually living on on Mars. is regarding the radiation. I believe one of the ways they're l kind of looking at preventing radiation from coming into the ship as much. You can't prevent it entirely, is by insulating the ship with water, because apparently water is a pretty good insulation against some of this radiation. Water's also kind of heavy to to bring into space, so I I think they wanna find a good balance between How much do we need to actually stop the radiation and and not not make it so heavy that we can get the ship off the ground or or or to use too much fuel. Did you hear hear about that as well? And and why do you why is water such a good method to prevent this or supposedly? Yeah, so right. So so you're right. So there's different kinds of materials that you can try to use to just block the radiation. And and it's simply put, the more matter, the more material you have. the more you block it. But here's the thing. you know, there are certain types of materials that if this kind of radiation passes through it, it actually can make it worse because what happens is it interacts with the material. And then you have basically almost like shrapnel. Let's it's sort of like, you know, like atomic shrapnel. So it's basically now you've you've interacted with that material, and now you've got some of that material that's kind of going now at high speed. So So you don't want that. So there's certain materials that are actually harmful to try to use to block. water is one of the better ones because you don't have to worry as much about it's just, hydrogen and oxygen. So you're not going to have this secondary effects as much. But yeah, you pointed out the biggest issue, which is weight. And so you have this real trade-off between sure, you can, in theory, have a a rocket that is fully, you know, protected so that nobody inside is going to be exposed to any radiation. But you'll never be able to get that rocket to lift off because it would take so much fuel that the rocket would have to be enormous. And then the bigger it gets, the more fuel, and you get this downward spiral. So one of the ways that people have thought about trying to to deal with that trade-off is rather than having the entire rocket be protected, you

try to have certain areas within the rocket that are reasonably protected. So maybe the places where the astronauts are sleeping and spending, you know, half or a third of their time, however long it is, they're sleeping on a daily basis inside of these almost like a bunker, like a little shelter inside. And so then you don't need as much material, so it doesn't weigh quite as much. So that's one way of reducing it doesn't it doesn't completely stop the radiation, but it it at least means that during part of the the the day or night or whatever, there is no day and night if you're at just flying through space, but you know what I mean. When they're sleeping, they would not be exposed to as much. The other thing you can do, and this is actually gets at one of the other sources of radiation, because I said the sun and then galactic cosmic rays. But the sun is actually, you know, normally just sort of putting out some amount of radiation, but then it occasionally has these bursts, these solar flares, right? Right. Where it'll put out a lot more all of a sudden. And that's quite dangerous. So so that's another concern. but the good news is that we can monitor it and know when it's coming and it takes some amount of time to reach, people out in space. So if you are aware that there has been a solar flare, you have some amount of time, whether it's minutes or hours, depending on how far away you are, to respond. So that allows you to then go into a more protected space, a sort of radiation shelter within the the spacecraft. And so that is another possibility is that you just kind of deal mainly with these hopefully rare solar flares. and then you just try to generally minimize your exposure to the more constant galactic cosmic radiation. But it's really hard to stop it altogether. Yeah, just have to follow the weather app, but That's right. The space weather. Yeah, it's true. Yeah. That's funny. But okay, so there's l a lot lots more to be said about how dangerous the journey is and some of the challenges, but I think one of the the most interesting problems arise from actually being on the planet itself, on Mars itself. Mars has around three-eighths of Earth's gravity, about a third, three-eighths. I I believe those numbers are more or less correct. Anyway, it's a much it's a lot less than Earth. It's a lot more than zero, but it's it's it's it's pretty, pretty light still. and I think this ties into one of my favorite parts of the book is reproduction, right? So if we're not talking about the situation where we just go to Mars and then do some science there and then head back, but people are actually talking about building a permanent settlement on Mars and we haven't even discussed this yet. But one of the reasons why we would even want to do it in the first place is of course it's pretty cool to go to a different planet, but also we're That's the argument always. We're putting all of our eggs in one basket, right? if one day an asteroid hit hits Earth, like it's not a question whether that will happen, it's a question of when, and maybe we can deflect it. But there's also some other dangers, nuclear warfare, another pandemic. There's a whole myriad of problems that could arise, climate change, all all of that. So the argument is we need a permanent permanent establishment on Mars, and we need people to live there permanently, essentially, have a second civilization on Mars. Okay, that sounds pretty cool. it sounds like like a science fiction movie I I'd watch. However, one of the first things you want to have in place if you build a civilization is reproduction. You wanna keep the population not only alive but Alive over decades and centuries. And one of the things you mentioned in the book is we are not really sure what will happen when we try to reproduce in space, Mars in this example. And that ties into the lower gravity problem. Can you maybe explain? What some of those challenges are and specifically regarding the the female body as well and the forces that are involved with giving birth. Yeah, this was to me when I was, researching this topic was was in some ways the most surprising thing that we don't know. Right? We've done all this research on people in space for literally 65 years. It's been 65 years since the first person. Yuri Gagarin, you flew to space. And since that time, we've been pretty intensively studying how does space affect the human body. And yet there is so little research on any aspects of reproduction in space. and to be fair, like this just hasn't been the focus of, you know, governmental space agencies like NASA or ESA or the, you know, Russian space agency or the Japanese w whatever. Like it's it just hasn't been the priority because that's not the mission. of those agencies, right? The mission of those agencies up until now at least has been get people to where they're going and get them back safely. So okay, fine. But yeah, as you point out, if our goals in the future are to be living in space and not just visiting, then we need to know. And so you know, there's a lot of questions here. And and and I try to highlight some of the possibilities for things that could really be what I would call showstoppers, things that if this is the case, then our whole idea of being able to live on another planet might just not work. and we need to know that if before we we get too far down that path. or it could be that it's possible, but you need to do things like have, you know, pregnant women go and be in a place with simulated gravity during some critical part of their pregnancy. or perhaps during childbirth, or maybe children need to grow up in an environment that has some minimal amount of gravity. And so we could figure that out, but we are so early in in the research towards being able to have any idea what would be necessary. But yeah, one of the scenarios that I explore in the book is the idea that, you know, as we talked about, being in a lower gravity

environment causes our bones to become weaker. Well Any kind of weakening of the bones sets up a scenario where a woman who is pregnant and now carrying all this extra weight might really be at in increased risk of having a bone fracture, having a broken bone. And you know, one of the things that's concerning here is that already during pregnancy, some of a woman's calcium from her bones is actually. transferred to the developing baby. So she's already losing a bit of bone density just by the fact that she is pregnant and growing a a human. And so now take being in a lower gravity environment, which as far as we know, tends to always cause bones to weaken. Now you have a really concerning scenario where it could actually be quite dangerous to that woman to, you know, be pregnant. To then experience childbirth and all of the forces on her body that she's going to be experiencing by giving birth. unfortunately, broken broken bones during childbirth are a a a thing that sometimes do happen to women giving birth here on earth. and when that does happen, it's often either the hip or part of the pelvis that is fractured. And that can be a life-threatening emergency. So If you imagine now all women having weaker bones, that becomes a much more concerning possibility. that could threaten the lives of of women giving birth. That in turn can threaten the lives of those children. so this is something that is, I think, a real possibility that we need to to better understand. And it's not that there's no way of of dealing with that, right? I mean, there are, like I said, you know. The possibility maybe more of a sci-fi idea, but of having a a s a simulated gravity type of environment. There have been a lot of proposals for how to do that. Nobody's actually come up with with anything that can do it yet. But we we know the kind of idea, like like a lot of rotation, right? A big kind of spinning space habitat kind of thing. you know, maybe that's what we need to do. Or maybe all of the berths are done by C-section. And that reduces some of the risk to to the mother, doesn't eliminate risk, but but it, reduces the risk of the, you know, fractures that we were talking about being a a problem. So and then, you know, as I I because you've read the book, I I get into some of the like, well, if if that happens, then it could lead to other kind of downstream consequences. So it leads us down this sort of rabbit hole of of, well, what if this and then what if that? I was going to ask you because that may introduce some other problems as well. Because I d there's a term for this that I now draw a blank on. But basically, if all of our babies are born through C section, that could eventually mean that You c you can probably explain it better than I do, but basically there's no selection anymore for the width that needs to be able to give birth in the first place. So we could get a scenario where women are literally biologically wouldn't even have enough room to give birth

anymore, which s would mean that we co become completely dependent on C sections going forward, which would kind of be terrifying thought as well. Yeah, and and so the idea is like, throughout human evolution, one of the the things that has changed is the the size of the human head. If you look back at the you know early human ancestors, they had much smaller brains and so smaller heads. So as our heads got larger, the birth canal had to expand as well. And so you can actually see these corresponding changes in the size of the pelvis and specifically the the you know diameter, the the width of the birth canal. and so that has put a constraint on how big the human head could get. Like there's an upper limit to how large our heads were able to get, because no matter what, like, yes, we have these big brains and they're great, but like you gotta fit through the birth canal. And so if now you imagine a scenario where all of the births are done by C-section, 100% of them. Then the head doesn't have to fit through the birth canal anymore. You've eliminated that constraint. And that then sets up a scenario where two things can happen. One is that the head can just keep getting bigger. That's an interesting thought. you know, what does that do for intelligence? Intelligence and brain size are not quite like as simply connected as as you might as you might think, but you know, there is at least a correlation there. but then the other thing, which is what you were alluding to, is that we might become completely dependent on C-sections. The only way that a child could be born is through a C-section. That's a scary thing because if for some reason you can't perform that C-section, then it becomes definitely a life-threatening thing for both mother and child. and you know, why would you not be able to perform a C-section? Well, there's a lot of scenarios you could you could think through, right? I mean, it's a surgical procedure that requires expertise, of course, it requires the right type of equipment, the right type of environment. you want it to be a sterile environment to avoid infections and all those kinds of things. So being born early happens a lot, right? There's many babies who exactly who yeah. Yeah. So that's and this is this is so fascinating to me. All of these things, like no nobody's ever really thought about it or at least like w went into the deep science and You just never heard these things when we're thinking about colonizing Mars, but it's so, so important. So let's assume we are able to reproduce in Earth. Women are able to give birth, whether through C-section or in in a regular way. So what do we currently know about living beings? We d we don't have any science. or or evidence what happens to to humans when they are born in in low gravity. But do we have any examples on science that was performed on animals, for example? What happens to them and also their earlier weeks, months of of development? What does it do to our development when we're born in in low er low gravity rather? Yeah. So there have been some studies trying to look at at How do organisms reproduce and grow and develop in space? There have been some studies with fish, with some rodents, with other animals like amphibians, frogs, and things like that, sea urchins. So here's the thing: there's so few of them that we can't actually draw any general conclusions. Some of those studies seem to suggest that things might be okay. So, for example, one of the earliest studies was done with some fish. and these fish went to space, mated, laid eggs, the eggs developed, the eggs hatched, the baby fish were born, the fish are swimming around, they seem to be okay. that seemed to suggest, maybe it's maybe it's all gonna work out fine. But of course, you know, humans are not fish. And there's a lot of ways in which their reproductive biology is fundamentally different than ours. The most obvious maybe being that their eggs develop outside of the body. the second one being they're swimming in water. So they have this kind of buoyancy that is is yeah, gravity still affects them, but you know, maybe somehow being in a being in water kind of you know mitigates some of the challenges that that we would experience. So it's not the best comparison. the closest you would want would be something with at least a mammal. So that's where the rodent studies are a little bit more informative. there was a study with some pregnant rats that went to space while they were already pregnant when they flew to space in the equivalent of the third trimester of their pregnancy. And then they were brought back to Earth. And those that were allowed to kind of proceed with the entire pregnancy, I think there were five of them, of which four gave birth to seemingly normal you know, rat pups. but the fifth. had a problem with the very first pup that was trying to to pass through the birth canal. It got stuck, died, and that then resulted in the death of the other pups in that same litter. Now, why did it die? Why did it get stuck in the in the birth canal? That's where it's hard to say, right? So the researchers speculated that the mother may have been exhausted, very tired from having been in space and the stress associated with that. Maybe the her her muscles being weaker from being in space may have played a role in some way. but again, just one individual and one kind of, you know, birth. So it's really hard to draw general conclusions from that. We need a lot more research on this topic. Yeah. And also if they are I if if a if a child is born on Mars, we we we have no evidence what it would do to their entire development, whether that's right because of the lower gravity, whether they would even become as tall as they normally would, or maybe it would become even taller than they normally would. you also wrote wrote about that, right? Whether we would get smaller or taller and kind of it could could be either. Yeah, yeah. So so okay. So there are

a few things here. One is it's it's worth pointing out everything that we know about how space affects the human body has been research done on adults. We just don't know about how a child's body is affected by the conditions of space, both, lower gravity, higher radiation and and everything else. so we can speculate, you know, we can do research on animals. Like I said, we've done very little, but we know that an adult, a healthy adult, because almost all the people that go to space tend to be among the healthiest people that we that that we have. and so a healthy adult loses bone density at a rate of between 1.5% or two percent per month. So that's a lot. And so if that's happening to a healthy adult who already has a fully built skeleton. What happens to a child whose bones are still growing and developing? you know, I think there's it's reasonable to expect that they're going to have a an impact on their growth. but what that impact is, we we just don't yet know. So if you imagine that there's some kind of an impact, one possibility is that they don't grow as much or as well. So that's one way that you could get shorter people, right? They just aren't fully developing their, their, their bones. but one of the other things that I I look at in the book is the idea that, living on other planets is very, to me, reminiscent of living on islands, right? So I again this is me as an evolutionary biologist trying to think how can we apply what we know from life on Earth to life out in space. And I look at the solar system and I see a cluster of islands. That's just, you know, I I see the Galapagos basically is, you know, I can't help it. so if we think of ourselves as, you know, Darwin's finches on these islands, what what would become of future generations? Well, one thing that we know often happens to species living on islands is that they change size. And some get bigger, like the giant tortoises of the Galapagos Islands. but quite often they get smaller. We have lots of examples of tiny versions of animals that live on islands. And one reason that that tends to happen, we think, is that. On islands, often there are fewer resources available just by virtue of the fact that it's a an an island, they tend to be a bit smaller and sometimes resources are scarce. So if you're smaller, that means you need less food, water, everything. so there's an advantage, a survival advantage, if you need a just a little bit less than your neighbors, because then, you know, maybe you live a little longer and have more chances to pass on your your genes to the next generation. So, that's another scenario where over time, over generations actually, you could have smaller bodied humans in this, you know, island that we call, you know, Mars out in space. Yeah, it sounds like we may actually start to resemble those aliens we often depict in science fiction movies with j gigantic heads and and tiny, tiny bodies. Well, this is the funny thing, right? Because I I really try

to approach this topic very much as a scientist and trying to apply what do we know from from science and and how can we use our our knowledge to extrapolate to things that we don't yet know. But yeah, in some ways, what you eventually reach are these ideas that have been explored by authors of, you know, science fiction books and and movies over the years, right? The idea of of you know, thin kind of tall, thin, you know, big head. I I try to challenge some of those possibilities. I like we were just talking about, shorter rather than tall and thin might actually be a more accurate prediction from what we know about evolutionary biology and from space medicine. But yeah, you know, big heads is always kind of the way that aliens seem to be depicted in in all the movies. And so there's a plausible scenario from science for how you could actually have. individuals on Mars with bigger heads. Yeah. And you mentioned islands there. I I wanna dive a little deeper into the comparison with islands because like I mentioned in the beginning, we often think when we are talking about evolution as this thing that takes millions of years and this very slow process. But after reading your book, it is my understanding that given the right circumstances, evolution can be pretty Quick, actually. Why is that the case? That's right. So this is one of the things that we've really learned about how evolution works since Darwin's lifetime. You know, Charles Darwin used the word slow 144 times in The Origin of Species. He was really emphasizing this is a slow, gradual process. And for a long time, that's what we that's what we assumed. That's what we thought. Evolution had to be. And yes, it can be a slow gradual process. But we know that given the right circumstances, natural selection can operate very quickly. And we actually see this all the time. So, for example, if you are, you know, using antibiotics to treat an infection, right? Any of the bacteria that happen to have any ability to resist that antibiotic. Are rapidly being selected for and will proliferate very quickly. And we can see that happen within a matter of literally days. You know, so so that is an example of natural selection operating very rapidly. but we also know, and I was alluding to this at the very beginning of our conversation, that you know, evolution isn't just natural selection. There are other ways that species can evolve. And to make this point very clear, I think I have to define what I mean by evolution. And so if I can just pause for a moment and just be be very clear that when I say evolution, I mean any change over one generation to the next in any sort of heritable trait. So anything that you can pass on to your children, right, that is something that is heritable. And if that kind of heritable thing becomes either more common or less common, Even over one generation, we call that evolutionary change. And that's different from how people I think often think about a species changing or a new species coming into existence or going extinct. That's evolution too. But it starts with just these tiny tweaks in in how common things are from one generation to the next. And once you understand that, you start to realize there's a lot of other ways to make it happen. Even just one individual moving from one place to another and bringing their genes, passing those genes on. That's evolutionary change. So the movement of individuals is an important mechanism of evolution. And then if you take a small number of individuals from one place and plop them down somewhere else, as happens all the time when an island gets colonized by, the the founders of a new population, right? The finches of Galapagos came from mainland South America. It was, probably just a few individuals that flew or got blown in a storm or however they made their way there. And now you have a small number of individuals taken from a larger source population. Those founding individuals are not going to be representative of the entire population that they came from, meaning they're not going to have all the same traits in the same proportions, So some things by chance are going to be lost. Some traits that were present in that initial population won't be present in the individuals that made it to this island. And some things maybe that were rare just happened to be common among those few founders. And so now those become common in this island population. We call that the founder effect. It's actually a known phenomenon in evolutionary biology. And you can very quickly get pretty dramatic changes in a population just from that kind of sampling effect. So anyway, that's that's a little technical maybe, but it's it's I think an important thing to think through as we think about how could you get rapid change. in just a few generations of people living elsewhere, you know, anywhere beyond Earth, whether it's the moon or Mars or or or anywhere, that's an evolutionary change that we should expect to happen. Yeah. And w what's interesting is you you mention i in the book that there comes a point to which we call something an entirely different species. And I believe the definition that's often used is whether those two species cannot reproduce something where the offspring is also able to reproduce. Yes, that's right. Yeah. Yeah. So I I there's probably more elegant ways to to phrase that, but that's that's more or less how how I understand it. How likely is it that we would that if we have people permanently living on Mars, how much time I know this is we have to guess here, but How fast could this happen? Yeah. Well, so one of the things that I I try to point out in the book is that there's a lot of things that could influence how quickly that happens. So we're talking about how fast do you get a new species of human living on Mars? And you know, there are ways in which it could be a very, very long, slow process or might not ever happen. But there are actually some ways in

which it could happen quite rapidly. So it might be worthwhile just kind of i you know. Describing some of those. So, what I've argued and what I argue in the book is that we should expect those changes to accumulate over time because of the things we've been talking about. Natural selection, founder effects, all these things are gonna be happening. But if you have people constantly moving back and forth between Earth and Mars, right, then it actually slows down the the the rate at which people on these two planets become different from one another. They're gonna, they're gonna basically all be one gene pool if you've got people moving back and forth. If there aren't people moving back and forth, or if the people moving back and forth aren't interacting, well, let's be more clear, aren't exchanging genes, right? Aren't having children together, then you don't have one gene pool. You have two separate gene pools. And then all of those evolutionary changes can accumulate independently on each planet. And eventually over time, they become more and more different from one another. So the key there is how often are people from Earth and people from Mars getting together in some way and and you know, having children. and you know, one of the things that that I I point to is the possibility that that sort of separation, like preventing people from having babies together, people from different planets, might happen faster than you you might imagine. Because it might actually be quite dangerous for them to come together. and specifically here, I'm talking about the risk of spreading disease. and this is another thing that I think has been often overlooked in in many conversations about the idea of space settlement or or truly living on other planets. Because as soon as you have people actually being born and growing up on Mars, they're going to be not only building their skeletons, as we talked about, but they're gonna be building their immune systems. And their immune systems are going to grow up and develop and respond to only whatever bacteria and viruses and other things they're exposed to in their environment. And those are only going to be the things that we have brought with us from Earth, because as far as we know, there is no life on Mars. That might change, but but for now that that is that is the case that we We have not found any evidence for anything currently living on Mars. So we will bring stuff with us. We will bring, you know, all the the microbes in our microbiome. We'll bring others with us in, you know, plants that we're gonna grow to eat. And if we bring any animals with us, we can't help but bring microbes with us. But whatever we bring is still gonna be just a very tiny sliver, a tiny fraction of all of the microbes that are present here on on Earth. And that means that the immune systems of people that are Growing up on Mars are going to be very limited in their ability to fight off infectious disease. So if that person were a person from Mars whose immune system is only able to fight off Martian diseases now comes into contact with a person from Earth, they might be at a really high risk of getting quite sick from that exposure. So that means that it might really be dangerous for people from these two planets to come together and have kids together. So that could make it much, much faster for, you know, the evolutionary changes happening to people on Mars as well as on Earth, right? for those changes to accumulate separately to the point where we would now have to consider those to be two distinct species of humans. Yeah. Is there any any specific time frame, some something that happened on Earth that we can draw inspiration from, or is it too difficult to make an accurate comparison. Well, one of the things I do point to is the fact that we've had isolated human populations on Earth for, you know, many, many years. Think about people living on Pacific Islands who were isolated for, you know, at least hundreds of years. in some cases, it could be even thousands of years. and they certainly did not evolve into a new species of human, and nowhere, nowhere close to that. and so that seems to suggest that it could take quite a long time. But a few things I'll point out. One is that the environments on Earth, even on remote Pacific Islands, are not so different from the environments elsewhere on Earth, you know. certainly not compared to how different Mars is from Earth, right? you know, and so so so that's one factor. Another factor is actually There's a lot of evidence that suggests that even people on the most remote islands in the Pacific, like the Hawaiian Islands, they actually were still moving across vast stretches of ocean to trade goods and and and actually to exchange genes, as people tend to do when they interact with one another. And so even what looks like long periods of isolation in human history. We're not so isolated as as you might see for, people on on other planets. So, you know, that's a way of saying, you know, okay, yes, you can have isolation geographically, physically, separation without actually getting speciation, even for, you know, hundreds and hundreds of years. But I still think that the conditions on Mars being so different from the conditions on Earth and the risk of spreading infectious disease could mean that in as few as I'll say 10 generations, you might see pretty dramatic changes because if those people are not able to come together and exchange genes, you combine that with the strong selection pressure, meaning natural selection will be strongly favoring any individual traits. genes that help people out on Mars and give them a little bit of a survival advantage, that is going to cause pretty rapid evolutionary change in people living on Mars compared with people living on Earth. So I I've argued that it could be as few as 10 generations, which, you know, that sounds like a long time, but in an evolutionary, you know, scale

timeframe, that's like nothing. that I I think you could see you know, I I don't know if it would be speciation, but you'd see pretty dramatic evolutionary change in in only about ten human generations. We'll go back to the conversation in just a second, but first I have an important announcement to make. If you've made it this far, I'm going to assume that you're enjoying the show. If you want to support the show, you can do so by leaving a like or a comment if you're watching on YouTube, or by rating the episode if you're listening on Spotify or Apple Podcasts. However, the single biggest thing you can do to support the show is by sharing it with someone you think might enjoy this episode. This could be a friend, it could be a family member, it could be a colleague. It doesn't really matter. If everyone who's currently listening to this episode would share it with just one person, the show would blow up in no time. Which also means that I could go full time. That means more episodes, it means better episodes, and it also means a happy host. So Please consider sharing the episode. It really helps me a lot. And I thank you. Now let's get back to talking. Yeah. And I think this also ties into one of the really important things when we're thinking about colonizing another planet and settling there, having a different civilization. Is let's say we figure out a way to let's say SpaceX continues to develop and or our rockets continue to improve and it would be possible to have a pretty continuous infrastructure to go back and forth to to Mars. So for Earthlings, for us, it will be pretty easy to go to Mars, pretty easy, relatively easy to go to Mars. And then perhaps we'll we'll stay a few months or or a year or however long is necessary in order to hop back when the planets are lined up perfectly again. And then we'll have some adjusting to do. But people have been in space for a long time. So maybe we'll know we'll have to do some adjusting to the to the gravity again and maybe we'll have to do some c quarantine. But I think it's likely to assume that for for the people that were born on Earth, have lived their entire lives on Earth, if they are able to make a trip, go back They might be able to to just survive. the human body is pretty resilient. However, if you are a Martian and you were born on Mars, and we don't know what that looks like, but I think it's it's pretty difficult for the let's even forget about the the potential diseases that you could be exposed to. But just the sheer force of the gravity on your your your your underdeveloped bones and and your muscles. I don't know if you've ever watched Dragon Ball Z, but they you they train in gravity chambers that are like 10x to gravity to to become stronger. But regular people that are not anime figures would get crushed if they walk in in three times the gravity. So I'm just curious to hear your thoughts on that. Yeah, I think so w y you're bringing up an important point, which is that it tends to be easier to go from a higher to a lower gravity. People tend to be able to adjust to that difference more easily than the reverse. And this is true when you see people, astronauts coming back from a long mission to the International Space Station and they come back to Earth, it takes them quite a long time to adjust to the increased gravity. And these are people that, you know, born and raised in Earth's gravity, but just being away for as you know little as six months or a year. it's quite challenging for them to come back. And now imagine somebody who was born and raised in a lower gravity environment and and maybe has a a you know a a weaker skeleton and and weaker muscles now coming and literally weighing three times as much as what they weighed on their home planet of Mars. that might be, you know, too much. That might be really, really difficult for them to to physically handle. And that doesn't even include the high G forces of entering Earth's atmosphere, right? Which is you know, hard enough for even the the the you know astronauts that are trained for this and in you know peak physical condition and they and they find it to be a very intense experience. So yeah, I think that's a real, real challenge that people have maybe not fully explored and appreciated. Yeah, and and what about the cardiovascular system, right? The heart, everything that was grown in such an environment, I can't even imagine what it would do to when they experience one G. It's it's pretty likely. I'm I'm not an expert, of course, but based on everything I've read so far, and my understanding is that it's pretty unlikely that if we do get a second civilization on Mars that they would ever be able to visit Earth. Yeah, and that brings up some really important ethical questions, I think. And I and I try to get at these in the book is that, it's one thing for an adult to to understand risks and agree to take them on. going to space, of course, we all understand is a risky thing. An individual adult can decide if they're comfortable with taking on those risks or not. Bringing a child into a dangerous scenario is a very different situation. And and they obviously can't consent to those risks. And then if you add on to that the possibility that that person might be stranded there, they might not be able to come back to the planet of their ancestors, right? I mean, that I think is a is a real ethical issue that we need to fully understand this before you know it would be responsible to have people being actually born on on another world and and having to deal with those scenarios. Yeah, no, I I completely agree. And there's there's And there's also w we we haven't touched on a lot of things and there won't be enough time to discuss everything, the diff the myriad of different problems that also arise when we are settling on Mars. One thing I do hope to touch on is the the f obviously we ha we need to have some sort of form of shelter in because there's higher

radiation on Mars because it does not have a magnetosphere and also a pretty thin atmosphere as well. So radiation is a problem. We would need to find a solution for that as well. but also we n would need to be self sustaining. And it was your estimation that also people are very likely to introduce a well a vegan diet essentially because it would just be too costly to raise cows or or other other animals on Mars because they would be competing for our resources. Yeah. I mean we have to eat something and we can't rely on you know sending food up the way that astronauts currently do on the International Space Station. They get resupplied with food constantly, not constantly, but you know regularly. And so yeah, what are we going to to produce? What's our agriculture going to be? and you know, your basic options are you can grow and eat plants. you can grow and eat animals, some combination of those. but the animals have to eat something. And the animals are most likely going to eat plants. So if the animals are eating plants, then basically you need even more plants. So this is a very inefficient way of getting, you know, calories and and nutrients. it's a much more efficient thing for us to just eat those plants. And so that's one of the reasons why I argue a vegan diet is the most logical choice for for a space settlement. you know, the other thing is, yeah, we're competing with those animals then for not only food, but other things like that we don't normally think about, like air, right? We have to produce an environment that we can live in. This is gonna be a pressurized environment that has oxygen for us to breathe. And that's going to be something we're constantly having to resupply. And so if you are bringing other animals that are also taking in oxygen and giving off carbon dioxide, then you have to make that much more of it. So it would make a lot more sense, I think, for us to just focus on growing and eating plants. So I say this as a carnivore myself. I I I I eat meat. I enjoy meat, you know, but but I think just thinking through the logic of living in this kind of you know, resource scarce environment, that's the only thing that makes sense to me. Yeah. And w what about lep grown meat? I did an episode about lep grown meat in the in the past and currently it's not really economically viable. And I don't think many people actually it's an interesting product because a lot of the people who do eat meat eat meat would just prefer a steak. And a lot of the people who are vegetarians or vegans probably also, yeah, probably wouldn't want that either. So it's a difficult product, but I assume like maybe if we if we figure that out, we can already create that. And it would only need a f a bunch of cells, which would be easier to carry. Have people thought about that? Yeah, no, this a good point. And that is a possibility. So you could produce you know, lab grown meat. So put meat in quotation marks here. and and and have that source of of nutrients. and you know, that is a possibility. I think you have to ask the question of why why? Why are we doing this? Are we doing it for health reasons? I mean, it's it's perfectly feasible to have a healthy vegan diet. And there are people that obviously do that here on on earth that are vegan and are and are quite healthy. So it's not necessary for a human to eat meat in order to be healthy. the question becomes, you know, are you doing it because you just enjoy meat or there's a cultural aspect to it, you know? Here in the States we like to have a a turkey on Thanksgiving dinner. And so, you know, there's a cultural tradition associated with that and there's plenty of other examples of cultural significance of certain types of meat for various reasons. so maybe that would be something, but I think over time, over generations, we might move away from that. And people will establish new traditions. There will be new cultures developing on Mars. And it seems like, you know, going through this elaborate process of creating something that is kind of meant to replicate meat, something that perhaps people would have no connection to, yeah, my great great great grandparents used to eat animal flesh, but now we're just growing it in a lab. Why are we doing that? I just feel like that kind of thing would eventually sort of fade away and people would just embrace eating, you know, the much more natural things that they can can grow themselves. So that that's just my own take on it. I will add one more quick possibility though, and that is other types of animal protein, insects. So Insects are a a a healthy source of animal protein and they require a lot less space and a lot less resources compared to, say, chickens or or pigs or or cows. and so that's a, you know, that's a real possibility if people feel like they need to have some kind of animal protein in their space settlements, bringing crickets or mealworms or other kinds of edible insects, which are actually consumed. by the majority of people on Earth. forget the exact numbers, but it's something like seventy percent of you know, people living on Earth are in cultures where eating some kind of insect is traditionally part of the diet. So yeah, I think that's a a a possibility worth considering. Yeah, yeah. I it's always strange to to think, but it's when you're from from the West, from the US or or Europe, but large parts of Asia. they consume it in in India and Africa as well. So Yeah, most of the world actually. We're the weird ones in the in as you said, in Europe and North America that don't think of insects as as a normal kind of food. But I this one of the things I love doing when I travel is trying new foods. And I've often encountered very delicious insects in in different you know, different regions. And so If you grow up with that being a normal part of the diet, nobody thinks twice about it. And so I think, that could be a possibility for for Martians of the future. Yeah, it's a lot

less heavy than a cow, that's for sure. yeah, be before before we wrap it up today, you mentioned ethics there. I think that's very important when we're talking about Mars. d there's also a a section near the end of the book is genetic modification, obviously. We can try and genetic genetically modify our own bodies to make us more resilient to radiation, for example, or to deal with some of the other challenges that Mars will throw at us. Are there any like significant techniques that are already in place but are currently not actually being used because we would deem those unethical or eugenics or or something like that? Yeah, this is a whole other, yeah, I think, important topic that we probably don't have time to to properly dive into. But yeah, the idea of making modifications to the human body, whether it's genetic modifications or technological modifications, embedding certain technologies. You know, I talk about like brain computer interfaces and things like that in the book. But I think the the genetic one is is is one that is representative and so it's a good one to To just talk about briefly. So we do have the technology now to make precise, deliberate edits to the genomes of any organisms, including humans. And we are already starting to use some of that technology to do things like treat certain types of heritable diseases, like sickle cell disease, for example. So that is a technology that already is being implemented. But here's the difference. What we're doing currently. Is making changes to an individual person's DNA that helps to cure that particular condition. What we're not doing yet is changing those genes in a way that is heritable, that would be passed on from the person whose genes are changed to that person's children. Once you start doing that, if you start doing that, then it does mean that we are changing our evolutionary. Future. Like that, that is, manipulating future generations' genomes, in ways that we may understand and we may not fully understand all of the implications and consequences of doing that. So you mentioned eugenics, and I think we have to address that here because, you know, that is basically what we're talking about, trying to make changes to quote unquote improve future generations. That was the very idea. Of eugenics when it was first proposed by Francis Galton in the 19th century, improvement of future generations of humans. And then, of course, that idea was very much distorted, misused, misconstrued, perverted, however you want to describe it, by all sorts of different people, starting in the US and and eventually in Nazi Germany. And so we know that there is a a long, dark, disturbing history of people trying to make changes to future generations of humans in ways that I think we can all agree are are are unacceptable. So the question becomes who gets to decide what are the desirable changes in future generations? And where do you draw the line with which changes are acceptable and which are unacceptable? It's one thing to treat a disease like sickle cell disease. It's another to say, this particular trait, whether what, you know, hair color, whatever it is, we're gonna, we're gonna do away with that or we're going to change it or or enhance it, or any number of other things that you might be able to think of. So that's the ethical issue, right? So it's not about the technology anymore. There are still things about the technology that need to be, you know, understood and improved upon. But a lot of the questions now are what are we comfortable with? Where's where are the lines? How do you how do you create a legal framework that would put some guardrails on this type of technology? and so yeah, it it is a whole can of worms that you know, living on another planet sort of forces you to think about those things because now you're talking about putting people in a very dangerous situation. And you might even be able to argue that not. using that technology would be unethical. If you could make changes to a person's DNA that would help them to deal with the high radiation, low gravity environment, and you don't do that, is that ethical? Right. So, you know, so so it really gets complicated quite quickly. And this is one of the reasons I wrote this book, is is I think we need to have these conversations now, not once the first people have been born on Mars. You know, we need to we need to talk about it before those rockets actually launch. Yeah, and I think that's that's the main takeaway. I just want to emphasize, we've we've touched on so many things already, so many unanswered questions, but we we haven't even touched on on a third of what's in the book. There's there's so many more cans of worms, so many rabbit holes to go down to. And I just really want to emphasize this is that Yes, there are still a lot of technical hur hurdles that we have to solve in order to even get to Mars. But if we are actually serious about building a civilization there, there are so many things that we have to think about. And yeah, the book really helps with that and and and having conversations about it hopefully helps a little bit too. finally, final remark. you mentioned therefore because of the sheer amount of unknowns, that we should wait. why why should we wait apart from the yeah the announced but well yeah so so you know I I in writing the book I I was actually not sure whether I wanted to share my opinion at the beginning of the book or wait until the end of the book and and I actually wait until the end to kind of share my my thoughts, you know, my my main kind of takeaways. because I w I want readers to be able to draw their own conclusions as they're hearing about some of the things that we've been talking about and and others, right? I wanted to kind of lay out what we know and what we don't know, make some informed speculation about what might happen in the future, and then come to this question which you've just posed, which is like, should you know, so should we do this or or not? And should we do it now if we're gonna do it? and my main conclusions are look, we don't know so much about these basic things like can we have kids in space? If we do have kids in space, will they be able to come back to Earth? Right. To me, it would be very irresponsible to start on a path that takes us to the possibility of having children stranded in a dangerous environment and not being able to bring them back. I I I would not be okay with that. So I think we at least need to have basic answers to some of those questions before we we start on that path. But I don't think that it means we never can do it, right? Like th there are ways that we can get those answers. And I think we need to be working on that. Yeah, and I also think to the argument is always we we are putting all of our axe in one basket, like I mentioned, and one day we will we might be wiped out by an asteroid. But that's like, okay, I agree. That's might happen, that will happen given a long enough time frame, but we're not in a rush. to to go to Mars? we can we can wait. we can do a lot of science in 50 years, right? And the asteroid might not be here for another millions of years. So I I like that Elon has a lot of urgency in everything that he's doing and he's pushing science forward and it's it's incredible to see what SpaceX is doing and some of these other companies and the science that be that's being done by NASA but I th I agree. I think there's so many it will be cool for me to still experience it though, to to see w whether it will be possible. But yeah, we don't we don't wanna be selfish when it comes to such yeah, heavy, heavy scenarios, if you will. Scott, thank you so much. This was incredibly awesome. I really appreciate it.