Becoming Martian (featuring Dr. Scott Solomon)

This is an iHeart podcast. Guaranteed Human. Rural Britain, you've suffered too long. Your days of sluggish broadband are over. We're connecting rural homes to full fiber with thousands more joining every month. T minus five. The gigaverse is expanding before my very eyes. Gigaclear, faster broadband for rural Britain from only 19 pounds per month. We have lived off. T's and C's apply. H-a month contract. Prices may rise during contract. Check availability at gigaclear.com. Long time listeners of DKU will know that I'm a wet blanket about... OK, well, I'm a wet blanket about just about everything. But in particular, I'm a wet blanket about the topic of settling Mars. But hear me out. OK, let's imagine a world where we do actually have thousands of people living on the Martian surface. And they live, they survive, and they start to have children. What might that be like? This future is imagined by my friend, colleague and regular DKU podcast guest, Dr. Scott Solomon, in his new book, Becoming Martian, how living in space will change our bodies and minds. Scott is an evolutionary biologist and his new book asks questions like whether evolutionary changes might happen to Martians across many generations and whether we might even see a new species of human emerging on Mars. So today we're going to chat with him about some of these evolutionary questions about what might happen to humans if we settle on the red planet. Welcome to Daniel and Kelly's Alien Universe. Hi, I'm Daniel. I'm a particle physicist who has evolved to live on Earth and on Earth. I will live. Hello, I'm Kelly Weiner Smith. I am a space settlement wet blanket and I love it here on Earth. You like snuggling up under that wet blanket and getting all cozy and damp. Well, I throw it in the dryer first. And then I snuggle up underneath it and it's really wonderful there. And then I look at the moths, which we find on this planet alone. Well, since we're extending this analogy, aren't you supposed to be throwing that wet blanket on other people's plans rather than snuggling up under it? You know, I don't want to dampen other people's joy really. And you know, I could be wrong. I just want to make sure. No, I really don't. I just want to like make sure everyone's aware of the complications. Let's solve these problems first and then we'll go out there. And people, the cosmos. So you do think that that's the future. You think we are going to be people in the cosmos? I mean, I kind of hope we do at some point because I like I also think the idea of somebody waking up on a foreign planet and seeing the sunrise or, you know, seeing two moons standing on the surface of Mars or something like, I don't know, that that's beautiful and that's exciting. But it's not beautiful and exciting to me if it kicks off a war between China and the US back here on Earth. Like there are conditions under which that is not a beautiful scenario. And I'd like to avoid those. I think a lot of the people who share that fantasy with you are sci-fi addicts like me. And, you know, we read books about this and it seems like a glorious future and so many adventures. But also in those books, there are a lot of wars. You know, that's what makes the books filled with drama and excitement. It's not like. And then we went to Jupiter and we lived happily in the and we smiled at each other. Like that's not a very interesting book. What? No, but like real life doesn't have to be like a book. But I was I was being interviewed by someone the other day and they asked, you know, what do you think the best outcome would be? And I was like, oh, you know, we could have like an international research station, you know, and, you know, I explained a scenario where maybe we wouldn't have conflict back on Earth. And he was like, yeah, but. You know, and I don't want to be mean here. Is that a little naive? And I was like, yes, it does feel naive saying that out loud right now. But I don't think we should go until something like that can happen. And so let's stay down here until that moment comes. And if we have to wait, then we have to wait. But that's my whole point is that our life is in the book and shouldn't be a book. And I think a lot of people who are excited about the future need to remember that the future they're excited about is when they read about in books filled with conflict and suffering and devastation. And that's not necessarily how we want things to go, you know, but as we push out into the stars, you know, there's lots of ways that we could make that work. Obviously, we're not just going to like land on Mars and have everything work out. We've all seen that movie. But, you know, there are ways we can improve our situation by changing ourselves. And then also, of course, ways we can improve our experience by developing technology, by finding solutions to these problems, ways that like, you know, earthy humans like Daniel could maybe actually have a pleasant experience on the surface. I know that we're going to talk to Scott in a minute about the human side of things, but how optimistic are you that like engineers are going to solve some of these problems for us before we have to like, you know, grow a third eyeball or like a red hard skin or something like that. I'm optimistic, but I think the first thing that we need to do is get a lot more people on board with thinking that this is important because at the moment, I don't think there's enough money to solve a lot of these problems. Like not a lot of people are convinced that this is a worthwhile thing to do. Doesn't Elon have a trillion now? What do you mean there's not enough money? He's not spending. He's spending it on the rockets, but he doesn't seem to be spending it on, you know, like satellites that are out beyond Earth's magnetic field that have, you know, rodents that are experiencing Martian gravity so we can see like, are they able to have babies and how are those babies doing? And so money isn't being spent on the kinds of things that you can read about in a city on Mars or you can read about in Becoming Martian, which is the book we're talking about today and is a really amazing book. And I should be embarrassed that I pitched my book, but I'm not because that's the kind of person I am. So you're saying that Elon should be spending more of his money on basic science research. Yeah, absolutely. Or somebody needs to, somebody needs to. And so I think that technology probably can find solutions to a lot of these problems. For example, you know, radiation might just be about finding the right kind of shielding or figuring out the right kind of technology for digging underground and, you know, then trying to find ways to make living underground pleasant, which could be very difficult, but, you know, we could experiment with that here on Earth. There's probably ways to solve a lot of these problems. But at the moment, the money isn't being released for those things. And I think part of it is because not enough people on Earth want to do this. And I think until people decide this is a worthwhile thing or until enough people decide this is a worthwhile thing, you know, I don't think that money is necessarily going to be released. Hold on. You mean if we took a poll of people and asked them, should we go to Mars? Most people would say no. Or do you mean that practically people don't want it enough to call their Congress people to get funding to do this kind of research? So one thing that's really surprised me is that when I go to space conferences, one thing they're frequently grousing about is that there's just not enough people in Congress who care about space settlement, who want to see money released for space settlement science, which is very different than like space exploration missions. And like, you know, this is a very particular kind of space science that needs to get done. And so I don't think there's a lot of Congress people who are clamoring for money to get released. There was a time when folks were excited, like Newt Gingrich really wanted to see space settlements on the moon and was like clamoring to make that happen. But at the moment, there's no, there's no person in Congress who's really like, you know, ringing the bell for space settlement as far as I know. And I guess that's sort of the headline of your book is like, yeah, this is a cool goal, but there's a lot of sort of unglamorous science that needs to happen first. Answer these questions. You can't just skip ahead to the good part. Right. And to be honest, one of the things that I was hoping to do with the book was get the message out there that like, OK, if you're a Congress person or probably much more realistically an aide to a Congress person or a scientific advisor to a Congress person, please understand all of these risks. And if you're a Congress person gets excited about space settlement, fine, but please make sure they understand all of these complications. Geopolitical, scientific, blah, blah, blah. It's a whole bag of complications. Please make sure they go in with their eyes wide open. Here's what they need to know. And so if any of you listening are aides to Congress people and want tips on how to talk to your boss about space settlement science, write to us. We will help you out. Absolutely. Yes. Yes. And please buy Becoming Martian and a city on Mars. OK, but you're right. Today we're not talking about the city on Mars and technological solutions to getting humans off the planet. We're talking about whether humans will actually need to change or whether we will evolve into a new species if we live in a very different environment, I.E. on Mars. And so Kelly, you went out there and asked folks what they thought about this question. Yeah, right. And so Scott's book imagines like, we're going to get people to Mars. What happens if they stay there for a while? How what kind of evolutionary trajectory might they take? And so we asked our extraordinary's if thousands of people settle on Mars, will a new species of humans evolve? And before we hear the answers, explain to me why you said thousands of people, not millions of people or just people. When you read the literature and the literature is mostly by the, quote, archaeologists, which are the people who imagine how many people you need to make interstellar travel work. The numbers are usually in the thousands, not in the millions. Elon Musk has sort of arbitrarily picked a million people for his self-sustaining settlement on Mars. But I think more realistically, we'll get thousands of people in the near ish term. If this happens at all. Yes, right. Yes, you know. And so I'm guessing we'll have thousands in the. It's going to be a while before we have a million people is what I'm thinking. Right. Yeah. But we can't have too small a group, right? It doesn't make sense to talk about evolving a new species if it's just like one guy. That's right. That's right. If you just send Daniel up there, please. No, don't send Daniel. All right. And so for those listeners who participate and have not read the archaeological literature before answering this question, here are their thoughts. Assuming that they are isolated and eventually yes, but it would probably take a very long time, something like hundreds or thousands of generations. If the cross communication, i.e. if the people going back and forth between Earth and Mars are few enough. And if the time is long enough that people have been settled on Mars, thousands, if not hundreds of thousands of years, then I would say yes, the new species would evolve due to genetic drift. Well, yeah, we're all evolving like constantly. And like it would be different. Like the people on Earth would get like zapped by different evolve rays. I forget what they're called, but then the people on Mars. So they would definitely evolve differently and be different. It would be a long time before a new species formed, because as it stands now, some humans have been separated by tens of thousands of years and they could still make babies just fine. I believe that if a new civilization moved to Mars, it would create a different species evolution of humans due to the isolation of genes there. It could, although that's a small sample of population to derive a new species from. If it does survive, it might have some issues. I think it's more likely that changes will occur through human mediated means rather than traditional evolution. No, we won't have a new species. For species is defined as not being able to interbreed. This won't happen unless they are completely isolated for quite a long time. And I don't think there would be there will be people coming back and forth. I don't think it would really be a new species of people, but maybe with a little genetic engineering, we might end up with a highly modified human being. Selection, pressure and mutation would both be pretty strong factors in that. So maybe that it would take a while. As with so many episodes, this comes down to definitions. Depending on how you define human species, the question could be answered. Yes or no, given enough time, of course, the new Martians would evolve into a new species. I don't think a new species of human will settle and evolve on Mars. It likes a global magnetic field, which would make the environment extremely hard for any human to survive in, be they an adult or a child. Given enough time, every species on this planet will evolve into another species. But if the thousand humans just die on Mars, they won't evolve. No, I think possibly not, because if we were able to live on Mars, if society would want life on Mars to be similar to life on Earth, then we would probably try to make Mars as similar to Earth as we could. One thing I appreciate about these answers is that it sort of reflects the experience that I had when interviewing the space settlement community is that you get extremes, you get a lot of people saying, no, obviously, you're not going to get another species because there's going to have to be gene flow. There's going to have to be resupply trips. And if there's gene flow, you're not going to get a new species. And then you get other people being like, it's a very different environment. Obviously, you're getting a new species. And I think that this reflects that people have very different assumptions about what it's going to be like when a Martian settlement starts. And I think that's very interesting. And it's a good way to start a conversation about what kind of assumptions people have about what it's going to be like living on Mars. Yeah, it also hinges very specifically on the definition of species, right? Which we've talked about is a little bit fuzzy. And hearing these answers, I was thinking, well, if the definition is can't interbreed, then like, you know, having a zillion miles of space between you is enough to prevent you from interbreeding. As long as there's no starships coming back and forth. Right. So like technically, if you have identical communities on Earth and Mars, but there's no way for them to like get it on, are they different species? Well, I guess you could say if there was some way that you could get them together, then you want to know if they could get it on. But I should say that Scott's colleague, Scott Egan, in a couple months is going to come on the show and talk to us about what is a species, how do you define it? And I'm looking forward to that conversation. Awesome. But I think there's also here a real understanding that life on Mars will be very different from life on Earth. And I was glad to see that these answers reflect people's appreciation that evolution is in response to the environment. It's not just like some trajectory towards more perfect humans in the future. Right. Yep. Yep. I also felt like there were a couple of people who were hedging their bets. They were like, look, we know this is a show that Kelly is on. And so the answer is probably they're just going to die out there. And so there are a couple of people who were like, no, because they're not going to make it because Kelly's on the show. That's what she's going to say. All right. Well, neither of us are experts on human evolution and neither of us are evolutionary biologists. However, we have a great friend who is and he just wrote a great book on this exact topic. So we're going to take a break and when we come back, we're going to talk to Scott Solomon about his book, Becoming Martian. Trends come and go. Your skin barrier doesn't. E 45 lotion is effective science backed hydration for everyday use. Light weight, fast absorbing and trusted to do what your skin needs. No fuss, no compromise. Just soft, smooth, healthy looking skin every day. Grab your E 45 lotion now. On today's show, we have Dr. Scott Solomon. Scott is a teaching professor in the Department of Biosciences at Rice University. He's the author of Future Humans Inside the Science of Our Continuing Evolution and has a new book, which is what we're going to talk about today called Becoming Martian, How Living in Space Will Change Our Bodies and Minds Out Through MIT Press. And he also hosts the podcast Wild World with Scott Solomon. Welcome back, Scott, for your third appearance on the show. Thank you. I'm excited to be back. So, Scott, all right, let's let's start with sort of the obvious question where these interviews typically tend to start. What made you want to write this book in particular? So this book really picks up where my first book left off in Future Humans. I was trying to answer whether humans are still evolving and how we might evolve in the future. Yeah. And at the very end of that book, I considered the scenario that would be like what happens if some people leave Earth? That would lead on a different evolutionary path. And I decided to kind of pick that thread up and run with it, in part, because it became clear that people are actively working on making that happen. Both commercial space companies like SpaceX and Blue Origin, but also governmental space agencies like NASA that are trying to create a base on the moon and eventually want to get people to Mars. So so my question as an evolutionary biologist is what happens if they're successful? Something I really enjoyed about your book is that it brings out an element of evolution, I think, is not widely enough understood, at least for nonbiologists, which is the role of the environment. Evolution is not some march towards some eventual perfect human. It's a response of an organization or population to changing stressors. And of course, if you change where you're going to live, then evolution is going to take a different path. I think your book really does a great job of bringing that out. Well, thanks. Yeah. I mean, look, the environment on Mars is pretty extreme, as you guys know. And so I wanted to consider like, first of all, if it's actually possible to live there, which is a big if, right? You know, how would people in just the first generation born on Mars, how would they be different? And then if they're able to keep reproducing and you've got multiple generations living there, like what happens later? Do they adapt and gradually get sort of better at living in that environment? And I basically think that's what we should expect. And I know there's no value judgment here, but do you think that's a good outcome? I mean, should we expect different Martian humans and have them be adapted to their local environment, even if it means like they can't come back to earth as easily? Well, that's where we end, Daniel. Oh, sorry. Conversation's got to flow naturally, Kelly. I mean, it's really where I start the book is like, OK, this is happening. Let's think through what the consequences would be. Like, what do we understand from a biological perspective that we can sort of like predict what would happen and what can we not say? And then at the end of the book, I get back to this question of, OK, knowing what we know, should we do this? All right, well, then let's save the answer for the end of the episode as Kelly designed. So in the book, you draw this beautiful comparison between the human explorers who want to go and settle Mars and the Polynesian people who explored and settled the Pacific Islands. Can you draw those parallels for us here? Yeah, so basically what I try to point out, because like, as you know, I'm evolutionary biologist by training, I've done field work on on islands in the Pacific, and I think we can think about planets as islands. So we know a lot about how when a species makes it to an island where that species didn't previously exist, we know a lot about kind of how the founders of that first population, influence later generations and how they adapt as they as they survive there. And so, you know, I wanted to basically ask, how can we apply what we know about evolution on islands to thinking about human evolution on planets? Planets are just big space islands, aren't they? It's just a different scale, right? And so, you know, the islands of the Pacific are, I'm not the first person to point this out, other authors, other people have, you know, recognized that like, in a way, the Pacific is like this, you know, vast expanse of water with tiny specks of land that reminds us a lot of space and the celestial bodies that occupy it. And so the Polynesian people are really, they're really the world's most successful navigators. I mean, it's just incredible that the ancestors of the modern Polynesians were able to discover all of these tiny specks of land by setting out in canoes without having maps they didn't know where to go. And yet they found these places and they successfully set up settlements there. I would die. It is really amazing. I've flown to some of these islands and you spend like hours of the plane over nothing but water and then you see a tiny dot emerge and you land on that tiny dot and it's like, wow, I'm so glad that dot is there. Yeah. Imagine not knowing it's there and just like setting out and hoping to find something. Incredible. It's remarkable. I mean, the ultimate needle in a haystack, right? So one of the amazing experiences I got to have in researching this book was actually going to this site on an island in the Society Island. So this is near Tahiti and this spot is thought to be the jumping off point for some of those great voyages of discovery by by the ancient Polynesians. So it's now it's an archaeological site. It's actually a sacred site called Tapu Tapu Atea on the island of Raiatea. And this is the the place that was a center of learning. It was a center of training for navigators and for leaders. And what they would do is they would take a stone from that structure and bring it with them on their voyage. And then when they made it to land, they would use that to establish this new site. So they think that that's where people who ultimately made it to Hawaii, to New Zealand and to Easter Island. That's where they started. And so when I was there, I'm looking at this place. It's this big, wide expanse right next to the edge of the sea. And it's like a flat square or rectangular area made of volcanic stone. And I'm looking at that and I'm realizing this is a launch pad. I mean, this is their equivalent of, you know, setting out into the unknown. You load up your canoe with all of the supplies that you need to to set up a new settlement somewhere you've never been. And it must have been as terrifying as, you know, loading up a rocket and setting out into space, because once you're out in the open ocean, it's not like you can stop and make repairs. If you forgot to bring something, you're pretty much out of luck. And I think, you know, Martian settlers would essentially have to do the same. Yeah, I'm going to note that my research brought me to Washington, DC, and yours brought you to Tahiti, so I did something wrong and you did something right. But do we know how long their journeys took? So like a mission to Mars is like what, six to nine months? Right. How long were the Polynesian people on the water en route to a new island? I don't think we actually know. I mean, we've only been able to reconstruct this from a combination of like archaeological records, as well as some genetic studies. So you can sort of see the genetic relationships among people living on different islands today and even some of the linguistic evolution that kind of, you know, tracks those same things. So I don't think we actually know that much about the voyages themselves. But I mean, it must have been, you know, weeks at least, if not months, right? Some of these are really far apart. I think Easter Island, the closest land is like 1200 miles away. So it's a long way. Wow. And so then bringing it back to Mars, the idea is that we can study migration on these islands to get a sense for what it might be like for humans to live on Mars. I guess some of the issues are things like population bottlenecks and founder effects. What do we learn from studying how this happened on these islands? And what does that tell us about what it might be like for humans on Mars? Yeah. So we know from studies of like animals and plants on islands that there are these things, like you said, like founder effects, where the founders of a new population have a really big impact on the potential for future evolution of that population once it's established. And one of the things that often happens is they are only a small subset of all of the diversity of the population that they came from. So usually you get a reduction in genetic diversity. They don't represent all of the traits, all of the characteristics of the population they came from. And you also can have random fluctuations in which certain traits become more common or less common, not because they're useful or harmful, but just because of random chance. And that happens a lot in really small populations. And we call that genetic drift. And so the question is, would that apply to humans in the same way that we know it applies to animals and plants? And so studies of people living on Pacific islands actually suggest that the answer is yes, there's some evidence of genetic drift and of founder effects happening in island populations. Can you give us some of those examples that you used in the book? There were some fun examples there. Absolutely. So one of the kind of famous examples comes from the HMS Bounty. So the famous mutiny on the bounty. Right. So this was in the late 1700s and the bounty was a British ship that was making its way through the South Pacific and they stopped at Tahiti. It's a lovely place. The crew got very attached to some of the inhabitants, some of the Tahitians. And they decided they didn't want to leave. And the captain was telling them, no, we got to leave. And the crew was like, we're staying here. And they had a mutiny and the mutineers ended up escaping and setting up on another island. So this is a small subset of the original crew. And they had some Tahitian wives. They ended up having children with those Tahitian wives. And the population kind of grew very slowly at first. But once it did start growing, they had to relocate to another island, the island of Norfolk. And if you go to Norfolk Island today, the majority of its inhabitants can trace their descendants back to the mutineers from the bounty. And so, interestingly, they show evidence of having genetic drift and having a founder effect because there's kind of a reduction of genetic diversity in that population compared to other human populations. And there was a study that showed that they are shorter on average than other folks, which seems to be connected to this reduction in genetic diversity. Are they more likely to mutiny? Or to mutate. Jury's still out on that, I think. But mutation on the bounty. That's the biological. Yeah, that's a good name. And I'll just share one more if I can, because there's another really interesting example, which is also a Pacific Island. In this case, it's an atoll called Rangalup in Micronesia. And in the late 1700s, around the same time as the mutiny on the bounty, there was a typhoon that unfortunately killed the majority of the human inhabitants of this island. Some of the few people that survived, I think there were only about 20 or so survivors. And one of the survivors, perhaps not surprisingly, was the king or the leader. And he happened to have a rare gene or an allele, a version of a gene, which is the allele for complete color blindness. So not like the more common red, green color blindness, but the basically if you have complete color blindness, you see the world in black and white. You don't see any color at all. Now, he didn't have complete color blindness. He just carried the allele. It's a recessive allele. So you need to have two copies of it to be completely colorblind. But because there were only a small number of survivors, and basically in the next few generations, you ended up getting a lot of inbreeding, then that meant that those recessive alleles were more likely to show up in the same individual. And in a few generations, you got the first truly colorblind individuals. And so now that island has the highest proportion of complete colorblind people in the world. And so again, it's not because that was advantageous. It's it's it doesn't seem to give you any advantage to be colorblind. And it might actually even be kind of a hindrance. But just because of that population bottleneck, because they were reduced to a few number of individuals, that trait became more common. Sometimes it's hard to anticipate whether a trait could evolve to be advantageous. I know in my research, we use genetic algorithms a lot where you have like a population of neural networks, for example, that you're training to do some task. And something we do a lot is we take a sub sample of them and we put them on their own genetic island and we allow them to evolve without competing against the mainland. And sometimes they do this thing where they have drift, whatever, but they evolve something new and interesting that wouldn't have survived in the first few generations on the mainland, but then comes back and dominates. It's really fascinating. Yeah. So then apply this to Mars. Is the Martian population going to be small enough to have these effects? How big do you have to be to effectively avoid these things? Because I thought Musk is talking about putting a million people on Mars. If we're going to take that at face value. Yeah. So I think what it tells us is that it matters who you send, like who are the founders of a new population makes a big difference. And if you were to choose, say, people that were all fairly similar to one another, right, that would be more likely to set up a scenario where you get genetic drift and random traits becoming more common or disappearing versus the same number of people. But if you have a very heterogeneous, a very diverse set of founding members of the population, then you're less likely to experience genetic drift. So it really matters how you choose the founders. So the size is important, but the composition of the founding population is even more important. So we shouldn't just send Musk and all his friends. Well, what I've said in the book is like what we would want to do, I think, if you're trying to set this, you know, the Martians up for success is you want as genetically diverse, a founding population as you can get, you want it to really be representative of as much human diversity as you can. So the way that we've historically chosen astronauts definitely doesn't do that, right? You sort of screen for the people who are kind of the best of the best, the elite, you know, the right stuff, that whole thing. You would want to do more than that. You would want to also consider, you know, are we representing human diversity as we know it and the more diversity, the better. So we can't just bring physicists and biologists. We have to invite the chemists along. You're saying, oh, no. If there's a gene for being a chemist, then yeah, you probably want to include it. I don't know. We found that gene yet. All right. So the Polynesians were separated for long periods of time, but they never became separate species and we're going to take a break. And when we come back, we're going to talk about what it might take for people to move to Mars and actually become a different species. Because you bought your robot vacuum on your Barclay card, you got zero percent interest for up to 24 months, which makes watching it hypnotically sweeping up your crumbs even more satisfying. Oh, Mr. Bit, what you buy is your business. Helping you pay less interest is ours. Barclay card backing your future. Subject to financial status, new customers only. Representative example, twenty four point nine percent APR representative variable, twenty four point nine percent purchase rate per annum based on one thousand two hundred pound credit limit, season C's apply. All right, we're back and we're talking to Scott Solomon, author of Becoming Martian and on the topic of being a separate species, a friend of mine who's like clearly a hundred percent white, did his DNA testing at twenty three and me and it came back that he was one percent Samoan, which I'm very skeptical of. But he used that as an excuse to never wear sunscreen again. He was like, Hey, man, I'm Samoan. Oh, no, bad choice, bad choice. Yeah. But natural selection will, will what that choice out pretty fast, maybe. But I hope not. I hope your friend decides to wear sunscreen. OK, so the Polynesians were separated for long periods of time, but they never became as far as we know, we never ended up with separate human species on these separate Pacific islands. And so, Scott, what does it take to get a separate species and do you think we'll end up with Martians becoming a different species? And because we have had separate human species on earth in the past. Yeah, it's interesting. And that was actually part of why I thought thinking about Pacific islands as as an analogy for space is useful because we tend to think of species evolving on islands, right? I mean, the reason Darwin was inspired by visiting the Galapagos islands and the reason why, you know, biologists like me still go to islands to study evolution is we think that being separated, like physically, geographically separated and living in different environments is kind of a set up for speciation. So why didn't that happen with the Polynesians? You know, all humans today are the same species. We have some subtle population differences, but nothing approaching the differences between species. So why not? Well, I think there's a couple of things. One is that they weren't actually isolated for very long. So the Polynesians were really the last people to reach habitable aspects of land on our planet. Some of the islands that they discovered and settled like Easter Island were only settled in like 1200 CE. Like that's like not that long ago in the, you know, the saga of human history. And so they were only perhaps isolated from one another for a few hundred years, because as soon as, you know, Europeans started making their way around the Pacific and, you know, having mutinies and whatnot, they, you know, they started moving between islands and creating more connection between them. Connection. Right. That's right. Well, one of the things I think I said in the book is like, you know, people exchange goods and when they do that, they also exchange genes. We know that's the case. But actually to that point, the idea that they were isolated also assumes that once they reached these islands, that that was it, that they weren't then going back and ever interacting with people from either where they came or other islands. And in a few cases, that seems to be the case. Like Easter Island was truly isolated. But for most of the Polynesian islands, people were actually still able to move back and forth and exchange goods and genes with one another. And, you know, we know there's some part from genetic studies, but we also know it from archaeology. There's stone tools that are widely used across the Pacific. But the stone that they used to make them is only found on like a small handful of islands, and yet you see that stone all over the place. They were they were trading goods as people do. So, you know, they weren't actually as isolated as you might think. And that's important to recognize because gene flow, the exchange of genes between populations is another mechanism of evolution, and it tends to prevent speciation from happening. So people might be living far away on Mars, far away from the people living on Earth. But if people are still moving between those planets and exchanging goods and genes, then it's less likely that speciation would happen. So I suspect that we're going to need resupply ships to keep the Martian settlers alive for a really long time. And so and I think that will keep gene flow going. But but what do you think? Do you think that there will be gene flow happening between the Martians and the Earthlings, or do you think that something will stop the gene? I mean, I think people would probably like to be able to come back to Earth if they're living on Mars. Mars is, as you very well know, is a very harsh place to live. And Earth is a pretty nice place. So if I was living on Mars, I'd should want to come visit Earth. But here's the thing. I'm concerned that it won't be as easy as some people have imagined to move between planets, and that's especially true for a child that's born on Mars. For one thing is their body is growing. They're in one third G, right? A one third of Earth's gravity. And we know that muscles and bones, they don't develop the same strength when we're in a lower gravity environment. Now, we don't actually know what happens to a child's growing body in a lower gravity environment because we've only ever studied adults. But I think there's a pretty good reason to suspect that a child's growing body would be affected by being in lower gravity. And if they don't build bones that are strong enough to be able to handle Earth gravity, it might be really hard for them to be able to handle being on Earth. So there's the gravity issue. But then there's another problem, which is our immune systems and infectious disease, because we know that a child's immune system develops in response to all of the microbes that we just interact with on a regular basis. And most of those don't end up being dangerous to us. But if you're exposed to something that you've never encountered before, then it can be dangerous. And we also know that when we travel, we bring our microbes, our microbiome with us. Right. And so people going to Mars will bring microbes that are in and on their body. And we'll probably bring other microbes. I mean, we have to have food, so we're going to bring plants and they come with their own microbes. Every every complex organism has a microbiome. But whatever we bring is still going to be a tiny subset of all of the microbial life on Earth. So a child born on Mars will never be exposed to the vast majority of microbes we have on our planet. So I worry that a child born on Mars who came to Earth would be really at risk of getting sick just from the stuff that isn't a big deal for you and me. But for them, it might be really dangerous. So then let's assume that there isn't a lot of gene flow back and forth. What are the other selection pressures on Mars that might influence the way humans evolve, the radiation environment, the rotation, the sunlight, these kinds of things. Yeah. So I mean, we know the gravity is likely to be a big factor. Right. We know that being in a lower gravity environment is tough for the body. So I think being in a lower gravity environment is likely to cause natural selection to favor people that have certain traits that make them better at surviving and thriving in that environment. So one of the things that could happen with adapting to lower gravity is that people might actually be better off if they start off life with denser bones because we expect they will lose bone density as they age. I mean, that's what happens to astronauts. They lose about one and a half percent to two percent bone density per month that they're in space and that's in a weightless environment. We don't know if one third gravity means you lose bone density at a lower rate, but you probably are still losing bone density. So what happens to a person who's born on Mars has been losing bone density their entire life and then by the time they go to have kids, you know, a woman who's going through childbirth is now doing that with a weakened skeleton. That could actually be really dangerous. I mean, childbirth is already dangerous enough. But if you're doing it with a weakened skeleton, it could be it could be really dangerous. And so natural selection might actually favor women who start off life with denser bones so that they're more likely to be able to survive childhood and that their their children are more likely to survive as well. So then you'd actually get like people with denser bones in future generations. I also thought it was interesting in your book that you suggested that you know, if that ends up being something that like, I don't know, maybe we don't have the genetic diversity available so that we can evolve denser bones, maybe we're just going to have to do C-sections every generation because it turns out this will be just way too dangerous. So kids have to be delivered via C-section to save mom. Yeah. And like the implications that could have. I thought that was a really interesting idea. Right. Because we know when we have complications with childbirth, like one of the best things you could do is deliver through a cesarean section, a C-section. And so if, you know, people are having complications with birth on on Mars, that might be the go to. And then if you get to the point where that just becomes the standard, everybody has C-section births. Then what are the evolutionary consequences? Well, at that point, the head no longer has to fit through the birth canal. And that's been a major constraint throughout human evolution. So if the head is no longer constrained to fit through the birth canal, at that point, the head could actually evolve to become larger. So, you know, it's funny because, you know, in one way, it's like kind of sounds like the sci-fi depictions of aliens, right? You know, these big headed aliens. But that's a plausible evolutionary scenario. Right. And in a lower gravity environment, you could hold up that giant head like more easily or something. And anyway. But then it's hard when you come back to Earth. So yet another reason why people born on Mars might struggle to come back to Earth. Yeah. But yeah, we were talking about the radiation environment. And I think that's another challenge because we know that, you know, Mars is bombarded by quite a lot of radiation because it has a very, very thin atmosphere and it has basically no magnetosphere. So, you know, people on Mars, if you're on the surface, you're exposed to, you know, nearly the full force of deep space radiation, galactic cosmic rays and everything else. So, you know, you'd need to have some protection from that just to be able to survive, you know, maybe we're living underground. But I like to imagine that people aren't going to be content to only be underground. I mean, I don't want to go to Mars if I don't ever get to go, you know, explore on the surface. And, you know, if you're growing crops and doing other activities, you might need to be on the surface. So if people are exposed to higher levels of radiation than we are on Earth, on the one hand, there's cancer risks, but on the other hand, mutation is the ultimate source of genetic diversity. So what you could find is that mutation rates overall are higher and that's really the raw material for natural selection. So that's a mechanism by which you could have more rapid adaptation to the environment on Mars because you have basically more raw material for natural selection to work with and then the advantages that would come with any mutation that happens to be beneficial. That's fascinating. I want to underline that you're saying that radiation itself could be creating the mutations which allow us to survive radiation. Exactly. Incredible. Physics is amazing. But, but what blanket Kelly is stepping in here? On average, what aren't most mutations likely to be negative? So aren't like a bunch of people probably going to kick the bucket from cancer and like 1% are going to like hit the genetic lottery and have like a great mutation that like and 1% am just picking a random number. I don't that's not like a scientifically justified number. Yeah, probably less than 1%. Yeah, you're right. So this is not a pleasant way forward. We're not talking about like like a happy way to see future generations become better adapted because what you're talking about is a lot of death and suffering. I mean, we're talking about a lot of people having, you know, cancer probably at a younger age, right? You're more susceptible to cancer caused by radiation exposures when you're young because your cells are dividing more rapidly and every time they divide, there's an opportunity for a mutation. And death is an essential part of this, right? If people don't die, if they live and have kids, then you don't evolve. That's right. People like to say that like physics moves forward one funeral at a time, but so does humanity. That's how evolution works. You know, it's not a pleasant process. And so that's why, you know, one thing that has been proposed is maybe we need to take matters into our own hands, right? Maybe we should be manipulating our genes to try to improve the ability to adapt without having to kind of wait for natural selection, to wait for mutation and then natural selection to discover new ways to do things better. If we could make those changes ourselves, it would help people by, you know, enabling them to be able to handle the high radiation, low gravity environment, you know, alleviate some of that death and suffering. Wow. Both of our eyebrows just went up because I thought you were going to go another direction and say we should be killing people because, you know, we might be like short on resources and, you know, if we get hungry, we might just have to decide in advance who we think is going to survive. And, you know, some of that flesh could be tasty. I don't know what Martians are going to like to eat. Daniel got to the cannibalism. It always happens naturally. That's right. That was the perfect transition to genetic engineering. And so then my question for you is, do we know what genes we would need to tinker with? So do we know what we would need to do to people to make them well adapted to the Martian surface? Or at this point, would we just be like making changes and crossing our fingers? I think that we're sort of at the yes and no point. We do know of some of the genes that we might be able to alter. So for example, tardigrades are famously really resilient and able to, you know, survive being in space for long amounts of time, etc. And we know that they have a gene called D-sub, which stands for damaged suppressor. So this is how they're able to suppress damage to their DNA caused by radiation exposure. And so one of the things I did when researching the book was visit Chris Mason's lab at Wheel Cornell Medicine in New York, where they're actually taking genes from tardigrades, including D-sub, and cloning them into human cells and culture. And they've been able to show that those human cells actually express the D-sub protein, suggesting that it might be possible to get some of that radiation protection in our own cells. Now, we haven't done that in a living human yet. But if you could do that safely and effectively, that could be really interesting. So I think we still have a lot of unanswered questions, both about what genes we would want to be editing and also being 100 percent sure that that's not going to have any unintended consequences. Right. And on earth, we're not comfortable with making those changes in humans ethically yet. So we would also have to like decide that we're going to, you know, eschew all of the ethical concerns that we have about making those changes on humans and then decide we're going to go ahead and make them on Martians. What do you think about that? Oh, absolutely. I mean, I think the ethical considerations are enormous and I try to, you know, address that a bit in the book. I mean, I think, look, we have a long history of trying to think that we can control our own evolution and that really not going well. I mean, the entire field of eugenics was based on the premise that we could make humanity better by controlling who lives, who dies and who reproduces. And we all know how that turned out. So we clearly don't want to repeat those those sins of our past. But part of what's interesting about this is that the ethics, I think, become a bit different once you're talking about living in this incredibly harsh environment. So if you had the ability to alleviate death and suffering by making gene edits, would it be unethical to do that? Or would it be unethical not to do that? But then it gets tricky too, because it's one thing to agree to edit your DNA knowing the risks. And it's a very different thing to edit the DNA of an unborn child who has no ability to understand the risks and to consent to that. And so, you know, doing a genetic edit to each individual is one thing. Doing germline gene editing, which is making changes to the cells that make sperm and eggs that would be heritable changes. At that point, you are manipulating the future evolution of our species. And you're making changes to future generations that weren't able to consent. But aren't you doing that anyway? Even if you only edit your own genes? I mean, if I edit my genes to give myself, you know, laser eyes or something, then my kids have laser eyes and, you know, kids are always brought into the world without consent anyway from the gene pool of their parents. So it depends which of your cells you're editing. So you could make changes to your own DNA that wouldn't be passed on to your kids. So it has to be the cells that make the gametes, the sperm and the eggs. Yeah. Given what you've learned, do you think we should become Martian? So here's the thing. I looked at some of the like motivations for why people are trying to do this in the first place, which I know Kelly, you and Zach get into this in your book as well, City on Mars. And I think I came to some similar conclusions as you guys did, which is that eventually maybe we should, like I'm not saying we should never go and live on Mars or any other planet. But I think there's enough unanswered questions such as, you know, is human reproduction even possible? Could a child born on Mars come back to Earth? We need to know those answers before I think we can responsibly start loading people onto ships and sending them out there. But I am kind of convinced by the idea that in the long run, eventually, if we don't do that, we might eventually go extinct. I mean, there could be a disaster on Earth and there will be a disaster if you wait long enough, you know, whether it's self-imposed or whether it's an asteroid impact or supervolcano eruption, it's going to happen. The thing that matters is the time frame. So I just don't think we're ready yet. I'd want to see more science, more answers to important questions that we don't know. We could know. We could find out about, you know, human reproductive biology in space. There just hasn't been enough research on it yet. And so that's what I'm saying. We need to do that science. Let's learn, let's discover, let's continue doing space science, human space exploration. But let's not start actually living out there until we know we can do it safely. So do you think that this is an issue that species around the galaxy face? You know, if you're an alien now, you're on some other home planet and you're wondering about hopping to the next planet, is this a conversation that's being had across the galaxy? Should we be shipping your book to Alpha Centauri? Oh, I gladly donate a copy to ship to Alpha Centauri, if you know of any missions that are heading that way. Yeah, I think some of the general conclusions of what I'm trying to argue in this book would be applicable to any species living anywhere in the cosmos. I mean, the idea that species adapt to new conditions, the idea that the founders of a population have a big influence on what can happen next. And the idea that it might be hard to move between planets because of how different those environments are and how well adapted species are to the planet that they came from. Those patterns are going to be true of any kind of life living anywhere. So I think it's really interesting that H.G. Wells back in 1898 wrote War of the Worlds. Imagining a future when sophisticated Martians came and attacked Earth and we couldn't stop them because their technology was too advanced. But what ultimately stopped them? Bacteria. It was the microbes that they had no defenses against that ultimately were their downfall. So I didn't come up with that idea. It's been around since at least 1898. But I think that's actually really prescient. I mean, I think he was onto something that is likely to be a challenge. It's not an insurmountable challenge, but we need to better understand it before we can expect that it'll be easy to move around between planets once we're actually living out there. All right. Well, thanks, Scott, for coming back on the show. Becoming Martian is available in all great bookstores everywhere. And all terrible ones and all terrible ones and everyone should run out and grab a copy. Thanks, Daniel. Thanks, Kelly. This is always so much fun to talk with you guys. I appreciate it. Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We would love to hear from you. We really would. We want to know what questions you have about this extraordinary universe. Want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you. We really mean it. We answer every message. 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