Ep 170 "Will Mars Create a New Species of Human?" with Scott Solomon

0:00Speaker 1:What happens once we start giving birth to babies on Mars? Might a Martian human become unable to survive on Earth because of differences in microbes and gravity? How much of your body is shaped by the details of this planet? Would radiation accelerate human evolution on Mars? Could living on Mars eventually create a new species of human? Would a Martian child find Earth's oceans as strange and awe-inspiring as we find another planet? Could two branches of humanity become too different to recognize each other? Today, we're joined by Scott Solomon, evolutionary biologist and author of the book, Becoming Martian, How Living in Space Will Change Our Bodies and Minds.

0:52Speaker 1:And we're going to look at a future of humanity that's not really that far away. Welcome to Inner Cosmos with me, David Eagleman. I'm a neuroscientist at Stanford. And in these episodes, we sail deeply into our three pound universe to understand why our lives look.

1:10Speaker 2:The way they do.

1:11Speaker 1:And sometimes we sail into the outer cosmos to understand what our lives might look like in the not so distant future. There's a strange thing about being human that we rarely think about because we've never had to. We might go for a morning jog and we breathe an atmosphere that feels completely ordinary. Maybe we watch the sunrise. Our bodies have evolved inside all of this setting of the planet for a very long time, hundreds of millions of years. And because this context has always been there, We think of it as background, if we think about it at all.

1:58Speaker 2:But the surprise is that.

2:00Speaker 1:This invisible background is part of the environment that shapes us. Our bones have been sculpted by gravity, and so have our muscles, and so has our cardiovascular system. Our sleep-wake cycles are synchronized to the rotation of the planet. Our immune systems became what they are because of the enormous microbial world that surrounds us. This is all part of the story of being human. We are Earth-adapted organisms. A human being, as we know it, and all we've ever known it as, is a product of Earth.

2:39Speaker 2:Now, if it's all background, why do we care?

2:42Speaker 1:Because we're standing now right at the doorstep of serious space exploration. And it won't be too long before we have humans living on the moon and then eventually on Mars. And someday, maybe for your great-grandchildren, we will see babies born on Mars who have never known the Earth at all. So let's really think about space exploration. Almost always, we think of this as a problem of engineering. We think about big rockets or building Mars habitats or life support systems or food and water and energy. All of that is part of the challenge of space exploration.

3:22Speaker 2:But there's another layer to the problem.

3:24Speaker 1:We have to take a human body somewhere it has never evolved to live. And that, it turns out, might be a huge problem, way bigger than the engineering.

3:36Speaker 2:Take gravity.

3:38Speaker 1:Your skeleton has a certain density because it spent your entire life supporting your weight. Your muscles are continually working against gravity, even when you're just standing still. Take away most of that gravity and the body starts to change. So when we imagine a permanent settlement on the moon or Mars, we are looking at an enormous biological experiment whose basic parameters we barely understand. What happens to a human body after 10 years in lower gravity? What happens during pregnancy? What happens to the infants who are born there?

4:17Speaker 1:Or we can ask, what happens to the immune system when a child grows up surrounded by a tiny fraction of the microbial diversity that exists here?

4:29Speaker 2:And then don't forget that our brains are Earth-adapted.

4:32Speaker 1:We organize our sleep around a 24-hour day, and we use light as a powerful signal for setting our internal biological clock. Just imagine living inside a habitat underground on Mars, surrounded by artificial light. So, what happens when humans become an off-world species? If humans live away from Earth for long enough... the environments will change the trajectories of human evolution. Just imagine coming to Earth after generations of your family living on another planet. I love this thought experiment. First, because it's not that far away, like a few generations.

5:14Speaker 2:And secondly... What this means is that space exploration is going to become a way of.

5:19Speaker 1:Understanding our own bodies and giving us a contrast point so that new discoveries about us will come into focus. I got turned on to all these issues in a new book by Scott Solomon called Becoming Martian, How Living in Space Will Change Our Bodies and Minds. which is all about this topic. So I immediately called Scott to be on the podcast. Scott Solomon is a biologist, a professor, and a science communicator at Rice University, where he teaches ecology and evolutionary biology. He's fascinated by the consequences of a future that we're only starting to get a glimpse of.

5:58Speaker 1:Here's my interview with Scott Solomon. So, Scott, we often imagine ourselves traveling to other planets, but the question is, how much of our bodies represents the Earth itself?

6:15Speaker 3:Oh, that's a great question.

6:16Speaker 2:Yeah.

6:17Speaker 4:I mean, I think in some ways it's everything, right? Like we evolved on this planet. We come from a lineage of three and a half billion years of evolutionary history. And so everything that we are is of this planet. But in another way, it's almost impossible to answer the question or to know the answer because we have no basis for comparison.

6:37Speaker 2:We're like fish and water in that sense.

6:38Speaker 3:Exactly right.

6:39Speaker 2:Yeah.

6:40Speaker 1:So what do we have here? We've got gravity. We've got sunlight. We've got microbes. We've got magnetic field. Give us a sense of how all this stuff shapes our bodies.

6:49Speaker 3:Yeah, absolutely.

6:50Speaker 4:I mean, the very material that we are composed of is of this Earth. But yes, the way that we evolve to be able to function is very much adapted to this planet. So you mentioned gravity, and that's a great thing to start with because it's so central to what will be different as we move beyond Earth. But yes, our bodies are really well adapted to function in 1G Earth's gravity. The ability for our muscles to function, our bones, and the density and the strength that they have is incredible.

7:21Speaker 4:perfectly well adapted for this planet. But yes, everything from the microorganisms that we now know are not just there and doing nothing, but actually essential for our health and well-being.

7:36Speaker 1:And there's a whole communication network between the microbiome and the brain, which we're still working to understand.

7:43Speaker 2:So we're shaped by the planet.

7:45Speaker 1:And the thing that you wonder about is people talk about engineering and rocketry as the real challenge we're facing to colonizing other planets or bodies. But you say it's the biology that's going to be a real challenge for us.

7:58Speaker 3:Well, right, because the rockets can get us there.

8:01Speaker 4:And if we can figure out the technology to allow us to be able to, you know, not just go and visit, but to stay for extended amounts of time, that's great. But we still need to understand how we will be affected. And there's other examples, too, about how our hormonal cycles are tied to metrics of time that are very much a function of Earth and its position in space. So I'm thinking about things like daily rhythms. When you wake up in the morning, you have hormones that help you to wake up. Some of us need a little caffeine maybe to help with that process to supplement.

8:37Speaker 4:But our bodies naturally have these daily rhythms. When we travel and experience jet lag, it's disrupting those natural rhythms.

8:45Speaker 3:When we're ready to sleep at.

8:46Speaker 4:Night, it's because we have other hormones like melatonin that are helping us to prepare for sleep. That's all tied to the amount of time it takes for the Earth to rotate, right? And so that is very much of this planet.

9:02Speaker 3:Annual cycles, right?

9:04Speaker 4:We have other hormones that help us to basically experience seasonal changes. And when people experience seasonal affective disorders, for example, if you're in a part of the world that doesn't have much sunlight in the winter months, right? And we maybe can compensate for that in certain ways, but it's an indication of how well adapted we are to those cues that we get from our environment, which are very much of this earth.

9:30Speaker 1:So we are all excited about the idea of getting off the planet.

9:35Speaker 2:Let's start with the moon.

9:37Speaker 1:If we ended up on the moon, these circadian rhythms that you're referring to, we don't have that, right?

9:43Speaker 3:That's right.

9:43Speaker 1:Because one side is always facing the sun and the other side is always facing away from the sun. So would you maybe envision colonists on the moon sort of going back and forth? They have two sides of their home that straddle that line?

9:56Speaker 4:I mean, that would be one way to deal with it. I think the practicality... would make that a bit challenging. But, yeah, I think that people will end up having to find ways to compensate.

10:06Speaker 3:Right. And so.

10:07Speaker 4:People experience this when they go and do polar research, for example. If you're at an Antarctic research station and you're overwintering, which is one of the really challenging things that some polar researchers have to do, you might compensate by using artificial light to kind of give you some of that, what you would naturally get from the sunlight. And so people on the moon might end up having to do that, too, when they're there for extended periods.

10:31Speaker 4:Astronauts already deal with this, for example, on the International Space Station because they experience, you know, sunrise and sunset from their perspective. I forget what the exact number is, but it's like every 40 minutes or something along those lines. So, you know, this is naturally going to throw them off in terms of sleep cycles and other aspects of their health.

10:53Speaker 2:Okay.

10:53Speaker 1:And then we're excited about getting to Mars. What is life on Mars like? Let's start with circadian rhythm and then we'll go to other aspects.

11:02Speaker 3:Yeah.

11:02Speaker 4:Life on Mars in some ways will be more similar to life on Earth than, say, the moon, right?

11:09Speaker 3:In part because gravity.

11:11Speaker 4:On the moon is one-sixth of what we have here on Earth. But On Mars, it's only about a third. And so that's going to be a very different environmental signal. But in terms of circadian rhythms, actually, a day on Mars is not that.

11:29Speaker 3:Different from a day on Earth. It's only about 40 minutes longer.

11:33Speaker 4:So that might feel somewhat familiar. But even those 40 minutes can.

11:39Speaker 3:Be enough to throw people off.

11:40Speaker 4:So, for example, researchers that are studying Mars, for example, through rovers, sometimes need to be on Martian time in order to do their research. And there's reports of them actually kind of experiencing a version of jet lag sometimes. because they're on Martian time as opposed to being on Earth time. Their bodies get out of sync with the sunrise and sunsets that their eyes are telling them are happening, but they're on Martian time.

12:07Speaker 2:Instead of a shift worker, I guess we'd call it a stretch worker or something.

12:11Speaker 3:Yeah, exactly.

12:11Speaker 1:Yeah.

12:12Speaker 2:So, okay. So, but the circadian rhythm is close. That's good.

12:16Speaker 1:But what does the change in gravity do for us living on Mars?

12:20Speaker 4:This is the thing that I think is going to be one of the most challenging aspects of trying to spend any prolonged amount of time on Mars.

12:28Speaker 3:And there's two ways I can answer your question.

12:30Speaker 4:One is that we suspect it will be a pretty profound difference because everything that we know from studying astronauts' bodies in space, which is in effectively zero gravity, right, they're weightless, shows us that it's very disruptive. So when astronauts first go to space, one of the immediate things that happens is All the fluids in our body that are normally being pushed down into our lower body start to become more evenly distributed. So if you ever look at pictures of astronauts when they first get to space, their faces look kind of puffy. And that's because they have all this excess fluid in their heads. And then their legs look kind of skinny. They call it chicken legs.

13:09Speaker 4:So this is, you know, it's kind of kind of funny, but like they actually also have nasal congestion because there's excess fluid there.

13:17Speaker 3:So that's the body kind of readjusting. Over time, it gets better.

13:22Speaker 1:Why?

13:22Speaker 4:Well, because basically the body can compensate by dumping excess fluid. And so the body perceives it as being too much fluid total overall.

13:33Speaker 3:It's not.

13:33Speaker 4:It's just how it's distributed. But what it will do is start to reduce the amount of fluid, for example, in the blood plasma. And that can actually cause some issues for astronauts because reducing that blood volume can then trigger things like anemia with, you know, too few red.

13:49Speaker 3:Blood cells in circulation. When they come back to Earth, that can create some issues.

13:54Speaker 1:Could it lead to increased stroke also in the sense that you have increased clotting?

13:59Speaker 3:That is a concern.

14:00Speaker 4:So, so far, fortunately, there haven't been any issues with people in space experiencing strokes, but it's one of the things that they do worry about and try to look out for.

14:10Speaker 3:Yeah.

14:11Speaker 4:But we also know that, for example, you know, astronauts have to do about two hours of resistance exercise every day to keep their muscles from completely atrophying because the muscles that we use just to hold ourselves up They're not doing anything in microgravity. And then bone responds to muscle. So bone starts to get weaker. And that's a real concern for extended periods of time because it could increase the chances that you could break a bone.

14:38Speaker 3:So that's in microgravity.

14:40Speaker 4:Now, if we think about Mars with about one third gravity of Earth's gravity, the question becomes, is one third gravity enough to overcome some of those challenges that we normally see in astronauts in microgravity? We don't actually know because nobody has.

14:56Speaker 3:Ever experienced it, right?

14:58Speaker 4:I mean, the only real experience that any humans have had in partial gravity between zero and 1G are the Apollo astronauts that walked on the moon. There were 12 of them. The most amount of time that anybody spent was three days. Wow. Beyond that, we just don't have any data. So we can make some extrapolations from what we know about their experiences and from what we know about being in zero gravity. But the bottom line is we're going to learn a lot when we start to spend more amounts of time in partial gravity, including on the moon.

15:31Speaker 3:Because there's just not much data. There's almost none.

15:34Speaker 2:Is there any way to simulate one-third gravity?

15:37Speaker 3:There is, but only for short amounts of time.

15:39Speaker 4:So one of the things that astronauts do to train for space is to do parabolic flights. This is affectionately known as the vomit comet. So this is an aircraft that is basically doing parabolas. So going up and then diving down. And that can, during that free fall, simulate either zero gravity or partial gravity, depending on the angle that the plane is going down with. but it's a maximum of only about 30 seconds. So there's a lot of research that can be done in those 30 seconds and they can do them over and over again, but it's not gonna help us understand the long-term effects of a person being in partial gravity.

16:17Speaker 1:So now when we think about people on Mars, we often picture astronauts, but let's move to the first infant born on Mars. What changes with that infant?

16:30Speaker 4:This is something that I think is essential for us to really... understand what is possible beyond Earth, because the bottom line is, again, there's almost no research on human reproduction beyond Earth. So I think that we need to actually know quite a bit more before we should be seriously considering having families raised on the moon or Mars. But there's a lot of aspects of pregnancy, birth and child development that do seem to be pretty closely linked to the environment on Earth. And I'm thinking about everything from the microbiome and how we first build our microbiome, because we're not born with it. It is something we acquire starting with birth.

17:16Speaker 3:Yeah, that's right.

17:17Speaker 4:From the environment, from our mother and from other people that we interact with and from the environment as well. So, you know, a toddler who's putting everything in their mouth... One of the things that's happening is they're seeding their microbiome, right? And so the microbes that we are surrounded by are going to influence how that microbiome develops. That's going to be very different on Mars because what microbes will there be? As far as we know, there's no microbes on Mars. yet, but we'll bring some with us, right? And so whatever we bring with us is the pool of possible microbes that can make up the microbiomes of future generations of Martians.

18:00Speaker 3:Wow.

18:00Speaker 2:And so, yeah, you're right. We have no idea which microbes are necessary.

18:04Speaker 1:I mean, maybe we can ship over lots of dirty toys from the floor and have maybe, you know, stick that in their mouth. But we don't actually know if we were missing them, the flexibility of the system we have. So what's your speculation on that?

18:18Speaker 2:Would it be? dangerous for the child?

18:20Speaker 1:Or would you simply get a very different kind of human because of plasticity? Yeah.

18:24Speaker 4:So there are some research studies that look at, for example, raising mice and other rodents with either no microbes or with a limited set of microbes. And they tend to not do well. So that does seem like it leads to adverse health outcomes. But in terms of whether we could deliberately bring microbes to help with the health of future space explorers and settlers, that's possible. I mean, we know that astronauts, when they go to space, they're bringing their microbes. There's some fascinating studies on the microbiomes of astronauts, including during The NASA twins study when astronaut Scott Kelly spent about a year in space and they looked at, among other things, the composition of his microbiome before, during and after that year. And then compared it with his identical twin brother, Mark Kelly, who was on Earth. So fascinating study. So we know that astronauts do bring their microbiomes.

19:20Speaker 4:And so people going to Mars are going to take microbes with them. Now, we may choose to, as you say, bring the dirty toys or other microbes, petri dishes maybe with us to space to make sure that we don't deprive future generations of the microbes that they need. But, yeah, you know, we're still learning the basics of what are the essential components of that microbiome. And so we don't yet really know which ones need to be there and which ones are just, well, you know, it depends. fine if it's there, but not a big deal if it's not.

19:52Speaker 1:So one of the things you emphasize is that all these tools that we now have, let's say like CRISPR and ways to edit the genome. And for that matter, brain computer interfaces in the near future and so on.

20:04Speaker 2:These might actually be a.

20:06Speaker 1:Part of the engineering challenge that we're going to have to do in order to do life on other planets.

20:12Speaker 2:Tell us about that.

20:13Speaker 3:Well, yeah, I think the bottom line is that, you know.

20:15Speaker 4:Mars, the moon, any environment that we know of beyond Earth, these are incredibly harsh places to live. The reality of it is that this is it's not a straightforward process to just get there, set up shop and survive. So it leads us to think about, well, what are some of the tools that we have to be able to make it a little bit easier for people living in those environments? And so I do think that robotics is going to play a very large part there. I think that robotics combined with AI is likely to be an essential aspect of how people can really thrive.

20:51Speaker 2:How will the physical AI help the people?

20:52Speaker 3:Yeah, that's right.

20:53Speaker 4:So I think if we think about something like, imagine there's a medical crisis, right? Currently in space, the protocol is that the crew on the International Space Station or any spacecraft would call back to mission control to get advice from a professional. You can't do that when you're on Mars because it takes as long as 20 minutes to send a signal from Mars to Earth. and another 20 minutes to get the reply. So you're looking at 40 minutes or more of time delay from when you send a message to when you get the response. That's not what you want in a medical crisis. So they need to be self-sufficient. And so either you send... you know, an entire society with all of the experts that you need for whatever crisis you might experience, or you need ways to be able to solve those problems without having experts.

21:45Speaker 3:And that's where I think AI is going to play an important role.

21:48Speaker 2:Yeah, that really changes everything rapidly.

21:50Speaker 1:I mean, three years ago, had we been having this conversation, we wouldn't have thought AI would be sufficient to act as your doctor. But now, with the quality of these frontier models, plus the robots... That seems like a very new door that opened.

22:05Speaker 3:Yeah, I think so.

22:05Speaker 4:We're not maybe quite there yet, but I've seen demonstrations of, you know, prototypes of essentially an AI physician going through a diagnosis and trying to sort out what might be going on. And it's getting there. You know, it may not be that far off that that becomes possible. Nearly as good as a trained physician.

22:25Speaker 1:The speculation a lot of people are making is that it's actually going to be better. You've seen these recent demos where robots are sewing stitches into a hard boiled egg and it's doing it with such precision, really superhuman precision and speed. Okay, so let's imagine we have the first astronaut couple that gets pregnant and the child is going.

22:58Speaker 2:To be born.

22:58Speaker 1:Do you foresee that we would have to do something with genetic editing as a possibility to allow that child to survive?

23:05Speaker 4:Yeah, I do think that gene editing is likely to be a tool that we'll have to at least consider for helping people to adapt to the conditions on Mars. And you can think about gravity, which we were talking about before, being one of the challenges, right? So our bodies are well-suited to a 1G environment, as we were discussing before. What happens to a child whose body is developing in.

23:27Speaker 3:Less than a 1G environment?

23:29Speaker 4:If you're in a 1 3rd G environment, like on Mars, we don't actually know whether the bones are going to grow in a way that will lead to a healthy adult body. So it may be that making some genetic manipulations, some gene edits using CRISPR or similar technologies would help the body to grow in a way that would lead to a healthy adult.

23:48Speaker 3:But here's the thing. There might also be a trade-off.

23:51Speaker 4:It could be the case that People living on Mars and people who are born there will need to basically either adapt to the conditions on Mars or... be able to come back to Earth. It might not be possible to achieve both simultaneously. And what I mean by that is, let's say you are trying to be well adapted to the Martian environment, one-third gravity. There's a certain bone density that might be optimal, a certain muscle strength, maybe a certain height, stature, build.

24:25Speaker 3:That might help you to do well in the Martian environment. But if you come back.

24:28Speaker 4:To Earth, where you'll weigh three times as much you might not be able to handle Earth's gravity. It might literally crush you.

24:36Speaker 2:Yeah.

24:37Speaker 3:And that's a real concern.

24:39Speaker 2:So it's a one-way ticket.

24:41Speaker 1:I mean, what's interesting is with our ancestors, for example, who came over from Europe, let's say in the 1800s, early 1900s, that was a one-way ticket also. You said goodbye to everyone you knew and loved and you got on a ship and you never went back. You know, just because of the length of the travel and so on, that this is what you're speculating. So what you're saying is it wouldn't, at least yet, be a speciation event where we become different species, which we'll get to in a second. But instead, just we develop so differently that we can't go visit each other at home. Right.

25:12Speaker 4:I think for a child who's born on Mars, it might really be challenging for them to actually come back to Earth because gravity being different, but also the microbiome that we were talking about earlier, the other component to that is the immune system. And our immune systems also develop in response to the viruses and bacteria and other microorganisms.

25:33Speaker 3:That we interact with, right?

25:34Speaker 4:You get a cold once or you get the flu once and you're better able to fight that same virus or bacteria off the next time you encounter it. And so what is the immune system going to be like for a child born on Mars? They're going to be exposed to a very limited set of infectious diseases there. If they come back to Earth, now all of a sudden you just take a deep breath of air and you're inhaling all of these microorganisms that for you and I are probably completely harmless because we've experienced them our entire lives.

26:08Speaker 3:Our immune systems are really good at fighting those off.

26:12Speaker 4:It might not be the case for somebody who had never had exposure. So think about those Europeans who first came to the Americas and the devastating effects of the transmission of infectious diseases like smallpox for Native Americans. but now scale it up to not just a few different species of microbes, but orders of magnitude differences in terms of just the type or the diversity of microbes. So I actually worry that infectious disease and the immune system generally, could be one of the biggest limiting factors in allowing people to move back and forth between planets once we're talking about people actually born on other worlds.

26:54Speaker 2:Okay, so it's possibly a one-way door.

26:57Speaker 1:What do you see in terms of a speciation event, meaning the populations become so different that they can no longer mate with each other, which is how we define species of animals.

27:09Speaker 2:How long does that take?

27:10Speaker 4:I think we can really apply what we know about evolutionary biology, say, on islands on Earth. to thinking about people living on different planets, which are effectively giant islands, right? And so on Earth, places like the Galapagos Islands that have inspired studies of evolution going back to Darwin, right? What we know is that the more different the environment is, the faster the rate of evolutionary change and speciation. But also there's another factor. It's how often are individuals able to move back and forth between that island and the place that they came from or between various islands.

27:48Speaker 3:So in the context of space, what.

27:50Speaker 4:We're talking about is how often are people going between Earth and Mars or Earth, the moon and Mars or anywhere else where people might live. That becomes a very important factor in predicting how long it would take for a new species of humans to evolve on Mars. The more often people are moving back and forth, the the slower that speciation would be.

28:13Speaker 3:So it's possible that it would take a while.

28:15Speaker 4:But on the other hand, if it becomes dangerous or risky or problematic in some way for people to move between planets, for example, because infectious disease is a risk. that might actually make it happen much faster.

28:29Speaker 1:And one of the things that greatly interests me is when we look at issues of plasticity, not only of the brain, but the whole body, it may be that we are not pre-programmed to be humans exactly like this, but instead have tremendous flexibility. And we could end up in a very different environment. And the biology just figures it out because every experiment that we do seems to indicate that same thing.

28:54Speaker 2:Sort of thing. In my book, LiveWired, I talk about lots of examples of this.

28:58Speaker 1:My colleague, Mike Levin, has beautiful examples of the way that you just change the environment or change the genome of things, and it just figures it out and says, okay, cool, I'll build this without a problem. So it is certainly imaginable that you could have a Martian species that we would at some point no longer call the same species of human.

29:18Speaker 4:Well, I mean, this is interesting because it really gets us into questions about what does it mean to be human, right? And I like to use what we know from the past as a precedent for thinking about the future.

29:27Speaker 3:So if we think.

29:28Speaker 4:About what we know about human origins, right, there were previously other species of human, other species of hominids, for example, Homo neanderthalensis or Neanderthals. Now, the thing that's interesting is we are starting to see more and more debate about whether those were, in fact, a distinct species or whether it was just homo.

29:50Speaker 3:A different type of homo sapiens.

29:52Speaker 4:And so this is very much, I think, relevant for these conversations about if we change in the future, if there's a branch of humanity that becomes different, how different do they have to be before they're no longer homo sapiens or they're no longer human?

30:06Speaker 3:What does it mean to be human?

30:09Speaker 4:I actually think that's one of the more fascinating aspects of thinking through the thought experiment of what happens next if we live beyond Earth.

30:17Speaker 2:I totally agree.

30:18Speaker 1:And we often envision, hey, maybe we'll get off the planet and humans will take over the solar system and beyond. But in your vision, it would be not humans. It would be lots of different species eventually.

30:31Speaker 3:Or different types of humans.

30:32Speaker 2:Yeah.

30:32Speaker 4:So if you play forward that thought experiment of, OK, we are successful in creating a settlement on Mars and they're self-sufficient and thriving and they evolve into a new.

30:42Speaker 3:Species, let's say.

30:43Speaker 4:And then we move on from there and we're inhabiting other worlds within our solar system. Maybe eventually we have the ability to inhabit other solar systems as well. Now you have this diaspora of humanity, each adapted to its own unique world. And In some ways, I think that's a fantastic vision of the future. It's an incredible vision to imagine what that would be like and how each type of humanity would have their own unique specialties and be really cool and interesting and the things that they would invent and.

31:16Speaker 3:Come up with. On the other hand.

31:19Speaker 4:I worry because, again, the precedent from history suggests that we don't tend to treat people that we see as different from us very well. And so that is a concern that I have is if settling space means becoming different, how are we going to treat one another? So to me, put it in sort of science fiction terms, is it going to be more like Star Trek, where it's sort of peaceful exploration in the name of science, or more like Star Wars, where we're basically battling one another? Obviously don't have the answer to that, but I do think it's something we need to be at least thinking about as we move forward in space exploration.

31:58Speaker 2:Absolutely.

31:59Speaker 1:And this is the whole history of humankind terrestrially is some island population splits up into two islands. Maybe they don't have much communication for 200 years and then they invade and kill each other. Yeah. Yeah.

32:10Speaker 2:We see it all the time. Gosh. Okay.

32:12Speaker 1:So if in 300 years from now, a Martian human came and visited here, whose ancestors had lived on Mars for the last 300 years, What would that Martian find the most surprising about us and what would we find the most surprising about that Martian?

32:29Speaker 3:That's a really interesting question. Yeah.

32:31Speaker 4:You know, I mean, in some ways it may be that it's just the aspects of our environment that are so different. I thought about this as I was researching my book in the context of what might my children experience. take for granted here on Earth that would be very different on Mars.

32:46Speaker 3:And to me, one big thing is the ocean, right?

32:50Speaker 4:You know, the ocean is something that maybe we take for granted.

32:54Speaker 3:Maybe not.

32:54Speaker 4:I grew up in the Midwest. I like to think I can appreciate a good ocean. But, you know, the ability to swim in water. This was actually something that Scott Kelly, who actually wrote the foreword for my book, he talked about after spending a year in space and The first thing he did when he came home, he didn't even take off his clothes.

33:15Speaker 3:He went straight into the swimming pool.

33:17Speaker 4:The feeling of being immersed in water, it's something that he missed and something that he really looked forward to being able to do again.

33:24Speaker 2:Why? What is that feeling?

33:26Speaker 4:Well, I guess it's something about, you know, just the feeling of having water on your skin.

33:32Speaker 3:Maybe it's something about being buoyant. I don't know. Because I haven't experienced it myself. I can't tell you for sure.

33:37Speaker 4:But something about being able to be immersed in water.

33:40Speaker 1:Hmm.

33:41Speaker 4:Apparently is something that you really miss, even if you're just, I mean, just a year. A year is a long time, but if you're imagining somebody who had never had the opportunity to experience that.

33:52Speaker 3:There's no ocean on Mars. There used to be.

33:55Speaker 4:If you go back billions of years, maybe someday we'll be able to recreate that kind of environment on Mars, but not anytime soon. So I think people coming to Earth from Mars One of the things that I imagine they will really be surprised by or appreciate is nature and the incredible environment, right? Being in a forest, being in, you know, in the ocean, going to the beach, playing in the waves. Those simple things that are really an important aspect of who we are and where we come from.

34:25Speaker 4:And we know that when people are removed or deprived from those experiences and those environments that they suffer. Nature deficit disorder and the idea of biophilia and this innate attraction and appeal that nature and other living organisms have, I think, is going to be a really important aspect of thinking about how to make life beyond Earth as pleasant and enjoyable and healthy as possible. But it's also something that for people coming back to Earth, I think they'll really appreciate and enjoy.

34:58Speaker 2:Will we be able to terraform Mars? And if so, how long will that take?

35:02Speaker 4:So this is an idea that I think we've really changed a lot of our thinking scientifically about it. It came originally from science fiction, then was taken quite seriously by planetary scientists, including Carl Sagan. Now, my understanding from talking with some of these researchers is that the concept of making another planet like Mars Earth-like, it's not that it's impossible. Part of the problem is that it's temporary. So you could make the environment on Mars a little bit more Earth-like, for example, by increasing the density of its atmosphere to the point where you wouldn't need a pressure suit to walk around on the surface. You might still need breathable oxygen, but your body fluids wouldn't boil off when you walk around outside.

35:44Speaker 3:And so that's possible. But the issue is.

35:48Speaker 4:The reason Mars doesn't have much of an atmosphere is that it lost it. It used to have a denser atmosphere, but it was stripped away by the solar wind, right? The sun is constantly bombarding the inner planets with radiation and particles, and those are going to strip away the atmosphere of a planet with lower gravity like Mars. So you could do it, and it would take probably thousands of years. So this is not a short-term solution. But even if you did, it would only be there temporarily unless you're constantly replenishing it. And that becomes a real challenge.

36:24Speaker 1:Mm-hmm. I thought Carl Sagan's proposal was if you plant the plants in the ice caps, then it would build the atmosphere to keep it in there, no?

36:32Speaker 4:So that would be one of the ways that you could try to replenish it. But you're actually still losing mass. So if you think about it as it's not actually a closed system where it's just recycling like it is on Earth.

36:44Speaker 3:It's actually losing mass to space.

36:47Speaker 1:Is that just because we're at the perfect distance, we're in the Goldilocks zone, and so that's why the solar wind doesn't strip our atmosphere away?

36:54Speaker 4:It's actually more about the fact that we have a magnetic field surrounding Earth that is largely shielding us from a lot of that radiation.

37:02Speaker 3:And Mars has just.

37:04Speaker 4:A tiny remnant of its magnetic field, basically doesn't have a magnetic field to to shield it. So those are two things that we haven't really talked about radiation much. That's one of the other real challenges on Mars without a magnetic field and with a very thin atmosphere. Those two things are causing us to not have to worry too much about radiation here on the surface of the Earth. We can walk around and maybe put on some sunscreen for the ultraviolet radiation. But for the most part, it's fine.

37:31Speaker 4:That won't be the case on the surface of Mars. Radiation exposure there is almost as intense as it is out in deep space. So that's another real challenge for anybody wanting to live on the surface of Mars.

37:43Speaker 1:And what do we do about that? Is it possible to build a magnetic field like terraforming?

37:48Speaker 4:That would be a major challenge. So I've heard some proposals, but none that sound feasible. So I think the more realistic solution is that you provide some shielding. And the easiest way to do that is actually to go underground. There's proposals for using, we think there are lava tubes on Mars. So like on Earth, where you have sort of a pre-made kind of tunnel that's conveniently going to a part of the underground region where there isn't going to be much radiation exposure. So that could work. But that leads to other issues, right? Like what happens to people who are living for prolonged amounts of time underground?

38:27Speaker 4:Now you're deprived of any kind of light cues from the environment, right?

38:32Speaker 3:Day, night, you know.

38:34Speaker 2:But we can make our own.

38:35Speaker 3:We can make our own. That's right. So we can mimic that. And so that's likely what people would do.

38:40Speaker 4:And again, that's what people do on the International Space Station as well. You turn off the lights when it's sleep time. But you're basically still trying to mimic the Earth environment. Eventually, people on Mars might decide there's no need to mimic the Earth environment. They're going to mimic the Mars environment, right? Even if they're living in the underground environment.

39:00Speaker 3:But I don't know about you.

39:01Speaker 4:I think people will not want to be living exclusively underground. They're going to want to go out on the surface and explore and– You see the sites, Olympus Mons, the tallest volcano in the solar system is there.

39:16Speaker 3:People are going to want to go and see that and experience it.

39:19Speaker 1:But it's like, what is it, the Morlock and the Eloy in the time travel?

39:22Speaker 3:HG Wells, yeah.

39:23Speaker 1:Where one half of humanity ends up living underground and the other half above ground.

39:28Speaker 2:And they speciate, they become different species. It might be like that.

39:31Speaker 1:And perhaps it's like the way that we live on the land and we go explore the ocean once in a while, maybe going to see the surface of Mars is like a day trip on a boat.

39:41Speaker 3:Yeah, that's right. I mean, it could be right. And it's also another example of ways in which we.

39:45Speaker 4:Might see adaptations in the future where people are perhaps able to better handle the radiation exposures on the surface of Mars that for us seem unimaginably challenging and harsh. But perhaps there would be. I mean, we know organisms on Earth do have different amounts of natural resistance to radiation and the ability to repair damage to DNA caused by radiation. So that is a possibility. It's one of the other ideas I explore in my book. But it's also the thing that we could one of the things that we could think about in terms of how do you choose who gets to go? This is another interesting question, because the way that we've historically selected astronauts or people, anyone going to space, we might need to think differently if we're talking about actually creating a settlement there, because maybe you want to ensure that the people that are going are the people that naturally tend to have already the greatest amount of ability to repair DNA damage from radiation.

40:42Speaker 3:Or maybe you just engineer it that way, right?

40:45Speaker 1:Or maybe you allow evolution to speed up by seeing new forms or genes or protections that come about naturally.

40:54Speaker 4:And that's where it gets interesting, too, because ultimately the source of all variety in all life is.

41:02Speaker 3:comes from mutations.

41:04Speaker 4:And we know that mutation rates increase with radiation exposure. So actually, in some ways, exposure to that radiation could be part of the engine that helps generate novel forms of solutions, right? Novel ways to handle the extreme environments on Mars.

41:24Speaker 2:That's right. And maybe.

41:26Speaker 1:In 500 years, Martians come back and say to Earthlings, like, hey, here's how you guys can take care of the cancers that you guys get. Because we went through that gauntlet the hard way and have now developed genetics to make sure that we don't get that anymore.

41:40Speaker 2:Yeah, that's right.

41:41Speaker 4:And it's one of the arguments that people often point to for why space exploration is so important is that consistently through history, what we've seen is that solving problems for space is helps people back on Earth. And I do think that would be very true for people attempting to live on other worlds like the Moon and Mars, is that if we can solve the problems that would be necessary to actually live there, it will lead to ways.

42:07Speaker 3:That we can improve life here on Earth.

42:09Speaker 4:I mean, just thinking about trying to grow food, another real challenge to being on Mars. If we can grow food in the very harsh and desolate environment of Mars, think about how that might improve the ability to grow food in challenging places here on Earth. So I think there's a lot of synergies there.

42:27Speaker 2:Yeah.

42:28Speaker 1:Now, by the way, one part of my research about the brain and the Earth is I hypothesized some years ago that it's the rotation of our planet that causes dreaming. Specifically, we end up with half our time in the dark and the visual cortex is in danger of getting taken over. And so dreaming is like a screensaver to make sure that in the dark where you can still touch and taste and smell.

42:49Speaker 2:And here you don't get that taken over.

42:51Speaker 1:So what's interesting is this is a great example for the kind of thing you're talking about. Let's say we ended up on Venus someday where a day is 238 Earth days equals a day on Venus.

43:04Speaker 2:So that would totally change.

43:05Speaker 1:What is necessary in terms of dreaming or if we're On the moon, let's say you're only living in the light, then you just don't need dreaming anymore to defend the visual cortex. So this will be a very slow change on evolutionary timescales. But that's another interesting one. Something as fundamental as dreaming. I suggested in my book LiveWire that it may turn out that we are some of the only dreamers in the cosmos.

43:32Speaker 3:Oh, that's really fascinating.

43:34Speaker 1:Yeah.

43:34Speaker 4:And what happens if we lose... Like what would that do to us or what happens if dreaming lasts longer or becomes a bigger part of the experience?

43:44Speaker 3:I'm thinking about going back to what you're.

43:45Speaker 2:Saying about the moon.

43:46Speaker 4:You know, the moon, depending on where you are on the moon, could have two weeks, birth weeks of of nighttime. I want to know what a two-week-long dream is like, and you hope it's not a nightmare.

44:00Speaker 2:I think it's.

44:00Speaker 1:Probably like hibernation for bears, that kind of thing. We don't know, of course, what their internal experience is, but my guess is that a bear's brain needs to generate lots of imagery so that when they wake up in the spring— their visual cortex hasn't been taken over and they're blind.

44:17Speaker 2:Yeah, yeah.

44:18Speaker 3:Oh, that's fascinating. Yeah, yeah. That would be really interesting.

44:21Speaker 4:And this is the thing that I think is so exciting about this moment that we're in, because we're really on the cusp of an era in which More and more people are going to be spending more and more time in space and deeper in space, whether it's the moon or farther like Mars.

44:36Speaker 3:We're going to learn so much.

44:38Speaker 4:Every time we go to space, every time we stay a little bit longer, every time we go a little bit farther, we learn so much not only about space and our solar system and our galaxy and our universe, but but about ourselves, right?

44:52Speaker 3:Our inner cosmos, right?

44:53Speaker 4:So yeah, I mean, we're going to learn so much about us as humans, the more and more that we push the boundary and go farther and farther away from Earth.

45:08Speaker 2:That was my interview with Scott Solomon.

45:10Speaker 1:We looked at what's going to happen with astronauts, then what happens to the people who really settle down somewhere new, and then to their children, and then what happens to the species. As we talked about, for all of human history, our evolutionary environment has been fixed at the planetary level. We humans have trooped across continents and moved into deserts and islands and forests and And more recently, we've changed our environments through technology, but this all happened inside the container of one planet and space travel.

45:44Speaker 2:Changes that, because.

45:46Speaker 1:For the first time, we're contemplating environments that differ from Earth in fundamental ways. Gravity now becomes a variable, as does radiation, or the length of the day and the amount of sunlight, and all those invisible microbes. Every one of those variables touches biology, and that is why human biology was is part of the infrastructure of space exploration. As we discussed, one future that Scott considers in his book is that adaptation to Mars could eventually come with a price. A body optimized for Mars might find it hard or impossible to function under Earth's stronger gravity and Earth's rich collection of microbes. And that creates the possibility that a new planet becomes a one-way biological door. Your grandkids might leave Earth and live on Mars and raise a family there, and the descendants of that family, your great grandkids and so on, could eventually become increasingly adapted to their new world, and their connection to Earth could become cultural and historical, the way that people tell stories about the old country. Mars would be an island separated from the Earth by millions of miles, and eventually, the

47:04Speaker 1:Gulf would become unbridgeable. Eventually, we could be looking at different kinds of humans. Now, humans used to have close relatives, like Neanderthal, but somehow we squeezed down to just one flavor of humans, Homo sapiens, and now finally we might be spreading back out as we move into the solar system. Maybe one population will become really well adapted to radiation. and another to low gravity, and another will live in some habitat where the cycle of light and dark is very different. And maybe, as Scott emphasized, we'll develop technologies that allow inhabitants to modify their biology directly. And eventually, what we're going to see is this diaspora of humanity, different environments, different bodies, different cultures.

47:55Speaker 2:And different evolutionary trajectories.

47:57Speaker 1:And what's fascinating about this is that the deeper we go into space, the more deeply we're going to understand the effects of Earth. We're gonna discover just how much of this planet we've been carrying around inside of us without realizing it, packed in there by three and a half billion.

48:16Speaker 2:Years of evolutionary history.

48:19Speaker 1:So we're going to get a great double benefit out of space exploration.

48:23Speaker 2:The more we go outward, the more we go inward.

48:28Speaker 1:Go to Eagleman.com slash podcast for more information and to find further reading. Join the weekly discussions on my sub stack and check out and subscribe to Inner Cosmos on YouTube for videos of each episode and to leave comments. Until next time, I'm David Eagleman and this is Inner Cosmos.