You know, that Oumuamua object that was discovered passing through, apparently accelerating at a rate, but it didn't have any gases coming off of it. So maybe it was a, you know, like a techno object or a spaceship from another solar system or something like that. The problem is it's gone and we're never going to get it back. And you just have this little data thing of a light signature or something like that. And so he went in search of maybe objects that crashed in the ocean, this interstellar object that crashed near Papua New Guinea. And he had that expedition there last year. I thought he was going to dredge up the Millennium Falcon dashboard or something. Wouldn't that

have been cool? But

instead he has these little microspheres. And this is what's always frustrating for me. It's like, it's so hard to say, but what is it exactly? And most people I talk to go, no, no, those are just industrial waste or something. So then you have to do a chemical analysis of what these things are made out of and how common is that on Earth versus somewhere else. I don't know. We just don't get definitive evidence, darn it.

Yeah. You know, extraordinary claims require extraordinary proof

is how it goes. Yeah. Yeah, for sure. Okay. So moving away from the left wall of simplicity, once life gets up and running and evolution is working its magic, what are the other major transitions that are part of the hard steps model that you are revising that maybe are not that hard?

candidate in time would be the origin of oxygen generating photosynthesis or oxygen, oxygenic photosynthesis, which Jen is, uh, is more of an expert on that than I am. So maybe you want to talk about cyanobacteria and when they arose or. Yeah,

sure. Um, right. So, so worth, worth making it clear that, um,ynthesis is different than photosynthesis in general. There's lots of photosynthetic microorganisms that harvest light and fix carbon into their biomass without producing any oxygen as a waste product. And so there's a long history of studying the evolution of photosynthetic genes and the evolution of photosynthetic lineages. And it's important to point out that light harvesting is not a single origin transition. Photosynthesis is found in many different lineages. And it's true that genes for photosynthetic apparatus, light harvesting enzymes, those have been swapped around quite a bit because they're incredibly useful. But photosynthesis is found in many, many different unrelated bacterial lineages. Cyanobacteria appear to be the only organisms, the only lineage that can produce oxygen as a byproduct of their light harvesting. And so this is the explanation for why this might be one of the transitions that's difficult. you know there are we we talk about this in a in a more detailed way in the paper and i think um you know i think like many of these transitions it's we need to test whether or not they actually are unique um and and what the relationship of the timing is between other events that might have made them more or less probable in terms of the environment. So you can imagine a scenario in which you've got all these light-harvesting bacteria, you've got plenty of nutrients, and you're running out of things to breathe because in order to do photosynthesis, you actually have to have something to breathe if you're going to fix CO2. And so in that scenario, there's a selective pressure to be able to breathe something new, which is exactly what cyanobacteria figured out how to do. They learned how to breathe water, which is never going to run out. And so if you suddenly are able to breathe water you're going to grow right as much as you want as long as the nutrients are there and then when the nutrients run out nobody else is free to evolve that because you've occupied all those niches and so this is one explanation of one scenario that is right in the in the category of pulling up the ladder pulling up the evolutionary ladder which is which is one thing that that can happen um you know if you if you're first to the if you're first to the cheese you can eat it all before anyone else can figure

out how to eat cheese that's

a great analogy dan you were going to say something

Yeah, no, and there's a lot of debate as to when oxygenic photosynthesis evolved. Some people think it evolved something like 3 billion years ago, but then some people say, no, it's closer to 2.4 or so, and that's a big, that's 600 million years. That's, you know, 600 million years ago, there were barely animals on the earth, so it's a long stretch of time. But we know by 2.4, that's when oxygen became a That's or less stable feature of the atmosphere, like above trace levels. That's the initial oxygenation of the atmosphere. So the people, especially the people who think oxygenic photosynthesis evolved close to this oxygenation event, it's clear that oxygenic photosynthesis is not one of the very first bacterial metabolisms on Earth. It came later compared to some of the other bacterial metabolisms. And usually, and this is the kind of stuff I get from my colleagues, like at the end of a conference session, they don't explicitly say in their talks, they don't put it in their papers, but we talk about it. And I think I've talked to people, they think that reflects just the inherent contingency involved in making that work. Because the idea is that to use water as your electron source for this whole process is really chemically difficult, biochemically difficult, and that is just hard for evolution to figure out. And this is a big contrast to how people think in the same field about the origin of animals, for example. Usually it's said animals originated late in Earth history because the environment was unconducive to animal life until relatively recently in Earth history. They don't usually apply the same logic to cyanobacteria, but there are people in our field who do. But it's very controversial because there are people who reconstruct really hot temperatures for the early Earth. Like, the Earth has always had liquid water, so that's like an upper bound. It can never not support liquid water. But think it could have been like 70 degrees Celsius or something like on average at the surface. And if that's true, you know, there are no hyperthermophilic cyanobacteria. So that so some people think once, you know, there are bacteria who can grow really high temperatures, but the phototrophs are not among them or cyanobacteria, especially are not among them. So they think as the Earth cooled, that controlled when that transition could happen. Of course, a lot of our colleagues don't even like us talking about this because they're convinced the early Earth was mild. But even then, some work recently has shown that the origin of oxygenic photosynthesis may have happened in fresh water, not in the ocean. And it looks like the extent of land above the surface of the ocean, we call this subaerial, below the air. Subaerial landmass was relatively limited on the early Earth, and then that would limit fresh water availability. So as continents grew and became more exposed above the ocean, there would have been more fresh water availability and more opportunities for oxygenic photosynthesis to originate. And maybe that explains the timing and not its inherent improbability. That's the suggestion we put out there. And

I think, Dan, listening to you talk, it makes me want to say, I think one of the strengths of this paper that we wrote is that it highlights some very distinct hypotheses that are testable. We just haven't, you know, geobiology is hard. The rock record is incomplete. You know, genes don't tell all. But we are, we do progress. And if we focus on, you know into some of these hypotheses that are raised in this discussion, we may find answers.

is to do more studies like this to try to reconstruct the ancestral conditions for this transition. And people are doing this already outside the context of hard steps because it's already interesting and important, even if you don't care about, you know, extraterrestrial life. So, for example, people have done work to try to figure out if it happened in freshwater or in the ocean or the temperatures involved. we need a more exhaustive list of the required conditions, like temperature, salinity, pH, other things like this. And then that comes more from people studying microbial physiology or the evolution of microbial genomes. But then there are people in our field who reconstruct these ancient environments using these rocks and the geochemical signatures they contain. Then we need them to help us reconstruct when those conditions were required. And this is already ongoing, but that's the kind of information we need. What did this transition require with respect to the environment? And when did the environment meet those conditions? And not only does this apply to the origin of oxygenic photosynthesis, the same logic applies to all of these candidate hard steps. Because something Carter, Carter imagined that these hard steps had equal probability of happening throughout Earth history. And we know that's not true because Earth's environment has transformed itself so radically that there are large, long intervals of Earth history where some of these hard step candidates were not viable. They were the environment did not support them. Um, it's not a coincidence that we find ourselves in the Phanerozoic Eon when atmospheric oxygen has never been higher and not in the Archean atmosphere when the atmosphere was anoxic. Like that's not a coincidence. That's, and that's actually an application of Carter's anthropic reasoning. Um, so we have to apply that reasoning to every hard step in context of Earth's changing surface environment.

Nice. Well, as we come up on an hour here, I want to be mindful of your time, but I don't want to let the subject of intelligence escape. Here's your final paragraph. This could be the dust jacket paragraph for your book. The implications of our proposed alternative to the hard steps model extend well beyond assessing the likelihood of human intelligence on Earth. This framework can be applied to any evolutionary innovation in Earth's past, whether or not the innovation in question led to the origin of H. sapiens. This framework raises the possibility that biospheric evolution generally proceeds in a coarsely deterministic or predictable fashion governed by long-term biospheric trends like increasing habitat diversity in response to unidirectional changes in Earth's surface environment. Not only would these trends and processes apply to Earth throughout time, but their analogs may apply to other inhabited Earth-like worlds in the universe. Yeah, in this sense, not only would the evolutionary origin of H. sapiens be more inherently probable than Carter predicted, but so would the evolutionary origins of human analogs beyond Earth. Okay, so there I think you do need to define intelligence. You sort of punted on that in the early part of the paper, I think, because it's a whole different subject, really. But, I mean, if a simple, I don't know bacterial grade organism is moving in the direction of a chemical gradient or toward the light or whatever to solve some particular problem isn't that a kind of intelligence yes

um yeah so i would say and this is something i've never written on or you know i'm not qualified with respect to my research but um yeah in that sense intelligence is pervasive across the tree of life in that general sense. I guess what we're trying to say is, and we do talk about this, because even Carter, what was he trying to explain the origin of? And sometimes he makes it sound like our species, Homo sapiens. Sometimes he makes it sound like a technological civilization, or even just observers observerhood beings who are able to reflect on their own origins the way we are now like bacteria probably can't do that but we can and so there's like an operational approach you could have like with the search for techno signatures you could just define it as um you know beings with a technology that leaves an atmospheric imprint that our instruments can detect. That's a very, like, pragmatic view. Or, like, in traditional SETI, it's anything that can build a radio telescope or something. So that kind of bypasses the question and just takes a more, you know, practical approach. But in the sense that you brought up yeah i do think intelligence and and is is widespread and but it's hard to put it into words um what is the difference between that kind of intelligence and and you know yeah it's it's

akin to the the the problems that we we've had as as human scientists to defining what life is right you know right the example of a of a bacterium going towards the light that that's that is a response to the environment and i think that that definition of intelligence is probably incomplete and and but it does highlight the fact that life fundamentally is something that responds to the environment right and and reacts to it right um and so that's certainly part of a definition of intelligence that i would i would sanction you know there's no there's no universally agreed definition of of even life so imagine the problems define an intelligent life um but but a lot of people think they know life when they see it um yeah then and probably a lot of a lot of people would say yeah i know intelligence when i see it uh but but when you come right down to it it's not an easy thing to define. Oh,

yeah. Dan, you're going to say something?

No, I agree. And that was actually, that was something in

the paper I tried to avoid. Like, I had to talk about it a bit, but I really think that would require a more interdisciplinary effort involving psychologists, anthropologists, I don't know, neuroscientists or people who are more well-versed in the evolutionary history of animals. So I think that's something really interesting. And it's actually, I would say, in the history of the hard steps model, it's never really been explicitly looked at. Like amongst astronomers, it's mostly just used in a colloquial or intuitive sense, or this very pragmatic sense like they have radio telescopes. this is something that I think this conversation would benefit from. Yeah, more, more insight coming from other disciplines to try to formalize this or try to figure out what are we even talking about? We're trying to assess the probability of what

exactly? I think we can say that consciousness, which is that sort of observerhood, ability to reflect on self, that is an area of intense research and considerable progress. So just like the origin of life or dark matter, consciousness is this area that inspires an immense amount of curiosity and scientific research. And so I think, you know, those sorts of folks that study consciousness are certainly should be part of that discussion.

Oh, yeah. I mean, but that's another one of those hard to define. What do you mean conscious? And it's usually defined as what it's like to be something. Well, how would I know what it's like to be something other than me? Unless I was that object. If I was a bat, I wouldn't be Michael Shermer now realizing what it's like to be a bat. I'd just be a bat. I'd have no idea how I'm thinking about this. Right?

Yep. It's a tough, it's a great unknown. And, you know, people are, there are experts on this who are in all those disciplines, they're named neuroscience, psychology, anthropology.

Oh, I've had them all on the show and they don't, they don't have an answer really. I mean, uh, Christophe Koch just paid, uh, David Chalmers, uh, a case of wine. Cause they, they bet 25 years ago last year that the hard problem of consciousness would be solved by 2024. And it wasn't. Interesting. Wow. And, you know, should we

be making bets?

Yeah. Yeah. Yeah. You should do that. Like Stephen Hawking did with was it with Kip Thorne on the nature black hole or I guess it was can radiation escape black holes or something like that. Yeah. That makes it kind of fun but um yeah you know the problem again with this intelligence stuff um you know i uh back in the day when it was just seti looking for uh signals from a technological civilization i thought you know you could get all the way to neanderthal level intelligence on earth and let's say we went extinct instead of the Neanderthals, and they were just still living in Europe, making stone tools. They wouldn't be making rocket ships and the internet and television for some other civilization to detect this. They would never know we're here. Now, I suppose with the biosignatures, maybe, or something like that, they'd know there's life anyway on Earth. But still, you could get all the way to that level, which is a lot. Massive brains, brains bigger than ours, and still have no technological space-faring civilization. Absolutely.

No,

that's right.

No, I think Neanderthals, we wouldn't be able to infer their presence from atmospheric spectra. I can't imagine how, but if we could observe them through other means, or actually visit a planet that had something like Neanderthals, even if they weren't making telescopes or spaceships, that would be absolutely amazing. Obviously, I'd be pretty impressed if they're Neanderthals. Though I guess people who advocate for the Great Filter would not like that, because then they mean it's relatively easy to get to that stage. But what's really hard is to get to the next, but in this situation, we're already visiting another planet. So I guess we figured it out. Um, but yeah, these are the sorts of things that it raises.

My answer to the Fermi Paradox is they probably are out there somewhere. It's just a mostly big, empty space. It's mostly just nothing between the stars. And so the chances of us finding them are vice versa, just low. Yeah, that was what

I remember reading that web book. I think that was his preferred explanation. And I was convinced of it. Also, as a rare Earth advocate, it's just very few inhabited planets make that transition. With this hard steps model, it does predict that this is the thing. We don't know how common Earth like planets are. I mean, more than just terrestrial planets in the habitable zone where liquid water is stable, but also planets that are able to accommodate the sorts of surface trends that we have been talking about, like they're capable of atmospheric oxygenation or they have active plate tectonics like we have on Earth. The physical properties need to be compatible with this sort of environmental and biological evolution. And it could be that once you have, as the early Earth was, planets with similar starting conditions, once they originate and have life, maybe this sort of biosphere trajectory is common, but it could be that those sorts of Earth-like planets are really rare. And that would then still explain the Fermi paradox. Even on the few cases where life does originate on these planets, they might evolve something like Neanderthals eventually. But even then, you know, they're not going to come and visit us or we're not going to see them anytime soon.

Yeah. Well, that was a question Robert Wright brought up in his book Non-Zero. He argued for an inevitability in evolutionary progress. And if it wasn't us, it would have been Neanderthals. It wasn't Neanderthals. It would have been Homo erectus. It wasn't them. It would have been chimps or gorillas or what. I don't really see it that, that way. I think that's too, too directionality for evolutionary theory to support, but it's an interesting idea. Yeah.

I heard. I think you can, I think you can, you could put that thought into this model of what life does you know it's it's a essentially a it's a definition of life life explores niche space life explores the space available for for living in the environment and you know if if humans homo sapiens had not pushed neanderthals out you know what what what space would that species have explored right

given the

time okay that's a good point i think it's not i think it's not crazy yeah

to me that sounds actually kind of reasonable okay yeah nice personally

if we were to go extinct right now i don't necessarily think like uh charlie lineweaver called this the planet of the apes idea like if we go extinct chimps, they're going to immediately fill in this vacant space. I don't know if I necessarily believe that. But let's say the biosphere has another billion years of supporting the sorts of conditions that exist now. even if all primates go extinct, in the next billion years, could there be another tetrapod lineage, you know, another vertebrate, land-dwelling vertebrate that can evolve comparable technology in that time? I'm actually more open-minded about that possibility than I was before. And I also agree we can't rule that out. I don't think it has to be, again, primates or chimps immediately, but in next billion years it could be a different lineage um exploring the same uh niche and again it only needs to be a couple lineages it's not not all lineages are trying to fill in that space and that's not how it works but you don't need all lineages to fill in that space for it to happen again um so i'd be more optimistic if we went extinct that something like us would appear before the earth

becomes completely sterile. Remember Dale Russell, the paleontologist who projected that bipedal spear carrying tool using dinosaur? I

think that was back in the 80s. that where like um i think i've seen pictures of this yeah yeah yeah it's on someone conway morris i think sometimes uses it in his talks it's like this lizard person yeah right and maybe yeah i don't know and yeah lizards i don't and this is interesting like what clades or groups of organisms would be more conducive to this like would it have to be a mammal or a bird can reptiles even do that i mean i guess um oh we are reptiles let's yeah right reptiles actually or birds are reptiles yeah there's uh well reptiles are not a natural group yeah we're fish these aren't clades um right so yeah i don't know but it yeah raises these sorts of questions which lineages would be good candidates or what what traits do these lineages need to have in order to make a transition like that? And I don't think we really know, or at least I don't know. Maybe people are working on that.

Yeah. Well, I think these are early days in what you're doing. I mean, it's probably centuries away from really having a full understanding, like maybe we're in Newton's time or Galileo's time for physics. And, you know, 400 years later, it's going to be very different.

Right. It's

a hard problem. Yes. Yeah. Way harder than physics, I think. I

have heard Simon Comey Morris wrote that we're kind of, biology is kind of like where physics was before Einstein. And then biology is awaiting its Einstein analog that's going to put biology in completely new territory, which is an interesting thought.

I don't think there's going to be an Einstein because it takes too many kinds of expertise these days to progress. Yeah. Yeah. I think it's going to be an Einstein collaborative.

Yeah.

Group of Einstein. Yeah. One of those papers with 300 co-authors. Yeah.

That's

going to do it. Yeah.

Or at least four. At

least four. That's right. Like your paper. All right, guys. Thank you so much. That was really super interesting. I'll hit the stop button there. Thanks for having us. This was fun. Thank you. That was really good. Such a great topic.