Looking at the chart of "Each colony hop has 90% the "diversity" of its parent", we see that by the 10th we only have 34% diversity left.
It's not at all clear that 34% of diversity is too small. On earth right now, we had smaller groups of people arrive at some general location and tend to mostly reproduce within that group, creating what we now call "ethnic groups". Is 34% diversity more or less diversity than currently exists in, say, Ireland, or Norway?
Furthermore, the article completely ignores that over time spontaneous mutations contribute new genetic diversity. It doesn't give a time scale for the "send a ship, wait for the colony to grow large enough to colonize a new world" iteration but I would imagine that in the time it takes that to happen 10 times sequentially you will have more than enough new genetic diversity.
This argument seems, frankly, absurd to me on multiple fronts.
First, it assumes that lack of genetic diversity in humans would be a serious handicap, when we're considering humans that are capable of making interstellar journeys. Assuming that genetics are going to be an issue compared to traveling/surviving 7 or more light year-journeys is a leap.
Second, it assumes that if this were a problem, humans would/could think of no way to address it. Two solutions come immediately to mind: 1. Choose the people making the journey more carefully to ensure diversity 2. Send frozen embryos chosen for diversity along.
Third, it ignores the time scale over which something like this would be likely to happen. Of course, you can't guarantee that beneficial diversity will re-occur, even over centuries, but a little effort on the front end combined with the time it would take to continue on to the next hop seems hopeful.
Fourth, it ignores the possibility of repeat journeys. If we're really going to constrain the available destinations in the way presented, it's silly to propose that there will be just one colonizing event.
But really, the first solution is all you need. The idea that we'll be able to survive multiple generations in space but not handle genetics issues is, just, a real stretch.
Are we conveniently assuming that only humans will be able to read and tweak their genomes, and do synthetic biology?
An odd assumption if we’re generously granting FTL or even regular space travel to aliens.
Everything from the lack of radio communication to the commonness of biological precursors like nucleic acids and amino acids in space points to multicellularity being the relatively rare thing, at least in our part of the galaxy.
We don’t hear from them or see them because if they’re out there, they’re still microbes eating each other. That one case of the two forming a symbiotic relationship, which leads to more endosymbiosis… that’s where I suspect our real rareness lies.
> Furthermore, light-speed lag and distance mean that child civilizations must be functionally independent of parent cultures.
Makes me wonder if a solar system wide civilization, with trillions of beings, wouldn't invest in ships to go to the next system, extract resources, and create a stream of resources ships going back to the original solar system.
That might sound uneconomical. Why not just go to the other system? But moving trillions of beings, and disrupting all their practical considerations and dependencies, would be a far more costly enterprise.
In the short run it would be resource acquisition. In the long run, the new system would accumulate entities, and then a civilization of its own. But there might still be strong value, or incentives, for the original system to continue acting as a kind of capital/dominant/higher value location.
Long distance/time dependencies could develop and be naturally maintained via complex decentralized indirect but intertwined economic arrangements. Just as shareholders who have done nothing but push a button on their phone to get an electronic record of having some stock in a company, have strong property rights over complex systems they may never see or understand, because it is in everyone's interest for the system to keep working.
Also, automated systems that defend themselves and their owners positions, even across a few light years. With the owners being able to trade their value in real time, even if the physical returns are long term.
> Long distance/time dependencies could develop and be naturally maintained via complex decentralized indirect but intertwined economic arrangements.
But that would require causality-breaking FTL, no? Otherwise the speed of light itself would create enough of an obstacle to make any trade impractical. Property rights only work if they are enforceable, which is the case on Earth but not over interstellar distances.
> Makes me wonder if a solar system wide civilization, with trillions of beings, wouldn't invest in ships to go to the next system, extract resources, and create a stream of resources ships going back to the original solar system.
This reminds me of those old 4X-type games like "Stars!" where I would often do exactly this. Basically some planets were good for living on and others were good for mining and you'd have a constant caravan of freighters from the latter to the former.
Didn't followed the reasoning. What is "one colony"? some genetically homogeneous expedition? Unless you get a more or less continuous flow of colonizers from the home world, to be viable it needs hundreds of diverse individuals to kickstart. And setting, viability, being self-sufficient, becoming widespread enough within the planet to survive climate/tectonic/etc events should be in the picture unless it is an elaborate and very expensive way to get rid of some troublesome individuals. Establishing one colony nearby in Mars is still far from being feasible with today's knowledge and technology, and probably not so close technology too.
Even generational ships are a challenge, but more important, if we are able to make long term self-sustaining generational ships maybe we won't need to land, or change the equation between traveling and settling.
In any case, we didn't reach any outer solar system planet yet, not even with probes. We might not be fully aware of many of the practical problems of reaching and settling on another solar system planet. We might be like ancient mesopothamians asking ourselves why we shouldn't be able to build a tower to the moon.
> Back of the envelope calculations suggest that even modest propulsion technology should be sufficient for a single technological species to spread throughout the galaxy in a geological instant
I think this is where it all went wrong. Overly optimistic assumptions from atomic age thinkers about how technology was going to overcome all obstacles in the near future based on their recent life experience. The thinkers seriously underestimated the amount of technological progress needed to produce an extremely complex machine that operates indefinitely with no outside support whatsoever in an environment where any error can be fatal and there is a constant stream of hazards to contend with.
You might be thinking: "So what, it just means it takes a few centuries longer to get started, in Geological terms that is nothing.", but the problem isn't that it is hard, it is that it makes the trip significantly harder than simply building orbital habitats in your home solar system. Once you have that, what is the point of spending vast amounts of resources in trying to colonize a mostly unknown star system tens or hundreds of light years away?
Sure there are always people who will want to climb Everest, but this problem is so big that it's unlikely that one person or even a small group will be able to undertake it. The resource investment is simply too colossal. It would be much harder to climb Everest if you had to convince the entire population of London to come with you.
I don't think they were wrong about that. I think what they were wrong about is that we could maintain our civilization at the same level they experienced long enough to make significant progress. We dropped the ball in less than two generations and it's yet to be determined if we can pick it back up.
My pet theory is that intelligence converges as it increases, and superintelligent beings inevitably reach the same conclusion, which is that they should not expand into the universe.
The reasons may or may not be something we could comprehend, but they could be simple ideas like
The corruption of the Fermi Paradox is a personal bugaboo of mine. Somewhere along the way everyone started getting it completely wrong, interpreting it as being about galactic colonization and the spread of intelligent life throughout the galaxy. I don't know where this came from but I deeply wish people would stop calling it the Fermi Paradox and give it its own name.
Fermi's contention of "where are they?" was predicated on two things 1) the probability that intelligent life exists elsewhere in the galaxy and 2) that faster than light travel is possible and would be discovered by a technological society.
The napkin math that Fermi did was essentially what we now know as the Drake equation. One important variable in this is the duration of a technological civilization. I personally believe that Fermi would assign the probability of a civilization existing for "geological timescales" necessary to colonize the galaxy using slower than light travel at zero which is a clear resolution to this Not-Fermi Paradox. His paradox is only so because he thought FTL would be discovered in the not very distant future which makes the duration required for a technological civilization quite small and allows them to visit many worlds quickly, with or without a galactic empire which in this interpretation could realistically exist for a normal timescale and not the frankly ridiculous millions of years that the Not-Fermi Paradox always seems to take for granted.
tldr; if it doesn't involve FTL it's not the Fermi Paradox, choose a different name
First, I would just naturally assume you are wrong as Fermi would have known that FTL was practically impossible.
Fermi evidently made the comment in the 1950s at Los Alamos, as I understand it became widely known due to Carl Sagan's 1963 paper "Direct contact among galactic civilizations by relativistic interstellar spaceflight"
What the Fermi paradox involves is near light speeds, because, as Sagan says in the paper above "Interstellar spaceflight at relativistic velocities has several obvious advantages... all points in the Galaxy are accessible within the lifetime of a human crew, due to relativistic time dilation."
There is also the Michael Hart paper "Explanation for the Absence of Extraterrestrials on Earth" from 1975 but I have not found any satisfactory for open reading source of this online.
At any rate it seems absurd that any famous physicist of the last 90 years at least would ever have suggested that aliens should have been here because they would have had faster than light travel. You are essentially saying Fermi thought Einstein's Theory of Relativity was very much wrong.
on edit: I said 90 years to hedge bets in case there was some really old guy still hanging around in 1935, science progressing one funeral at a time and all that. But it seems really unlikely that there would have been.
This is an interesting article, but I think most of it does not seem applicable to a reasonable civilization attempting colonization, that is aware of these problems.
1. The population size in the colony will be very small. Maybe? It should be at least MVP (minimum viable population, not product) that is a relatively well researched concept. I'd argue that it won't be a colony below that. More of an outpost. And when talking about aliens and Fermi paradox, we don't even know what their MVP might be. It may not be even close to MVP of vertebrates on Earth.
2. That selecting the colonists by some criteria is not useful. It is, it's just not selecting by the "best genes". It's selecting for more diversity in the first place. Lack of diversity in the colony is much less of a problem, if more of it is introduced in the first place.
3. That colonization is an isolated thing and people won't arrive/leave over time. Why wouldn't there be more than one colony ship, if sending them becomes viable overall?
4. The population does not grow and remains at the original diversity levels. Combined with 2 and 3, it may not even matter that much. Unless it experiences a series of catastrophes, it should keep growing and becoming more diverse over time again. This is of course the most questionable case. Will it? I think considering how humanity has spread like a plague on Earth, it won't be a problem.
What I think is that the table might look very different with the above taken into account. Maybe 99% of diversity in the first colony and none of it will necessarily remain static or diminishing.
> Cheetahs experienced diverse catastrophes (see what I did there?)
Almost stopped reading after that one (I groaned, it's still to early!) but feel that's when the article kind of lost its plot. Worth reading though some good nuggets here.
I am firmly convinced the observable universe is just too exceedingly vast for intelligent life to sustain contact. Maybe i'm wrong!
I wish there was more background on Percolation Theory because that's not something I'd been exposed to before. But after looking into it more it am happy I did: [0]
As a kid sitting in the backseat of the car (or adult driving looking through a windshield) I always noticed how raindrops would hit the glass, then continue to coalesce with other drops and form larger drops before flying off the pane. Is it the same thing?
The discussions around that 1140b Super-Earth made me realize if most of life is on 10G planets, they aren't making it out of orbit, maybe not even into orbit
Even just 2G would require much more advanced technology than we have now to escape the planet
This is a weak argument. Genetic engineering and artificial repair of major genetic disorders and artificial ways to boost genetic diversity are all way way easier than building a starship.
This is a kinda silly argument. Interstellar colonies would have the opposite problem: they'd cease to be the same species due to genetic drift.
If you look at the (im)practicalities of interstellar travel, it's going to take centuries. That means a generational ship of some kind. That means having a sufficient population to get there, which really means tens of thousands of people. Plus, the kind of ship that would make that would likely host up to millions. That's just not going to create a genetic bottleneck.
Also, you could even mitigate that by bringing frozen genetic material.
I don't know if a generational ship is absolutely required. There's this assumption that interstellar ships would be full of human astronauts who are alive and awake. But that might not be strictly required. You might be able to have everybody go there frozen. Or have a robot ship that gives birth to the colonists from an artificial womb on arrival.
The assumption that biological life will be doing galactic colonization seems myopic in the extreme. Let's just consider the progression here. Life on Earth appears around 4.5 billion years ago. Humans start evolving around 2.8 million years ago. Use of language appears around 100,000 years ago. Writing is invented around 5500 years ago.
Inventions of language and writing are the landmark moment here. Before language was invented the only way information could be passed down from ancestors to offspring was via mutations in our DNA. If an individual learned some new idea it would be lost with them when they died. Language allowed humans to communicate ideas to future generations and start accumulating knowledge beyond what a single individual could hold in their head. Writing made this process even more efficient.
So, after millions of years of life on Earth no technological development happened. Then when language was invented humans started creating technology, and in a blink of an eye on cosmological scale we went from living in caves to visiting space in our rocket ships. It’s worth taking a moment to really appreciate just how fast our technology evolved once we were able to start accumulating knowledge using language and writing.
Now let’s take a look at how technology itself has been evolving. Once we discovered radio communication we went through a noisy period where we were leaking a lot of our broadcasts into space, and within a span of a 100 years we started using more efficient communication, and encryption. If somebody intercepted our broadcasts today they would look like noise because they’re designed to look like noise. Our society today is utterly and completely unrecognizable to somebody from even a 100 years ago. If we don’t go extinct, I imagine that in another thousand years future humans will be completely alien to us as well.
So the period during which intelligent life would be recognizable to us during its course of evolution is infinitesimally small. The time between creating language and becoming an advanced technological society is measured in thousands of years, while evolution of life is measured in millions of years. The chance of two different intelligences finding each other at exact same stage of development where they might be able to communicate is incredibly unlikely.
Based on that, I would imagine that the biological phase for intelligent life is rather short. We’re likely to develop human style AIs within a century, and they will be the ones to go out and explore the universe. Meat did not evolve to live in space, we’re adapted to gravity wells. An artificial life form could be engineered to thrive in space without ever needing to visit planets. This is the kind of life that’s most likely to be prolific in space. Furthermore, post biological intelligences would likely be running at much faster speeds than our mental processes operate on. What we consider real-time would be might we consider to be geological scales. Such beings might consider what we view as real time akin to the way we look at continental drift. We’re aware that it’s happening, but it’s of little interest to use on day to day basis. It’s quite possible that advanced civilizations become solipsistic and care little for the outside universe.
For all we know the Universe may be teeming with intelligent life and we just don’t recognize it as such. We might be like an ant hill next to a highway looking to see if there are other ant hills around.
> For all we know the Universe may be teeming with intelligent life and we just don’t recognize it as such.
This is my preferred answer to the Fermi question as well. Unless two civilisations are in a precise (and likely small) window where they both can and want to communicate, it's likely the less advanced one wouldn't even recognise the other one. Especially if the other one doesn't "want" to be recognised.
> Before language was invented the only way information could be passed down from ancestors to offspring was via mutations in our DNA.
Language (in the sense of "use of language appears around 100,000 years ago") is not the only way to communicate information, and many animal species are perfectly capable of communicating information despite not having evolved what is being called "language" in this sense.
I’m thinking along my similar lines. Expansion, if it happens, will likely not be on a recognizably human substrate, but rather something else. But currently it’s more of an intuition than a rigorous argument for me. How do would you formulate a more solid argument around this idea?
Against Mind-Blindness: Recognizing and Communicating with Diverse Intelligences - King's College London Neuropsychiatry Research & Education Group - https://www.youtube.com/watch?v=RHkFmUwW0kM
This argument doesn't resonate with me.
Looking at the chart of "Each colony hop has 90% the "diversity" of its parent", we see that by the 10th we only have 34% diversity left.
It's not at all clear that 34% of diversity is too small. On earth right now, we had smaller groups of people arrive at some general location and tend to mostly reproduce within that group, creating what we now call "ethnic groups". Is 34% diversity more or less diversity than currently exists in, say, Ireland, or Norway?
Furthermore, the article completely ignores that over time spontaneous mutations contribute new genetic diversity. It doesn't give a time scale for the "send a ship, wait for the colony to grow large enough to colonize a new world" iteration but I would imagine that in the time it takes that to happen 10 times sequentially you will have more than enough new genetic diversity.
This argument seems, frankly, absurd to me on multiple fronts.
First, it assumes that lack of genetic diversity in humans would be a serious handicap, when we're considering humans that are capable of making interstellar journeys. Assuming that genetics are going to be an issue compared to traveling/surviving 7 or more light year-journeys is a leap.
Second, it assumes that if this were a problem, humans would/could think of no way to address it. Two solutions come immediately to mind: 1. Choose the people making the journey more carefully to ensure diversity 2. Send frozen embryos chosen for diversity along.
Third, it ignores the time scale over which something like this would be likely to happen. Of course, you can't guarantee that beneficial diversity will re-occur, even over centuries, but a little effort on the front end combined with the time it would take to continue on to the next hop seems hopeful.
Fourth, it ignores the possibility of repeat journeys. If we're really going to constrain the available destinations in the way presented, it's silly to propose that there will be just one colonizing event.
But really, the first solution is all you need. The idea that we'll be able to survive multiple generations in space but not handle genetics issues is, just, a real stretch.
Are we conveniently assuming that only humans will be able to read and tweak their genomes, and do synthetic biology?
An odd assumption if we’re generously granting FTL or even regular space travel to aliens.
Everything from the lack of radio communication to the commonness of biological precursors like nucleic acids and amino acids in space points to multicellularity being the relatively rare thing, at least in our part of the galaxy.
We don’t hear from them or see them because if they’re out there, they’re still microbes eating each other. That one case of the two forming a symbiotic relationship, which leads to more endosymbiosis… that’s where I suspect our real rareness lies.
> Furthermore, light-speed lag and distance mean that child civilizations must be functionally independent of parent cultures.
Makes me wonder if a solar system wide civilization, with trillions of beings, wouldn't invest in ships to go to the next system, extract resources, and create a stream of resources ships going back to the original solar system.
That might sound uneconomical. Why not just go to the other system? But moving trillions of beings, and disrupting all their practical considerations and dependencies, would be a far more costly enterprise.
In the short run it would be resource acquisition. In the long run, the new system would accumulate entities, and then a civilization of its own. But there might still be strong value, or incentives, for the original system to continue acting as a kind of capital/dominant/higher value location.
Long distance/time dependencies could develop and be naturally maintained via complex decentralized indirect but intertwined economic arrangements. Just as shareholders who have done nothing but push a button on their phone to get an electronic record of having some stock in a company, have strong property rights over complex systems they may never see or understand, because it is in everyone's interest for the system to keep working.
Also, automated systems that defend themselves and their owners positions, even across a few light years. With the owners being able to trade their value in real time, even if the physical returns are long term.
> Long distance/time dependencies could develop and be naturally maintained via complex decentralized indirect but intertwined economic arrangements.
But that would require causality-breaking FTL, no? Otherwise the speed of light itself would create enough of an obstacle to make any trade impractical. Property rights only work if they are enforceable, which is the case on Earth but not over interstellar distances.
> Makes me wonder if a solar system wide civilization, with trillions of beings, wouldn't invest in ships to go to the next system, extract resources, and create a stream of resources ships going back to the original solar system.
This reminds me of those old 4X-type games like "Stars!" where I would often do exactly this. Basically some planets were good for living on and others were good for mining and you'd have a constant caravan of freighters from the latter to the former.
Didn't followed the reasoning. What is "one colony"? some genetically homogeneous expedition? Unless you get a more or less continuous flow of colonizers from the home world, to be viable it needs hundreds of diverse individuals to kickstart. And setting, viability, being self-sufficient, becoming widespread enough within the planet to survive climate/tectonic/etc events should be in the picture unless it is an elaborate and very expensive way to get rid of some troublesome individuals. Establishing one colony nearby in Mars is still far from being feasible with today's knowledge and technology, and probably not so close technology too.
Even generational ships are a challenge, but more important, if we are able to make long term self-sustaining generational ships maybe we won't need to land, or change the equation between traveling and settling.
In any case, we didn't reach any outer solar system planet yet, not even with probes. We might not be fully aware of many of the practical problems of reaching and settling on another solar system planet. We might be like ancient mesopothamians asking ourselves why we shouldn't be able to build a tower to the moon.
> Back of the envelope calculations suggest that even modest propulsion technology should be sufficient for a single technological species to spread throughout the galaxy in a geological instant
I think this is where it all went wrong. Overly optimistic assumptions from atomic age thinkers about how technology was going to overcome all obstacles in the near future based on their recent life experience. The thinkers seriously underestimated the amount of technological progress needed to produce an extremely complex machine that operates indefinitely with no outside support whatsoever in an environment where any error can be fatal and there is a constant stream of hazards to contend with.
You might be thinking: "So what, it just means it takes a few centuries longer to get started, in Geological terms that is nothing.", but the problem isn't that it is hard, it is that it makes the trip significantly harder than simply building orbital habitats in your home solar system. Once you have that, what is the point of spending vast amounts of resources in trying to colonize a mostly unknown star system tens or hundreds of light years away?
Sure there are always people who will want to climb Everest, but this problem is so big that it's unlikely that one person or even a small group will be able to undertake it. The resource investment is simply too colossal. It would be much harder to climb Everest if you had to convince the entire population of London to come with you.
I don't think they were wrong about that. I think what they were wrong about is that we could maintain our civilization at the same level they experienced long enough to make significant progress. We dropped the ball in less than two generations and it's yet to be determined if we can pick it back up.
AI is not bound by genetic bottlenecks.
You can absolutely select founding population to be maximally genetically diverse and of large enough number to avoid inbreeding.
Speciation is a likely outcome for interplanetary and interstellar colonies, yes.
You can also carry with you frozen gametes or digital genomes. Digital genetic information can be transmitted between systems at trivial cost.
My pet theory is that intelligence converges as it increases, and superintelligent beings inevitably reach the same conclusion, which is that they should not expand into the universe.
The reasons may or may not be something we could comprehend, but they could be simple ideas like
1. Not being motivated by novelty
2. Not wanting to interfere with other life
3. Being completely inward-focused
Maybe expanding beyond your home planet never gets as easy as we think it will be in the future.
The corruption of the Fermi Paradox is a personal bugaboo of mine. Somewhere along the way everyone started getting it completely wrong, interpreting it as being about galactic colonization and the spread of intelligent life throughout the galaxy. I don't know where this came from but I deeply wish people would stop calling it the Fermi Paradox and give it its own name.
Fermi's contention of "where are they?" was predicated on two things 1) the probability that intelligent life exists elsewhere in the galaxy and 2) that faster than light travel is possible and would be discovered by a technological society.
The napkin math that Fermi did was essentially what we now know as the Drake equation. One important variable in this is the duration of a technological civilization. I personally believe that Fermi would assign the probability of a civilization existing for "geological timescales" necessary to colonize the galaxy using slower than light travel at zero which is a clear resolution to this Not-Fermi Paradox. His paradox is only so because he thought FTL would be discovered in the not very distant future which makes the duration required for a technological civilization quite small and allows them to visit many worlds quickly, with or without a galactic empire which in this interpretation could realistically exist for a normal timescale and not the frankly ridiculous millions of years that the Not-Fermi Paradox always seems to take for granted.
tldr; if it doesn't involve FTL it's not the Fermi Paradox, choose a different name
You are wrong.
First, I would just naturally assume you are wrong as Fermi would have known that FTL was practically impossible.
Fermi evidently made the comment in the 1950s at Los Alamos, as I understand it became widely known due to Carl Sagan's 1963 paper "Direct contact among galactic civilizations by relativistic interstellar spaceflight"
https://www.sciencedirect.com/science/article/abs/pii/003206...
What the Fermi paradox involves is near light speeds, because, as Sagan says in the paper above "Interstellar spaceflight at relativistic velocities has several obvious advantages... all points in the Galaxy are accessible within the lifetime of a human crew, due to relativistic time dilation."
There is also the Michael Hart paper "Explanation for the Absence of Extraterrestrials on Earth" from 1975 but I have not found any satisfactory for open reading source of this online.
At any rate it seems absurd that any famous physicist of the last 90 years at least would ever have suggested that aliens should have been here because they would have had faster than light travel. You are essentially saying Fermi thought Einstein's Theory of Relativity was very much wrong.
on edit: I said 90 years to hedge bets in case there was some really old guy still hanging around in 1935, science progressing one funeral at a time and all that. But it seems really unlikely that there would have been.
This is an interesting article, but I think most of it does not seem applicable to a reasonable civilization attempting colonization, that is aware of these problems.
What I think is that the table might look very different with the above taken into account. Maybe 99% of diversity in the first colony and none of it will necessarily remain static or diminishing.> Cheetahs experienced diverse catastrophes (see what I did there?)
Almost stopped reading after that one (I groaned, it's still to early!) but feel that's when the article kind of lost its plot. Worth reading though some good nuggets here.
I am firmly convinced the observable universe is just too exceedingly vast for intelligent life to sustain contact. Maybe i'm wrong!
I wish there was more background on Percolation Theory because that's not something I'd been exposed to before. But after looking into it more it am happy I did: [0]
As a kid sitting in the backseat of the car (or adult driving looking through a windshield) I always noticed how raindrops would hit the glass, then continue to coalesce with other drops and form larger drops before flying off the pane. Is it the same thing?
https://en.wikipedia.org/wiki/Percolation_theory
The discussions around that 1140b Super-Earth made me realize if most of life is on 10G planets, they aren't making it out of orbit, maybe not even into orbit
Even just 2G would require much more advanced technology than we have now to escape the planet
This is a weak argument. Genetic engineering and artificial repair of major genetic disorders and artificial ways to boost genetic diversity are all way way easier than building a starship.
This is a kinda silly argument. Interstellar colonies would have the opposite problem: they'd cease to be the same species due to genetic drift.
If you look at the (im)practicalities of interstellar travel, it's going to take centuries. That means a generational ship of some kind. That means having a sufficient population to get there, which really means tens of thousands of people. Plus, the kind of ship that would make that would likely host up to millions. That's just not going to create a genetic bottleneck.
Also, you could even mitigate that by bringing frozen genetic material.
I don't know if a generational ship is absolutely required. There's this assumption that interstellar ships would be full of human astronauts who are alive and awake. But that might not be strictly required. You might be able to have everybody go there frozen. Or have a robot ship that gives birth to the colonists from an artificial womb on arrival.
The assumption that biological life will be doing galactic colonization seems myopic in the extreme. Let's just consider the progression here. Life on Earth appears around 4.5 billion years ago. Humans start evolving around 2.8 million years ago. Use of language appears around 100,000 years ago. Writing is invented around 5500 years ago.
Inventions of language and writing are the landmark moment here. Before language was invented the only way information could be passed down from ancestors to offspring was via mutations in our DNA. If an individual learned some new idea it would be lost with them when they died. Language allowed humans to communicate ideas to future generations and start accumulating knowledge beyond what a single individual could hold in their head. Writing made this process even more efficient.
So, after millions of years of life on Earth no technological development happened. Then when language was invented humans started creating technology, and in a blink of an eye on cosmological scale we went from living in caves to visiting space in our rocket ships. It’s worth taking a moment to really appreciate just how fast our technology evolved once we were able to start accumulating knowledge using language and writing.
Now let’s take a look at how technology itself has been evolving. Once we discovered radio communication we went through a noisy period where we were leaking a lot of our broadcasts into space, and within a span of a 100 years we started using more efficient communication, and encryption. If somebody intercepted our broadcasts today they would look like noise because they’re designed to look like noise. Our society today is utterly and completely unrecognizable to somebody from even a 100 years ago. If we don’t go extinct, I imagine that in another thousand years future humans will be completely alien to us as well.
So the period during which intelligent life would be recognizable to us during its course of evolution is infinitesimally small. The time between creating language and becoming an advanced technological society is measured in thousands of years, while evolution of life is measured in millions of years. The chance of two different intelligences finding each other at exact same stage of development where they might be able to communicate is incredibly unlikely.
Based on that, I would imagine that the biological phase for intelligent life is rather short. We’re likely to develop human style AIs within a century, and they will be the ones to go out and explore the universe. Meat did not evolve to live in space, we’re adapted to gravity wells. An artificial life form could be engineered to thrive in space without ever needing to visit planets. This is the kind of life that’s most likely to be prolific in space. Furthermore, post biological intelligences would likely be running at much faster speeds than our mental processes operate on. What we consider real-time would be might we consider to be geological scales. Such beings might consider what we view as real time akin to the way we look at continental drift. We’re aware that it’s happening, but it’s of little interest to use on day to day basis. It’s quite possible that advanced civilizations become solipsistic and care little for the outside universe.
For all we know the Universe may be teeming with intelligent life and we just don’t recognize it as such. We might be like an ant hill next to a highway looking to see if there are other ant hills around.
> For all we know the Universe may be teeming with intelligent life and we just don’t recognize it as such.
This is my preferred answer to the Fermi question as well. Unless two civilisations are in a precise (and likely small) window where they both can and want to communicate, it's likely the less advanced one wouldn't even recognise the other one. Especially if the other one doesn't "want" to be recognised.
> Before language was invented the only way information could be passed down from ancestors to offspring was via mutations in our DNA.
Language (in the sense of "use of language appears around 100,000 years ago") is not the only way to communicate information, and many animal species are perfectly capable of communicating information despite not having evolved what is being called "language" in this sense.
I’m thinking along my similar lines. Expansion, if it happens, will likely not be on a recognizably human substrate, but rather something else. But currently it’s more of an intuition than a rigorous argument for me. How do would you formulate a more solid argument around this idea?
Against Mind-Blindness: Recognizing and Communicating with Diverse Intelligences - King's College London Neuropsychiatry Research & Education Group - https://www.youtube.com/watch?v=RHkFmUwW0kM
each leg takes hundreds of years to establish, increased "Diversity" is free on these time scales.