It's one of a whole class of problems that (1) we will have to solve or we will go extinct, but (2) are completely and utterly pointless to actually try to solve now because they are so far beyond our level.
When some far future people finally have the ability to seriously start working on one of these problems, they will have techniques and knowledge so far ahead of us that anything our best and brightest could do in a lifetime's work now on the problem will be something the future people can trivially do in a day.
The only contribution we can make now to these problems is to just continue to improve our science and engineering in general, in the hope that if we do that for enough generations then eventually our successors will have enough accumulated knowledge to actually tackle these problems.
Patently ridiculous to make the assumption that given a billion years, no multicellular photosynthesizing organisms will adapt to the changing environment. A billion years.
It's literally enough time to even lift heavier elements from the Sun to extend it's stable life cycle by several billion years.
Another commenter suggested moving the planet and got down voted to oblivion but it's not at all a ridiculous suggestion in these kinds of time scales. You could place giant ion thrusters on the moon and set it in an orbit where tidal effects would nudge the Earth outwards over a few million years. This can be made subtle enough as to not even be noticeable to life on Earth.
Of course a cheaper solution is to just use a solar shade that can incrementally decrease it's opacity to compensate for the brightening sun but this would not be enough when the Sun transitions into it's red giant phase
The problem isn't the engineering, as usual, it's political. Can you realistically foresee humanity taking on such long term projects? We can't even get people to stop burning fossil fuels to "mine" cryptocurrency.
Sure but you're thinking current humanity and contrary to modern times, there were plenty of civilisations that did engage in long term infrastructure in the past.
We're talking millions of years in the future and assuming "we" are still around, I doubt that a 21st century layperson would be able to deduce that they ever stemmed from the same genus, never mind species - even assuming no genetic engineering or cyborgs.
Life extension is also likely going to play a major factor in the future and it's a lot harder to dismiss the merits of long term thinking when it's a very likely possibility that you will be around to experience the consequences of your current short-sightedness.
It does not give me great confidence in the modeling. Perhaps the paper goes into great detail about the formulas used in the code, and explains those variables and naming choices (those not in the Constants file with comments), or the fitting coefficients.
Of course, I really wonder how the complexity of the natural world could be captured by a few hundred variables.
My impression is that a large amount of what we think as non-biological is in fact the product of life. Making the prediction that life will be unable keep the environment the same despite external factors seems like a bold predication; let's see how it plays out.
Separating presentation by subdomain feels like a relic from the 2000s or earlier. Wikipedia is one site that could do to be modernised with dynamic formatting or whatever it's called. Even BBC moved news.bbc.co.uk to bbc.co.uk/news although that is not quite the same thing.
If I'm reading that right, that's only C3 plants. C4 plants would keep going until 800–900 million years. And who knows if something else doesn't evolve or is engineered for the different conditions.
I wonder if the great filter is not one, but multiple coincidences brought upon by "intelligent" life and the natural lifetime of a planet and/or solar system.
If Mars had intelligent life and now it doesn't how does that bode for Earthlings? Can life really adapt given the lack of evidence anywhere?
I wonder how will space travel to the next possible habitable planets work. Shoot in all directions and hope that life spawns on a few of those possible habitable planets that are light years away.
I think we can all but rule out a dead, ancient planet-spanning civilization on Mars now. We have medium resolution imagery of the entire planet and high resolution (meter or submeter) imagery of a lot of the surface, in a wide distribution. Mars hasn’t had enough volcanic activity to hide evidence of a planet-spanning civilization unless it occurred while large asteroid impacts were much more common.
Venus, however, is sheathed in clouds. So we only have low resolution radar images of most of the planet, and we’ve only sent a few very short-lived landers with low resolution cameras to the surface. They could have landed in areas that were once oceans or otherwise uninhabited. And secondly, Venus has been basically completely resurfaced with lava over time. Venus may once have had large oceans before runaway greenhouse effect. (And keep in mind that the Sun has gotten significantly brighter over billions of years, besides the increased greenhouse effect on Venus.) And so we can’t even rule out a planet-spanning civilization like our own. It’d take a lot more exploration and drilling to rule that out.
I always wondered what it would be like if Mars and Venus were swapped. Would Mars be warmer, or would it be even more devoid of atmosphere? And would Venus (with its greenhouse gas) be a more livable temperature if it was in Mars's orbit? It still wouldn't be survivable due to the atmospheric composition, but I was just wondering about raw climate.
The atmospheric composition is likely driven in part by the higher intensity of the Sun. At Mars, it’d have gotten a quarter of the sunlight. That means more water in its atmosphere (as there’s have been less UV to dissociate the water and less light pressure and less solar wind to blow the hydrogen away), less release of CO2 from carbonates, etc.
Yes, mars is too small to hold its atmosphere at its current distance from the sun, moving it closer would only make the problem worse. Like our moon, the bright side would be hot during the day, but it would be cold at night with very little atmosphere to retain heat, and even in temperate regions at the poles liquid water would not be stable.
We're not really sure what kicked off Venus' runaway greenhouse, so it's possible that would still occur, though it does seem less likely. Without the runaway greenhouse, Venus' atmosphere would likely remain primarily nitrogen. Its atmosphere would still be significantly thicker than Earth's but by a factor of 5 instead of a factor of 100. With the additional atmosphere, it might remain quite temperate even at the greater distance.
Of course had Venus and Mars developed in eachother's places, Venus would have developed as a smaller world with a thinner atmosphere (generally more mars-like) and Mars would have been larger with a thicker atmosphere (generally more venus-like), so the whole point is somewhat moot.
A planet spanning civilization on Mars is less likely. However, there are still ways it could be found, depending on how long ago it was. I list three ways below, and suspect there are more.
First, there is the possibility of a civilization dying and evidence being erased by tectonic plate recycling. Mars is approximately 4.6 billion years old. We know it has volcanic activity, and most consider it to have inactive tectonics now. Some scientists believe it could have had significant activity in the past, based on the 3 distinct regions of Mars. Earth's tectonic plates vary in their rates of recycling: the oldest non-oceanic tectonic plate is 3.6 billion years old, and shows no sign of recycling. Oceanic plates recycle on the average of every 180 million years though.
Second, there is the possibility of technology that didn't leave a visible trace. This is not supported by any evidence and is mere conjecture. If the society tore down non-organic structures and converted to using all biodegradable/organic materials then evidence of the society would be scarce, if existent at all, especially if bodies were cremated as many do today. Chemical analysis could detect this I suspect, or more importantly prove it wrong.
Last, if for some reason civilization evolved underground and stayed underground, then there wouldn't be any visible evidence above ground. This is also pure conjecture. Micro-robots that explore Mars' caves might find something, as might ground penetrating radar.
Mars has volcanism but not tectonic plate recycling. That’s an Earth thing. There are large parts of the surface of Mars that are MUCH older than any significant surface areas of the Earth for this reason. And that’s my point.
As far as your latter point about life spreading, what’s interesting to me is that the most strict interpretation of our “planetary protection” guidelines at NASA actually prohibit life spreading to other worlds.
It would not surprise me if civilizations evolved in the same way life did on Earth.
Life evolved in the sea. At some point life evolved to leave the sea and go to land, whether the sea was no longer hospitable enough, or in search of better food. Life continued to evolve on Land, specializing into different groups and colonizing different lands.
Perhaps civilizations evolve on their planet, then at some point they leave their planet and go into space (when their planet is no longer hospitable or they need more/better food). Finally, while in space they evolve more, founding different colonies that evolve differently due to culture and environmental differences.
TL;DR: It's basically just than speculation based on the sun being hotter in a Billion years.
So, two people ran one model described in one paper. Even if that was the whole issue, it would merit "may last only" rather than "will last only".
Additionally, the authors are making a variety of assumptions with little or no basis about the behavior and development of Earth Flora and Fauna; specifically, that it will be mostly static in most ways, with no adaptation in genetics, inter-species interaction, prevalence in different places on Earth etc.
Having said that - in 5 Billion years, Sol will become a Red Giant, so this planet is going South at some point between now and then.
That's an incredibly long time, and there's no reason to assume our technology can't get better in that time (if we are around). Another solution is to move spaceship Earth:
https://dwheeler.com/essays/move-spaceship-earth.html
As I understand it the sun has another 4.5 billion or so years of life remaining but the earth has only another billion years or so of being habitable. That's interesting. Complex life first appeared on earth about 2.5 billion years or so ago and has 1 billion more years to go for a total span of 3.5 billion years. In earth's projected 9 billion year lifespan it will only have been habitable for 3.5 billion years, or 39% of that time. A technologically advanced civilization will have only existed for 1 billion years - or 11% of that time (that's assuming of course some form of advanced civilization continues on earth for another billion years).
Those are interesting numbers to consider when searching for extraterrestrial life in other planetary systems: 39% of planetary lifespan had advanced life, 11% of planetary lifespan had technologically advanced civilization.
Is there enough selective pressure to keep human-style intelligence in the gene pool for another billion years? Look at the abundance of species on Earth, and only one species has a space program. Is there enough selective pressure for other species to eventually evolve advanced intelligence (considering how much of it that crows and dolphins have) or is it just an accident that humans have it, and it may not stay in our genes forever?
Evolution takes a very long time. If we manage to not kill our own civilisation we will be fine as our technology will advance many orders of magnitude faster than evolution will be able to cause any significant changes to our intelligence via natural selection.
Anatomically modern humans evolved 300k years ago and didn't change much since. Can you imagine what kind of progress we will make in the next 300k years? I can't even imagine the next 1000 years.
That's a fascinating question! First, it raises the idea that human intelligence may actually decrease over time, especially as we offload our thinking to machines. It's hard to tell whether that will increase or decrease our intelligence or leave it roughly the same. I have a hunch, and it's just a hunch, that our intelligence will increase over time.
With regards to dolphins and crows - wow! What a find animals like that would be on another planet! Quite intelligent - but not technologically advanced. You raise an interesting question: assuming a planet has evolved life having the intelligence of a crow or dolphin, what's the probability that planet will evolve a technologically advanced life form? How likely is it earth is the only planet to have evolved such a life form?
That question is definitely unknowable in advance, because our intelligence level leads to radical changes in the environment in which we exist.
If we really, really, cared, we could set up a momentum exchange between Earth and Jupiter mediated by an asteroid, moving Earth further out and Jupiter (slightly) further in, chasing the outward drift of the Sol habitable zone: https://arxiv.org/abs/astro-ph/0102126
Also, we could (in principle, not saying we will or we should) engage in selective breeding or genetic engineering of ourselves; and while mind-uploading is currently SciFi, it’s in the category of “we recon this is eventually possible” rather than “convenient plot device”.
If you want to expand semi human traits to other planets (anywhere) you will need genetic engineering. Full stop. The idea that humans can be transplanted as-is does not hold given the results on the home planet.
OTOH, O’Neill cylinders are an alternative instead of planets, while the bad previous experiences with eugenics (and the tendency people have towards appeal-to-nature fallacy) may make people actively reject GM humans.
Here's a real-estate tip: when the sun bloats up into a red giant, Uranus will be a hoppin' joint with spiffy weather. I just hope they change the name by then.
The pace of current technology seems like it is speeding up more and more. Feels like a solid prediction even in hundreds of years of not thousands but of course if there is no civilization-ending thing that happens.
I think the point was a billion years is quite a long time and many things we know today will not be the same. Predictions were made about the amount of horse dung that will overrun new york city if the pace of traffic continues, as an example.
I can imagine a scenario where civilization collapses and humankind exists in a permanent dark age without abundant oil to launch a new industrial revolution.
Edit: Another alternative is technology progresses but political and cultural institutions do not, so the requisite level of global cooperation never materializes.
Interesting. Life emerged 4 billion years ago and the window of habitability for complex lifeforms will end in one more billion years. So terrestrial natural selection required 80% of the window of opprtunity to produce human intelligence. That's a tighter margin than I would have guessed.
This is predicted by the hypothesis that the origin of intelligent life requires the occurrence of several hard steps, each of which take at least several billion years (but with no upper bound) in expectation.
If that hypothesis holds, then conditional on all the steps having completed on a given planet, they will have done so roughly equally spaced in the time allotted, regardless of their relative difficulty.
So, for example, if the window on Earth is 5 billion years, and there are four hard steps to complete, then, conditional on all four steps finishing, we expect each step to have taken about 1 billion years, give or take, with about 1 billion years left to go.
Why do we think the origin of intelligent life requires a few hard steps and not just a continuous progression or perhaps one hard step and otherwise a steady progression?
I think the hard steps are sharp divisions that had a long time in the status quo, then a sudden random development. Single-cell to multi-cellular. Development of nerve tissue that can collect information, make decisions, and influence the organism. Centralization of a bundle of nerves into a decision making center. Then you get to higher order steps that probably aren't as complicated, such as communications and organization, then all the steps that humans went through that took a while, without having major biological changes that enabled them.
I think any step which occurred independently on multiple occasions is probably not a hard step. The origin of multicellular life from unicellular life occurred on at least three separate occasions independently.
However, I think at the very least that the origin of the first cells, as well as perhaps the transition from Archaean/Prokaryotic cells to our symbiotic Eukaryotic ancestor may qualify.
So basically there is only a limited window for life to kickstart from microbes to multi-cellular lifeforms to sapient beings and finally to spacefaring, terraforming civilisations.
I am not getting this kind of journalism. Guardianmag magazine article is a direct copy paste from https://phys.org/news/2021-03-simulations-earth-oxygen-rich-.... Yes, they cite that as a source (oddly enough, Guardianmag has not added web site address as a clickable link, why?). They didn't have any incentives to add some more details, anything, just copy paste.
It would be so great to learn some more details about the model, etc.
That article really doesn't give a very good explanation at all, it doesn't make sense.
When CO2 breaks down it produces oxygen and carbon, so if oxygen gets burned to produce CO2 it's just gonna get converted back into oxygen when the CO2 breaks down.
If the oxygen reacts with the atmospheric nitrogen then surely this will also get broken down since AFAIK less energy is needed to break down NO2 than CO2.
Currently the amount of oxygen in the atmosphere is over 500x more than the amount of CO2, so where is all that oxygen going to go?
There’s an immense amount of buried carbon. If you include all burnable carbon sources underground (including under the oceans), there’s approximately enough to burn up all the oxygen in the atmosphere. Plus there are lots of minerals that can be oxidized.
Plants require a certain temperature range to live (and also replenish CO2 slower than digging up and burning the carbon). And the sun directly is not very effective at producing oxygen. No discovered planet or exoplanet has an oxygen concentration like the Earth’s because it takes photosynthesis to be so extremely far from chemical equilibrium. UV dissociation just isn’t enough to get several psi of oxygen.
That is the sort of explanation I expected, but when I read the article, it presents a different causal sequence, in which photosynthesizing plants become ineffective, not because of increasing temperatures, but because of decreasing atmospheric CO2, as a result of its photodissociation. [1]
As presented in the news article, there is no explanation for why the apparently still-abundant oxygen does not react with, for example, the increased methane flux that the article also mentions, or just the carbon that has been liberated by dissociation, to maintain a CO2 level adequate for photosynthesis.
I don't doubt that the researchers have answers to these questions (quite likely the one you gave) but something seems to have gone missing in the creation of this news article.
[1] The article actually says "due to the gas absorbing the heat and breaking down", but AFAIK, CO2 is pretty resistant to this. Perhaps this is a garbled version of CO2 reacting more vigorously with rocks and soil at higher temperatures?
Oh, I see. Yeah, well my understanding of this is Earth as a self-balancing system:
The Sun gets brighter over time. Plants (over tens of thousands of years) absorb enough CO2 to keep the temperature from rising too much. But eventually the Sun is so bright that in order to keep the temperature in the right range, plants would have to absorb so much CO2 that there wouldn’t be enough for effective photosynthesis so that eventually in the future this negative feedback mechanism would no longer be able to compensate for the increased brightness of the Sun and so the temperatures would rise, perhaps eventually killing off enough plants to allow CO2 to start to be released and then you get runaway greenhouse effect like Venus.
That is all ignoring humans, of course.
EDIT: actually, it may make more sense to see the feedback coming from the other side of the temperature range: plants will keep absorbing as much CO2 as they can until temperatures drop (think ice ages) and photosynthesis slows. Volcanic emissions (and also occasional natural emissions of fossil carbon) keep a certain amount of CO2 being added which is then kept in equilibrium by plants. As the Sun warms, it takes a lower and lower amount of CO2 to get to ice ages that slow photosynthesis. The Sun over the ages increases in brightness until eventually CO2 levels can’t drop any more without slowing photosynthesis to a stop, so you stop getting ice ages and then eventually the temperatures get so high that photosynthesis is limited by die-off from high temperatures, removing the negative feedback mechanism of photosynthesis and you get runaway greenhouse effect.
That’s why pre-industrial CO2 levels were so low. Primates developed and later intelligent humans developed during the last few million and few hundred thousand years, when CO2 levels have been at their lowest levels ever in our planet’s history (and it shows that we evolved under low CO2 conditions, since human mental processing becomes somewhat less effective at even moderate CO2 levels like 800-1000ppm). Plants (unlike human brains) actually like higher CO2 levels and so they do function as an effective negative feedback mechanism as long you don’t outrun their photosynthesis capability and as long as you don’t kill them off with higher temperatures.
That is in line with what I thought was the scientific consensus too, but when I read the abstract (I should have done that first!) I see it saying "Our results suggest that the planetary carbonate–silicate cycle will tend to lead to terminally CO2-limited biospheres and rapid atmospheric deoxygenation", where I assume the carbonate-silicate cycle is the reactions between CO2 and rocks/soil, and if so, then this model seems to be suggesting that this will come into play before a runaway greenhouse scenario.
In that case, I think they’re saying that both CO2 and O2 will be absorbed over time by minerals (as well as CO2 being absorbed by plants), and once CO2 levels drop too much, photosynthesis stops (or slows), which means oxygen stops (or slows) being replenished as well, so oxidization of minerals will also lead to a reduction in oxygen levels.
(And less volcanic activity over time also means less CO2 being added back to the atmosphere, so the chemical weathering process that absorbs both CO2 and O2 into minerals will no longer have an active counterbalancing force from volcanoes.)
Life on Earth already survived one transition from an anoxic environment to an oxygen-rich environment, I see no reason to expect that it could not make the transition back to an anoxic environment. Granted it may not look anything like the life we're accustomed to today, but I suspect life will exist on Earth in some way, shape, or form for a long time to come.
For simple life-forms, perhaps, but complex life probably requires rather special or rare circumstances. In areas of Earth low in oxygen, the life-forms there are similar to ediacaran fauna: slow and soft. Increases in oxygen are probably a key cause of the Cambrian explosion.
Perhaps it's possible there is another high-metabolism cycle that doesn't involve much oxygen, but nobody really knows both if a pathway exists, and if evolution can "find" it in time. Any biochemists here who want to weigh in?
I find articles like this rich.
We don't even know by what mechanism the medication I take every day works, yet people think they can confidently postulate on far distant and far future events with any kind of certainty.
89 comments
[ 2.7 ms ] story [ 155 ms ] thread(I'm joking; the article is interesting, and I'm not trying to frame it as trying to portray this as an urgent threat)
It's one of a whole class of problems that (1) we will have to solve or we will go extinct, but (2) are completely and utterly pointless to actually try to solve now because they are so far beyond our level.
When some far future people finally have the ability to seriously start working on one of these problems, they will have techniques and knowledge so far ahead of us that anything our best and brightest could do in a lifetime's work now on the problem will be something the future people can trivially do in a day.
The only contribution we can make now to these problems is to just continue to improve our science and engineering in general, in the hope that if we do that for enough generations then eventually our successors will have enough accumulated knowledge to actually tackle these problems.
Another commenter suggested moving the planet and got down voted to oblivion but it's not at all a ridiculous suggestion in these kinds of time scales. You could place giant ion thrusters on the moon and set it in an orbit where tidal effects would nudge the Earth outwards over a few million years. This can be made subtle enough as to not even be noticeable to life on Earth.
Of course a cheaper solution is to just use a solar shade that can incrementally decrease it's opacity to compensate for the brightening sun but this would not be enough when the Sun transitions into it's red giant phase
We're talking millions of years in the future and assuming "we" are still around, I doubt that a 21st century layperson would be able to deduce that they ever stemmed from the same genus, never mind species - even assuming no genetic engineering or cyborgs.
Life extension is also likely going to play a major factor in the future and it's a lot harder to dismiss the merits of long term thinking when it's a very likely possibility that you will be around to experience the consequences of your current short-sightedness.
But the code is here: https://github.com/kazumi-ozaki/lifespan/blob/master/main.f9...
It does not give me great confidence in the modeling. Perhaps the paper goes into great detail about the formulas used in the code, and explains those variables and naming choices (those not in the Constants file with comments), or the fitting coefficients.
Of course, I really wonder how the complexity of the natural world could be captured by a few hundred variables.
1. https://www.nature.com/articles/s41561-021-00693-5#data-avai...
https://science.sciencemag.org/content/340/6134/822.full
Get to work on those planet hunting.
[0]: https://en.wikipedia.org/wiki/Timeline_of_the_far_future
If you're on a phone, does the non-mobile link redirect to mobile?
The formatting on the mobile site looked just fine to me on a laptop. I'm sure there's a good reason I'm missing.
IIRC, mobile Wikipedia has a bigger font, is less information dense, and the navigation doesn't work as well.
> If you're on a phone, does the non-mobile link redirect to mobile?
Pretty sure they do, but the reverse isn't true.
Why is Wikipedia not doing this?
If I'm reading that right, that's only C3 plants. C4 plants would keep going until 800–900 million years. And who knows if something else doesn't evolve or is engineered for the different conditions.
If Mars had intelligent life and now it doesn't how does that bode for Earthlings? Can life really adapt given the lack of evidence anywhere?
I wonder how will space travel to the next possible habitable planets work. Shoot in all directions and hope that life spawns on a few of those possible habitable planets that are light years away.
Venus, however, is sheathed in clouds. So we only have low resolution radar images of most of the planet, and we’ve only sent a few very short-lived landers with low resolution cameras to the surface. They could have landed in areas that were once oceans or otherwise uninhabited. And secondly, Venus has been basically completely resurfaced with lava over time. Venus may once have had large oceans before runaway greenhouse effect. (And keep in mind that the Sun has gotten significantly brighter over billions of years, besides the increased greenhouse effect on Venus.) And so we can’t even rule out a planet-spanning civilization like our own. It’d take a lot more exploration and drilling to rule that out.
We're not really sure what kicked off Venus' runaway greenhouse, so it's possible that would still occur, though it does seem less likely. Without the runaway greenhouse, Venus' atmosphere would likely remain primarily nitrogen. Its atmosphere would still be significantly thicker than Earth's but by a factor of 5 instead of a factor of 100. With the additional atmosphere, it might remain quite temperate even at the greater distance.
Of course had Venus and Mars developed in eachother's places, Venus would have developed as a smaller world with a thinner atmosphere (generally more mars-like) and Mars would have been larger with a thicker atmosphere (generally more venus-like), so the whole point is somewhat moot.
First, there is the possibility of a civilization dying and evidence being erased by tectonic plate recycling. Mars is approximately 4.6 billion years old. We know it has volcanic activity, and most consider it to have inactive tectonics now. Some scientists believe it could have had significant activity in the past, based on the 3 distinct regions of Mars. Earth's tectonic plates vary in their rates of recycling: the oldest non-oceanic tectonic plate is 3.6 billion years old, and shows no sign of recycling. Oceanic plates recycle on the average of every 180 million years though.
Second, there is the possibility of technology that didn't leave a visible trace. This is not supported by any evidence and is mere conjecture. If the society tore down non-organic structures and converted to using all biodegradable/organic materials then evidence of the society would be scarce, if existent at all, especially if bodies were cremated as many do today. Chemical analysis could detect this I suspect, or more importantly prove it wrong.
Last, if for some reason civilization evolved underground and stayed underground, then there wouldn't be any visible evidence above ground. This is also pure conjecture. Micro-robots that explore Mars' caves might find something, as might ground penetrating radar.
Red Tape as the real Great Filter...
Life evolved in the sea. At some point life evolved to leave the sea and go to land, whether the sea was no longer hospitable enough, or in search of better food. Life continued to evolve on Land, specializing into different groups and colonizing different lands.
Perhaps civilizations evolve on their planet, then at some point they leave their planet and go into space (when their planet is no longer hospitable or they need more/better food). Finally, while in space they evolve more, founding different colonies that evolve differently due to culture and environmental differences.
The most probable scenario is that life is born multiple times, in multiple places, when conditions permit it.
There's no evidence of life moving across planets of different star systems.
So, two people ran one model described in one paper. Even if that was the whole issue, it would merit "may last only" rather than "will last only".
Additionally, the authors are making a variety of assumptions with little or no basis about the behavior and development of Earth Flora and Fauna; specifically, that it will be mostly static in most ways, with no adaptation in genetics, inter-species interaction, prevalence in different places on Earth etc.
Having said that - in 5 Billion years, Sol will become a Red Giant, so this planet is going South at some point between now and then.
And it's very hard to conceptualise what a billion of years in the future actually means.
Those are interesting numbers to consider when searching for extraterrestrial life in other planetary systems: 39% of planetary lifespan had advanced life, 11% of planetary lifespan had technologically advanced civilization.
Anatomically modern humans evolved 300k years ago and didn't change much since. Can you imagine what kind of progress we will make in the next 300k years? I can't even imagine the next 1000 years.
With regards to dolphins and crows - wow! What a find animals like that would be on another planet! Quite intelligent - but not technologically advanced. You raise an interesting question: assuming a planet has evolved life having the intelligence of a crow or dolphin, what's the probability that planet will evolve a technologically advanced life form? How likely is it earth is the only planet to have evolved such a life form?
If we really, really, cared, we could set up a momentum exchange between Earth and Jupiter mediated by an asteroid, moving Earth further out and Jupiter (slightly) further in, chasing the outward drift of the Sol habitable zone: https://arxiv.org/abs/astro-ph/0102126
Also, we could (in principle, not saying we will or we should) engage in selective breeding or genetic engineering of ourselves; and while mind-uploading is currently SciFi, it’s in the category of “we recon this is eventually possible” rather than “convenient plot device”.
Kind of makes it a tautology.
Edit: Another alternative is technology progresses but political and cultural institutions do not, so the requisite level of global cooperation never materializes.
If that hypothesis holds, then conditional on all the steps having completed on a given planet, they will have done so roughly equally spaced in the time allotted, regardless of their relative difficulty.
So, for example, if the window on Earth is 5 billion years, and there are four hard steps to complete, then, conditional on all four steps finishing, we expect each step to have taken about 1 billion years, give or take, with about 1 billion years left to go.
(See the Technical Appendix to Robin Hanson's Great Filter essay: http://mason.gmu.edu/~rhanson/greatfilter.html#appendix, or his more detailed discussion of this particular point: http://mason.gmu.edu/~rhanson/HARDSTEP.PS)
However, I think at the very least that the origin of the first cells, as well as perhaps the transition from Archaean/Prokaryotic cells to our symbiotic Eukaryotic ancestor may qualify.
It would be so great to learn some more details about the model, etc.
As presented in the news article, there is no explanation for why the apparently still-abundant oxygen does not react with, for example, the increased methane flux that the article also mentions, or just the carbon that has been liberated by dissociation, to maintain a CO2 level adequate for photosynthesis.
I don't doubt that the researchers have answers to these questions (quite likely the one you gave) but something seems to have gone missing in the creation of this news article.
[1] The article actually says "due to the gas absorbing the heat and breaking down", but AFAIK, CO2 is pretty resistant to this. Perhaps this is a garbled version of CO2 reacting more vigorously with rocks and soil at higher temperatures?
The Sun gets brighter over time. Plants (over tens of thousands of years) absorb enough CO2 to keep the temperature from rising too much. But eventually the Sun is so bright that in order to keep the temperature in the right range, plants would have to absorb so much CO2 that there wouldn’t be enough for effective photosynthesis so that eventually in the future this negative feedback mechanism would no longer be able to compensate for the increased brightness of the Sun and so the temperatures would rise, perhaps eventually killing off enough plants to allow CO2 to start to be released and then you get runaway greenhouse effect like Venus.
That is all ignoring humans, of course.
EDIT: actually, it may make more sense to see the feedback coming from the other side of the temperature range: plants will keep absorbing as much CO2 as they can until temperatures drop (think ice ages) and photosynthesis slows. Volcanic emissions (and also occasional natural emissions of fossil carbon) keep a certain amount of CO2 being added which is then kept in equilibrium by plants. As the Sun warms, it takes a lower and lower amount of CO2 to get to ice ages that slow photosynthesis. The Sun over the ages increases in brightness until eventually CO2 levels can’t drop any more without slowing photosynthesis to a stop, so you stop getting ice ages and then eventually the temperatures get so high that photosynthesis is limited by die-off from high temperatures, removing the negative feedback mechanism of photosynthesis and you get runaway greenhouse effect.
That’s why pre-industrial CO2 levels were so low. Primates developed and later intelligent humans developed during the last few million and few hundred thousand years, when CO2 levels have been at their lowest levels ever in our planet’s history (and it shows that we evolved under low CO2 conditions, since human mental processing becomes somewhat less effective at even moderate CO2 levels like 800-1000ppm). Plants (unlike human brains) actually like higher CO2 levels and so they do function as an effective negative feedback mechanism as long you don’t outrun their photosynthesis capability and as long as you don’t kill them off with higher temperatures.
(And less volcanic activity over time also means less CO2 being added back to the atmosphere, so the chemical weathering process that absorbs both CO2 and O2 into minerals will no longer have an active counterbalancing force from volcanoes.)
https://news.ycombinator.com/item?id=26296596
Perhaps it's possible there is another high-metabolism cycle that doesn't involve much oxygen, but nobody really knows both if a pathway exists, and if evolution can "find" it in time. Any biochemists here who want to weigh in?