5 ms·

If we assume single celled life is common, and exists in either all star systems, or in all systems without a hot Jupiter close to the star; then given the leng

If we assume single celled life is common, and exists in either all star systems, or in all systems without a hot Jupiter close to the star; then given the length of time involved here before eukaryotes, can we estimate how many planets in the galaxy have eukaryotes? Or how long it will be before some do? Presumably increasing the length of time increases the probability of occurrence as would increasing the number of stars involved. Though how can we know if the event was statistically likely after that amount of time or whether we are deviations from the centre of the distribution (other than observing the quiet galaxy). Surely we can have a rough idea now of where we stand

JumpCrisscross 4y ago
> can we estimate how many planets in the galaxy have eukaryotes? Not yet. In the history of life on Earth, this has happened once. Knowing what we know about cellular biology, it’s stupidly unlikely. Beyond our present theories’ ability to quantify. By the way, I think this is one of—if not the—great filters. It’s unlikely to happen, to not promptly get smote by its primordial planet’s tantrums and to get it so right it perpetuates for billions of years.
- echelon 4y ago
  > Not yet. In the history of life on Earth, this has happened once. 1) That we know about. 2) Not unlike startups vs. established business, any newly emerging "eukaryotes" have to out-compete the already-evolved incumbents, which are already quite good at harnessing energy. You're much more likely to find success in business than in an entirely new evolutionary branch, though I doubt biological "gray goo" is outright impossible [1]. [1] Reverse chirality autotrophs sound like a scary sci-fi novel plot https://news.ycombinator.com/item?id=28038505 https://news.ycombinator.com/item?id=28038505
  - ajuc 4y ago
    Additionally the environment changed significantly since then (for one example oxygen which was highly toxic to most forms of life that existed back then is now over 20% of atmosphere). > Reverse chirality autotrophs sound like a scary sci-fi novel plot Very ice-9-like.
  - yyyk 4y ago
    >Reverse chirality autotrophs sound like a scary sci-fi novel plot I doubt this. 'Not being digestible' is very far from 'being invulnerable' or even 'being able to spread quickly'. The kingdom of life has many ways to kill stuff, ways which don't care about chirality, and our typical R-sided lifeforms have all the evolutionary 'motivation' to come up with new ways just the off the competition. That's before humans get into the picture, which we have the tech to do. There may be an accumulation of non-digestible stuff until nature reaches a balance. However, there's a very large recent accumulation of non-digestible materials called 'plastics', and while somewhat harmful, they're not a life-ending threat. Nature is already finding ways to process these materials[0]. [0] https://en.wikipedia.org/wiki/Plastic_degradation_by_marine_bacteria https://en.wikipedia.org/wiki/Plastic_degradation_by_marine_...
    - echelon 4y ago
      Sure, but I did say "sci-fi". And I think there are a lot of unaddressed points. Plastics don't self-manufacture. You might not be able to control the rate. Just because you kill something doesn't mean you break down its carbohydrates. Reverse chiral organism skeletons could bioaccumulate and we could have a situation similar to the Carboniferous. Someone might be able to synthesize a bacteria in the lab given enough time and effort from an organism that proliferates quickly. It doesn't have to capture all the carbon. Just out-compete a keystone species. Plankton, mycorrhizae, etc. Or attack a large percentage of the plant biomass.
      - yyyk 4y ago
        >Plastics don't self-manufacture. You might not be able to control the rate. The rate is limited by the process. Since no precursors exist, it must 'self-manufacture' from scratch. This has inherent limits even before introducing competition for food, poison, predators that eat you even despite them not being able to really digest, etc. >Just because you kill something doesn't mean you break down its carbohydrates. Reverse chiral organism skeletons could bioaccumulate and we could have a situation similar to the Carboniferous. So you don't break it down. Nature will have plenty of time to adapt. Humans will step in if needed. >Someone might be able to synthesize a bacteria in the lab given enough time and effort from an organism that proliferates quickly. That's an incredibly messy way - create an entire L-chiral biochemistery - to get a weapon which doesn't have a setting between 'kill everything' and 'do rather little' (IMHO, the second being much likelier). There are far worse and more directed things one can do with a lab. Even the absurd 'kill everything' goal is far more likely to be reached in different ways.
- sterlind 4y ago
  per the article, endosymbiosis has happened a bunch of times. multiple different kinds of chloroplasts, several prokaryotes, a parasite etc. this was all when eukaryotes engulfed prokaryotes, but still, how does this mean unlikely? it seems imminently likely, since.. it happened a bunch of times. seems to me like prokaryotes evolve a strategy of engulfing others for their resources, then one day engulf a prokaryote infected by a virus, which transfers DNA across, rinse and repeat. how is this more of a filter than abiogenesis?
  - kylebenzlee 4y ago
    Yes, this (nonsense) discuassion is when you have computer progammers discuss biology. Is strange because they know nothing but all seem to think they must be experts of evrything because they get paid a lot to sit infront of a computer all day.
  - JumpCrisscross 4y ago
    > how is this more of a filter than abiogenesis? Common chemistries get us very close to molecular systems subject to evolutionary pressure. (Simplest: RNA world hypothesis.) We are missing links. But the pathway is plausible. Chloroplasts, as you mention, are a potent counter argument. But once you have surplus cellular energy, additional endosymbiosis has a lower threshold. Based on current research, all life has a similar mitochondria. Different kingdoms didn’t nom their own and go. That uniqueness suggests difficulty.
    - XorNot 4y ago
      Or simply that success produces logarithmic returns: in the context of when this was happening, the first species to do it rapidly outcompeted all others and functionally ended exploration of the possibility space.
  - simonh 4y ago
    The thing that only happened once on Earth and that's a prerequisite to developing complex life forms is not endosymbiosis, it's life going multi-cellular. They are not the same thing. Endosymbiosis is not identical with going multi-cellular, and it seems that all but perhaps one of the known instances of endosymbiosis didn't play any role in us going multi-cellular anyway. In fact this article makes the case that it may not have been critical at all.
marcosdumay 4y ago
Well, that's not a good assumption to make. Our most capable life detector¹ is analyzing the atmosphere of planets, captures stuff similar to our simplest single celled life. So, it's not a good guess that it's common. 1 - Actually our second best. The best one is the fact that nobody colonized Earth before we existed, that is tuned in space-faring life.
323 4y ago
You make a big assumption, that there must be only two kinds of cells, "simple" and "complex", like on earth. That could well be an accidental fact. Maybe on some planets we have a gradient of cell complexity. Also, we don't really know what even simpler kinds existed on earth but were lost, since bacteria, the "simple" kind, it's obviously too complex to have been the first ever life form.
- andrewflnr 4y ago
  That's not even true on earth. Archaea exist, and eukaryotes span a pretty wide range of complexity themselves.
kylebenzlee 4y ago
lkrubner 4y ago
Maybe, but there are other narratives that are easy to spin. Our solar system has 3 planets all of which might have had single-celled organisms, at some point: Venus, Earth, and Mars. And for the first 3.7 billion years, the 3 planets might have followed a similar path. And then all 3 planets reach old age and basically die, Venus becoming too hot, while Earth and Mars become mostly dead ice covered snow balls. And maybe that is the normal history of most planets, even planets that develop single-celled life. In that narrative, the emphasis is on the extraordinary re-birth of Earth, after the end of Snowball Earth. Almost everything that we regard as interesting about Earth happens after this late-in-its history revival. That raises some other questions, such as, why did Snowball Earth end? Why does multicellular life take off then, but not before? What is it that makes the Earth/moon system so unusually dynamic that it hasn't settled down to some dead equilibrium, even after 3.7 billion years? What allows Earth to have such an extraordinary additional era?
maneesh 4y ago
Just us if we live in a simulation

JumpCrisscross 4y ago

> can we estimate how many planets in the galaxy have eukaryotes? Not yet. In the history of life on Earth, this has happened once. Knowing what we know about cellular biology, it’s stupidly unlikely. Beyond our present theories’ ability to quantify. By the way, I think this is one of—if not the—great filters. It’s unlikely to happen, to not promptly get smote by its primordial planet’s tantrums and to get it so right it perpetuates for billions of years.

echelon 4y ago
> Not yet. In the history of life on Earth, this has happened once. 1) That we know about. 2) Not unlike startups vs. established business, any newly emerging "eukaryotes" have to out-compete the already-evolved incumbents, which are already quite good at harnessing energy. You're much more likely to find success in business than in an entirely new evolutionary branch, though I doubt biological "gray goo" is outright impossible [1]. [1] Reverse chirality autotrophs sound like a scary sci-fi novel plot https://news.ycombinator.com/item?id=28038505 https://news.ycombinator.com/item?id=28038505
- ajuc 4y ago
  Additionally the environment changed significantly since then (for one example oxygen which was highly toxic to most forms of life that existed back then is now over 20% of atmosphere). > Reverse chirality autotrophs sound like a scary sci-fi novel plot Very ice-9-like.
- yyyk 4y ago
  >Reverse chirality autotrophs sound like a scary sci-fi novel plot I doubt this. 'Not being digestible' is very far from 'being invulnerable' or even 'being able to spread quickly'. The kingdom of life has many ways to kill stuff, ways which don't care about chirality, and our typical R-sided lifeforms have all the evolutionary 'motivation' to come up with new ways just the off the competition. That's before humans get into the picture, which we have the tech to do. There may be an accumulation of non-digestible stuff until nature reaches a balance. However, there's a very large recent accumulation of non-digestible materials called 'plastics', and while somewhat harmful, they're not a life-ending threat. Nature is already finding ways to process these materials[0]. [0] https://en.wikipedia.org/wiki/Plastic_degradation_by_marine_bacteria https://en.wikipedia.org/wiki/Plastic_degradation_by_marine_...
  - echelon 4y ago
    Sure, but I did say "sci-fi". And I think there are a lot of unaddressed points. Plastics don't self-manufacture. You might not be able to control the rate. Just because you kill something doesn't mean you break down its carbohydrates. Reverse chiral organism skeletons could bioaccumulate and we could have a situation similar to the Carboniferous. Someone might be able to synthesize a bacteria in the lab given enough time and effort from an organism that proliferates quickly. It doesn't have to capture all the carbon. Just out-compete a keystone species. Plankton, mycorrhizae, etc. Or attack a large percentage of the plant biomass.
    - yyyk 4y ago
      >Plastics don't self-manufacture. You might not be able to control the rate. The rate is limited by the process. Since no precursors exist, it must 'self-manufacture' from scratch. This has inherent limits even before introducing competition for food, poison, predators that eat you even despite them not being able to really digest, etc. >Just because you kill something doesn't mean you break down its carbohydrates. Reverse chiral organism skeletons could bioaccumulate and we could have a situation similar to the Carboniferous. So you don't break it down. Nature will have plenty of time to adapt. Humans will step in if needed. >Someone might be able to synthesize a bacteria in the lab given enough time and effort from an organism that proliferates quickly. That's an incredibly messy way - create an entire L-chiral biochemistery - to get a weapon which doesn't have a setting between 'kill everything' and 'do rather little' (IMHO, the second being much likelier). There are far worse and more directed things one can do with a lab. Even the absurd 'kill everything' goal is far more likely to be reached in different ways.
sterlind 4y ago
per the article, endosymbiosis has happened a bunch of times. multiple different kinds of chloroplasts, several prokaryotes, a parasite etc. this was all when eukaryotes engulfed prokaryotes, but still, how does this mean unlikely? it seems imminently likely, since.. it happened a bunch of times. seems to me like prokaryotes evolve a strategy of engulfing others for their resources, then one day engulf a prokaryote infected by a virus, which transfers DNA across, rinse and repeat. how is this more of a filter than abiogenesis?
- kylebenzlee 4y ago
  Yes, this (nonsense) discuassion is when you have computer progammers discuss biology. Is strange because they know nothing but all seem to think they must be experts of evrything because they get paid a lot to sit infront of a computer all day.
- JumpCrisscross 4y ago
  > how is this more of a filter than abiogenesis? Common chemistries get us very close to molecular systems subject to evolutionary pressure. (Simplest: RNA world hypothesis.) We are missing links. But the pathway is plausible. Chloroplasts, as you mention, are a potent counter argument. But once you have surplus cellular energy, additional endosymbiosis has a lower threshold. Based on current research, all life has a similar mitochondria. Different kingdoms didn’t nom their own and go. That uniqueness suggests difficulty.
  - XorNot 4y ago
    Or simply that success produces logarithmic returns: in the context of when this was happening, the first species to do it rapidly outcompeted all others and functionally ended exploration of the possibility space.
- simonh 4y ago
  The thing that only happened once on Earth and that's a prerequisite to developing complex life forms is not endosymbiosis, it's life going multi-cellular. They are not the same thing. Endosymbiosis is not identical with going multi-cellular, and it seems that all but perhaps one of the known instances of endosymbiosis didn't play any role in us going multi-cellular anyway. In fact this article makes the case that it may not have been critical at all.

marcosdumay 4y ago

Well, that's not a good assumption to make. Our most capable life detector¹ is analyzing the atmosphere of planets, captures stuff similar to our simplest single celled life. So, it's not a good guess that it's common. 1 - Actually our second best. The best one is the fact that nobody colonized Earth before we existed, that is tuned in space-faring life.

323 4y ago

You make a big assumption, that there must be only two kinds of cells, "simple" and "complex", like on earth. That could well be an accidental fact. Maybe on some planets we have a gradient of cell complexity. Also, we don't really know what even simpler kinds existed on earth but were lost, since bacteria, the "simple" kind, it's obviously too complex to have been the first ever life form.

andrewflnr 4y ago
That's not even true on earth. Archaea exist, and eukaryotes span a pretty wide range of complexity themselves.

kylebenzlee 4y ago

lkrubner 4y ago

Maybe, but there are other narratives that are easy to spin. Our solar system has 3 planets all of which might have had single-celled organisms, at some point: Venus, Earth, and Mars. And for the first 3.7 billion years, the 3 planets might have followed a similar path. And then all 3 planets reach old age and basically die, Venus becoming too hot, while Earth and Mars become mostly dead ice covered snow balls. And maybe that is the normal history of most planets, even planets that develop single-celled life. In that narrative, the emphasis is on the extraordinary re-birth of Earth, after the end of Snowball Earth. Almost everything that we regard as interesting about Earth happens after this late-in-its history revival. That raises some other questions, such as, why did Snowball Earth end? Why does multicellular life take off then, but not before? What is it that makes the Earth/moon system so unusually dynamic that it hasn't settled down to some dead equilibrium, even after 3.7 billion years? What allows Earth to have such an extraordinary additional era?

maneesh 4y ago

Just us if we live in a simulation