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Amino acids are common enough -- glycine has been found in comets and, controversially, even in the interstellar medium. Other amino acids have also been found

Amino acids are common enough -- glycine has been found in comets and, controversially, even in the interstellar medium. Other amino acids have also been found in comets. Comet organics, under pressure, can turn into amino acids in situ: https://www.llnl.gov/article/36016/amino-acids-could-be-produced-within-impacting-comets-bringing-life-earth https://www.llnl.gov/article/36016/amino-acids-could-be-prod... It's also presumed that cometary ice bombardment is the source of Earth's surface water, as ice or water present any earlier would have boiled off when the planet was young and hot. It's not much of a stretch to imagine that comets brought amino acids, organic compounds, and minerals to Earth as they were bringing water ice. A lot of those aminos and organics would turn into tar, but some would be protected from UV radiation by that same tar. With a heat source, maybe some lightning strikes, a good location, and a lot of luck, you get RNA... What we can't yet do is assign a probability or likelihood to this process. But the ingredients should be common enough.

dboreham 2y ago
Probability is believed to be quite low based on nobody having reproduced the process in the lab.
- A_D_E_P_T 2y ago
  It's not clear what the probability is over the ~hundreds of millions of years that it took on Earth. Could be that, under the conditions and on that timescale, we're an average or statistically unremarkable case.
  - jolt42 2y ago
    Time means more entropy, so I would think that makes the calculation much more problematic, no?
    - halfcat 2y ago
      Time may correlate with increase in entropy in general. But also consider assembly theory. Once certain assemblies dominate an environment, they constrain future possibilities. Environments and the life it supports evolve together.
- snakeyjake 2y ago
  Low probabilities become certainties with billions of tests per year over hundreds of millions of years.
  - jerf 2y ago
    A common belief, but manifestly false. Probabilities tend to combine exponentially, and that defeats our polynomial universe. Or, to put it another way, it does not matter how many times you try to roll a million fair dice and get them to all come up six. It doesn't matter if the entire observable universe does nothing but that for the entire time from the start of the universe to the heat death end. It will still never happen. Probabilities can easily be "larger" than our entire universe considered across both space and time. It isn't even a particularly remarkable thing to encounter such a probability.
    - A_D_E_P_T 2y ago
      > polynomial universe That's the mistake, right there. Surely you realize that the universe could well be infinite -- and, to all appearances, is in any case not bounded in time. As such, every low probability thing will "at some point" occur. Thus the repugnant conclusion: Boltzmann Brains. But also Boltzmann planets, Boltzmann galaxies, and whatever else can occur will occur.
      - prmph 2y ago
        Then "God creating things" will also inevitably occur, right?
        p_j_w 2y ago
        It depends on the definition of God.
      - Y_Y 2y ago
        > every low probability thing will "at some point" This is the "ergodic hypothesis" and is not necessarily true.
soco 2y ago
But boiling off would have still kept that water in the atmosphere right?
- HPsquared 2y ago
  Not if it's hot enough that the water molecules reach escape velocity in the exosphere! (As happens with helium today, helium atoms being lighter move faster at a given temperature than water molecules)
adastra22 2y ago
Been a while since I interacted with this science, but I think the assumption about the magma ocean “boiling off” the water was an early idea that doesn’t hold up? The mantle holds an impressive amount of water dissolved inside it, as it turns out.
adrian_b 2y ago
About a half of the amino acids used in proteins, i.e. ten of them, can form easily in abiotic conditions and they are widespread in some celestial bodies. They are easily distinguished from terrestrial contaminants, because they are a mixture of left-handed and right-handed isomers. When analyzing the genetic code in order to determine which amino acids have already been used in the earlier versions of the genetic code and which have been added more recently, the same simpler amino acids that are easy to synthesize even in the absence of life are also those that appear to have been the only amino acids used earlier. The article contains the phrase "Given the fact that the current scenario is that life on Earth started with RNA". This is a fact that it is too often repeated like if it were true, when in reality one of the few things that can be said with certainty about the origin of life is that it has not started with RNA. What must be true is only that RNA had existed a very long time before DNA and DNA has been an innovation that has been the result of a long evolution of already existing life forms, long before the last ancestor of all living beings that still exist now on Earth. On the other hand, proteins, or more correctly said peptides, must have existed before any RNA. Moreover, ATP must have existed long before any RNA. RNA has two main functions based on its information-storage property: the replication of RNA using a template of RNA (which was the single form of nucleic acid replication before the existence of DNA) and the synthesis of proteins using RNA as a template. Both processes require complex molecular machines, so it is impossible for both of them to have appeared simultaneously. One process must have appeared before the other and there can be no doubt that the replication of RNA must have appeared before the synthesis of proteins. Had synthesis of proteins appeared first, it would have been instantly lost at the death of the host living being, because the RNA able to be used as a template for proteins could not have been replicated, therefore it could not have been transmitted to descendants. So in the beginning RNA must have been only a molecule with the ability of self replication. All its other functions have evolved in living beings where abundant RNA existed, being produced by self replication. The RNA replication process requires energy and monomers, in the form of ATP together with the other 3 phosphorylated nucleotides. Therefore all 4 nucleotides and their phosphorylated forms like ATP must have existed before RNA. ATP must have been used long before RNA, like today, as a means of extracting water from organic molecules, causing the condensations of monomers like amino acids into polymers like peptides. The chemical reactions in the early living forms were certainly regulated much less well than in the present living beings, so many secondary undesirable reactions must have happened concurrently with the useful chemical reactions. So the existence of abundant ATP and other phosphorylated nucleotides must have had as a consequence the initially undesirable polymerization and co-polymerization of the nucleotides, forming random RNA molecules, until by chance a self-replicating RNA molecule was produced. Because the first self-replicating RNA molecule did not perform any useful function for the host life form, but it diverted useful nucleotides from its metabolism, this first self-replicating RNA molecule must be considered as the first virus. Only much later, after these early viruses have evolved the ability to synthesize proteins, some of them must have become integrated with their hosts, becoming their genome. The catalytic functions that are now performed mostly by proteins, i.e. amino acid polymers that are synthesized using an RNA template, must have been performed earlier by peptides, i.e. typically shorter amino acid polymers that are synthesized without the use of RNA templates. Even today, all living beings contain many non-ribosomal peptides, which are made without RNA, using processes that are much less understood than those that involve nucleic acids. The difference between a living being that would be able to make only non-ribosomal peptides and one that makes proteins using RNA templates is pretty much the same difference as between a CPU with hard-wired control and a CPU with micro-programmed control, with the same advantages and disadvantages. Life forms able to reproduce themselves must have existed before the appearance of the nucleic acids, but they must have been incapable of significant evolution, because any random change in the structure of the molecules that composed them would have been very likely to result in a defective organism that would have died without descendants. This is similar with a hard-wired control, where small random changes in the circuits are unlikely to result in a functional device. On the other hand, once the structure of the enzymes was written in molecules of nucleic acids, the random copying errors could result in structures very different from the original structures, which could not have been obtained by gradual changes in the original structures without passing through non functional structures that could not have been inherited. So the use of molecules that can store the structural information of a living being has enabled the evolution towards much more complex life forms, but it cannot have had any role in the apparition of the first life forms, because the replication of any such molecule requires energy that can be provided only by an already existing life form.
__loam 2y ago
You don't need that much luck when you have billions of years.

dboreham 2y ago

Probability is believed to be quite low based on nobody having reproduced the process in the lab.

A_D_E_P_T 2y ago
It's not clear what the probability is over the ~hundreds of millions of years that it took on Earth. Could be that, under the conditions and on that timescale, we're an average or statistically unremarkable case.
- jolt42 2y ago
  Time means more entropy, so I would think that makes the calculation much more problematic, no?
  - halfcat 2y ago
    Time may correlate with increase in entropy in general. But also consider assembly theory. Once certain assemblies dominate an environment, they constrain future possibilities. Environments and the life it supports evolve together.
snakeyjake 2y ago
Low probabilities become certainties with billions of tests per year over hundreds of millions of years.
- jerf 2y ago
  A common belief, but manifestly false. Probabilities tend to combine exponentially, and that defeats our polynomial universe. Or, to put it another way, it does not matter how many times you try to roll a million fair dice and get them to all come up six. It doesn't matter if the entire observable universe does nothing but that for the entire time from the start of the universe to the heat death end. It will still never happen. Probabilities can easily be "larger" than our entire universe considered across both space and time. It isn't even a particularly remarkable thing to encounter such a probability.
  - A_D_E_P_T 2y ago
    > polynomial universe That's the mistake, right there. Surely you realize that the universe could well be infinite -- and, to all appearances, is in any case not bounded in time. As such, every low probability thing will "at some point" occur. Thus the repugnant conclusion: Boltzmann Brains. But also Boltzmann planets, Boltzmann galaxies, and whatever else can occur will occur.
    - prmph 2y ago
      Then "God creating things" will also inevitably occur, right?
      - p_j_w 2y ago
        It depends on the definition of God.
    - Y_Y 2y ago
      > every low probability thing will "at some point" This is the "ergodic hypothesis" and is not necessarily true.

soco 2y ago

But boiling off would have still kept that water in the atmosphere right?

HPsquared 2y ago
Not if it's hot enough that the water molecules reach escape velocity in the exosphere! (As happens with helium today, helium atoms being lighter move faster at a given temperature than water molecules)

adastra22 2y ago

Been a while since I interacted with this science, but I think the assumption about the magma ocean “boiling off” the water was an early idea that doesn’t hold up? The mantle holds an impressive amount of water dissolved inside it, as it turns out.

adrian_b 2y ago

About a half of the amino acids used in proteins, i.e. ten of them, can form easily in abiotic conditions and they are widespread in some celestial bodies. They are easily distinguished from terrestrial contaminants, because they are a mixture of left-handed and right-handed isomers. When analyzing the genetic code in order to determine which amino acids have already been used in the earlier versions of the genetic code and which have been added more recently, the same simpler amino acids that are easy to synthesize even in the absence of life are also those that appear to have been the only amino acids used earlier. The article contains the phrase "Given the fact that the current scenario is that life on Earth started with RNA". This is a fact that it is too often repeated like if it were true, when in reality one of the few things that can be said with certainty about the origin of life is that it has not started with RNA. What must be true is only that RNA had existed a very long time before DNA and DNA has been an innovation that has been the result of a long evolution of already existing life forms, long before the last ancestor of all living beings that still exist now on Earth. On the other hand, proteins, or more correctly said peptides, must have existed before any RNA. Moreover, ATP must have existed long before any RNA. RNA has two main functions based on its information-storage property: the replication of RNA using a template of RNA (which was the single form of nucleic acid replication before the existence of DNA) and the synthesis of proteins using RNA as a template. Both processes require complex molecular machines, so it is impossible for both of them to have appeared simultaneously. One process must have appeared before the other and there can be no doubt that the replication of RNA must have appeared before the synthesis of proteins. Had synthesis of proteins appeared first, it would have been instantly lost at the death of the host living being, because the RNA able to be used as a template for proteins could not have been replicated, therefore it could not have been transmitted to descendants. So in the beginning RNA must have been only a molecule with the ability of self replication. All its other functions have evolved in living beings where abundant RNA existed, being produced by self replication. The RNA replication process requires energy and monomers, in the form of ATP together with the other 3 phosphorylated nucleotides. Therefore all 4 nucleotides and their phosphorylated forms like ATP must have existed before RNA. ATP must have been used long before RNA, like today, as a means of extracting water from organic molecules, causing the condensations of monomers like amino acids into polymers like peptides. The chemical reactions in the early living forms were certainly regulated much less well than in the present living beings, so many secondary undesirable reactions must have happened concurrently with the useful chemical reactions. So the existence of abundant ATP and other phosphorylated nucleotides must have had as a consequence the initially undesirable polymerization and co-polymerization of the nucleotides, forming random RNA molecules, until by chance a self-replicating RNA molecule was produced. Because the first self-replicating RNA molecule did not perform any useful function for the host life form, but it diverted useful nucleotides from its metabolism, this first self-replicating RNA molecule must be considered as the first virus. Only much later, after these early viruses have evolved the ability to synthesize proteins, some of them must have become integrated with their hosts, becoming their genome. The catalytic functions that are now performed mostly by proteins, i.e. amino acid polymers that are synthesized using an RNA template, must have been performed earlier by peptides, i.e. typically shorter amino acid polymers that are synthesized without the use of RNA templates. Even today, all living beings contain many non-ribosomal peptides, which are made without RNA, using processes that are much less understood than those that involve nucleic acids. The difference between a living being that would be able to make only non-ribosomal peptides and one that makes proteins using RNA templates is pretty much the same difference as between a CPU with hard-wired control and a CPU with micro-programmed control, with the same advantages and disadvantages. Life forms able to reproduce themselves must have existed before the appearance of the nucleic acids, but they must have been incapable of significant evolution, because any random change in the structure of the molecules that composed them would have been very likely to result in a defective organism that would have died without descendants. This is similar with a hard-wired control, where small random changes in the circuits are unlikely to result in a functional device. On the other hand, once the structure of the enzymes was written in molecules of nucleic acids, the random copying errors could result in structures very different from the original structures, which could not have been obtained by gradual changes in the original structures without passing through non functional structures that could not have been inherited. So the use of molecules that can store the structural information of a living being has enabled the evolution towards much more complex life forms, but it cannot have had any role in the apparition of the first life forms, because the replication of any such molecule requires energy that can be provided only by an already existing life form.

__loam 2y ago

You don't need that much luck when you have billions of years.